Belt grinder build question-steel tube wall thickness

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Randydb

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Sep 27, 2014
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Hi,
I'm just setting up to build a grinder like this....http://dcknives.blogspot.ca/p/2-x-72-belt-grinder.html . I'm visiting my bro in law who has the tools knowledge and time to do some welding with a newb like me so it is just a matter of getting the steel tubing and doing a bit of work.

This one is built with 2x2" 3/16" walled steel tubing. Is there a reason it needs to be that thick? Can I build with 1/8" walled steel instead? He has some 1/8 " walled steel tube around so I would prefer not to have to buy more steel if I don't have to.

Problem I think I can see is that the 1.5x1.5" tubing won't be as tight a fit. Right? Is it a strength thing too? Stability? Vibration? Or is 1/8 fine too?

Thanks for the info in advance.
Randy
 
I guess one more question. Any advantage of using aluminum instead? My bro in law is an aviation mechanic.
 
Hello Randydb. I have a Canadian Bee grinder and a clown I've built. Very different from what you want to make. I'm saying go with the 3/16" for the very reasons you have said. These Bees have run for 40years plus without any unusual problems. I have VSD direct drive on both. The 1HP. motors are okay for the folders I make but I definitety would want more for making straight knives. I hope the build goes good for you.
Frank
 
In my experience with machine tools, make it as heavy as you can tolerate working with.
 
Randydb said:
Have you started your build yet? Are you doing the same build with the tension pillar? How much play do you have in the pillar?

Thanks
Randy
Click to expand...

Mine is a slightly different design, and my tenioner is different. Here is my WIP.

I'm using 2" x 2" x 1/4" large tubes and 1 1/2" x 1 1/2" x 1/4" smaller tubes. You'll need to take a file and file down the seam weld on the inside of the larger tubes and it's a great fit. It's not hard, just do it before any welding a test. took me maybe 5 mins with a crappy 3/8" round rasp. I also took a 4 1/2" grinder and laid it completely flat and grinded the outside four sides of the smaller tube till all the mill scale was off the high spots (image below is dramatized of what the tubes actually come like. They aren't completely flat. I just knocked the high parts down some so it was a little looser for after paint. I have virtually no play and my parts slide in and out with ease.

One more thing to note when you weld the main body parts together, make sure the seam weld is on the opposite side you want the belt that way when you tighten the tooling arms in place it tightens against the flat side and not the seam weld.



 
Ha! I've been following your post about your build. I just didn't look at the name and recognized it.

One of the problems with the builds with the tracking pillar style using 3/16 walled tubing is that there is some play in the fit of the 1.5" inside the 2". The guys seem to remedy that with plastic shims from milk jugs. Using thicker 1/4 walled tubing like you are doing might fix that problem too.

Thanks for the extra info about the fit. I understood about filing the weld seam down but I could see myself trying to slide it in afterwards and going, "$%^* this doesn't fit!" and taking a while to stumble across the idea of grinding a bit to knock down the high points.
Randy
 
Randydb said:
Ha! I've been following your post about your build. I just didn't look at the name and recognized it.

One of the problems with the builds with the tracking pillar style using 3/16 walled tubing is that there is some play in the fit of the 1.5" inside the 2". The guys seem to remedy that with plastic shims from milk jugs. Using thicker 1/4 walled tubing like you are doing might fix that problem too.

Thanks for the extra info about the fit. I understood about filing the weld seam down but I could see myself trying to slide it in afterwards and going, "$%^* this doesn't fit!" and taking a while to stumble across the idea of grinding a bit to knock down the high points.
Randy
Click to expand...

I'll take a short video this evening when I get home and show you how mine fits.
 
I was over at princess auto checking out the fit of 3/16" walled hollow steel. There is a fair bit of play...about 1/8". Enough that I could fit the 1.5" tube inside the 2" tube without filing down the seam weld.

I think I will track down some 1/4" walled tubing and use it. Then I don't have to fiddle around trying to tighten the fit. Just a bit extra grinding/filing needed but I will get a good fit.
 
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