DIY, my plans how accurate do I need to be

[Hobbiest]

But it is going to have to be located so as not to disrupt the straightness in any direction. Here is another idea, just JB weld some allthread to the rail. Do them all at the same time. With 1/4" allthread, lay the rod on a table, then lay a piece of shimming stock 1/8" less than the radius of your rod. With the allthread laying on the shim stock, it will center and square the allthread on the rod. Clamp everything down to the table until it dries.

Doing this, you can then adjust the height of the rail with on nut above, and one nut below watever your frame is. With enlarged holes and washers, you can also adjust for side to side parrallel.

[maxxgraphix]

I think I have an easy solution. First let me describe the design. This is 8020 T-Slot 1515 aluminum frame. It's already straight. 2" x 2"x 3" precision drilled blocks mount the 20mm rod to the T-slot. The rods run parallel with the T-Slot. It's not moving. The only problem was the 20mm rods would flex downward. So I have used split linear bearing blocks. Now all I need is a few center supports that are adjustable. Duh, a few t-nuts and bolts will do that. I can V cut the head of the bolt if needed. I could even mount a solid rail support the entire lenght of the rod. If the support was grooved with a router bit then it would even provide stability side to side. This should work well.

[Nonoriginal]

Originally Posted by maxxgraphix Duh, a few t-nuts and bolts will do that. I can V cut the head of the bolt if needed. I could even mount a solid rail support the entire length of the rod. If the support was grooved with a router bit then it would even provide stability side to side. This should work well.

I have thought about that too, as I have SS shaft with open pillow block bearings. I don't want to be a bummer or rain on anyone, but tramming in a round piece of stock to a vee along the longitudinal axis is very, very hard. (if you want to do it with any sort of accuracy)

This is what I see as potential game killers with the bolt idea:

First, you are limited to one half revolution of travel based on the TPI of the bolt that gets vee'd. what if you need something in the middle? 1/8 turn or 1/4 turn?

The vees themselves can become the problem at any point. a small burr of .002 can translate into .002 (acceptable...close to perfection) to .250 TIR (runout), again based on how many bolts get cut, and the accuracy they are cut with.

Second, You can't just slap a craftsman level on the rails and call it good. You have to have something perfectly strait (or close to it) to tram against. Then you need run a dial indicator along the axis to dial her in. fussing with the bolts just seems like a waste of time.

you could;

Cut the head of the bolt off.

buy some durable plastic (delrin, Nylatron) that is .0005 to .010 larger than the I.D. of the bolt's O.D.(or a bit smaller to press fit) Make sure that the O.D. is smaller than the width of your gap on the open bearing.

Cut them into 1 or 2 inch increments.

take them to a machine shop and have them mill a groove onto one side using a 20mm endmill. ensuring that they are all XX.XX + or minus .002 (or whatever you are comfortable with. Should cost you around 75 for the milling based on 10 to 15. + materials.

fit to bolt and slide the rail on!

After all of that I would probably just wait to buy some supported rails on Ebay or go to a liquidator. Because over time the plactic will deform, and you will have to start again.

Hope that helps! Good Luck!

[maxxgraphix]

I see your point. So no V-Cut bolt head. I'm just looking to make this thing work for now. Later I will upgrade to better slides when a good deal comes my way. With a little center support will this machine cut to .015? That would be just fine with me! It's just for plastic sign letters!

Thanks for all your advice. I'll show some pics of it this weekend. It's building time. Whether it works or NOT.