CBN Wheel for Tormek

[Rem]

Rem, I did not know that banjo playing was a "hanging offense" in the great white north. Took me about three seconds to understand your meaning.  I wore short pants and a T shirt yesterday. What did you wear?

Jeff .....  that's just sooooooooo  wrong.   Well, just so you know, I was walking around nekked last night outside.   From the sauna to the house, at which point the sweat had frozen.   Actually, we're having a very mild winter here.  The coldest it's been was minus 20 (think -4 for you rogue temperature types).  This morning, it's a scant -10 up at my place, -4 downtown (think 14 and 25 F, respectively).  It could just as easily be -30 ish, so no complaints from me.  I'm loving it. 

Regarding the banjo ....  yes, one strives to "stay in the closet" for as long as possible.  Given the volume associated with your average banjo, it's a challenge.   R

[Ken S]

Back to the original topic, here is another email from Dave Schweitzer:

Ken, the 8" is just a little slower that the larger one. Just mount the 180
grit on your Tormek and grind away either wet or dry, wet does give a little
better finish.
If you don't like it with in the first week just send it back.

As an update, I joined Wootz and took the plunge. I ordered a 180 grit straight eight inch diameter CBN wheel from D-Way. It will come with a steel 12mm bushing. I debated whether to order it for the T4 or T7. I finally opted for the smaller T4 size. It just felt like the right choice.

I will post my thoughts after using it. Coincidentally, I ordered three more 3/4" Irwin sharpening chisels.

So ends my Black Friday binge shopping.

Ken

[bobl]

Ref C.B.N.
On Knife grinding only. I currently use 2 different machines with interlocking spiral wheels. the faster machine uses C.B.N. 126
( that is the coursnes or grade ) The slower and smaller wheels use C.B.N. 107 Grade.
Both these wheels are no where near the size of the Tormek wheel.
They are as follows and in the respective order.
100mm diameter for C.B.N. 126
55mm diameter for C.B.N. 107

I have tried re-plating the larger wheel 100mm with the finer 107 C.B.N. but it just runs out more quickly.

I know there is a HUGE forum debate at the moment on C.B.N.
If you are only knife sharpening as I am, as a small business, please let me know the costs you are paying for RE-PLATING your wheels.That is, electroplating not resin .
I would like to know the costs for a Tormek T7 sized wheel in C.B.N. suitable for knife grinding at the speed of the T7  and the cost of re-plating there of.
Also of the Diamond type that is shown on the T2 and its replating there of.
Cheers.

[Ken S]

Sorry, Bob.

I know nothing about the other machine(s). When my CBN wheel arrives, it will be the first time I have even seen one. i have no clue about replacing; in fact, I can't imagine me ever needing it with my home shop.

I think you need to contact a more specialized source for some high powered advice.

Ken

[grepper]

Ken - Cool!  You got one.  I'm really looking FW to your review!  When do you take possession?

Bobl - How often do you have to have your wheels replated?  How many knives between replating?  Are you just sharpening or making knives?  I'm curious because I don't have a CBN wheel and from what I've read that they have a very long MTBF, so long in fact that in most applications they may never need replacing or replating.  Maybe I'm misreading what you are saying, but it sounds like you have to have it done quite often.

There is not really a debate here, but more a discussion because nobody has any experience with them.  Any details about your experience would be appreciated! 

Are you sharpening on high speed wheels?  Any problems with heat?  What do you think about the surface on the knife they produce?  That kind of thing.  "Interlocking spiral wheels".  What machine uses that?

[Ken S]

Grepper,

According to the post office tracker, it should arrive Friday. I will post my comments on using it.

Ken

[Ken S]

Grepper,

The CBN wheel just arrived. A day ahead of schedule; I''m impressed!

Grandchildren's holiday concert at school is this evening. No time to try it today.

Ken

[grepper]

Not a problem Ken.  All you have to do is give the school a quick call and tell them they are just going to have to delay the concert for a week. 

[SharpenADullWitt]

Grepper,

The CBN wheel just arrived. A day ahead of schedule; I''m impressed!

Grandchildren's holiday concert at school is this evening. No time to try it today.

Ken

That would depend on how well they sing/play.

[Elden]

Due to the fact that the CBN wheels are machined, they should be concentric, balanced and true.  .......  Could you point us to a negative review?  I'd be interested in reading that.

What make/model of sharpener do you have?

If your machine requires something other than concentric, balanced and true then, well, that would be a problem.  I'd suggest contacting the manufacturer of your sharpener if you suspect there might be issues.

Mark (grepper),

   I apologize for taking so long to answer. The fact of the matter is that I have not been able to find the "negative" I thought I remembered reading. As you mentioned somewhere, the cost has been the most negative I have been able to find. Following that would be the "loading up" of the wheel (chainsaw chain is known for its cleanliness due to pitch and gum). So far, I have not seen any concentricity issues mentioned.

   The grinder is an Oregon 511a which is made by Tecomec in Italy. I will have to try verifying the concentricity of the flanges without the grinding wheel mounted.

[Ken S]

I had a short chance to handle the CBN wheel today. I was concerned because the CBN is heavier than the SG-200. I thought the extra weight might be a problem for the motor. It turned out not to be an issue. I weighed both with the postal scale I use with my original Edgeonup tester.

The SG-200 weighed 2.448Kg (Weight is slightly reduced by some use and a couple truings.)

The D-Way steel CBN wheel (with steel 12mm reducing bushing) weighs 2.910 Kg.

The difference was not as much as I had thought. I planned to time the start up time needed to reach full velocity. Both were too quick to measure. I ruled "no problem".

I did not notice any difference in running noise between the two.

The machining of the wheel and bushing look quite good. The bushing fits nicely.

I am impressed so far and am looking forward to actually using the CBN wheel.

I believe the CBN wheel may work well with the planer jig. I don't think it will glaze with high speed steel, it will not need any depth compensation midway through. Someone else will have to verify that.

CBN wheels run coarser initially. I want to reshape a turning gouge. I had very good luck doing this with the Norton 3X wheels on the Tormek.I am curious to see how the CBN compares.

Most of my woodworking tools are older, high carbon steel. As such, I believe the SG will remain my general go to wheel.

I will keep you posted.

Ken

[SharpenADullWitt]

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.

[Ken S]

Interesting observation, SADW.

This is the youtube which gave me concern about the weight of the wheel:

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

The T4 starts up with no hesitation with the CBN wheel. I had not thought about any issue with the nylon bushings.

The 250mm and 200mm wheel diameter Tormek models use the same nylon bushings. ( In fact, most of the parts are the same.) The shafts are the same diameter. The only shaft difference is the length, to compensate for the 10mm difference in grinding wheel thickness and the size of the motor/housing.

The SG-250 weighs about twice the weight of the SG-200 and substantially more than my eight inch CBN wheel. I will weigh my SG-250 and SB -250 after my family is awake.

I chose a simple flat wheel. There are radius wheels (1/4" or 6mm radius on each side). There are also "4 in 1" wheels with a larger area of the flat sides covered with CBN. The thicker metal core of these wheels adds weight. (My wheel has around a quarter inch of the flat side covered with CBN.) This is from woodturnerswonders.com :

"We don't have them for the T-4 but we can make them if we have a drawing.  The T-7 wheel that is straight across with no material down the sides is about 5 pounds and the 4-1 design with 1 inch of material down the sides is about 10 pounds"

The other factor in weight is whether the wheel is steel (mine is) or 6061 "aircraft" aluminum. I am researching the practical differences, but do not have an answer at this point.

Some doubts have been raised about aligning the CBN wheel with the universal support. (The truings tool is not used with CBN.) The CBN wheels are turned on a lathe and balanced two different ways. I would be surprised if misalignment was a problem.

I hope to have time to use the new wheel this weekend. One of the first tests will be reshaping the half inch turning gouge I have on loan from Affinity Tool. It arrived with jig setting 2. I reshaped it to jig setting 4 and then back to 2 using the Norton 3X wheels (wet) on the Tormek. The 3X wheels did the reshaping in good time. I will see how the CBN wheel compares.The 3X wheels are 80 and 46 grit. I chose the 180 grit for my CBN wheel. There is an 80 grit option. I get the impression from Dave Sweitzer of D-Way that the two grits are largely interchangeable, with the 80 cutting a little faster and the 180 leaving a slightly smoother surface. I chose the slower, smoother path, at least for my first excursion. Incidentally, Dave also said using the wheel wet also leaves a slightly smoother finish. Unlike the Tormek wheels, these CBN wheels are single grit only.

I will post more after using the wheel.

Ken

[Jan]

For a grinding wheel not only the mass but also its angular mass (moment of inertia) about the rotational axes is important. Two wheels with the same mass can have significantly different moments of inertia.

The mass of the CBN wheel is often concentrated at its periphery and such a wheel behaves like a flywheel. It needs much more torque to reach the desired angular acceleration. It was probably Ken's subconscious reason to worry if the T4 motor spins the wheel. Congrats Ken, you have a good physical intuition. 

A wheel on a bench grinder with 3450 rpm has kinetic energy more than 800 times larger than the same wheel rotating on the T4 with 120 rpm!

Jan

[Ken S]

E=MC(3450)   

Ken

ps Thanks for your compliment about my intuition. I will endeavor to live up to those expectations......