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lsfoils
07-19-2003, 06:21 PM
How about a vote on which will be better and why? I feel the slide with the horizontal screws will deform sooner than the one with the vertical ones. The vertical ones will take longer to make. I am planing on using one of these on cold rolled mild steel with an aluminum support.
Insight, suggestions or laughter will be appreciated.

HuFlungDung
07-19-2003, 06:59 PM
Hi Isfoils,

I think you might experience an unfavourable stacking of tolerances in either design. If the mounts pull the bearing out of line with the shaft, you will get binding (against its opposing mate). So, you need super accurate machining to ensure that the bearing bore axis is parallel to the sides of your block mounting surfaces.

Now, since you need to bore this block anyways in a lathe, you can easily face the one end perfectly square at that time. This should be the mounting face. So thread your mounting screw into the face parallel with the bore.

This way you have created two perfectly square features in one operation. You still have the problem of finding squared up mounting surfaces on your machine, but you'd have that problem anyways.

lsfoils
07-19-2003, 07:47 PM
My intended approach was to bore these mounted to an angle plate on a mill... screw the mounting surface (the top of the blocks in the rendering) to the plate and swing a boring head. I was hoping to bore one axis at a time. Press the bronze bushing into them and slot the bottoms of the blocks in a vise. This, after securing the bushings with either of the wear take-ups schemes.

lsfoils
07-19-2003, 07:49 PM
Oh, a sacrificial shaft in the bushing (before milling the slot) to boot...

HuFlungDung
07-20-2003, 12:00 AM
Yes there would be no harm doing it that way. Maybe even finish the holes and leave a little bit to face off the mounting surfaces while you have them both mounted on a sacrificial shaft. You could dial in the opposite ends of your shaft to make sure it is parallel to the table before the final facing cut. That should make a real nice matched set.

balsaman
07-20-2003, 12:30 AM
I like example a. Why? It's easier to make and that's important on a prototype, since your not sure if it will even work at all. If you find it works great, your next set can be an improvement one way or another based on what you have learned from the first.

Eric

tahlinc
07-20-2003, 06:09 AM
You might consider TG&P instead of cold rolled for your rails. Its cheap and will hold up better.
Jim:)

lsfoils
07-20-2003, 03:37 PM
tahlinc,
Found a source for that item on the web. Awaiting a quote. Is this stuff much more expensive than cold rolled? I am not too concerned about durability as I plan on making a more permanent machine using THKs eventually. I am concerned about precision and figured some deviation into the design. Looks like interesting stuff if it doesn't add to the cost too much.
Thank you for your input and all who have answered this post.