Re: [CAD_CAM_EDM_DRO] Re: Machining both ends (depth stop)?

Hi Ron and others:
There is another very convenient stop that is available to all, without mods
to the machine, and is usually overlooked.
Simply use the edge of the tool as a length stop.
This works well in 3 jaw chucks and is repeatable within 0.001" routinely.
On another note, it is possible to get excellent precision from a 3 jaw
chuck...even a chuck of modest quality ( and price!!!).
The two best ways in order of my preference:
1) Take the backplate off the chuck and turn the register down 0.020" or so.
Then either install 4 screws around the periphery of the chuck to use as
adjusters (just like Bison and Buck use on their Set Tru setup), or put
Belleville washers under the bolt heads and then tap the chuck body into
concentric position with a chunk of copper before you snug the bolts up
tight.
You'll find that you can get repeatability of 0.0005" TIR from part to part
so long as the parts are all roughly the same diameter and so long as you
always use the same pinion to tighten the chuck.
You can also take amazingly heavy cuts without having anything shift on
you...0.200" cuts are perfectly fine in 4140 HT!!
2) Get a chuck that allows you to use soft jaws.
Bore them to size and get the same repeatability ( so long as you remember
to use the same pinion!!!).

Way #2 is a pain in the butt, but very nice for skinny parts or parts with
weird shapes that are otherwise hard to grab.
On a Sherline or Taig, way #2 is the only way to go because there is no
separate backplate to allow radial adjustment.
Sherline sells soft jaw blanks...very worthwhile in my opinion.

Cheers

Marcus

----- Original Message -----
From: "R Rogers" <rogersmach@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, October 09, 2004 6:34 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Machining both ends (depth stop)?


>
> Sure there are lathes that use collets. Of course their spindle must
accept them. For precision and unmatched concentric repeatability, collets
are the way to go in a lathe. The next best thing is a 4-jaw chuck that is
dialed in for each individual workpiece. 3-jaw chucks are the worst. Their
mechanism in their center hole being open and centrifugal force loading
chips in the scroll they are not at all dependable for concentricity. They
are the easiest and the fastest but, least accurate.
>
> I have to be honest when I suggested a rod stop through the collet I
thought we were talking about an E5 type of collet. Which uses a hollow draw
bar. I went and looked at them and that would not work.
>
> Here is how I adddressed the issue of stops for blind hole workholding
fixtures in the past. I made a stop that swings away and bushed for
accuracy. It mounts to the table, has a pivoting arm with stop-rod that
swings over the part. Place the part in the fixture and pull it out to the
stop and secure it. Then simply swing the stop out of the way and machine
the workpiece. They also work well for long bars in a production operation
that will be profile milled on both ends. Bring the bar up to the stop,
pivot it away to allow clearance for the cutter.
>
> Ron
>
> "David A. Frantz" <wizard@...> wrote:
>
> Just wait a bit, one of the Chinese lathe builders has a lathe with such
> a spindle. I do not know of anybody importing it yet but if you cruise
> around some of the Chinese tool manufactures web sites you will find it.
>
> For a modern shop I actually think that this would be a nice lathe to
> have. I'm rather surprised it is not being imported yet. Probally
> costs to much relative to the perception of Chinese tools.
>
> Dave
>
>
> metlmunchr wrote:
>
> >Most collet chucks have a stop screw in them. Are you holding the
> >part in the spindle and holding the tool stationary? Just trying to
> >get some mental picture of what you're trying to achieve since I've
> >never seen ER collets used in the spindle of a lather as a workholding
> >collet.
> >
> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers wrote:
> >
> >
> >>If its a lathe, you set a stop inside the spindle. Long rod that
> >>
> >>
> >goes all the way through it.
> >
> >
> >>Ken Gracey wrote:
> >>
> >>Hey there,
> >>
> >>The solution must be so simple I can't see it, so I'm interested in
> >>how the group steers me on this question.
> >>
> >>I'm machining a part with two ends. Both ends need to be machined. I
> >>will hold the part in ER25 collet, machine one side and flip it
> >>around. How do I know the depth in the collet when I've flipped it
> >>around?
> >>
> >>Is there a trick or another tool to help me out? I'd like to be able
> >>to make multiple units efficiently.
> >>
> >>Thanks,
> >>
> >>Ken
> >>
> >>
> >>
> >>
> >>
> >>Addresses:
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>
>
> Addresses:
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> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
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[Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
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>
>
>
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> [Non-text portions of this message have been removed]
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>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
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> Moderator: pentam@... indigo_red@... davemucha@...
[Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>