8" slow speed grinder.

[Dave Lehnert]

I was reading how you are just as well off with a 6" high speed grinder with white wheels as a 8" slow speed grinder. Said the bigger wheels on a slow speed turn just as fast as the 6" high speed would.
Anyone have experience if this is true?
A 6" 3,400 rpm can be had cheap over a 1,700 rpm grinder.

[Dick Strauss]

Dave,
Woodcraft carries an 8" slow speed grinder that comes with 60 and 120 grit white AlOx wheels. It's on sale through the end of the month for $80. Lots of turners use these and think they are a good buy for the money.

http://www.woodcraft.com/family.aspx?familyid=4605


Good luck!

[Gene Michael]

Do the math and you will see that the wheel surface passes by whatever is being sharpened more slowly on the slow speed grinder with 8" wheels. I thought the same way as you until I did the math. Bought the slow speed grinder and it works well. It's still possible to overheat a blade, but not like on my old 6" 3450 rpm grinder.

[Bruce Wrenn]

I've used both, 6"- 3450, and 8"-1750. The main thing is to have a fresh, non glazed, friable wheel. I can show you how to burn an edge of either, as I have plenty of experience doing so. When Garret Hack taught a sharpening and plane tune up class in 2000, we used a standard 6", 3450 grinder, with the original gray wheel. Dressed the wheel, and used a light touch.

[Frank Drew]

A light touch is the key, but no matter what the speed I'd still prefer a larger wheel if I had the choice because of the arc of the hollow grind is shallower on a larger wheel.

[Dana Vogel]

Depends on what you will be grinding or what hardness of steel.
Softer steels i.e. plane blades and chisels are soft steels which temper put at <400 degrees they would require friable soft wheels with slow speed but wood turning tools are made from HSS or High Speed Steels which can withstand much higher temps and according to one of the industries leading experts on sharpening tool accessories and lathe tools OneWay Mfg. they actually recommend an 8" 3400 RPM grinder with a harder grade Blue wheel either one of theirs or Norton's blue wheel series K, I or SG. They claim a slow speed grinder does not cut HSS tools fast enough which can lead to over temping the tool. They have a video on their website which shows a demo of their setup and sharpening turning tools.

[Jim Becker]

The 8" grinder wheels leave a shallower hollow grind than a 6" unit and generally, the wheels are also wider by 1/4". I use a "high speed" 8" grinder with Norton 3X wheels (60 and 100 grit) and the OneWay balancing system and am extremely pleased with the performance. Note that I'm primarily sharpening turning tools with this setup. I use water stones for my fine flat-work blades and irons.