grinder help

[Gevir Knives]

i made this homemade 2x72 grinder almost 8 months ago. I'm not in any way a machinist or engineer but i did a good job with what i had and it works really goo, even if it ain't pretty.
From the start my tension wheel set up was not great and it finally gave out a few weeks ago, so i made a new and improved set up
I have no pics of the original set up but these are pics of the new set up and i'm super happy with it except one thing.....
the bolt/lever i have to adjust the tension fits snug into the holes and the threads catch, but it won't stay threaded and pops out while it's on from the tension and pull from activity and my belt goes flying off the grinder
anyone have and idea how to keep it in place, while letting it be adjustable? some sort of lock pin or something?
feel like i'm missing a easy fix.



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[Grayzer86]

Looks like the wall thickness of your tubing is too thin to get a proper bite from the threads. What i did was drill the holes slightly oversize, and weld a nut to the non wheel side, This gave me a full threaded fitting without actually having to tap anything. This is how all of the holes on my grinder are done that should be tapped. I didnt want to mess with tapping, so i just welded nuts on instead. quick and easy.

 

[Drew Riley]

If I see what I think you're trying to show, I agree with Grayzer86. Not enough thread engagement in your thin wall tube. Ideally, I believe you want AT LEAST 2 to 3 threads worth of engagement.

I would make the same suggestion as far as welding a nut into place. Now, if you don't have a welder, you might try just using a thicker walled tubing. I'd recommend at least 3/16, though 1/4 is better.

 

[Stromberg Knives]

You could use a rivnut if you don't have the means to weld. And don't forget a spring on the bolt, so it doesn't unscrew itself by vibrations.

 

[Gevir Knives]

Looks like the wall thickness of your tubing is too thin to get a proper bite from the threads. What i did was drill the holes slightly oversize, and weld a nut to the non wheel side, This gave me a full threaded fitting without actually having to tap anything. This is how all of the holes on my grinder are done that should be tapped. I didnt want to mess with tapping, so i just welded nuts on instead. quick and easy.

yea the wall thickness is preventing the bolt to bite, i figured it's why it was not catching. on the last set up i was using three nuts(one on the outside where the adjustment is made and two in the tubing) to keep it from moving because i don't have a welder or access to one but also thought that a nut welded would work but as i saaid , no welder......also thought a thicker tubing would to the trick bu i don't have any on hand
Thanks for the advice guys!And the reassurance i was at least thinking on the right path. this is the first machine i 've made it's been all trial and error.
i'm going to try currenthill's rivnut idea and if that doesn't fly i'll have to find a welder. I'd like to weld the grinder together sooner than later anyhow, bolts and brackets are keeping it sturdy for the mean time

 

[Grayzer86]

iguess if you dont have a welder you could try a big heap of JB Weld. At this stage there isnt much to lose by giving it a shot.

 

[Stacy E. Apelt - Bladesmith]

While I congratulate anyone for working with what they have, this looks like an accident waiting to happen.

The tubing is far to light gauge for a grinder.
The lawn mower wheel isn't made or balanced for these speeds and load.
The tracking problem you already know about ... A belt coming off can slice you like a loop of razor blades.
I won't even comment on the home brew drive wheel.

I would re-build it with heavy wall tube and 1/4" plate. Tap all holes and bolt solid with grade 8 bolts. Try and find a better drive and contact wheel.

 

[Gevir Knives]

While I congratulate anyone for working with what they have, this looks like an accident waiting to happen.

The tubing is far to light gauge for a grinder.
The lawn mower wheel isn't made or balanced for these speeds and load.
The tracking problem you already know about ... A belt coming off can slice you like a loop of razor blades.
I won't even comment on the home brew drive wheel.

I would re-build it with heavy wall tube and 1/4" plate. Tap all holes and bolt solid with grade 8 bolts. Try and find a better drive and contact wheel.

yes it's time to upgrade, well over time i know, but it was more of a project to see if i could make one on the cheap as the funds were low and i just started out so i wanted to make sure i was going to be into knife makeing enough to invest in a good grinder.
the tubing you're talking about is just on the trnsion system and is going to be switched out with thicker steel, which the rest of the grinder frame is made out of , it's at least 3/16 or 1/4 and strong, i've broken more than one drill bit trying to put some holes in it. i'm also going to weld it together finally to really re-enforce it
wheels will also be bought soon. had an expensive last year but now it's settling a bit so the investment can be made
it's scarier than it looks, there were a few times the belt or a wheel came off but as it's frankensteined together i paid great attention to it and accidents were avoided, but i'm getting more serious about doing this long term so i need to proper tools