CBN Wheel Grit for 'Flat' Woodworkers

[Hasin Haroon]

Thanks Derek, Patrick.

Being able to grind accurately all the way to the edge would save some time and wear at the waterstones, so that's a big plus for the 180 in my mind.

I read your write up on CBN wheels as my first point of research Derek, I hope you keep posting (and sharing) your articles regularly.

[Hasin Haroon]

That's very helpful John. I've tried out a 180 grit wheel on a friend's grinder, but only to touch up gouges. It did seem to cut very fast, but that was also the first CBN wheel I was exposed to. I did read Reed Grey's article but it seemed to focus more on HSS lathe tools.

[Hasin Haroon]

Thanks for the suggestion Rob, 180 does seem like the best bet. I was so glad to see LV carrying the CBN wheels. It's great to have them available locally.

Also, thanks for the kind offer, but it seems like too much trouble to put your staff through. I don't doubt I'll be pleased with whichever wheel I choose, or that LV CS will make things right if there's any issues (Also, a lot of the Edmonton staff recognize my face by now, I really need to stop frequenting so often).

[David Silverson]

Is there any chance LV will carry a 10" CBN wheel for use on the Tormek? Or, might LV carry the new diamond stone from Tormek?

[brian zawatsky]

Hi Hasin -

I would recommend the 180 grit - it's not really that much slower, and will yield a better finish for moving on to final honing.

While turners have been early adapters of CBN wheels - they have been slower to penetrate the "flat" world. Derek was kind enough to run me through his set-up when I was in Australia, and he's really worked through his workflow with CBN. Not only has he been using them for years, he's worked through various grits and styles as well.

I'd be happy to arrange a session at the Edmonton store, where you could bring in some blades or chisels, and give each wheel a try. Just mail me directly at rlee@leevalley.com to set it up. In any event - we are always happy to take back products that don't meet your expectation.

Cheers -

Rob

Now that's customer service!!

[Sean Nagle]

On the Tools for Working Wood site, Joel is offering only very coarse 60# and 80# CBN wheels. However, his wheels are crowned compared to the flat Lee Valley CBN wheels. Joel has a blog on grinding and recommends dressing a wheel with a crown. I have always dressed my wheels flat. What is the general consensus for crowned or flat wheels?

[Patrick Chase]

On the Tools for Working Wood site, Joel is offering only very coarse 60# and 80# CBN wheels. However, his wheels are crowned compared to the flat Lee Valley CBN wheels. Joel has a blog on grinding and recommends dressing a wheel with a crown. I have always dressed my wheels flat. What is the general consensus for crowned or flat wheels?

My impression of Joel's offerings is that he hasn't really thought through the differences between conventional and CBN, and so he's basically offering CBN versions of what he's always used/recommended in conventional wheels.

I've already noted why CBN favors higher grits, and there's similar logic at work with crowning. The challenge with flat wheels is that it's difficult to apply perfectly uniform pressure all the way across the face, and so one corner ends up with more pressure than the other, leading to localized heating. If you tilt the workpiece such that only the corner is cutting then the problem becomes particularly acute. Crowning avoids that by relieving the wheel edges such that only a broad (not pointy) section in the center cuts. The downside to crowning is that it can be a bit wasteful of abrasive, since the center takes most of the cutting load.

CBN wheels run cool enough that it's simply not necessary to crown the wheel IMO. Even if one corner or the other gets more pressure, it won't create enough local heating to be a problem. If you're used to working with crowned wheels you might subjectively prefer to work with a crowned CBN, but other than that I don't think it's worthwhile. If corner heating were an issue then one obvious "intermediate" solution would be a rounded-corner CBN wheel.

EDIT: I don't crown my conventional wheels either, FWIW. I grind freehand off of a tool rest, but am very careful about how I present the tool to the wheel. In particular I always hold the tool such that I see sparks all the way across during grinding, even when adjusting skew (in the latter case I might apply more pressure on one side than the other, but always with the whole wheel cutting).

[Derek Cohen]

I would just echo all you have written, Patrick. Well covered.

Regards from Auckland

Derek

[Tom M King]

If I ever set up a CBN wheel for sharpening mower blades, I'll get an 80 grit, or so. For several years, a 180 has done everything I need to do with irons, and chisels, and speed is very important to me. When going from the 180 to stones, it's just like going from one stone to the next, with no noticeable extra time required.

I'll only be going back to wet grinding, when the Tormek diamond wheels come out, because I can't dry grind in the houses I work on, even with CBN wheels. While you don't have all the mess from friable wheels, metal chips still accumulate, and some get thrown where you don't want them.

[Patrick Chase]

Thanks for the suggestion Rob, 180 does seem like the best bet. I was so glad to see LV carrying the CBN wheels. It's great to have them available locally.

On a related note, LV have also started carrying the 1 hp Rikon grinder, which is a great choice for CBN wheels IMO. It has beefy bearings and more than enough power to handle solid steel CBN wheels (though I use the lightweight Aluminum ones from WoodTurners Wonders now). One benefit they don't mention is that the flanges are made out of solid discs rather than the usual sheet-metal stampings, and provide a lot of registration to both the arbor and the wheel face. Conventional wheels run much truer on my 1 hp Rikons than on my variable-speed Delta, for example.

[Todd Stock]

I don't think it's a heat build-up issue so much as whether the tool is jigged up or ground freehand (e.g., Tormek or the Veritas blade holder/rest system vs. tool rest setting only angle). For freehand grinding on planes and chisels, it's easier for me to move the tool into the wheel at the center of a crowned wheel, and move left and right to remove material. Any minor misalignment between the plane of rotation and the centerline of the blade is corrected after the tool is in contact.

For those jigging chisel or plane blades for grinding, there's little danger of feeding the blade into the wheel off-axis, so a flat wheel face makes more sense. We grind tools infrequently, as we use a ground and honed bevel on most tools. The job usually takes a couple dips in the coolant even with an 80 grit CBN wheel, so the rationale for crowning wheels - whether SG or CBN - remains valid (at least in this shop).

We did trial crowned and flat-faced wheels...after running them side-by-side for a few months, I passed the flat-faced wheel to my repair tech, who prefers to grind her tools using a jig (a repurposed spare Tormek bar and plane blade jig).

Given the reduced numbers of cycles from wheel face to coolant trough and back with CBN, an aversion to the time spent on jigs on flat grinding jobs might merit a relook, but once the skill set is established to do the job freehand, jigging up for flatwork seems a little cumbersome.

[Alan Schwabacher]

One possible advantage of a metal wheel with bonded grit is that it is safer for grinding on the flat side. For those of you with CBN wheels, do you use the side? It seems the wide flat on some wheels might make flattening of old plane iron or chisel backs very quick -- or it could be that they could be quickly damaged. Can anyone comment on this? It could affect which CBN wheel is most desirable.

[John K Jordan]

For those of you with CBN wheels, do you use the side? It seems the wide flat on some wheels might make flattening of old plane iron or chisel backs very quick -- or it could be that they could be quickly damaged. Can anyone comment on this? It could affect which CBN wheel is most desirable.

All mine have 1" of flat down the side. I do use it, mostly when grinding special lathe tools where I take advantage of the corner between the front and the side. I have flattened the back of some chisels but only on the 1200 grit wheel on the Tormek - the others turn too fast and I'm afraid I'd mess up the chisel. I do use the sides on the bench grinder to touch up screwdrivers and such. Note that if you grind too much non-hardened steel or nonferrous metal you can load up the CBN wheel. Reed Grey once described fixing a wheel that was loaded up with mild steel by grinding a heavy HSS scraper.

Someone mentioned sharpening mower blades - seems like that might be a problem if the blades are not hardened tool steel.

JKJ

[Devon Curtis]

Is there any chance LV will carry a 10" CBN wheel for use on the Tormek? Or, might LV carry the new diamond stone from Tormek?

According to my local Lee Valley, their CBN wheels will also fit the Tormek. Haven't tried it myself, though.

[Shane MacMillan]

Picked up the new 180 CBN wheel from Lee Valley to try out following Dereks Ultimate Sharpening guide. Need to wait till may to get the Tormek parts with the May $10 discounts.

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