Dry grinder - silicon carbide or aluminum oxide wheel?

[tdacon]

I'm in the final stages of setting up my new BGM-100 on a Delta 6" variable-speed dry grinder (pictures to come when it's finished). The grinder's currently set up with the pair of white aluminum oxide wheels it came with. What's the consensus here at Tormek and among the BGM-100 users - stay with these wheels, or mount silicon carbide wheels? I'm a little concerned about excessively fast wear on the wheels when a turning tool needs considerable reshaping, as these will, but I'm also concerned about overheating the tools. The tools that came with this venerable old "starter" Craftsman lathe I just added to the shop are in pretty bad shape, which is the reason I got the BGM-100 in the first place.

Thanks,
Tom

[Herman Trivilino]

From what I've read, the white aluminum oxide wheels are superior in that they don't generate as much heat.  I recall seeing posts from people who report liking them.  They are more expensive, though.

[Rob]

I've got a 40 grit white wheel on mine and it works ok. It does heat up though to be honest. I just can't see any way round that with dry grinders, at least not if you want to go fast

I've been experimenting with belt sanders for the fast removal stage just recently and I'm getting really good results. I have a bit of a pet hate when shaping difficult tools like large skews etc. thus far I've found using sanding belts to give a combination of best speed of steel removal with least heat build up. I use 60 grit ceramic belts for HSS turning tools

[Herman Trivilino]

Rob, I see a MultiTool in your future.

[Jambe]

Rob, I see a MultiTool in your future.

I could comment on the MultiTool but I understand that discussion of other tools is not allowed on this Tormek forum.

[Ken S]

Tom,

Welcome to the forum.  You didn't happen to mention if the turning tools with your venerable Craftsman lathe are of the same vintage.  I inherited my grandfather's 1930s vintage Sears lathe and turning tools. The tools are carbon steel. If I needed to reshape any of them I would do so with the slower but cooler Tormek. 

Of course, modern high speed steel and powder tools are much more forgiving with overheating.

Like Rob, I use a forty grit wheel on one side of my forty year old (and still going strong) Craftsman sex inch dry grinder.  I use a Norton 3X wheel.  It cuts quickly and leaves a surprisingly smooth edge.  The other wheel is a  Norton friable 80grit "white wheel".  I have not used it since getting a Tormek, although I was pleased with it up to then.

With either grinder it is important to keep the wheels dressed regularly.  Do a google on "Moskowitz grinding" for an excellent online article about dry grinding.

Keep posting.

Ken

[Rob]

Rob, I see a MultiTool in your future.

In fact Herman I have already invested in a Linisher style sharpening tool which given its competitive nature I won't mention here.  I don't find dry grinders are that great at removing a lot of steel, cool enough.  Whereas a belt system is extremely fast, very controllable and nothing like as "hot" so it wins hands down for me.  I use it for HSS turning tools when I want to experiment with different grinds and need to remove a lot of metal.  I also use it for skews and parting tools.  Skews are also a major pain on the Tormek.

I think I might even get shot of my dry grinder.  The only thing I use it for now is round nose scrapers and that's because the Torlok is permanently setup on the BGM-100 with that angle set so its very easy to just keep it locked on that setting.

[tdacon]

I'll answer my own question from the original post, now that I have some experience with the grinder jig. It turns out that a Norton 46-grit aluminum oxide wheel is working just fine for me for woodturning tool shaping. On my setup (see my post 6/16 for pictures), it's easy to switch from one side of the grinder to the other without losing adjustment, so when I'm done shaping I switch to the Norton 80-grit wheel on the other side to smooth the big scratches out a bit before I take it over to the Tormek wet grinder to finish things up and do the honing.

Tom

[tdacon]

To Ken S: yes, the tools that came with the lathe are all carbon steel. I've only sharpened a couple of them so far with the dry grinder and they did just fine if I took my time with them. I turned the grinder down to its lowest speed and watched the temp carefully, with my thumb on the metal an inch or two behind the bevel. When things started getting warm on my thumb I just lifted the bevel off the wheel and let the wind generated by the spinning wheel cool things down. I'd read somewhere that it's a bad idea to dunk the tool in water, because it can crystallize the metal.

A month or so ago I took a weekend turning class from a delightful lady by the name of Bonnie Klein. I showed her what I had and she identified them as carbon steel, and explained to me why I really needed to invest in some HSS tools instead of using these old citizens.

Tom
 

[Rob]

That's a lovely tale Tom but I agree with her....HSS is the way forward for turning.  You want that edge holding as long as you can while you're "in the zone" with the work.  Once you get addicted to turning (which won't be long) you'll find sharpening becomes an interruption that you want to minimise as the call of the lathe is going on in the background :-)

[boehme]

I'll answer my own question from the original post, now that I have some experience with the grinder jig. It turns out that a Norton 46-grit aluminum oxide wheel is working just fine for me for woodturning tool shaping. On my setup (see my post 6/16 for pictures), it's easy to switch from one side of the grinder to the other without losing adjustment, so when I'm done shaping I switch to the Norton 80-grit wheel on the other side to smooth the big scratches out a bit before I take it over to the Tormek wet grinder to finish things up and do the honing.

Tom

Tom, I am glad that you have everything well in hand.  I attended a Bonnie Klein demo many years ago and she is a wonderful person and an outstanding turner and teacher.  While the white wheels do shed a lot of grit, they work far better than the gray wheels and generate far less heat although tool steel can still be burned by the white wheels.  While burning isn't an issue with the Tormek, edge retention is still very poor compared to HSS.  However, don't toss them out because when you need a very sharp edge that doesn't need to last long, they are just the right tool for a very keen edge.

[Rob]

something else about the older carbon tool steel turning tools is that because they're soft it can give the occasional advantage.  For example, just recently I needed an edge tool for a miniature hat so I ground a side bevel on an old carbon steel square end scraper with no jig directly on the white wheel.  It went really quickly and the edge was fabulously sharp.  I didn't mind ruining the scraper as I'll keep it for those particular jobs.

So the point is a collection of carbon steel tools are useful for customising quickly for a tricky one off situation.  They're inexpensive to acquire 2nd hand from flea markets etc and can come in really handy.

[tdacon]

This sounds like good advice. Just as a learning exercise for sharpening I shaped and sharpened the whole set of original carbon steel tools. Two of them were scrapers, and I've actually been using them experimentally (the new HSS tools I've bought so far are all better suited to spindle-turning). I think I'll keep them around just to do what you guys suggest - quickly reshape them for special purposes.

This old '70's-era Craftsman lathe of mine will be a decent spindle-turner, now that I've restored it, but as I was warned it's not rigid enough to be a good bowl-turner. Nevertheless I can get some end-grain and faceplate experience with it, on small stuff.

[Ken S]

Tom,

I just discovered this you tube which should be useful for you.  The presenter, Doug Thompson, is an Ohio based turning tool maker.  (His tools are first-rate.)  Although he does not demonstrate with a BGM-100 and Tormek jigs, the material covered would work just as well with the Tormek gear.  His talk is primarily about sharpening turning tools.  He discusses not only wheel choice, but how to prepare them.  The you tube is an hour long, but well worth your time.

Ken

http://www.youtube.com/watch?v=ZOc6giDP39A