Just curious on what speed grinders you guys use when sharpening lathe tools. I understand that slow speed is best. My question is - I have two bench grinders but both are 3450 rpm. I would like to set one up as a dedicated sharpener with the Wolverine jig system and would like opinions as to whether this is feasible or if I HAVE to bite the bullet and buy a slow speed grinder.

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

It is still feasible, with a friable wheel as the cutting edges will stay sharp (they slough off so new edges are constantly exposed). What tends to heat up the tool edge is contact with a fast running wheel for longer periods of time. The sharper your wheel's cutting grit edges are, the less time it's going to take to do the sharpening.

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Thanks, Tom,

I plan on using good wheels from Woodcraft (pink or white is what has been recommended). What grit would you recommend? Not trying to sound cheap but I have 2 perfectly good grinders and would like to avoid buying a third unless absolutely necessary. I plan to have the sharpening set up right next to my lathe so, hopefully my tools will never really get very dull. When actually shaping new tools, would it make a difference if I only made contact with the wheel for short periods of time??

Mike (Southgate, MI)
If I don't want to, I don't have to and nobody can make me (except my wife) cuz I'm RETIRED!!

If you want to do things in the very best way, you'll grind them and then hone them to a mirror finish. Most of the really good turners take the time to do that short of thing. I don't, but I'm not a great turner. I just grind them on a 100 grit water wheel and go to work, touching up as needed. I skip the honing and that's why my tools don't stay sharp as long.

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I did buy the slower speed grinder. Under $100 for the grinder with 2 of the white wheels. The wheels are fairly expensive if you buy them seperately for your present grinder , so the grinder itself does not add but about $60 of cost. The slower grinder also seems to vibrate less. And yeah, I already had 2 high speed grinders. One is sitting around in case I need to do some fast, rough grinding on something other than a cutting tool and the other is sitting on the bench next to the lathe tool grinding setup and has muslin wheels for honing on it. I grind, then hone on that setup. I can generally just hone 4 or 5 times before I go back to the grinding setup.


There are just so many ways to sharpen tools. You just gotta pick what is good for you and go with it. But you can burn an edge in a heartbeat with a high speed grinder and a dull grey wheel.



Edited 2 time(s). Last edit at 07/12/2006 01:28PM by Bill Moschler.

I have one of the Delta sharpening tool centers and it is a great tool to have. I can't remember the speed but I thought it was about 1700 rpms. The nice thing with this is the 1000 grit wet stone it is great for touching up the edges as well as smoothing out the tool marks after you grind the tools. I think I paid about 150.00 for the center at Farm and Fleet but it will put a good edge on anything.

Speed of the wheel in RPM is only part of the equation - need to know what diameter wheel we're talking about. An 8" wheel at 3450 'moves' at about 7230 ft per minute, while at 1725 rpm its down to 3613 fpm, but a 6" wheel at 3450 is moving at 5419 fpm... (calculator available on line at [www.abrasiveengineering.com]). I've read that to sharpen lathe tools you should have at least 4,000 fpm or else you're creating more heat than sharpening...but, I use an 8" "slow speed industrial" grinder at 1725 and get good results with the stock wheels, and would likely do much better with good wheels. I'm pretty sure Oneway recommends an 8" 3450 rpm grinder. Bottom line, I would try it out with what I have and see what you think. Throw in better wheels, balancers and good technique and you can probably get away with most grinders...

==dave==

For sure the cooler you keep the bit when sharpening the longer the edge will last and be sure to keep the bits cutting edge at center or a smidgeon below center of the material centerline when turning. If you get above center it might feel like the tool is dull (actually it will dulll the tool quickly). I use a cup wheel that is diamond impregnated for my carbide bits but it isnt really necessary for the high speed steel bits or tool steel bits. On softer materials I always relieve or clearance the bit about 7degs at a point normally starting about .015" below the cutting edge which I sharpen at 3 degs. The clearance lets the "chips" get out of the way which is more important when turning steel and Im thinking most of the turning done in rod building would be cork, wood or other soft materials. Now that I think about it are you guys talking about sharpening gouge type or hand held tools used like when turning on a wood lathe? If so then in the words of the famous Rosanna Rosanna Danna "Never Mind!"

Hi Mike,
The white friable wheels are a good choice, get a dressing stick to keep them properly shaped and clean. A leather power strop will also save you some honing time. 3450 is a bit faster than optimum for sharpening but work lightly and keep a can of water to quench the tool when it gets too hot to hold. Turning tools for the most part have a longer bevels so often the tool rest on a bench grinder is a little small. A great book is Mike Darlow's 'Fundamentals of Woodturning'- he covers the subjects of tool use and sharpening very thoroughly, plus some jigs to make it easier.

Sharpening tools is a lot like turning brittle material, like polyester resin. You need to use very little pressure or you can de-temper the tool very quickly. Put the cutting in the water often so it doesn't overheat. If you let it get too hot to touch you risk removing the temper. And I would say that 3450 rpm on either a 6" or 8" wheel is too fast, but that's only my opinion.

"If we weren't all crazy, we would go insane." Jimmy Buffet



Edited 1 time(s). Last edit at 07/13/2006 08:16AM by Gerry Rhoades.