Final report, CBN grinding wheels

[Ken S]

 I want to conclude my CBN tests with the Tormek. The purpose of these tests was to determine if using CBN grinding wheels on the Tormek, wet and/or dry, was possible and practical.

In a nutshell, I was pleased with the results. I found the CBN wheels useful adjunct units for the Tormek for specific operations. CBN made reshaping turning tools pleasant instead of a dreaded chore. I was unable to obtain sample planer blades, however, I am convinced that CBN would make sharpening planer blades much more efficient. CBN does not glaze with tool steel. The wheels do not need to be dressed or trued.

During my standard five minute test grinding a metal lathe tool bit mounted in the square edge jig, I found the CBN wheels cut as well at the end of the test as in the beginning. This was a marked improvement over the standard wheels, especially the SB blackstone.

I would consider a CBN wheel essential for anyone sharpening planer blades. I would consider them highly desirable for turners, especially those who do a lot of reshaping.

The 180 grit CBN wheel did an adequate job with initial sharpening of wood chisels, however, I prefer the standard Tormek SG wheel. It is designed for high carbon steel. I like the feel of the grinding with the SG. The SG. Like the SB, can be graded to be coarse or fine. The CBN wheels are single grit. I did notice a sharpness difference in the 80 grit wheel depending on whether it was used grinding into or away from the tool. Into the tool, the BESS reading was 495. Grinding away produced a BESS reading of 400, just about the same as the 180 grit made grinding into the tool. Lower BESS readings mean sharper edges. The "gold standard" reading with BESS, 50, is typical for a new double edge razor blade. Grinding away took considerably longer. I would  use CBN wheels grinding into the wheel for heavy grinding.

Although the CBN wheels cannot be graded like the Tormek wheels, going directly from the wheel to the leather honing wheel produced a BESS reading of 130, surprisingly respectable, not quite a match for the 100 obtained with the SG, but close.

The CBN wheels ran surprisingly cool with the Tormek. Even with dry grinding to reshape a turning gouge, the tool was warm, but not hot. I would not consider wet grinding necessary to control heat. Sparks did not appear to be a problem.

The grinding dust from CBN wheels is only tool steel. There is no abrasive grinding dust from the wheel. When used wet, it is entirely contained, as it is with any Tormek wheel. When used dry, it is easily controlled with magnets.

One noticeable characteristic with CBN wheels is being much coarser when new. This soon wears off and the wheel becomes its intended grit. First use should be reserved for a major grinding project, which it will do well.

I did not notice any real difference in noise compared with conventional grinding wheels.

The three CBN wheels I used were steel D-Way wheels (dwaytools.com) One was 80 grit and ten inch diameter. The other two were 180 grit, one eight inch diameter and one ten inch diameter. The two ten inch wheels were used and generously provided by Dave Schweitzer of D-Way. I initially purchased the eight inch wheel from D-Way for my T4. I decided to  purchase the two ten inch wheels at the end of the test.

When used wet, I encountered a rust problem with plain water. Adding Honerite Gold rust preventing additive solved this problem. Honerite Gold (not the same as Honerite) is diluted one part to twenty five parts with water. I used the following amounts.  With the T4, 75ml water with 3ml Honerite Gold.   With the T8, 125 ml water 5 ml HG. With the T7, 200 ml water 8 ml HG
The CBN wheels do not absorb water.

Both eight inch and ten inch CBN wheels fit directly with the Tormek. In fact the eight inch also fits directly with the larger size T7 and T8 The eight inch wheel used wet with the T8 required only 225ml water with 9 ml HG. Using the eight inch CBN wheel would be a possibility for someone who also wanted an eight inch dry grinder. (I question the practicality of this arrangement.)

Whenever I drained the water trough and stored the Tormek, I sprayed a protective covering of WD40 on the steel bushing and wiped the sides and bore of the wheel with WD-40 or light oil.

With the 180 grit mounted dry, the Tormek becomes a very quick touch up grinder.

The D Way wheels are 1 1/2", or approximately 38mm. While this is narrower than the standard 50mm of the 250mm Tormek wheels, I had no trouble quickly adapting. It was not a problem.

In summation, while the Tormek SG remains my "go to" wheel, for turners and planer blade sharpeners, a CBN wheel is a serious candidate for the second wheel. CBN makes the Tormek, a fine sharpening system, into a very respectable reshaping machine.

Ken

[jeffs55]

So, Ken; I only sharpen knives and chisels at this point in my life...................far, far more knives than chisels. Would you think that I needed a CBN wheel? thanx

[Ken S]

Jeff,

Good question. In general, I would say no. Most knives are carbon steel, of something similar. Tormek users have been sharpening conventional knives successfully with the SG for decades. I would include chisels with this group.

OBR has posted about working very busy Saturday mornings, where the sharpening volume would make truing and dressing difficult. In that case, I would give a finer grit, say 600, CBN wheel serious consideration. There are also some more exotic knives which are too hard for conventional grinding wheels. These would be another CBN situation.

CBN wheels in 80 and 180 grit are prilarily marketed for turners who need to reshape their tools occasionally or often.

Ken

[Elden]

   Thank you for the completion of the saga (said tongue-in-cheek), Ken. I appreciate the time and the effort you spent! It is great information to have.

[Ken S]

You are most welcome, Eldon. I try to make sure the forum gets good information.

Ken

[Rob]

Excellent all round research Ken.  Very kind of you to go to such effort and cost and then share your findings in this way.  You truly ARE a hero member :-)

Your findings are also very relevant to some of my woodworking activities so its very useful and topical for my situation and helps to extend the value of the Tormek for me.

Thanks again my friend.

[Ken S]

De nada, amigo.

Ken

[SharpenADullWitt]

I think the fact that you found them great for turning tools and think they will be good for planer blades, kind of self explains why we haven't seen more posters of that kind on the forum.  Where when we first discussed why we hadn't seen this here, most of the stuff I found, was in the turning section of woodworking forums, with active turners who spend more time doing charity stuff (wounded warrior/patriot pens, etc), then want to spend sharpening.

Same tools, just different goals.  This is a good forum to learn, but don't be afraid to go outside our comfort zones for learning.

[Ken S]

SADW,

Your points are well taken; I agree. "This is a good forum to learn, but don't be afraid to go outside our comfort zones for learning. " For the record, I found numerous posts on CBN wheels on other sources and forums, especially the sawmill creek forum.I recently became a member of sawmill creek, and posted perhaps three times. Except for that, I do not post on other forums. My constraint is time. Incidentally, Jeff Farris posted on several forums.

I regularly search other sources of Tormek and sharpening related information, usually several times a week. The CBN posts are almost exclusively turning oriented, and generally with dry grinders. I have no prejudice against other sharpening methods or for using non Tormek made accessories with my Tormek.

Among the information I found on other sources, I did not find anything which offered practical advice for using CBN wheels with the Tormek, or reasons not to use them with the Tormek. I tried to approach the subject in an unbiased manner. Having the name "Tormek" of an accessory does not get an automatic approval from me, nor does an accessory not named "Tormek" have any harder judging standards. In the case of CBN wheels, I realize that they represent a substantial investment for a Tormek owner. I hope to provide our members with a better starting point to make their own independent judgements.

Ken

[WolfY]

Ken,

Thanks for the well and thorow full report.

[Ken S]

I just "liberated" a ten milliliter liquid medicine scoop my granddaughter had used with cough syrup. It says Kroger Pharmacy (a local chain grocery store, although most pharmacies should have them). It should work very well with Honerite Gold.

Ken

[larcal]

Also much thanks for this fine report Ken, but there's one thing I don't get.

Why is it detrimental to use CBN on Carbon Steel? Is Wheel damaged some how, or what? How about stainless steel blades?

Sure is appealing to have wheel that never has to be trued and lasts forever

[Ken S]

Larcal,

Welcome to the forum. You have asked two very good questions.

Not being a metalirgist, I may have used a confusing term in "carbon steel". Mild, unhardened steel would be more accurate. CBN is designed primarily to grind harder steel alloys, such as high speed steel. As part of my testing, I ground several Irwin Blue Chip chisels. These would be considered high carbon steel. They are also heat treated. They are typical of the traditional steel used for woodworking tools and knives. Due to the fine grain structure of the heat treated steel, high carbon steel tools can be sharpened to a higher degree of sharpness than A2, HSS or carbide steel. The trade off is this high degree of sharpness does not last, and the tool must be frequently sharpened.

I had no problem grinding several high carbon chusels with my CBN wheels. At last count, I have around eight 3/4" Irwin Blue Chip chisels. Having this many let me compare the surface of bevels ground with different grits.

The loading or clogging occurs only with very soft steel. This is essentially the same problem conventional grind stone have when someone tries to grind aluminum. The fix is easy, just grind a piece of hardened steel such as hss. It will unclog the wheel. You should watch the you tubes made by D-Way Tools. Dave Schweitzer demonstrates this declogging. I found the D-Way videos very informstive. They were my major source of information for my testing.

I also tested a garden variety "stain resistant" kitchen knife. An 80 grit wheel will give your knife edge all the tooth you want! To my surprise, the 80 grit wheel followed directly by the Tormek leather honing wheel loaded with the standard Tormek honing compound gave a surprisingly respectable edge. I should note that this edge was almost, but not quite as sharp as the traditional Tormek SG-250 technique.

I would not claim that CBN wheels last "forever". They do last a very long time. I found the initial excessive coarseness broke in quickly. I expect that whoever eventually purchases my lightly used wheels from my estate will get a lot of use from them. I would expect that someone like Curt, who gets a year out og an SB-250, will eventually need to replace a CBN wheel. Longevity aside, the main advantage for someone like Curt is that the wheel will not need dressing and truing.

There is a flip side to this longevity. I lent my 180 grit wheel to Curt to try. He noticed a slight high spot. I had not noticed the high spot; Curt is a far more experienced sharpener than I am. With a conventional Tormek wheel, the next wheel truing would eliminate the high spot. With a CBN wheel, the slight high spot will be there "forever". In fairness to D-Way, Dave generously loaned me two older wheels. My original purpose was to test how the wheels performed when used wet. (The steel wheels and steel reducing bushing work fine wet as long as Honerite Gold is added to the water and the wheels are left dry. I wipe on a bit of oil before storing them.

Dave offered to sell me the wheels at a generous used price. From my limited testing, the two used wheels seemed to cut as well as the new eight inch wheel I purchased initially from D-Way. A CBN wheel on a T4 is a lot of firepower in a compact package!

I have a DMT diamond flat plate. It is a marvel for flattening water stones and India oil stones. I made the mistake of flattening a Carborundum stone with it. It flattened the stone, but lost much of its useful life in the process. It still works with water stones, but the process takes longer. If diamond wears, I am sure CBN will wear, also.

I think a turner who does a lot of reshaping should have a CBN wheel for his Tormek. I found it made that lengthy chore pleasant. Although I have not tried it, I am convinced that CBN is the answer for planer blades. I do not think CBN should be the only wheel for a general Tormek sharpener. For everyday sharpening, like woodworking tools and kitchen knives, the SG is still my go to wheel.

Ken

[wootz]

We've been using CBN wheels for over half a year, on a few hundred knives by now.
Can only confirm what Ken has said above.

The leaflet that comes with CBN wheels warns against high carbon steels, however, carbide type matters.

With conventionally cast high carbon steel, e.g. 1095 (Carbon 0.95%), and those that Ken calls "mild", the ground metal fills in the CBN pores, and the wheel grinds worse and slower.

But as soon as the steel is stainless, will it be mainstream (chromium carbides), or high-end homogeneous powder-metallurgy alloys (vanadium carbides, tungsten, molybdenum) -  works perfect on CBN even when Carbon contents nears 2% (e.g. M390 or S290), with all the advantages the CBN can offer over the stone wheels.

larcal, feel free to ask more questions if any left.

[Ken S]

Excellent post, Wootz!

Ken