RE: [CAD_CAM_EDM_DRO] Digest Number 1173

I?m sorry, I'm pretty new on this mail-list and I directly attached the
web-page as a link, but it disn't follow the message.
The link for Camtronics is: http://www.seanet.com/~dmauch/
on this link you get the decription of the EDM kit/plans available:
http://www.seanet.com/~dmauch/Products2.htm
on this one you have some nice shots of the machine built:
http://www.seanet.com/~dmauch/images.htm
I hope it will help.

Paolo

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]
Sent: martedì 6 marzo 2001 9.05
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Digest Number 1173


Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
discussion of shop built systems, for CAD, CAM, EDM, and DRO.

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------------------------------------------------------------------------

There are 8 messages in this issue.

Topics in this digest:

1. Re: Re: Thread milling!!
From: Jon Anderson <janders@...>
2. Re: Re: Thread milling!!
From: Jon Anderson <janders@...>
3. Re: Re: Dead Grizzly speed control/VFD
From: John Murphy <john@...>
4. RE: a little EDM machine
From: "Paolo Velcich" <pavel@...>
5. Re: Re: cutting speed and feed for 3/4" dovetail cutter
From: marble here <marble_h@...>
6. Re: cutting speed and feed for 3/4" dovetail cutter
From: marble here <marble_h@...>
7. Re: Phase Control of SCR's; Hi Current
From: "Henry H. Armstrong" <hharms@...>
8. Re: Re: Thread milling!!
From: Jon Elson <jmelson@...>


________________________________________________________________________
________________________________________________________________________

Message: 1
Date: Mon, 05 Mar 2001 16:03:21 -0800
From: Jon Anderson <janders@...>
Subject: Re: Re: Thread milling!!

John,

I'd like to see a picture when you find it. I have some chaser style
inserts that were included with a Geometric die head I bought, but they
are certainly not Geometric chasers. Perhaps I can adapt your design to
make these useful.

Jon


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________________________________________________________________________

Message: 2
Date: Mon, 05 Mar 2001 16:10:36 -0800
From: Jon Anderson <janders@...>
Subject: Re: Re: Thread milling!!

John,

I just happened to have those strange chaser inserts at my desk, started
looking at them and realized they have the helix angle ground in them.
Do you relieve the back side? I'd thought for a second about inclining
the tool to match the angle, but that would have the top and bottom
threads sitting further out from center than the threads in the center.

Jon


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________________________________________________________________________

Message: 3
Date: Mon, 05 Mar 2001 17:52:25 -0700
From: John Murphy <john@...>
Subject: Re: Re: Dead Grizzly speed control/VFD

Ray Wins!!! Thanks!

When I got home today, first thing I did was open the "switch panel"
which
has the motor leads terminating in it. I clipped my meter on them and
ran through the power range.... 44V DC to 110VDC. Drive looks good.

Next, I powered it up (of course it didn't spin up) and slowly turned
the
spindle by hand. Around 3/4 of a turn around, the motor "caught" and
the spindle spun perhaps 1/16 th of a turn! Definitly looking like
brushes.

Then I unplugged everything and removed the brushes (which I had not
really noticed before)... and pulled them out. Each was around 9/16's
of an inch long, and one had a pretty high carbon buildup. (The other
had some, but not as much). I cleaned them up with some emery paper,
re-installed them, and viola! It's running smooth as ever. (I only
wish I had the sense to do that when it first started (I had paused EMC
and re-starting the part would have been much easier!).

Back to running the poor mill 40 hours a week (I've been machining robot
parts pretty hard when I get home at night)... Someday I'll have room
for
a "real" machine.

Thanks folks. This group is simply amazing.

murph


Ray wrote:

>
> John M.
>
> If this is the G8689. It uses a DC motor with brushes. I'd suspect the
> brushes before the drive. If one brush hangs up it will cuase the motor

to

> stutter and draw a lot of current when contact is made.
>
> For these, a VFD is no good but a low cost DC control might work. You
> would need to compare V and A.
>
> Ray
>
> From: John Murphy <john@...>
>
> >I've got the tiny grizzly mini mill, and my drive has cut out. I'm
> >going to try to get it replaced under warranty, but I'm not willing to
> >go through the trouble of shipping the mill back as it says they
> >might do under their warranty.
>
> >The symptoms were fluctuating speed and horrible blinking of the
> >flourescent lights in the shop, then it died. I waited a couple of
> >hours, tried again, and it started up OK, but erratic, before it died
> >again. Now it won't start up at all.
>
> >If I'm going to replace it myself, can anybody recommend a compatible
> >VFD, perhaps something with a speed control input?
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the

discussion of shop built systems, for CAD, CAM, EDM, and DRO.

>
> Addresses:
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> Moderator: jmelson@... timg@... [Moderator]
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> bill,
> List Manager
>
> FAQ: http://www.ktmarketing.com/faq.html
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

________________________________________________________________________
________________________________________________________________________

Message: 4
Date: Tue, 6 Mar 2001 03:19:17 +0100
From: "Paolo Velcich" <pavel@...>
Subject: RE: a little EDM machine


Here you can find some nice images and a source of informations about a DIY
EDM machine.
Follow the links "images" or "what's new".
Have fun

Paolo

-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]
Sent: martedì 6 marzo 2001 0.59
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Digest Number 1172


Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
discussion of shop built systems, for CAD, CAM, EDM, and DRO.

Addresses:
Post message: CAD_CAM_EDM_DRO@yahoogroups.com
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bill,
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FAQ: http://www.ktmarketing.com/faq.html
------------------------------------------------------------------------

There are 25 messages in this issue.

Topics in this digest:

1. Re:dovetail cutting
From: Bradford Chaucer <bradford.chaucer@...>
2. Re: mill/drill recomendations
From: ptengin@...
3. Phase Control of SCR's; Hi Current
From: jmw@...
4. Re: cutting speed and feed for 3/4" dovetail cutter
From: marble here <marble_h@...>
5. Re: Dead Grizzly speed control/VFD
From: Ray <rehenry@...>
6. Re: Re:dovetail cutting
From: Joe Vicars <jvicars@...>
7. Re: Re: 4 Bar Linkages
From: Joe Vicars <jvicars@...>
8. RE: Dead Grizzly speed control/VFD
From: ron ginger <ronginger@...>
9. Re: cutting speed and feed for 3/4" dovetail cutter
From: Jon Anderson <janders@...>
10. Re: RE: Dead Grizzly speed control/VFD
From: "Dan Mauch" <dmauch@...>
11. Re: Phase Control of SCR's; Hi Current
From: arcstarter@...
12. RE: EDM? Was: Phase Control of SCR's; Hi Curren t
From: Tim Goldstein <timg@...>
13. RE: Re: Phase Control of SCR's; Hi Current
From: "Carlos Guillermo" <carlos@...>
14. Re: Quick RF-45/VFD question
From: Drew Rogge <drew@...>
15. Re: 4 Bar Linkages
From: Greg Jackson <jackson@...>
16. Re: EDM? Was: Phase Control of SCR's; Hi Curren t
From: arcstarter@...
17. Re: Quick RF-45/VFD question
From: ptengin@...
18. Re: cutting speed and feed for 3/4" dovetail cutter
From: Jon Elson <jmelson@...>
19. Re: Re: Thread milling!!
From: Jon Elson <jmelson@...>
20. Re: EDM? Was: Phase Control of SCR's; Hi Curren t
From: <e.heritage@...>
21. Re: EDM? Was: Phase Control of SCR's; Hi Curren t
From: dave engvall <dengvall@...>
22. Re: EDM? Was: Phase Control of SCR's; Hi Curren t
From: Jon Elson <jmelson@...>
23. Re: mill/drill recomendations
From: tmay@...
24. Re: cutting speed and feed for 3/4" dovetail cutter
From: "John Stevenson" <machines@...>
25. Re: Thread milling!!
From: "John Stevenson" <machines@...>


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________________________________________________________________________

Message: 1
Date: Mon, 05 Mar 2001 03:09:23 -0500
From: Bradford Chaucer <bradford.chaucer@...>
Subject: Re:dovetail cutting

At 03:04 AM 3/5/2001, you wrote:

>I have been cutting at 160 rpm's and a feed of .002 per rev but I
>snapped the cutter ,boy $59.00 down the drain and I have 15 more cuts
>to do..

Were you cutting into solid material or undercutting in an existing
groove?? I think that you first need to remove the central portion of the
dovetail slot with a straight sided cutter of the proper diameter
Regards,
Bradford Chaucer
bradford.chaucer@...



________________________________________________________________________
________________________________________________________________________

Message: 2
Date: Mon, 5 Mar 2001 04:47:05 EST
From: ptengin@...
Subject: Re: mill/drill recomendations

In a message dated 03/04/2001 7:22:22 AM Hawaiian Standard Time,
jackson@... writes:

> Does anyone know who imports the RF 45? I see it on the RF website but I
> don't find it in any of the catalogs I have.
>
> G. Jackson
>
>
>

Try MSC.

Peter
THRD, Inc.


[Non-text portions of this message have been removed]



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Message: 3
Date: Mon, 05 Mar 2001 10:02:44 -0000
From: jmw@...
Subject: Phase Control of SCR's; Hi Current

I know this is a little off-topic, but the talent level of the group
is so tempting...

Can someone steer me to a circuit for triggering SCR's at a user-
selectable point in the AC cycle? I've seen circuit snippets in asst
cookbooks, but not being an ee I'd like to find something a little
more complete. The rectifiers will be working at 50v 250amps max in a
mig welding application; duty cyle at max output would be in the nbhd
of 20-30%. Ideally, I'd like to be able to chop out the middle of the
AC cycle rather than the initial segment--but I guess SCR's don't
play that way. Triacs do, right, but not at 250A?

The block diagrams I've seen for commercial migs using transformers
with electronic control (instead of multiple taps) use SCR's as
described above. But wouldn't it also be possible just to use
ordinary diodes on the secondary and control the primary side? It
sounds easier to switch 240VAC at 40A rather than 250A. The
transformer doesn't mind getting an AC waveform with a bite taken
out, does it?

One final question. MIGS generally run "constant voltage" volt-amp
profiles, meaning that the output voltage tends to change relatively
little even though amperage may change significantly. So far as I can
tell by looking at several units, this is accomplised with a big
honkin' iron core inductor in series with the output. The inductor
tends to be about 2/3 the size of the power transformer with roughly
the same number of turns as the transformer secondary. A healthy bank
of caps on the order of 100k uf, is also part of the equation. (The
inductor air gap, if any, I don't know about.) My question is this:
Can the volt-amp curve be tuned--its slope changed--by phase control,
possibly active phase control during operation? This would make the
design of inductor less critical. My intuition is that there're too
many df in the problem to conrol with single parameter (trigger
point.) But maybe not ... I guess a scheme like this would require
microprocessor control and amps / volts feedback. There are some
interesting Nuts and Volts articles back in Dec / Jan about
microcontrollers and SCRs.

Thanks in advance.

--Jack



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________________________________________________________________________

Message: 4
Date: Mon, 5 Mar 2001 02:34:56 -0800 (PST)
From: marble here <marble_h@...>
Subject: Re: cutting speed and feed for 3/4" dovetail cutter

Sorry all yes I have milled out the pocket first and
the steel is D2 tool steel only one part is so I
thought I should get that done first and the cutter is
a 3/4 "8 flute

John
--- Jon Elson <jmelson@...> wrote:

>
>
> marble_h@... wrote:
>
> > Can anyone tell me what the feed and cutting
> speed is for it
> >
> > I have been cutting at 160 rpm's and a feed of
> .002 per rev but I
> > snapped the cutter ,boy $59.00 down the drain and
> I have 15 more cuts
> > to do..
>
> What is the diameter? How many cutting edges? What
> is the
> tool made of (HSS, I'm guessing)? What is the
> workpiece material?
>
> You first figure the correct surface speed in
> Feet/Minute, based on
> tool and work materials. For HSS cutters on mild
> steel, it is about 100 SFPM.
> For HSS on aluminum alloy, it is 600 or so.
>
> Now, a dovetail cutter has a varied diameter, so you
> have to come up
> with a compromise speed. But, using the widest
> diameter of the cutter
> should be good. RPM = SFPM * 12 / (diameter * Pi)
>
> For 100 SFPM with a 2" cutter, the RPM should be
> about 190.
>
> Now, most dovetail cutters have a lot of cutting
> teeth. So, you take a
> guess at chip load per tooth, multiply by number of
> teeth, and RPM, and
> you get feed rate in inches/minute. So, for a
> 16-tooth cutter, and a chip
> load of .002"/tooth, you get feed= .002" * 16 * 190
> = 6 IPM.
>
> Now, one thing is you should mill the center of the
> dovetail out as far as
> you can with a standard end mill first, so the
> dovetail cutter only needs
> to remove the material under the dovetail itself.
>
> If you are doing this in aluminum or steel, you need
> to use a coolant to
> keep the cutter and work cool, and flush away the
> chips. Cast Iron is
> usually cut dry, or with a touch of cutting oil.
>
> Jon
>
>
> Welcome to CAD_CAM_EDM_DRO@...,an
> unmoderated list for the discussion of shop built
> systems, for CAD, CAM, EDM, and DRO.
>
> Addresses:
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>
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>
>

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Message: 5
Date: Mon, 5 Mar 2001 07:00:08 -0600
From: Ray <rehenry@...>
Subject: Re: Dead Grizzly speed control/VFD


John M.

If this is the G8689. It uses a DC motor with brushes. I'd suspect the
brushes before the drive. If one brush hangs up it will cuase the motor to
stutter and draw a lot of current when contact is made.

For these, a VFD is no good but a low cost DC control might work. You
would need to compare V and A.

Ray


From: John Murphy <john@...>

>I've got the tiny grizzly mini mill, and my drive has cut out. I'm
>going to try to get it replaced under warranty, but I'm not willing to
>go through the trouble of shipping the mill back as it says they
>might do under their warranty.

>The symptoms were fluctuating speed and horrible blinking of the
>flourescent lights in the shop, then it died. I waited a couple of
>hours, tried again, and it started up OK, but erratic, before it died
>again. Now it won't start up at all.

>If I'm going to replace it myself, can anybody recommend a compatible
>VFD, perhaps something with a speed control input?

________________________________________________________________________
________________________________________________________________________

Message: 6
Date: Mon, 05 Mar 2001 09:08:07 -0500
From: Joe Vicars <jvicars@...>
Subject: Re: Re:dovetail cutting

Yes,
Dovetailing (milling) a long groove can be very frustrating especially
in steel. You want rough the groove as much as possible
with a key cutter, T-slot tool or similar. It should look like a "T" before
you start with the dovetail.
A shaper is really good for dovetailing..

Bradford Chaucer wrote:

> At 03:04 AM 3/5/2001, you wrote:
> >I have been cutting at 160 rpm's and a feed of .002 per rev but I
> >snapped the cutter ,boy $59.00 down the drain and I have 15 more cuts
> >to do..
>
> Were you cutting into solid material or undercutting in an existing
> groove?? I think that you first need to remove the central portion of the
> dovetail slot with a straight sided cutter of the proper diameter
> Regards,
> Bradford Chaucer
> bradford.chaucer@...
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the

discussion of shop built systems, for CAD, CAM, EDM, and DRO.

>
> Addresses:
> Post message: CAD_CAM_EDM_DRO@yahoogroups.com
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> bill,
> List Manager
>
> FAQ: http://www.ktmarketing.com/faq.html
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

________________________________________________________________________
________________________________________________________________________

Message: 7
Date: Mon, 05 Mar 2001 09:09:15 -0500
From: Joe Vicars <jvicars@...>
Subject: Re: Re: 4 Bar Linkages

To what term were you reffering?

ballendo@... wrote:

> Joe,
>
> This is a new term to me. What is it?
>
> Thank you in advance.
>
> Ballendo
>
> P.S. Sounds like my 20's, where the Friday night motion path was:
> Go to the 1st bar, try to "come up with" linkage, Go to the 2nd
> bar...
> Eccentricities tended to enter the motion path at the 3rd and 4th
> Bars, and "linkage" was never assured... :-)
>
> --- In CAD_CAM_EDM_DRO@y..., Joe Vicars <jvicars@c...> wrote:
> > Can someone recommend a text, website, software, or any other
> utilities
> > for 4 bar linkages? I need a method of comming up with a 4 bar,
> knowing
> > the motion path.
> > Thanks
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the

discussion of shop built systems, for CAD, CAM, EDM, and DRO.

>
> Addresses:
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> bill,
> List Manager
>
> FAQ: http://www.ktmarketing.com/faq.html
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

________________________________________________________________________
________________________________________________________________________

Message: 8
Date: Mon, 05 Mar 2001 10:55:31 -0500
From: ron ginger <ronginger@...>
Subject: RE: Dead Grizzly speed control/VFD

Mine died suddenly. One time it worked fine, next it wouldnt come on. I
opened the switch box and the fuse holder was broken off- must have
simply been the spring pressure of the fuse holder that just blew the
end off the plastic fuse holder. A simple replacement with a better
quality holder.

Doesnt sound like your problem, but you could have had a similar
connection going loose. At least open the box and look for obvious
mechanical failures.

ron


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________________________________________________________________________

Message: 9
Date: Mon, 05 Mar 2001 07:01:26 -0800
From: Jon Anderson <janders@...>
Subject: Re: cutting speed and feed for 3/4" dovetail cutter

marble here wrote:

>
> Sorry all yes I have milled out the pocket first and
> the steel is D2 tool steel only one part is so I
> thought I should get that done first and the cutter is
> a 3/4 "8 flute

Uhg.... D2 is not nice stuff. I had problems cutting a dovetail in 440C
with HHS cutters, I can't imagine D2 is easier. You are aware of course,
that D2 is a hardenable steel. It is totally imperative that you NEVER
allow the cutter to rub and not cut. Rubbing on hardening steels will
quickly harden a very thin layer, and start dulling the cutter. The
situation never gets better. You might consider carbide if you can stand
the expense. I'd also recommend Moly Dee for a lubricant. It's always
worked for me when I get into trouble with tough materials.

Jon


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________________________________________________________________________

Message: 10
Date: Mon, 5 Mar 2001 07:24:38 -0800
From: "Dan Mauch" <dmauch@...>
Subject: Re: RE: Dead Grizzly speed control/VFD

I have worked on several Variable speed controllers like the infamous
treadmill motors with VSC and found the parts tend to unsolder themselves.
The symptoms are just like you mentions. Works fine, works erratic, starts
next day, then nothing.
Look for a bad solder joint with power disconnected.
Dan




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Message: 11
Date: Mon, 05 Mar 2001 16:28:27 -0000
From: arcstarter@...
Subject: Re: Phase Control of SCR's; Hi Current

--- In CAD_CAM_EDM_DRO@y..., jmw@c... wrote:
> I know this is a little off-topic, but the talent level of the group
> is so tempting...
>
> Can someone steer me to a circuit for triggering SCR's at a user-
> selectable point in the AC cycle? I've seen circuit snippets in asst
> cookbooks, but not being an ee I'd like to find something a little
> more complete.

Greetings list!

This might be off-topic (I'm de-lurking to reply) but here goes
nothing...

I've done it using a zero-crossing detection scheme to reset an R-C
element. The RC voltage will start to rise once the zero crossing has
passed. If you feed this RC voltage into a comparator which is
comparing it to some other input 'contrl' voltage - you will find that
the time at which the comparator's output 'flips' will be delayed past
the zero crossing in (rough) proportion to the controlling voltage.

In this way the comparator's output can be used to trigger an SCR at a
known selectable phase.

The RC reset is as simple as full wave rectifying the incoming power,
resistor-zenering the voltage to limit it, and using it to control
some small transistor (2N2222 etc) which shorts out the cap in the
main RC timing element. If you are paranoid some opto-coupling is
never a bad idea too!

I think Motorola makes a nice opto-coupled zero crossing detector used
for firing scrs etc. In reality it is a non-zero inhibitor -
precluding the firing of the scr once the mains voltage is 1-2 volts
either side of zero...

>.The rectifiers will be working at 50v 250amps max in
a
> mig welding application; duty cyle at max output would be in the
nbhd
> of 20-30%. Ideally, I'd like to be able to chop out the middle of
the
> AC cycle rather than the initial segment--but I guess SCR's don't
> play that way. Triacs do, right, but not at 250A?

Both triacs and SCRs will stay ON until the current flowing through
the device drops below a certain threshhold value.

A triac acts as two back-to-back scrs. Generally using triacs in
inductive applications (transformer) is a bad idea since the
switch-off dv/dt tends to turn on the other scr (they share the same
silicon die) and power control is lost - followed by device failure.
:(

If you want to extract the center chunk out of the AC waveform - I'm
told that IGBT devices could do that - since they act more like a
conventional transitor - ie - can be turned off before the end of the
cycle... But I haven't tried them yet.

> The block diagrams I've seen for commercial migs using transformers
> with electronic control (instead of multiple taps) use SCR's as
> described above.

Yea I'm pretty sure most of them are operating in 'lamp-dimmer' mode.
That is - they use a trigger circuit which closely resembles that
found in a residential lamp dimmer (open loop phase control).

It is possible to use a residential lamp-dimmer as your phase
adjusting component - but the dimmer will have to in turn fire another
pair of SCRs which pass the main current. Residential dimmers can't
handle inductive loads for more than 16 mS. :)

I'm running a large pair of SCRs in 'lamp-dimmer' phase control mode -
powering a large stick welder. A foot pedal controls the phase and
thus the welding current. A large diode bridge, large filtering
inductor and a $100 TIG torch complete the job! DIY TIG on the cheap!
:)

> But wouldn't it also be possible just to use
> ordinary diodes on the secondary and control the primary side? It
> sounds easier to switch 240VAC at 40A rather than 250A.

Agreed. I found that it is easier to switch the higher voltage side
than the lower. Be sure to properly snub your devices to keep the
turn-off inductive dv/dt from destroying the switching component!

>The
> transformer doesn't mind getting an AC waveform with a bite taken
> out, does it?

Not as long as the transformer doesn't see any long term DC bias. For
long term - I'd suggest using one full period of the incoming power.
If you feed the transformer any DC - it'll saturate the core. This
will cause a large current spike into the transformer which will
likely kill your SCR etc. Ask me how I know this! :)

> One final question. MIGS generally run "constant voltage" volt-amp
> profiles, meaning that the output voltage tends to change relatively
> little even though amperage may change significantly.

Confirmed! Mig power supplys are this way. Stick and TIG are
constant current.

> So far as I
can
> tell by looking at several units, this is accomplised with a big
> honkin' iron core inductor in series with the output. The inductor
> tends to be about 2/3 the size of the power transformer with roughly
> the same number of turns as the transformer secondary. A healthy
bank
> of caps on the order of 100k uf, is also part of the equation.

You may note that within a TIG (which is more of a constant current
power suppply) you won't find the huge bank of capacitors. From my
dealings it is apparent that it is this large cap bank which
contributes to the MIG's constant voltage characteristic. The
inductor tends to smooth out the cap voltage as well as average out
the current swings within the rectifier bank (but not the welding arc)
to some extent.

>(The
> inductor air gap, if any, I don't know about.)

The inductor is certainly special as far as the fact that it carries a
large DC component w/o saturating etc. The gap is important!

> My question is this:
> Can the volt-amp curve be tuned--its slope changed--by phase
control,
> possibly active phase control during operation?

I'm not 100% sure but my Guess would be NO.

The commercial units with programmable slope etc are all high
frequency switchers - a different design than the old style
scr/transformer units.

>This would make the
> design of inductor less critical. My intuition is that there're too
> many df in the problem to conrol with single parameter (trigger
> point.) But maybe not ... I guess a scheme like this would require
> microprocessor control and amps / volts feedback. There are some
> interesting Nuts and Volts articles back in Dec / Jan about
> microcontrollers and SCRs.
>
> Thanks in advance.
>
> --Jack

-Bill
DIY EDM




________________________________________________________________________
________________________________________________________________________

Message: 12
Date: Mon, 5 Mar 2001 09:58:54 -0700
From: Tim Goldstein <timg@...>
Subject: RE: EDM? Was: Phase Control of SCR's; Hi Curren t

Bill,

I see in your tagline the DIY EDM. Can you tell us what it is all about???

Tim
[Denver, CO]

> -Bill
> DIY EDM


________________________________________________________________________
________________________________________________________________________

Message: 13
Date: Mon, 5 Mar 2001 12:51:10 -0500
From: "Carlos Guillermo" <carlos@...>
Subject: RE: Re: Phase Control of SCR's; Hi Current

Bill -

Can you tell us about the "DIY EDM"? I'm hoping to rig my CNC mill to be a
part-time EDM sinker, and I'm looking for all the info I can find.

Thanks in advance,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: arcstarter@... [mailto:arcstarter@...]
Sent: Monday, March 05, 2001 11:28 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Phase Control of SCR's; Hi Current

--- In CAD_CAM_EDM_DRO@y..., jmw@c... wrote:
> I know this is a little off-topic, but the talent level of the group
> is so tempting...
>
> Can someone steer me to a circuit for triggering SCR's at a user-
> selectable point in the AC cycle? I've seen circuit snippets in asst
> cookbooks, but not being an ee I'd like to find something a little
> more complete.

Greetings list!

This might be off-topic (I'm de-lurking to reply) but here goes
nothing...

<snipped>

-Bill
DIY EDM





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________________________________________________________________________

Message: 14
Date: Mon, 05 Mar 2001 09:56:26 -0800
From: Drew Rogge <drew@...>
Subject: Re: Quick RF-45/VFD question


Just wanted to thank everone who replyed to my questions. Current
answers seem to be that there isn't a hand brake on the spindle
of an RF-45 and spindle power switching should be done via the
VFD.

Thanks again,
Drew

--
Drew Rogge
drew@...


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________________________________________________________________________

Message: 15
Date: Mon, 05 Mar 2001 12:52:10 -0600
From: Greg Jackson <jackson@...>
Subject: Re: 4 Bar Linkages

Try my website at www.mecheng.asme.org

When I used the search system for "linkage bar" I found several program
references. The database has about 6500 unique engineering programs
listed, a few are on kinematics.

G. Jackson




At 04:48 PM 3/2/01 -0500, you wrote:
>Can someone recommend a text, website, software, or any other utilities
>for 4 bar linkages? I need a method of comming up with a 4 bar, knowing
>the motion path.
>Thanks
>
>
>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
>discussion of shop built systems, for CAD, CAM, EDM, and DRO.
>
>Addresses:




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________________________________________________________________________

Message: 16
Date: Mon, 05 Mar 2001 18:58:45 -0000
From: arcstarter@...
Subject: Re: EDM? Was: Phase Control of SCR's; Hi Curren t

--- In CAD_CAM_EDM_DRO@y..., Tim Goldstein <timg@k...> wrote:
> Bill,
>
> I see in your tagline the DIY EDM. Can you tell us what it is all
about???

Sure - Real quick - here's my poor-man's EDM experience:

Back in 1994-1995 I'd hacked together a neat 3-axis CNC Dremel tool
'mill' - made from 2x4s, cabinet drawer slides, surplus 4-phase
bipolar stepper motors, and hardware threaded rod. Used an old 8088
PC to step the three axes around. Could do three axis linear, two
axis circular interpolation. Carved out a bunch of foam positives for
lost foam metal sand castings and the like. Could also mill Balsa and
other soft woods... Software was all in C - used some tricks to get
the speed up on the circular parts. Didn't use the printer port -
instead used an i/o expander (8255?) wired into the ISA bus and mapped
at user i/o address $320 I think...

Shaft encoders attached to each threaded rod were used in conjunction
with associated hardware to display the "real" position of the
steppers, in counts. Note that this does not acocunt for backlash,
and I never completed the loop with this data. The stepper motions
were constant velocity, no acceleration profiles etc.

For EDM mode - I replaced the Dremel (which was mounted on a form of
"Quick Change" tooling (plywood w/ wingnuts). :) For an EDM
electrode I was using either thin brass rod from the hobby store, or
mechanical pencil leads (0.5 mm diam, HB). Turns out mech pencil
leads are about half/half graphite and clay - but they do conduct
reasonably well enough - and they were all I could scavenge up on my
budget. Used WD-40 and a small windshield pump motor to slosh the oil
over the part. Didn't have any filtration. It was somewhat of a fire
hazard but I never had a problem since I always kept the area being
EDM'd well submerged.

Scrounged up a 72 volt DC power supply. Ran the power through about
a 100 ohm power resistor to limit the short circuit current draw.
Next the current traveled to a bank of between (I think) 100 - 300 uF
power factor correction capacitors (low resistance, or ESR caps). The
capacitor bank was connected from the graphite to the workpiece.

In practice- the Z-axis software was modified to not step the Z axis
unless the cap voltage was over about 65 volts etc. In this way as
long as the EDM arcing action was still taking place - the feed was
stopped. Once sufficient material had been removed - feed would
resume. Feed rate was slow - I recall 3-4 steps per second max -
using probably 18 tpi rod and a (?) 200 step/rev motor... My setup
wasn't mechanically rigid - and suffered from severe problems due to
rocking etc.

I managed to EDM some holes through some pennies, sheet metal and the
like - even EDM'd a series of holes on the perimeter of a larger hole
to knockout a disk etc. Metal removal rate was SLOW - something like
5 minutes per hole in a copper penny - but copper doesn't EDM well it
turns out... Electrode wear was also an issue but since I was just
plunging a hole clean through the other side of the work it didn't
matter. The pencil leads seemed to outlast the brass wires/tubes. I
never tried anything deeper than about 1/8th inch since I knew my oil
wouldn't flush out the contaminants and I didn't want to write any
'pecking' software to allow for flushing etc.

Well that about wraps it up. My biggest problems were mechanical -
involving my sloppy XYZ rigging. I'm in the process of rebuilding
some of this using more appropriate materials - things should go
better this time. I've been really impressed at the availability of
freeware etc CNC software - there was nothing like that available 5-6
years ago.

I see this list was started in conjunction with NAMES 1999. I hope
to be able to attend this year - any other EDM'ers going to be up
there? I've heard rumors of somebody working on an actual
wire-cutting EDM - using moly wire or something. Anyone know about
this? Reminds me of the hot-wire foam cutters for model airplanes and
the like - only this time it's for metal!

My sources indicate that graphite is nearly the best general purpose
electrode for EDM. Not sure where to get the proper dimensions etc
for EDM. I might try using TIG welding electrodes - pure tungsten-
available in 0.020 diameter for about $2 per 6 inch rod...

Comments encouraged.

-Bill (Cinci, OHIO)



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________________________________________________________________________

Message: 17
Date: Mon, 5 Mar 2001 14:12:59 EST
From: ptengin@...
Subject: Re: Quick RF-45/VFD question

In a message dated 03/05/2001 8:14:22 AM Hawaiian Standard Time,
drew@... writes:


> Just wanted to thank everone who replyed to my questions. Current
> answers seem to be that there isn't a hand brake on the spindle
> of an RF-45 and spindle power switching should be done via the
> VFD.
>
> Thanks again,
> Drew
>
>

Drew,

On geared head machines like the Rf-45, usually, there is enough inertial
resistance to loosen the drawbar if the machine is set in its lowest gear. I
was hoping to fit a pneumatic power drawbar such as a Kurt or Aussie. If
this
is done, I don't think it matters which gear the head is in.....

Peter
THRD, Inc.


[Non-text portions of this message have been removed]



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Message: 18
Date: Mon, 05 Mar 2001 13:40:38 -0600
From: Jon Elson <jmelson@...>
Subject: Re: cutting speed and feed for 3/4" dovetail cutter



marble here wrote:

> Sorry all yes I have milled out the pocket first and
> the steel is D2 tool steel only one part is so I
> thought I should get that done first and the cutter is
> a 3/4 "8 flute

Oh, well the D2 is why you are having a problem. You might try increasing
the speed a little, and the feed a bit more than that, to get a good .001 -
.002"
per tooth, at least. What is the shank diameter?

You may have to get a stronger tool, either M-42 or some other Cobalt HSS,
or go all the way to carbide. Yes, I know, a carbide tool will be REALLY
expensive.

You might try to analyze the failed tool to determine why it broke. Look at
the
cutting edge under bright light, with a strong magnifier. See if the edge
is worn
or chipped. I'm guessing the cutter wore out first, then broke due to
increased
cutting forces.

Jon



________________________________________________________________________
________________________________________________________________________

Message: 19
Date: Mon, 05 Mar 2001 14:02:54 -0600
From: Jon Elson <jmelson@...>
Subject: Re: Re: Thread milling!!



Jon Anderson wrote:

> Jon,
>
> Who was your source for that cutter, and what pitch range does it have?
> The one MSC sells for a 5/8 thread is .500 in dia.
> One of the attractive things about a lathe threading bar is that inserts
> are available in a range of pitches. But it would only take 3-4 of the
> single row type to cover most threads anyway.
> For the job at hand, if it went into production as designed, I'd surely
> buy the full thread type and spin the thread in one pass. With a
> potential for hundreds of holes threaded, the time savings would cover
> buying a dedicated pitch cutter.
> If the job doesn't go through, I'll just start laying in a collection of
> the single row type.

I'll have to look up where I got the single row thread mill. I suspect MSC,
but it could be some other source. As for pitch range, I think it will take
anything on the fine-pitch end, and probably down to 20 or so on the coarse.
The only parameters of interest are the side relief (it looked pretty steep)
and
the difference between tip radius and the bottom of the 60 degree cutting
tooth. This tool STILL cuts the full thread in one pass. You just run it
at
a little slower feed, since all the cutting is being done at one point.

I cut my threads backwards (ie. from the bottom upwards to the top) so
I can climb mill the cutting action.

Jon



________________________________________________________________________
________________________________________________________________________

Message: 20
Date: Mon, 5 Mar 2001 20:38:07 -0000
From: <e.heritage@...>
Subject: Re: EDM? Was: Phase Control of SCR's; Hi Curren t

I've been looking all over for info on DIY EDM. I've only found so far two
sites about it. One is just a simple broken tap drill that has an X and Z
axis, I assume a broken tap refers to a broken threading? There was a link
for plans but I couldn't find anything following it. The other was just an
experiment someone was doing to see if it worked. It looks really
interesting but there so far seems to be a serious lack of information on
setting up an EDM with your own bed and supply. The only other stuff I've
found is EDM (Electrostatic Discharge Machining) companies who either mill
bits for you or sell you the £8K machine they build.

It appears to be so neglected by hobbyists who want to make their own
because it's quite a tricky thing to get going I've read. The second guy I
mentioned had to start it up, cut a tiny hole, stop, back it up, wash out
the dielectric, bring it back down, drill, stop, bring it back up.... etc.
I'm not sure how far you could take it as a hobbyist if you wanted to build
your own. I'm pretty sure it'd take about three minutes to solve the
problems with the dielectric from the talents I've seen on here so far. The
guy was saying he couldn't find any hollow electrode thin enough, so he
couldn't pump the fluid down it. I'd just try pumping it straight down the
sides of the electrode myself, you've seen the You Only Live Twice... I
hope. I think as well it's one to steer away from because it's pretty slow.
If you needed something to be incredibly accurate I could see the point but
then you'd also need an incredibly accurate movement and the time to do it.
Maybe someone could give us a clue as to where there is some information on
this. I'll let you know if I find anything that looks worth while. There is
a description of it on the FAQ page.

John


----- Original Message -----
From: "Tim Goldstein" <timg@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, March 05, 2001 4:58 PM
Subject: RE: [CAD_CAM_EDM_DRO] EDM? Was: Phase Control of SCR's; Hi Curren t


> Bill,
>
> I see in your tagline the DIY EDM. Can you tell us what it is all about???
>
> Tim
> [Denver, CO]
>
> > -Bill
> > DIY EDM
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
discussion of shop built systems, for CAD, CAM, EDM, and DRO.
>
> Addresses:
> Post message: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
> FAQ: http://www.ktmarketing.com/faq.html
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>



________________________________________________________________________
________________________________________________________________________

Message: 21
Date: Mon, 05 Mar 2001 10:35:29 -0800
From: dave engvall <dengvall@...>
Subject: Re: EDM? Was: Phase Control of SCR's; Hi Curren t

e.heritage@... wrote:

> It appears to be so neglected by hobbyists who want to make their own
> because it's quite a tricky thing to get going I've read. The second guy I
> mentioned had to start it up, cut a tiny hole, stop, back it up, wash out
> the dielectric, bring it back down, drill, stop, bring it back up.... etc.
> I'm not sure how far you could take it as a hobbyist if you wanted to
build
> your own. I'm pretty sure it'd take about three minutes to solve the
> problems with the dielectric from the talents I've seen on here so far.
The
> guy was saying he couldn't find any hollow electrode thin enough, so he
> couldn't pump the fluid down it. I'd just try pumping it straight down the
> sides of the electrode myself, you've seen the You Only Live Twice...

Dave....just out of lurk mode:
Unless you drill really small holes the hobby brass tubing should do the
job. According to the liturature one does well to spin
the rod AND inject dielectric thru the rod to flush. One article I read
(either "EDM today" or 'MMS" was using really high pressure
dielectric and it not only flushed but stabilized the rod in the hole for
less wander of the wall. IIRC 1000 psi was in the right
range. They also drilled deep holes very quickly; like 0.040 500 thou deep
in a few minutes.
HOH

Dave

>
>
> John
>
> ----- Original Message -----
> From: "Tim Goldstein" <timg@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Monday, March 05, 2001 4:58 PM
> Subject: RE: [CAD_CAM_EDM_DRO] EDM? Was: Phase Control of SCR's; Hi Curren
t
>
> > Bill,
> >
> > I see in your tagline the DIY EDM. Can you tell us what it is all
about???
> >
> > Tim
> > [Denver, CO]
> >
> > > -Bill
> > > DIY EDM
> >
> > Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
> discussion of shop built systems, for CAD, CAM, EDM, and DRO.
> >
> > Addresses:
> > Post message: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> > Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> > List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> > Moderator: jmelson@... timg@... [Moderator]
> > URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> > bill,
> > List Manager
> >
> > FAQ: http://www.ktmarketing.com/faq.html
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >
>
> Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
discussion of shop built systems, for CAD, CAM, EDM, and DRO.
>
> Addresses:
> Post message: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...
> Moderator: jmelson@... timg@... [Moderator]
> URL to this page: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
> bill,
> List Manager
>
> FAQ: http://www.ktmarketing.com/faq.html
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/



________________________________________________________________________
________________________________________________________________________

Message: 22
Date: Mon, 05 Mar 2001 16:46:46 -0600
From: Jon Elson <jmelson@...>
Subject: Re: EDM? Was: Phase Control of SCR's; Hi Curren t



dave engvall wrote:

> e.heritage@... wrote:
>
> > It appears to be so neglected by hobbyists who want to make their own
> > because it's quite a tricky thing to get going I've read. The second guy
I
> > mentioned had to start it up, cut a tiny hole, stop, back it up, wash
out
> > the dielectric, bring it back down, drill, stop, bring it back up....
etc.
> > I'm not sure how far you could take it as a hobbyist if you wanted to
build
> > your own. I'm pretty sure it'd take about three minutes to solve the
> > problems with the dielectric from the talents I've seen on here so far.
The
> > guy was saying he couldn't find any hollow electrode thin enough, so he
> > couldn't pump the fluid down it. I'd just try pumping it straight down
the
> > sides of the electrode myself, you've seen the You Only Live Twice...
>
> Dave....just out of lurk mode:
> Unless you drill really small holes the hobby brass tubing should do
the job. According to the liturature one does well to spin
> the rod AND inject dielectric thru the rod to flush. One article I read
(either "EDM today" or 'MMS" was using really high pressure
> dielectric and it not only flushed but stabilized the rod in the hole for
less wander of the wall. IIRC 1000 psi was in the right
> range. They also drilled deep holes very quickly; like 0.040 500 thou deep
in a few minutes.

Yes, I was the guy who "couldn't find hollow electrodes", but that was late
at night, digging
in my junk box. I needed to burn out a couple of broken taps in parts. The
hollow tubing
in the K&S displays at the local hobby shop are just right for this.

Jon



________________________________________________________________________
________________________________________________________________________

Message: 23
Date: Mon, 05 Mar 2001 23:35:07 -0000
From: tmay@...
Subject: Re: mill/drill recomendations

Actually with the optional power X-axis added to the Penn Tool
machine to make it the same as the Grizzly they are the same price
before shipping.

I bought mine from Penn Tool because I was close enough to go pick it
up and inspect it. Someone further away from a supplier might choose
differently and add weight to Grizzly's good mail order customer
service reputation. By the way the Grizzly is a G9748.
Terry

--- In CAD_CAM_EDM_DRO@y..., Jerry Kimberlin <kimberln@h...> wrote:
> tmay@u... wrote:
> >
> > Greg,
> >
> > Don't know where you are located, but on the east coast Penn Tool
in
> > Maplewood NJ is a retailer. They have a web site;
> >
> > www.penntoolco.com
> >
> > Also you might want to check Grizzly, they show a G-45 or
something
> > like that on their web catalog which looks like it is an RF-45.
>
> If the Grizzly machine is actually an RF-45, it is too expensive
> at $3000. Penn Tool is cheaper at $2195-2495 plus shipping.
>
> http://grizzly.com/fcgi-bin/lookup.fcgi/products/lookup.cfg?
q=item&kw=G9748
> http://www.penntoolco.com/catalog/products/474.cfm
>
> JerryK



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________________________________________________________________________

Message: 24
Date: Mon, 05 Mar 2001 23:48:11 -0000
From: "John Stevenson" <machines@...>
Subject: Re: cutting speed and feed for 3/4" dovetail cutter

--- In CAD_CAM_EDM_DRO@e..., Jon Elson <jmelson@a...> wrote:
>
>
> marble here wrote:
>
> > Sorry all yes I have milled out the pocket first and
> > the steel is D2 tool steel only one part is so I
> > thought I should get that done first and the cutter is
> > a 3/4 "8 flute
>
> Oh, well the D2 is why you are having a problem. You might try
increasing
> the speed a little, and the feed a bit more than that, to get a
good .001 - .002"
> per tooth, at least. What is the shank diameter?
>
> You may have to get a stronger tool, either M-42 or some other
Cobalt HSS,
> or go all the way to carbide. Yes, I know, a carbide tool will be
REALLY
> expensive.
>
Possibly not as expensive as you think.
J&L here in the UK do a small 3/4" tool with one carbide insert.
Incidently it's the triangular one that seems to be standard in face
mills. cost here is about 72 UKP so judging by your prices it should
be about that in dollars. I can look the part number up but not
certain if US numbers are the same as Uk ones. I would have thought
they would be.



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________________________________________________________________________

Message: 25
Date: Mon, 05 Mar 2001 23:58:24 -0000
From: "John Stevenson" <machines@...>
Subject: Re: Thread milling!!

I have made a tool up for thread milling either internal or external
threads. This uses one of the inserts out of a Coventry Die head.
They are very easy to pick up and one will do any thread of that
pitch.
I had some photo's as well but they must be on another hard drive. If
there is any interest I'll either look them out and post them or take
some 'staged' ones to show the setup.
The internal threads can get down to about 3/4 due to physical
constraints but the external has no limit.
You can also do tapered pipe threads by tilting the insert in the
holder.
Steadram does thread milling programs for anybody who needs one.



________________________________________________________________________
________________________________________________________________________



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/





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________________________________________________________________________

Message: 5
Date: Mon, 5 Mar 2001 19:41:11 -0800 (PST)
From: marble here <marble_h@...>
Subject: Re: Re: cutting speed and feed for 3/4" dovetail cutter

John
It is a 3/8 " shank I have cut all the pockets
to night looks like I will have get a new one I will
look at a cobalt looks like the cost of it is 52.00
cdn .I found a cheeper vender Thank you all for the
information..

John



--- John Stevenson <machines@...> wrote:
> --- In CAD_CAM_EDM_DRO@e..., Jon Elson
> <jmelson@a...> wrote:
> >
> >
> > marble here wrote:
> >
> > > Sorry all yes I have milled out the pocket
> first and
> > > the steel is D2 tool steel only one part is so I
> > > thought I should get that done first and the
> cutter is
> > > a 3/4 "8 flute
> >
> > Oh, well the D2 is why you are having a problem.
> You might try
> increasing
> > the speed a little, and the feed a bit more than
> that, to get a
> good .001 - .002"
> > per tooth, at least. What is the shank diameter?
> >
> > You may have to get a stronger tool, either M-42
> or some other
> Cobalt HSS,
> > or go all the way to carbide. Yes, I know, a
> carbide tool will be
> REALLY
> > expensive.
> >
> Possibly not as expensive as you think.
> J&L here in the UK do a small 3/4" tool with one
> carbide insert.
> Incidently it's the triangular one that seems to be
> standard in face
> mills. cost here is about 72 UKP so judging by your
> prices it should
> be about that in dollars. I can look the part number
> up but not
> certain if US numbers are the same as Uk ones. I
> would have thought
> they would be.
>
>
> Welcome to CAD_CAM_EDM_DRO@...,an
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> systems, for CAD, CAM, EDM, and DRO.
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Message: 6
Date: Mon, 5 Mar 2001 19:44:08 -0800 (PST)
From: marble here <marble_h@...>
Subject: Re: cutting speed and feed for 3/4" dovetail cutter

Jon your right it was dull and then it snaped.
thanks


--- Jon Elson <jmelson@...> wrote:
>
>
> marble here wrote:
>
> > Sorry all yes I have milled out the pocket first
> and
> > the steel is D2 tool steel only one part is so I
> > thought I should get that done first and the
> cutter is
> > a 3/4 "8 flute
>
> Oh, well the D2 is why you are having a problem.
> You might try increasing
> the speed a little, and the feed a bit more than
> that, to get a good .001 - .002"
> per tooth, at least. What is the shank diameter?
>
> You may have to get a stronger tool, either M-42 or
> some other Cobalt HSS,
> or go all the way to carbide. Yes, I know, a
> carbide tool will be REALLY
> expensive.
>
> You might try to analyze the failed tool to
> determine why it broke. Look at the
> cutting edge under bright light, with a strong
> magnifier. See if the edge is worn
> or chipped. I'm guessing the cutter wore out first,
> then broke due to increased
> cutting forces.
>
> Jon
>
>
> Welcome to CAD_CAM_EDM_DRO@...,an
> unmoderated list for the discussion of shop built
> systems, for CAD, CAM, EDM, and DRO.
>
> Addresses:
> Post message: CAD_CAM_EDM_DRO@yahoogroups.com
> Subscribe:
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>
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Message: 7
Date: Mon, 05 Mar 2001 20:14:46 -0800
From: "Henry H. Armstrong" <hharms@...>
Subject: Re: Phase Control of SCR's; Hi Current

Jack,
There are some commercial DC power supplies which use a scheme similar to
what you describe, but on the DC side of the transformer. If you truncate
the sin wave on the primary (mains) side of the transformer, you will get a
funny looking sin wave on the secondary side at a much reduced power (due to
the transformer action). Say, if you cut off the first 10% of the cycle on
the primary, you get somewhere near 40% reduction in power on the secondary.

And yes, you are right. The engineers who design the power supplies I
mention above make $100K plus per year to do so. There is a great deal of
feedback design, finessing and testing to make such designs hold up for the
long haul. I'd stick with commercial stuff -- it's cheaper in the long
run.
Henry
----- Original Message -----
From: <jmw@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, March 05, 2001 2:02 AM
Subject: [CAD_CAM_EDM_DRO] Phase Control of SCR's; Hi Current


> I know this is a little off-topic, but the talent level of the group
> is so tempting...
>
> Can someone steer me to a circuit for triggering SCR's at a user-
> selectable point in the AC cycle? I've seen circuit snippets in asst
> cookbooks, but not being an ee I'd like to find something a little
> more complete. The rectifiers will be working at 50v 250amps max in a
<<<SNIP>>>




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Message: 8
Date: Tue, 06 Mar 2001 01:30:33 -0600
From: Jon Elson <jmelson@...>
Subject: Re: Re: Thread milling!!



Jon Anderson wrote:

> Jon,
>
> Who was your source for that cutter, and what pitch range does it have?
> The one MSC sells for a 5/8 thread is .500 in dia.

It was from MSC, part # 81262164

http://www.mscdirect.com/IWCatProductPage.process?Merchant_Id=1&Section_Id=7
26&pcount=&Product_Id=351690&SearchFlag=
currently at $42.10. It will do anything over about 3/8" diameter,
and about any thread of 20 TPI or finer.

Since I haven't done any large amount of threading over 1/4", I couldn't
justify a single-pitch thread mill. At $42, this was a fairly reasonable
unit. I really haven't used it much, as a standard tap is a lot faster.
I bought it once because I didn't want to buy a special tap (something
like 3/8-28 UNS) for one project, but then a flyer came in from Grand
Tool, I think, with about 20 pages of UNS and other special taps for
bargain prices. But, sometime I will probably have a need to thread
something large with a fine thread, like camera lenses or something,
and it will come in real handy!

Jon



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