Belt Grinder Small Wheels

T

ThomStewart

Joined
Nov 1, 2015
Messages
31
Gents, I am in need of a small wheel set-up for my KMG grinder. I have the flat platen with a 2-inch rubber wheel on top and a big 10-inch wheel on another arm. I need the small set so i can really do my coil and handles right.

Thoughts? I'd prefer rubber coated as the results are better.
 
I keep burning out the bearings in my small wheel rollers. But I have a constant speed (fast) drive motor. If you have variable speed they last longer. So I've been using spindle type sanding drums with sandpaper tubes on my drill press or on a hand held drill. If I rough grind the choil curve on the platen edge of the belt sander, it only takes seconds to clean the grind with various grit tubes. I typically use a 1 inch diameter drum, and 100, 220 grits.
 
I have tried the same thing. Just a pain to change all of the sanding drums. I'd prefer the small wheels so i can just use my 2x72 belts.
 
ThomStewart said:
I have tried the same thing. Just a pain to change all of the sanding drums. I'd prefer the small wheels so i can just use my 2x72 belts.
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Something like this would be my choice .....if I have 2x 72 grinder
hRIzHg6.jpg
 
I have an OBM (origin/Oregon Blade Maker) small wheel set up. It works well, wasn’t too spendy... it has steel wheels though.
 
Small wheels have to be run at much lower speed. About 25% of full speed is the max if you want the bearings to last. a 1" wheel being driven by the belt on a grinder with a 1700RPM motor is running at 8000+ RPM. Those small bearings are not able to handle that speed, and will burn up quickly.
 
The small bearings used in skateboards and small wheels have a max speed of around 5000 RPM and a practical speed of around 2000 RPM.
 
The only small wheel I have is 3/4" and you can definitely use it for larger inside curves as well. An assortment on a quick change deal like the above would be nice though. Or if you have some wheels on your flat platen that you could use.
 
Stacy E. Apelt - Bladesmith said:
Small wheels have to be run at much lower speed. About 25% of full speed is the max if you want the bearings to last. a 1" wheel being driven by the belt on a grinder with a 1700RPM motor is running at 8000+ RPM. Those small bearings are not able to handle that speed, and will burn up quickly.
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I don t know from where you get that data , but Max. RPM for 6203-2RS bearing is 24,000 .... smaller faster .This is tool for engraving one friend make for me ,runs on very,very small ball bearing on over 30000 RPM
AYZD0h9.jpg

On 40 m/s belt speed , my two idler wheel run 12000 RPM without any problem , that is 6000 RPM on 20 m/s which is speed I use most time .It is almost three years how I use that grinder and bearing are good .
 
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Apples to Oranges. I was commenting on the builds using skateboard wheels. Also your high speed grinder has high speed bearings, which is not the bearings we are talking about.

Th R6 bearings in 2" wheels may be rated at 30,000 RPM, but I guarantee they won't last long on a grinder at that speed. Since they are 2.5 times smaller than a 5" drive wheel, on a grinder with a 3600 RPM motor they turn at 9000 RPM. Add to that that many are cheap Chinese bearings not really of good quality.
A .5" small wheel would turn at 36,000 RPM.

As bearings get smaller, they cannot take side load as well, either. Force that high speed dental handpiece sideways when sculpting too hard and you will roach the bearings quickly.
 
If you go on Knife dogs .com I believe Tracy, the owner sells a after market arm for a 2x72 kmg That also has a wheel to keep the belt flat as it approaches & leaves your small wheel. Chris Williams of Wilmont grinders makes one for a 2x72 machine of his I own. You have to call him to ask if it fits a kmg?
 
So, I just went and bought my set-up in pieces.

Holder is from AmeriBrade and it has a deflector wheel
Arm is aluminum from KnifeGrinderParts.com - 'KMG style' and 20" long
3/4" small contact wheel with rubber coat from BMW

Now I get to put it together.
 
The parts came in and I put my setup together, and it works like a champ. 3 different manufacturers and they all fit like a bug in a rug. I have knives I’m finishing the handles on the small wheel did the handle bottom clean up in seconds.

Next I’ll collect some different size wheels as needed.
 
A small wheel will make very lt=rge serrations. 1/8" is as large as you want.
I made a fixture from a HF powered chainsaw sharpener that worked OK,but it wasn't worth the effort.

A 1/8" chainsaw file taped to a 1/8" brass rod will cut them fast and perfectly spaced. For post HT cleanup, switch out the chainsaw file for a 1/8" ceramic rod or a 1/8" diamond file.
 
I just ordered a set of small wheels, and it looks like the seller uses inexpensive bearings. I found bearings rated at 32,000 RPM at McMaster-Carr. Not cheap, however. They have 38,000-RPM bearings, but they aren't sealed or shielded.

I figure I will usually want about 22K RPM for a 1/2" wheel, based on what I do now, and the top speed in normal use would be 28,800. At the same SFM, the RPM would drop off proportionally.

I guess the thing to do is wait for the first set of bearings to blow out, consider how long it took, and ask myself if I really want $12 bearings.
 
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