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

----- Original Message -----
From: Harvey White <madyn@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, May 21, 2003 1:48 PM
Subject: Re: [CAD_CAM_EDM_DRO] Beginners screws ( was ACME ( was Re:
leadscrew,


> On Wed, 21 May 2003 09:37:03 -0400, you wrote:
>
> >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.
>
> Metal supermarket was where I got the 4 inch angle that wasn't
> right....
>
>
>
> >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).
>
> Actually, it isn't.
>
> Here's what you can do.
>
> consider the design as a shallow U. The rails are mounted on the top
> pieces to complete a square.
>
> take the two sides, bolt them together. Finish them as well as you
> can, taking care to make the sides as parallel on the top and bottom
> as possible, or at least, the bottom, assuming that's the reference
> edge.
>
> Space and drill the holes for the bars. Since both pieces are exactly
> the same size, and bolted together, the holes will be pretty much dead
> on.
>
> To make the rails parallel, just make the end pieces parallel. Use a
> cheat stick to get them the same distance apart, and align to an edge
> you know is straight.
>
> That ought to get it close.
>
>
>
>
> I'll try ascii art...
>
> _______________________________________________________
> --------------------------------------------------------------------------
------------------
> (c) | |________|
> / \ \ / | |
> / \ \ / | | (a)
> / \ \ O / | |
> / \ / | |
> (b) \ / / \ | |
> \ / O \ | |
> \ / / \ | |
> \/ \ | |
>
>
>
> The top plate is the nice horizontal line. (a) is an angle bracket
> mounted on that, giving you a vertical line. The triangular line next
> to it is a piece of 45 degree angle. (b) is the square tubing, set on
> edge. All of it's angle are 45 degrees to the vertical. Notice that
> if you butt the tubing against the angle bracket, the sides will
> continue, they are parallel to each other.
>
> On the face of the angle bracket attached to (a), the shaft of a
> bearing is indicated by the "O". Mounted on that shaft is a bearing
> assembly that runs like a wheel. that's the three \\\ lines. Those
> bearings will ride square on the square tubing's walls.
>
> This gives you the minimum number of bearings to resist up, down, and
> (for this one) leftwards forces.. RIghtwards forces are handled by
> the mirror image of this assembly on the other side of the table.
>
> 8 bearings ought to do it.
>
>
>
>
>
> >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
>
> Hope that this helps a bit.
>
> Harvey
>
> >
> >----- 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/
> >>
> >>
> >
> >
> >
> >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/
> >
>
>
>
> 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/
>
>