CBN Wheel for Tormek

[Ken S]

Last evening I finally had a chance to put CBN to steel.

First, I want to pay homage to Wootz for being the pioneer. I am following in his footsteps and benefitting from his experience.

My first test was reshaping a half inch turning gouge from jig setting 2 to jig setting 4. (I used the new SVD-186 jig on the T4.) This seemed a logical way to test the difference between wet and dry. The gouge has two wings. I ground the left side with the Tormek dry. My CBN wheel is 180 grit. I set a timer to give a rough idea of time passed. By the one minute mark the left side was reshaped. I was impressed. This wheel definitely cuts!

I filled the trough with just enough water to cover the edge of the grinding wheel. Using the same light touch as I did on the dry side, the wet wheel also completed the side reshaping handily in a minute. The cutting action seemed somewhat muffled by the water. The cut seemed ever so slightly smoother. The CBN wheel required no extra water for absorption. The only water spillage was from a little drippage from the turkey baster. I was convinced that for this operation, the CBN wheel could be used wet or dry.

For the second test, I used the same procedure I had used previously with the 3X wheels and the two Tormek wheels (SG and SB). I placed a 3/8" metal lathe tool bit in the SE-77 square edge and set the bevel angle to 30° with the Anglemaster. I then ground for a timed five minutes. The amount of grinding easily matched the 80 grit 3X wheel and was reasonably close to the 3X 46 grit.

I used the recommended lighter touch. For the record, the CBN wheel removed considerably more steel than the SG had removed earlier. In that earlier test, surprisingly, the SG surpassed the SB. I have since learned that the SB responds better to a light touch and plan to retest it.

I chose 180 grit instead of 80. For an active turner doing a lot of reshaping, the 80 grit wheel would be faster. The 180 leaves a surface like the SG graded coarse. My wheel is the flat model eight inch diameter. It is steel, although I have it on good authority that either steel or the aircraft grade aluminum work fine.

I think CBN may be what we need for planer blades. This may well require more than one wheel with different grits.

If I was limited to only one grinding wheel with my Tormek, it would be the SG. Based on this initial experience, assuming the wheel remains flat, I can see one or more CBN wheels as useful adjunct components.

I will post more after using it more.

Ken

[Ken S]

How much does the normally used stone, way weight?

Seems to me, if there were going to be an issue, it would most likely be with the plastic bushings on the shaft, over time.

SADW,
I weighed a fairly new SG-250. It weighs approximately 4.9 Kg, or twice the weight of the SG-200.

Incidentally, I started to reshape the turning gouge back to jig setting 2 with the SB-250 blackstone. It was cutting, but not nearly as well as the CBN. After ten minutes I suspended the operation. I have never had much luck with the SB. I keep thinking I am doing something wrong; I have not given up on it.

Ken

[Ken S]

Wootz,
The last paragraph mentions that CBN wheels are often dressed with diamond tools. It might be worth exploring further.

http://www.grindingprocesssolutions.com/CBN/vitrified.html

Ken

[wootz]

Thank you for that, Ken.
Unfortunately, I don't believe this dressing is for electroplated CBN wheels.

As to my problem CBN wheel, the factory promised to send me a proper one, so the saga may end up with me having two wheels, the concaved and the rightly flat, for the price of one.

The only question is why would I need a defective wheel even for free?
But do you remember a discussion on middle overgrinding of long knives?
I noticed that longer knives sharpened on that concaved CBN wheel have less of this problem.
I wouldn't be able to foresee this advantage of the otherwise defective wheel, but post-factum it is easy to understand why it works it.

Cheers

[Ken S]

Wootz,

I am glad you will end up with a proper wheel.

It goes against my thrifty nature, however, I would suggest you just recycle the defective wheel. Life is too short to clutter your mind and shop with tools which don't work.

Thanks for being the pioneer.

Ken

[Jan]

The only question is why would I need a defective wheel even for free?
But do you remember a discussion on middle overgrinding of long knives?
I noticed that longer knives sharpened on that concaved CBN wheel have less of this problem.
I wouldn't be able to foresee this advantage of the otherwise defective wheel, but post-factum it is easy to understand why it works it.

Cheers

Every cloud has a silver lining. 
Jan

[Ken S]

Wootz,

Don't throw away the saddled wheel. I have a use for it which needs your help.

Details to follow.........

Ken

[Ken S]

I have run into a glitch with my idea of using my CBN wheel wet like a regular Tormek wheel.After the sharpening session I carefully dried the wheel and the steel reducing bushing. I wiped them with Starrett oil and hung the wheel. Last night I examined them for any rust. I found the slightest bit of rust on the 12mm bore of the reducing bushing. Also, while the wheel itself did not show any rust, the shallow drill holes made to balance the wheel showed definite light rust.

Based on my initial use, wet grinding seems to offer some advantages. It does trap the grinding dust in the water. It does offer some slight advantage with not heating the steel, however, due to the slow speed of the Tormek, that difference is minute. I also find the nuisance in using the water trough minimal. The rust problem is not minimal.

I will be exploring the options for reducing both sides of the "rust and dust" problem. I have a bottle of Honerite Gold on order. I will see if this water additive eliminates the rust problem (combined with good care). I will do this in two steps. The first step will be a relatively short sharpening session, typical of my work, and then careful storage. I will examine the wheel and bushing carefully for signs of rust..  If several short sessions are rust free, I will leave the wheel in solution for longer times with the motor running intermittently. This would simulate working conditions for a professional sharpener or turner.

I will also test the Honerite Gold with the SG to see if it prevents rust staining from imbedded steel particles, as asked by Jan.

On the dust side (from dry grinding), I will follow Tormek's path (as used in the T2) and rig up one or more magnets. Borrowing an idea from the T8, the removable magnet is a real convenience. The magnet holds the steel grindings. When the magnet is removed, the grindings are released. I will start with placing the magnet(s) in a plastic sandwich bag. Removing the magnet will release the grindings.

Related, I purchased the CBN wheel to use with the T4. Using it wet, I will try using it with the T8 to take advantage of the removable magnet. (The magnet on my T4 trough is attached with electrician's tape.)

I have searched unsuccessfully for related tests. The Honerite Gold online search results are all "at such and such a dealer", no test results. Incidentally, Honerite and Honerite Gold are different formulas. The gold is for water stones; the non gold is for oilstones. In the US, the product is sold under the Boratool label and imported by Affinity Tool (as is the Tormek). I contacted Affinity. They are not aware of any previous tests. However, they generously offered to send me a bittle of Honerite Gold for the tests.

Not all testing has the luxury of being done under strict scientific scrutiny by scientists in a lab. Sometimes we amateurs just have to do our own best guess basement workshop testing.

(Henry Ford first tested his gasoline engine in the kitchen. Needless to say, his wife was not happy that the noise awakened the baby!)

Ken

[Herman Trivilino]

As to my problem CBN wheel, the factory promised to send me a proper one, so the saga may end up with me having two wheels, the concaved and the rightly flat, for the price of one.

The only question is why would I need a defective wheel even for free?

The concave one could be used for anything with a convex edge, such as pruning shears, bypass loppers, pizza cutter wheels, etc. You can also use it for experimental work where you're afraid you might damage the good one.

[Ken S]

My standard test for grinding wheel efficiency is to put a square metal lathe bit into the square edge jig (set at a 30° bevel) and grind for five minutes. I would be interested to see what happened if you did five or ten minutes on one of the high spots. You could measure the amount of concavity with feeler gages. If ten minutes made any difference, carry on. If the first high point wears down, work on the other end.

Ken

I described this procedure in my posts about testing the Norton 3X wheels.

[Ken S]

Someone asked about the configuration of my CBN wheel. I chose a flat wheel, with no radaii. The two sides each have a narrow strip of CBN abrasive. My intentions are to use just the flat part of the wheel, just like the Tormek wheels.

Ken

[Ken S]

I reran my standard five minute metal lathe bit with the now broken in CBN wheel. It now cuts like a 180 grit wheel. It cut well through the entire five minute test.

Dave Sweitzer of D-Way emailed me today that he has shipped me two ten inch CBN wheels for testing. I look forward to running more tests and will report the results. These wheels will also let me compare the T4 and T7/8 with CBN wheels.

Ken

[Jan]

Ken, I would be interested if some of the 10 inch CBN wheels you are testing would be suitable for flattening the back of chisels or plane irons. I am afraid that the side strip of CBN abrasive may be too narrow. 

Jan

[Ken S]

Interesting question, Jan.

Let's look at plane blades first. David Charlesworth has devised a very clever solution. The only part of the back which needs to be pristine is the last small fraction of an inch or centimeter. David devised "the ruler trick" to polish just the end of the blade. In the link he demonstrates it.

https://m.youtube.com/watch?v=nykVPKbUGTo

Chisels are different. If the chisel back is convex, the chisel will not track properly. The English vernacular term for this convex back is having a "belly". The late Leonard Lee gave excellent advice for handling a new chisel with a belly: "return it to the dealer".

I have a favorite very old small Buck chisel which had a belly. I flattened the back using the side of my SG-250. It was a labor intensive process.   In fact, my original motivation for buying a Tormek was when my hands hurt after preparing new chisels for a dovetail class.

Fortunately, most of the chisels I have worked on are either flat or (more commonly) have a concave back. With a concave back, I just polish the end.

This is leading up to a statement that for most users, I would not worry about whether the CBN wheel had grit on flat side. Mine has a small amount. This was supposedly added for carvers. I am not a carver; I am quite content with the basic flat surface. Other members may feel differently.

Ken

PS I will keep your question in mind when the two wheels arrive (hopefully Monday or Tuesday).

[Jan]

Ken, I like the David Charlesworth approach but it is only for blade with already flattened back. He describes a ruler trick how to remove a burr after sharpening the edge while blade back should be reasonably flat before the edge sharpening.

Based on my experience the plane blades are often concave and you have to flatten circa 25 mm from the edge. Recently I was sharpening a 50 mm (2 ") plane iron with 59-60 HRC and I needed 15 minutes to flatten its back on the side of the SG stone graded coarse. It was a very difficult task. I had to de-clog the stone side several times during the flattening. I cannot imagine to do this flattening by hand using the waterstones.

My client was a violin maker, so his claims were quite high. He told me that after the blade flattening and sharpening the chips thickness dropped by one third. 

Jan