Re: [CAD_CAM_EDM_DRO] Beginners screws ( was ACME ( was Re: leadscrew,

Harvey, thank you for pointing out weak spots of the design - first thing I
do, will go to the
Metal Supermarket and try to verify accuracy of the angles. I was playing
with one
not that far ago and it appeared to be quite good- hope its consistent.
There are definitely much better designs then offered, but this one is
within my manufacturing and budget limits - even easier then sliding
bushings on 2 parallel shafts ( making
shafts truly parallel may be a challenge without milling machine with DRO).
I have some difficulties visualizing your idea of the 45 degree guides. Can
you be so kind
to draw a sketch of it - will be a great help.
Regards, Alex

----- Original Message -----
From: Harvey White <madyn@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, May 21, 2003 10:11 AM
Subject: Re: [CAD_CAM_EDM_DRO] Beginners screws ( was ACME ( was Re:
leadscrew,


> On Tue, 20 May 2003 16:45:52 -0400, you wrote:
>
> >OK,
> >just uploaded the file of DIY linear guide.
> >It is done for somebody with limited machining capabilities, but with
> >burning desire to learn CNC, like myself.
> >Alex
>
> Couple of comments, if you would.
>
> 1) that angle is not precision. None of the stuff is, unless it's
> specifically made that way. I had some 4 inch aluminum angle that was
> off a good 1/8 inch at the end of the 4 inches... So your bearings
> might not ride squarely. Square tubing might, and I do say *might*
> be more square. It's also more rigid, I suspect.
>
> 2) On the bottom (l/r) rail, the forces will twist the angle
> counterclockwise, which might be something you want to look out for.
>
> 3) The inside of an angle is not a controlled dimension (and seeing
> what I found out with the 4 inch stuff, sometimes the outside is not
> controlled either....) It is neither necessarily smooth nor even
> parallel to the side, and that's not considering the fillet at the
> angle.
>
> There's a simpler method I've seen that was used for a sliding table
> for wood saws. You do need to make an accurate 45 degree angle.
>
> You take two square tubes, put them on a 45 degree angle, and these
> become your rails. You take an aluminum angle, and mount it on the
> bottom of the table, inside the rails. On this angle, you take
> another piece of aluminum angle (or steel, if you want) and mount it
> so that the edges are 45 degrees to the vertical. The angle is
> rotated to match the sides of the rails, and there's perhaps an eighth
> of an inch gap between the angle and the rails on each side.
>
> >From those edges, you put the bearings in, so that they will ride on
> the surfaces (one top, 45 degree angle, but flat against the rail,
> ditto bottom).
>
> The adjustments might be easier to do, and it seems mechanically
> simpler.
>
> I've tried the same kind of idea on a circular rod, but the bearings
> do not ride well, too much pressure on one contact point.
>
> Harvey
>
>
>
> >
> >
> >----- Original Message -----
> >From: CL <datac@...>
> >To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> >Sent: Monday, May 19, 2003 10:47 PM
> >Subject: Re: [CAD_CAM_EDM_DRO] Beginners screws ( was ACME ( was Re:
> >leadscrew,
> >
> >
> >>
> >>
> >> alex wrote:
> >>
> >> >Thank you, Ross - I'm more or less sure now what to do.
> >> >Will place sprocket directly on the shaft of stepper, then pull
carriage
> >in
> >> >a loop by the chain.
> >> >
> >> You might want to slide that sprocket in a little further so you can at
> >> least get a smidget of support on the end of that motor shaft with an
> >> outbound bearing....
> >>
> >> It still is not enough, but that would be better than nothing.
> >> Most steppers are not made to take much of any side load on their
> >bearings.
> >>
> >> Ultimately, you need to put the sprocket between two bearings on a
shaft
> >> that is driven direct by the stepper with a Helical coupler.
> >> Or, mount the motor to a short section of square aluminum tubing with a
> >> bearing on each side. One bearing can be right on the motor shaft, the
> >> other on an extension with the Sprocket.
> >>
> >> That obviously takes more work.
> >>
> >> Then again, if motors are cheap enough, just replace the motor when it
> >> goes "south".
> >>
> >> Chris L
> >>
>
>
>
> 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
>
> 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@...,
timg@...
> Moderator: pentam@... indigo_red@... [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
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>