Bench Grinder help needed

[Jamie]

I have been sharpening my tools on an old (3600 +/- rpm) bench grinder with good AO wheels and never burning a tool. A few days ago I got a slow speed (1725 rpm) grinder at Woodcraft. I mounted it up to my Wolverine, dressed the wheel and burnt my gouge on the first try. The 120 grit wheel ate into the steel like butter, I put no pressure on the tool.
It took me two hours to get the grinder and jig perfect but I'm ready to return to my old grinder and use the new one for sharpening shovels and hoes. Is there a trick to using a low speed grinder or did I just make a bad decision?

 

[Paul in OKC]

To each his own on this subjuect. I use a cheap 6" bench grinder for my tools. I use a very light touch on the side of the finer grit wheel. I know, I know. I can hear it now and have heard it before, DON'T GRIND ON THE SIDE OF THE WHEEL. Any mass removal is done on the front, then 'honed' on the side. Just my opinion.

 

[ctEaglesc]

SAme tool, same wheel, different motor at a lower speed and you burned it?
Somethng doesn't sound right.

 

[GBusardo]

Originally posted by ctEaglesc
<br />SAme tool, same wheel, different motor at a lower speed and you burned it?
Somethng doesn't sound right.

Same wheel? Not sure if I read it right.

 

[Jamie]

Same tool but not the same wheel. I went from 6" to 8" wheels and I can't remember the grits on my old wheels but should be about the same. The 160 (fine) grit wheel feels like a 30 grit wheel when I put the tool on it, could the slower speed make it feel that much rougher? It's as smooth to the touch as my old wheel but running a tool over the old one was smooooth, no bounce, no chatter, the tool almost guided itself. Maybe the new grinder has cheap wheels. Each wheel on my old grinder cost more than the grinder. Could it be the wheels?
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James A Girard
Tucson, AZ USA

 

[Russb]

I don't know the physics behind it but the 8" wheel moves more wheel surface past the tool than a 6" does. Then there is the speed difference so I don't know which on will actually be moving more wheel past the tool. Someone who knows the formula will have to figure that out. I do have a friend and club member that replaced his Woodcraft wheels with some Nortons and was very surprised and pleased with the difference. I would think with the price of the Woodcraft ginder/wheel combination the wheels can't be great, but they are not bad either.

 

[ctEaglesc]

My diamond stone only has one speed...
Mine[]

 

[vick]

You may need to face the wheel prior to dressing to make sure that it is flat. Also if you dressed it with a star style dresser I find the wheels are very aggresive as apposed to the t style diamond dressers that give you a less agressive grind. I do not know what grit your other wheel is but usually a 120 grit wheel will grind a lot hotter than a lower grit wheel. I have a strange setup on my grinder with a 120 and and 80 to see what I liked better and I pretty much only use the 80 grit wheel now. Many pro turners have stated in sharpening articles that they like even lower grit wheels than 80.

 

[godfreytoddanderson]

I just ordered the Delta low speed grinder and I worked this all out. Here is what it comes down to. The numbers below are relative to an 8", 3600 RPM grinder which seems to be the standard.

100% 8", 3600 RPM
75% 6", 3600 RPM
48% 8", 1725 RPM
36% 6", 1725 RPM

The percentages represent the linear speed on the grinding surface of the wheel. So, for example, an 8" grinder turing at 1725 RPM has a grinding surface that is moving at 48% the speed of the 8" grinder turning at 3600 RPM.

Todd

 

[woodbutcher]

I have the grinder in quedtion also. The wheels are junk. When you can afford it get some better wheels and the burning should stop.
Jim