Still another CBN question

[wagon willie]

I have been making small, medium and big ugly tools, mostly scrapers, but also other shapes like a fluteless gouge. I love that they stay sharp for a long time right off of my aluminum oxide wheels, but not quite as sharp as my HSS tools, which lose their burr or edge fairly quickly. It's a good trade off in my book, and when I need a really sharp tool for finish cuts then my Tormek gets gouges and other tools very sharp after they have been shaped elsewhere.

OK, so I talked to Ken at Woodturner's Wonders and have read what Reed Gray has to say on his site and watched his videos, but I still don't know if I can sharpen my "hybrid" Uglies on CBN wheels without loading the wheels. Ken was ambivalent, but he has not tried the Big Ugly that he got from Reed as yet. Reed and Ken both say to not use the CBN wheels with softer steels, like the cold rolled steel that I silver solder my Tantung bits to. Reed suggests that the CBN wheels can be cleaned up after "abusing" them with soft steel by grinding hard steels like V10 or other CPM steels. Since I'm grinding really hard Tantung and pretty soft cold rolled steel at the same time will I be OK, or will I just load up the wheels quickly? If they do load up is cleaning them constantly too time consuming as opposed to using something like Norton's SG wheels instead? I'm considering getting the 80/180 combo pack that Ken offers. Reed, you're probably the most knowledgeable about both CBN and Big Uglies, so I'm hoping you'll weigh in here. I'd love to get other comments from anybody else too!

Also, on a vaguely related note, has anyone tried to burnish Tantung with a carbide burnisher? Results?

Thanks! I'm new to woodturning and I'm trying to get up to speed by watching videos and reading stuff on the 'Net. One lesson so far.....

[Bob Bouis]

Is there anyone who's actually, personally irreparably clogged a CBN wheel by grinding regular steel with it? I'm not saying the common wisdom is wrong, I'm just curious.

[Reed Gray]

I was off camping for the weekend.... Two questions here, so first, the Big Ugly on CBN wheels, yes, I sharpen mine on them, but.... I grind off most of the softer steel under the tantung first. I will have a clip up about this shortly. So, softer steel can build up and clog a CBN wheel. The standard way for cleaning them up is to take a heavy scraper to the wheel and sharpen it as normal. I have loaded up my wheels a bit just to see what happens. You can see, feel, and hear it when it does. The feel and hear is a ticking because it tends to build up in spots rather than one solid streak all the way around the wheel. My guess it that the M2 or V10 or other harder metals will cut through the softer stuff that is built up, and take the surface back to the clean CBN. When sharpening the Big Ugly on the CBN wheels, the tantung is very hard, and I figure it cuts the softer cold rolled that it is soldered to, so maybe (no proof, just 'educated' guess) is that the tantung removes most of the soft steel as you cut. So, I don't want to take any chances of ruining my wheels, which is why I grind off/relieve the heal of the tool, like I do my gouges. Tantung is 1/8 inch thick, cold rolled is about 5/16, so I grind off the cold rolled almost all the way up to the tantung on a standard grinder or my 36 grit belt. When the bevel gets to 1/8 inch long or so, then I take it back to the belt or grinder to remove more. Thus far, no build up problems.

There is also one other thing I do to prevent build up, and that is to apply fairly regularly, Trend Lapping fluid. There was a long thread about this not long ago. I have been amazed at how it cleans up the wheels. When I do get some build up/clogging on my wheels, when using just a scraper to remove the build up, it takes a sharpening or three to get the wheel clean. When I use the Trend, it seems to do it in one sharpening. I like to keep a little of the Trend on the wheel at all times. I need to perfect the application process, and may need to use a brush like Cindy Drozda did in a video when she was using the Green River (house brand for Woodcraft) diamond wheel which was 3/16 inch of matrix bonded to an aluminum hub. Cindy has taken that video down now.

I have heard of one CBN wheel being worn out, but couldn't get the specifics of what kind of wheel it was and how it was used. Impression was that it may not have been one of the electroplated types, and it was 'abused' rather than 'used properly.

robo hippy

[wagon willie]

Thanks Reed! I agree that relieving the heel is a good idea regardless of the abrasive used. I'm also finding that my 6X48 belt sander is a great way to shape and sharpen scrapers including the the Uglies. It's cheap to buy belts, relatively anyway, and pretty quick to change from shaping to sharpening with a finer grit.

Have you tried the carbide burnisher on the tantung?

[Reed Gray]

I have burnished burrs on the tantung with both a triangle standard type burnisher and a carbide tipped burnisher. It seems that no matter how I raise a burr, I get the same burr, from 80 grit wheel to 1000 grit wheel, to burnisher. No idea why.

I guess I should add to the above and the use of Trend lapping fluid, this is still experimental. I don't know if it will remove all metal build up/clogging, and don't suggest that you try to sharpen soft steels on your wheels. There is still a chance that you could damage your wheels, but thus far, it doesn't look like it will.

robo hippy

[John K Jordan]

...I guess I should add to the above and the use of Trend lapping fluid, this is still experimental....

A smart CBN vendor might do well to send you a used wheel or two for you to abuse and test with mild steel. A wide, flat faced one might have room for a couple of bands for comparison tests. If you can show that you can't damage a wheel it could be a selling point.

JKJ

[Reed Gray]

I am pondering that one John, might need to get Trend in line with this one...

robo hippy