DIY Belt Grinder Question

[Rata222]

I want to build a 2” belt grinder attachment to install on my 8” bench grinder. I am not real familiar with belt grinders and have been looking at a few builds online. I was planning on using only the drive wheel and one pulley with the tracking adjustment.

Most the belt sander builds I have seen utilize a spring tensioner – to take up the slack in the belt. Since there will not be a spring loaded idler arm, the top wheel assembly (wheel and tracking adjusters) will have to move up and down to take up slack..

My question is …… Does this assembly have to be able to move while the sander is in operation – so that the spring is continually applying pressure to the belt as it runs? Maybe for variation belt thickness at the joint or length changes with humidity or ….. can the assembly be locked in place – once it is tensioned – like on the 4x6 band saws.

On one build Ilooked at, I could not see where a spring tensioner was utilized and didn’t know if that was common practice also.

Thanks

Jim

 

[Packard V8]

Yes, No, Maybe. They're built and work both ways. Most 2" I see have a spring in compression.

jack vines

 

[mikey]

The Sears 2x42 had a belt tensioner that mated to the upper wheel and this kept the belt under tension and running true. That upper wheel was crowned so it also served as a tracking adjuster. You can see these parts here. See parts 55 & 62. If you can find the tensioner (Porter Cable and others now sell this machine and you may be able to find the part listed under those brands) and wheel then making a chassis from steel plate might be doable, Jim.

 

[francist]

Here’s what I just pulled off my bench grinder a couple months ago. I have another belt and disc combination that I prefer to use so never cottoned on to the one on the grinder.

Anyway, at the top the belt is constantly under tension by the spring. Tension is taken down using the lever to change belts. The idler drum is mounted eccentrically to the lever axle, so 1/4 rotation on the lever will swing the idler drum from about 12 o’clock to 9 o’clock . The knurled wheel at top affects the tracking with a flexure just below the lever action.





-frank

 

[Rata222]

Thanks guys for the quick responses !!! Big help.

They're built and work both ways. Most 2" I see have a spring in compression.

Good to know - I had little experience with belt grinders. Stationary would be a simpler design, but if most are built to have dynamic tension- there must be performance benefits that warrant the added cost..


Mike & Frank - Thank you for taking the time to find the links and post the pictures. They show a nice clean way of providing flex and still have a solid setups. But does that leaf spring provide lateral tension? Is there a torque spring inside the cammed shaft mechanism?
Thanks

Jim

 

[jwmelvin]

at the top the belt is constantly under tension by the spring.

The spring is internal to the cylindrical assembly where the handle protrudes? Thanks for showing this it’s a neat assembly with the eccentric and flexure.

 

[Rata222]

The spring is internal to the cylindrical assembly where the handle protrudes? Thanks for showing this it’s a neat assembly with the eccentric and flexure

Thanks jwmelvin You answered the question -right as I was editing my post for clarification on that.

 

[C-Bag]

I've used a lot of belt sanders in my career and most I didn't like the tension and tracking systems. I happend to bumble onto the combo belt/disc setup mounted to a Jet 6" bench grinder. It's sold under the name MultiTool and now are way expensive but I bought the last close out floor model. It has a very simple but cool setup for tension and tracking. The spring is inside at tube that the end wheel is mounted on. There is a little catch lever that if you bump the wheel in really hard it catches and holds the spring compressed making it super easy to change the belt. This whole tube/spring mechanism rotates by a lever on the other side mounted into the base. Rotating the end wheel is how you track the belt. It's super quick and easy. Because it's easy to pull the belt off and there is the disk sander on the hub I don't keep the belt on until I need it. To mount the belt you slip it on and reach up under the platen for the little catch lever and squeeze it up to release and pop! the belt is on and tensioned. I'm not sure any other belt grinder uses this twisting of the end wheel to track the belt but it is bombdiddly. NFI even though I sound like a salesman.

 

[francist]

Thanks jwmelvin You answered the question -right as I was editing my post for clarification on that.

Yes, jwmelvin has is correct. There will be a torsion spring inside that hub where the lever attaches. Feels pretty stout but I have not had it apart to look at it.
And yes again, the leaf spring / flexure provides positioning of the drum but still allows it to tilt for tracking. Because of the eccentric mounting of the drum there is no requirement for anything to slide vertically to maintain tension. I think that’s what makes it a pretty compact mechanism.

-frank

 

[Rata222]

C-Bag,
I had previously looked at the design of the multitool. That is a nice grinder. I saw a video on its operation and found a parts break down. I believe I have a pretty good idea on how it works. I am considering this design also.
Having gotten a better idea of operation and parts needed for a belt grinder build, my next step is to see what materials I can scrounge up - that will greatly influence my design.
For the multi-tool type tensioning I will need to find a tube that can slip fit into a larger tube - or turn one piece down . Some grinder designs will require only flat stock.
Lots of options. Thanks all for the information and adviice.
Jim