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At what diameter would you toss out your grinding wheels?

M

Mark Pruitt

Joined
Jul 28, 2006
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Martinsburg WV
I have an 8" Woodcraft grinder. Over the 2+ years I've used it, I've reduced the wheels to just under 7". Just wondering, at what point do you consider the wheels "used up" and replace them? 7"? 6"? The other thought that comes to mind is, I use a Wolverine system. I know they recommend an 8" grinder, so I wonder if there is a point at which my Wolverine Jig loses its effectiveness due to wheel diameter reduction.

TIA for any advice.
 
replace

it was not size that made me replace a grinding wheel,

everyonce in a while i would sharpen at the Southern Virginia Artisan Center, and Terry has all 110 wheels, not sure who made them, but the grinder is the same as mine in the studio, and i was getting a really nice edge at the Center,

anyway, i bought a 100 grit norton 32a white wheel (looks grey/blue) it does much better than the 110 white grit wheel that came with the grinder

as long as you are happy with your edge i would not replace, but every chance you get to turn somewhere else take special note of what kind of wheels they have 😀
 
Replace when the wheel gets to the point that your sharpening is getting too near the center line. If you get near the center line the tool could catch and damage the tool, blow up the wheel, or hurt you. My last one worked down to 5" but I sharpened mostly by hand. Using a jig as your wheel gets smaller the tool will be grinding closer and closer to the danger point. Use your judgement here.
 
I couldn't resist the temptation of doing a Q&D chart, and some crude arithmetic.

Most 8" grinders run at 1725rpm, for a surface speed of 575 feet per minute.

Most 6" grinders run at 3450rpm, for a surface speed of 863 fpm (~1.5x).

So, the "ideal" crossover is about (8/1.5 = ) 5.33 inches to match surface speeds, assuming the wheels are occasionally dressed.

All other things being equal (which they seldom are), Gil's and Doug's assessments are closest to the mark. Of course, the smaller wheel produces a more pronounced hollow grind, which might be more suitable for hand chisels and lawn mower blades. Except freehand twirling can overcome that. All the named grinds, Wolverines, etc., didn't fall out of the sky in their final form. Some R&D got into the act.

In a perfect world, blah, blah, blah.

Joe
 
Mark Pruitt said:
I have an 8" Woodcraft grinder. Over the 2+ years I've used it, I've reduced the wheels to just under 7". Just wondering, at what point do you consider the wheels "used up" and replace them? 7"? 6"? The other thought that comes to mind is, I use a Wolverine system. I know they recommend an 8" grinder, so I wonder if there is a point at which my Wolverine Jig loses its effectiveness due to wheel diameter reduction.

TIA for any advice.
Click to expand...

Depends on how long a bevel you're grinding. You want less curve (degrees of arc) for longer bevels. Of course, you could grind in two stages if you're really cheap. 4" for me on my 1725 6" grinder, which also has one inch wide wheels, in spite of people who say such a combination doesn't happen.
 
comment:

I use a 10" diameter wheel at work, and that one is mounted on a two piece machined steel arbor. The center hole is 6" in diameter.

Since most of us turners are only getting about 2" of usable diameter out of our wheels, I'm wondering why this isn't a standard practice for the commonly used wheels in turning......?

Seems like this would only make sense, since the more premium wheels are very expensive.....and having a large center hole would greatly cut down on their expense. It would also mean more of us would have more a variety of premium wheels in grits suitable to our particular needs.

ooc

Edit note: The two piece steel arbor I use at work, has movable weights for balancing purposes. This would also seem to be something most serious turners would have a need for....or, at least, a great desire for. I know I'd definitely love to have that balancing system on the grinder wheels I use for turning........
 
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Thanks for the replies.

This morning I fitted a bowl gouge into my vari-grind and checked the cutting edge's position relative to the grinder's axis. It appears that I can take another inch off of the wheels' diameter before approaching the danger zone John was referring to. That was the only grinding setup I checked, but it is the setup that is the most critical.

So, that's one expense that is not imminent!🙂
 
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