Tell me about grinders!

J

jgourlay

Joined
Mar 13, 2007
Messages
13
All, I looked around the stickies, and didn't see much on this subject. So...talk me through the general logic of belt grinders used in knife making. For example, why the very long thin belt, as opposed to a ww'ing sander with the 6" x 48" belt? Why the multiple wheels? Where do you grind: on the wheel, on the suspended flat, both? Etc?
 
jgourlay said:
All, I looked around the stickies, and didn't see much on this subject. So...talk me through the general logic of belt grinders used in knife making. For example, why the very long thin belt, as opposed to a ww'ing sander with the 6" x 48" belt? Why the multiple wheels? Where do you grind: on the wheel, on the suspended flat, both? Etc?
Click to expand...

I would suggest you do some searching with the search function. To answer your questions briefly, the narrow belt is because when you are grinding steel, especially hardened steel, you can only reasonably work a very limited surface area at one time. Presenting 4" or 6" of a blade to the abrasive reduces the amount of pressure per unit of area, to the point where the abrasive no longer engages the surface of the steel effectively. The smaller contact area of a 2" belt is much more efficient for removing steel. The belts that are commonly availible for woodworking sanders are not usually sufficient for grinding hardened steel, the belts that are availible for the 2"x72" (or longer) grinders are availible with abrasives that are designed for this use and work much, much better than typical AO abrasives.
The length of the belt aids in keeping things cool and also, when you buy a belt, a fair portion of the cost is in the splice. The longer the belt vs. the size of the splice, the more abrasive you get for your money.
Grinding can be done on the contact wheel, on a small-diameter contact wheel attatchment, on a flat platen that backs the belt, or on a slack portion of the belt where there is nothing supporting it other than tension. The number of wheels and overall configuration of the machine is where you really need to do your research, they vary quite a bit and some configs. do certain things better than others.
 
Thanks Chris, I was going to post that link myself. Justin's remarks are correct for sure. Belt economy and availability are best for the knifemaker in the 2x72 size.
 
Holy crow guys, I had no idea. I went to the KMG site and looked at the videos. Never in a 1000 years would I dream a grinding belt could just.....dissolve steel that way. When I think of all the time over the years I've spent on various projects using files and hacksaws, well it made the hair on my arms stand up.

Then I look at the prices! Agh!
 
That's one reason why so many folks build clones. I been working on one on and off for quite some time. You can build it cheaper, but if you put a dollar amount on the time spent, his pricr usually ain't that bad.
 
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