I have the jet/wilton 3 wheel 2x42 belt grinder (w the disk on the left).  

I have a way to reduce the tension of the tension pulley to make for more slack.  I was thinking about getting a 2” wide non seivel caster and attaching in place of where the patten goes as a contact wheel so i dont have to grind against the patten and so I could do a small hollow grind.

Casters can be had pretty cheap at mcmaster and i could screw the plate mount right to the grinder guard such that it can be slid back and forth a bit, it would be much easier than trying to cobble together a bracket to mounr a wheel as I do not weld.

Anyone have any experience using casters in this application?

Thanks

It could work, but.
I'd be questioning the max speed of the caster bearings, and the ability of the bonding of the rubber tread to hold up to the rpm.
I have a home built belt grinder attachment I made for a bench grinder that I used glued up MDF for the wheels and they have been holding up fine so far.

Use bearings and a short piece of shaft material instead. Still pretty cheap and will hold up to the RPMs.

But how will o mount the shaft?

Wood arms mounted to the machine.  Drill hole size of the shaft cut one side and put a screw through it to tighten down. Use washers as a spacer to keep it off the wood.

I see what you mean, use self tapping screws to secure a wood or mild steel bridge and bring a shaft out its side.  I assume you can get shafts that are drilled and tapped so I could use a SHCS to hold the shaft.

Ill probably just buy a small contact wheel, should make the belt run smoother.

so i can put a wheel 5 7/8" diameter plate in that space where the paten goes.  But some different plates/bowls etc agains the hollow grinds of some knives I have it looks like they were made with 9-10" wheels.  So, I won't both trying to get it as big as I can to fit in there, or to deflect the current belt track; I'll just get a smaller wheel to serve as a sort of rotating patten so I can hog metal off faster w/ less heat when profiling to shape.

this grinder is 3450 rpm w/ 3 7/16" direct drive wheel = 3104 SPPM (Surface feet/minute)

Per this page:
https://www.hawkinsknifemakingsupplies.com/17.shtml
"Wheels 1/2" through 3" diameter should not be run at speeds in excess of 3000 SFPM."

So, I will need a 4 or 5" wheel just to keep the bearing speed at a reasonable level.

This page has a wheel "w/ shaft & bearing" for $100.

A 4 or 5 inch wheel wont hollow grind much. A 6 inch wheel can just barely hollow grind a 3/32" thick and 1/2" wide blade.

Also, the wheel needs durometer around 70 or so or the chatter starts fucking it up.

Here is a link. You can buy some wheels as is, or you can custom order whatever you want. They deal with knifemakers, and handle small orders, but you need $100 min.

https://www.sunray-inc.com/online-store/idler-wheels-with-bearings/

@randomcrash

are you saying it needs to be 70 or softer or 70 or firmer?

Yeah, you are right about that radius being too small for hollow grinding.  the 5" will run at 2372 RPM on my machine, the 4" at 2965 RPM.  Probably use the 6" just to keep the RPM down tho.

thanks for that suray link.   They have lots of sizes.  Will at least file that away for when I might build a 2x72 someday.

How do you like that grinder? Is it a good jump up from a 1x30?

oh fuck yes, they are not even in the ball park.

i bought that one to begin with.  it can remove metal a a pretty good pace w/ 36 grit belts of proper compound w/o too much heat.  the 42" belt is NOT  a limitation for a beginner, not at all and the 3/4 horse motor is plenty powerful.

If I was starting out i might look at a 48" Coote grinder with a slower 1 horse regular induction motor, a little bit of a DIY job but I believe there is more selection in 48" belts than 42s.

I did have one of those HF 1x30 grinders, I made it into a sharpener.  It, of course sucked, wheels out of round, always too tight for 30" belts, weak as motor that is loud and too fast.  I guess you could make like little 4" skinning knives w/ it if you were desperate but that Jet grinder is a great turn key set up for not too much money.

The disk grinder, I ended up taking it off, even cutting off the L side shaft so I could turn the unit sideways and get close to it turned either left or right for certain beveling operations so i can see the side of the blade being cut, but it was kind of handy, but mostly the belt was the main thing I did w/ it.

Durometer is from 0 to 100, where 100 is perfectly hard. Durometer can vary a lot and an error tolerance of +/- 5 is common. The harder the wheel is, the more chatter you will get. So 70 or softer.

Also, since the wheel you are talking about is an idler wheel, changing its diameter has no affect whatsoever on the belt speed.

RPM of that wheel and its bearing, is determined soley by its diameter, what with the SF/M of the belt being a constant.  The smaller wheels are spun at hifher RPMs by the belt and this have shorter bearing life.