Can Norton 3x wheels be paired?

[pnwPat]

In reading prior posts I saw that the use of 8" Norton 3X grinding wheels on a Tormek to improve grinding efficiency (especially over SG or SB wheels) while retaining the advantages of wet grinding has been discussed in this forum under different topics. Ken did some testing and reported that the advantage was real and worth considering when heavy grinding is needed.

One 3x wheel disadvantage mentioned is the maximum size suitable for the Tormek: just 8" dia by 1" wide. For my own preference, if the need arose, I'd be inclined live with this, or if feeling particularly flush I might consider an 8" dia CBN wheel at roughly triple the price for a supposedly more durable 1.5" wide wheel.

However, it occurred to me that if a 2" wide wheel that can do efficient wet rough grinding was wanted at only twice the price, how about pairing identical 3x wheels side by side? If one of the inside paper blotters were removed first then I would guess the assembly could be "trued" after mounting such that the remaining gap would not materially affect the rough grinding operation. Slight imperfections in the trueness of the assembly should not matter at that stage. As Ken previously mentioned, final sharpening after rough shaping should be done on SG or SB wheels, which can be perfectly trued.

Are there any technical reasons that a 2" wide paired 3X wheel approach would not work? Ken, will two 3x wheels fit on a current Tormek shaft with threads still available for the Ezlock nut to grab? There is probably some risk that if one or both of the adjacent 3x wheel sides were not flat enough, compressing them together might fracture one. I've no experience with that, but wouldn't the remaining paper blotter between the paired wheels provide enough cushion to prevent cracking without the resultant gap causing any serious functional loss?

Might be a crazy idea, but still food for thought. Someone please set me straight if I've overlooked something obvious.

[Ken S]

Pat,

Your idea may or may not be crazy. (Iam leaning toward crazy.).

I will check out the 3X wheels tommorow and report.

Ken

[grepper]

Huh.  Interesting idea.  Crazy or not, you are not the only person to think of it.  Who knows if this person knows what he is talking, about but anyway:

http://www.practicalmachinist.com/vb/archive/index.php/t-296535.html
"You don't want to put two wheel faces right next to each other, they need to have some sort of cushion between them (at least the standard blotter paper). I'd recommend against it regardless, the sides aren't flat enough for proper mating."

If don't know if the Tormek super slow speed would make some difference or not.

[pnwPat]

Thanks for the feedback.

I should have made it clearer that the idea applied solely to a low rotational speed environment. Wheel failure (for any cause) should be a relatively "low drama" event in that environment. The specific catalyst for the idea was limited availability of 2" wide Tormek compatible aggressive grinding wheels.

For dry grinders things are completely different. Wheel failure at those speeds would be catastrophic and potentially life threatening. Ganged wheels probably have more risk of damaging contact due to vibrations at speed. The nail in the coffin is that there are more wheel choices available for dry grinders, so the original idea catalyst doesn't apply in that environment.

Even for the Tormek the bottom line is that ganged wheels are just an interesting thought with inherently limited value and appeal. No matter if this might work under specific conditions with very important reservations and caveats, the ability of humans to predictably do things improperly or carelessly means that it can't really be endorsed. Certainly OSHA and/or manufacturers will never approve, I think. I also suspect over time any perceived advantage will probably evaporate as CBN wheel production matures.

[Ken S]

Pat,

I measured the thickness of the 3X wheels and the length of the shaft. Clever idea; it just doesn't work. Only a thread or two emerges when both wheels are placed on the shaft.

More soon.

Ken

[Ken S]

Pat,

I originally began the 3X project because of posts about excessively ong times reshaping turning tools. I had read a forum post years ago by a guy who tried using a cheap dry grinding wheel (wet) with his Tormek. He and his post faded away.

At the time I had a six inch 46 grit 3X wheel on my dry grinder. When I acquired my T4, I decided to try the 3X wheel with it. At six inches, it was like a wheel almost worn out, however, it ground a bolt handily.

Encourages by this, I purchased two 3X wheels, first the 46 grit, and then the 80 grit. I ran tests with metal lathe tool bits and was impressed how well the wheels cut when used wet with the Tormek.

Later, when preparing to demonstrate the Tormek, I used the 46 grit wheel to reshape a turning gouge. I posted the result at the time; I was very pleased.

As I do not do enough hss sharpening to justify the expense of a CBN wheel, atjustover $50 US, a 3X wheel seems a workable, low cost option. I am glad I made the test, however, in hindsight, the extra cost for a CBN wheel would have been a better choice.Today I would buy a 250mm x 50mm wheel with a proper 12mm steel bushing. I am still debating the grit size. From what I have read, 180 would be coarse enough. 600 might be better for finer work.

The 3X wheel is a workable and inexpensive expedient. For a much used long term choice, a full size wheel seems a good investment.

I salute Wootz for being the first to step up and make the purchase. His posts give us a first hand look from the trenches at the new CBNtechnology.

Ken