Tutorial (sort of) on how to modify the GIB for step pulley OP

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GIB Mods for Step Pulley Operation

I put this together for folks wanting to build the “Grinder in a Box”. I gleaned information from posts by Ed Caffrey, Jason Wilder, and other unknown authors, with a few additions of my own (mostly the crappy welding). Feel free to add, move stuff around, or virtually anything you want to do with it except comment on my crappy welding skills. The only thing I ask is that if you make it your own that you give credit to Ed and Jason.

We will assume that you have some basic mechanical and fab skills. I just built two of the GIBs because they are a bargain to say the least.

After bolting or welding the GIB main frame to the baseplate you will need to add an additional
½”x7”x8 ½” to the base. Weld it to the main base plate being mindful that when adding heat such as in welding, stuff is going to warp. Make sure it stays flat and true to the main baseplate.



For your motor mount you are going to need two 4” hinges. I got mine from TSC (Tractor Supply Co.). You will also need a piece of 3/16”x7”x8” plate for the motor mount. Bolt sizes are your choice. I mounted the motor assembly measuring 6 ½” from main frame to the hinge. In hind sight, it really needed to be a couple of more inches away from the main frame. It is a bit tight but not hard at all to change the belt speeds.
For the flange bearing mount you will need a piece of ¼”x6”x6”. Just square it and clamp it to the main frame. Make your holes via the holes that Jamie at Polar Bear Forge has jetted into the main frame. You can mark out for flange bearing at the same time or bolt it up to the main frame after drilling. I personally chose the latter method because if it can be screwed up, well…

Drill the holes, FYI, I used 3/8” bolts for the assembly.
If you go the latter route, put a couple of bolts in it and tighten them up. Put the right side (if looking from the front of the grinder) flange bearing inside the motor mounting hole, center it, mark it, and then remove the mounting plate/assembly. Make sure you drill or cut a large enough hole for the drive shaft to go through. Once you have completed all of that, mount her up again. And the right side should look similar to this.


DSC_0005-2.jpg
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and the left side





In the photo you will also notice that my work table arm locking bolt is on the right side of the grinder. Putting them both on the same side (such as on the left side) is an experiment in aggravation. You will also see that I welded a nut onto it rather than tap it out. I broke the tap and went this route and it works fine. I used 5/16” bolts for the locks rather than ¼”.

Ed Caffrey suggested tossing the idea of a tension spring and using a compression spring, and I could not agree with him more. Compression is the way to go. Ed also suggested drilling a new hole for the tension/tracking arm and I encourage it as well. You will need a bit more arm and it helps with tracking.



Compression Spring assembly: Lowes sells a set of porch swing springs that are “ginormous” but work perfectly. Best I can recall they were around 10 bucks for a pair. Cut and remove the metal rods from the middle of the spring and you are set to go. Weld a1 ½” piece of 2” OD square tubing to the GIB in a position that is just to the rear of your idler/tracking adjustment. Check it to make sure it is not too close to the idler/tracking assembly. This serves as a cup for the spring and you really do not need a guide for the top of the spring.




You will also notice that the idler mounting bracket is slotted in the front. Someone else did this and I thought it was a good idea so I added it to the grinders. Also, your idler/tracking screw should be 5/16”. ¼” is too small for rough use.

Platen mount: 2 pieces of ¼”x 2 ¼” x 2 ¼” angle iron cut in a 1 1/4” width works well for this. The holes that mount to the platen frame should be 5/16” and the platen mounting bolts can be ¼”. Slot the angle iron for the platen bolts and slot the platen frame. These are handy for making minute adjustments.




Idler/tensioning arm: because you have added a beast of a spring you will have to have a way to pull down on the idler/tensioning arm. I drilled out the handle hole in the arm to ½”. Take a ½” x 3 ½” bolt and grind the head of it down until it slips into a piece of 5/8” ID x 10” pipe. Weld it up and then heat and bend a 90 into it.





These instructions coupled with what is already out there on the web should get you up and running. The GIB was designed for a direct motor mount so any mods to it are going to be a bit of a challenge. They are not difficult, just take your time. Regards, Curtis K.
 
One thing I always wonder about these is why does everyone use ordinary bolts instead of shoulder bolts to run the bearings on? It seems universal and strange to me at least when I see it from machine builders. Is it just that normal bolts are good enough and you don't need the precision of shoulder bolts?
 
One thing I always wonder about these is why does everyone use ordinary bolts instead of shoulder bolts to run the bearings on? It seems universal and strange to me at least when I see it from machine builders. Is it just that normal bolts are good enough and you don't need the precision of shoulder bolts?

Because it would require custom made shoulder bolts and that is very expensive. In the bolt making world, shoulders are usually two-thirds the length plus 1/4". There may be tens of thousands of bolt options out there but if you consider how many applications there are, that's not much.

Bob
 
Because it would require custom made shoulder bolts and that is very expensive. In the bolt making world, shoulders are usually two-thirds the length plus 1/4". There may be tens of thousands of bolt options out there but if you consider how many applications there are, that's not much.

Bob

I order shoulder bolts of varying length regularly from McMaster car. You might need to round out to the nearest 1/4" but I figured 2 1/2" would likely work nicely and they are less than $3 in Mcmaster- Carr. Item number 90298A722. For a GIB you might need to use a Helicoil as the holes are to large to tap for a 3/8"-16.

http://www.mcmaster.com/#91259a722/=r15zie

Nothing custom needed. And if you designed your wheels for it you could just use a 2" one with a washer on each side. Just you would have one of the bearing recessed slighting and the other flush with the surface.

It would be a slight increase in price over basic bolts sure, but not anything custom and expensive, just higher precision.
 
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The nice thing about the GIB is that each can build to suit their needs. My GIB build is here. I considered mounting with shoulder bolts as you linked to but there were a couple issues I didn't like. First was the ability to adjust preload on the bearings. Those shoulder bolts only have full strength when torqued down tight. If they are not fully seated at the shoulder, they can bend or shear at the thread/shoulder fillet. The other issue for me was that I used aluminum tool arms. I would have had to put inserts into the arms to get the strength needed to resist thread tearout. I also considered using shoulder bolts mounted the same way I did my flat head cap screws but, they were not available in an appropriate length. I certainly would not say that shoulder bolts couldn't work but, I don't think they are the best solution. They would give the cleanest finished appearance however, once I started grinding I cared far more about how my grinder performed than how it looked.

Bob
 
My concern is that bearings are ment to ride on a shaft of fairly specific size. The fine adjustments would be done with spacers. That is why I cited a 2.5" bolt for a 2" roller. When I tried to use normal bolts for some actuations at work I was not pleased with their consistency and straightness.
 
Also for steel to aluminum helicoils can give you higher strength as they ballance the uneven elasticity of the materials better.

Of course a precision rod with a set screw and a couple of collars would work for mounting wheels to tool arms. I was thinking more about tracking wheels and platens.
 
Nothing custom needed. And if you designed your wheels for it you could just use a 2" one with a washer on each side. Just you would have one of the bearing recessed slighting and the other flush with the surface.

It would be a slight increase in price over basic bolts sure, but not anything custom and expensive, just higher precision.

If the threads on not tapped perfectly perpendicular to the plate it cause big problem.

A bolt all the way through is precise enough when mounting the wheels.
 
Your build looks good. I am going to upgrade mine soon to the tension method similar to yours thought I plan to use the gas compression spring.
 
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