Tormek Community

In the Shop => Knife Sharpening => Topic started by: Sharpco on December 05, 2017, 10:33:16 am

Title: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Sharpco on December 05, 2017, 10:33:16 am
CBN wheel has several advantages. No need truing, No wear out, Alway same grit......

And, if it is made of a non-rusting material, it can also be used with water.

But Tormek has not replaced the stone with a CBN wheel.

Why?

Is there a drawback to the CBN wheel?
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 05, 2017, 12:37:57 pm
Good question.

As you state, CBN wheels are always the same grit (after a very brief wear in period). Traditional Tormek thinking was one grinding wheel. Originally this was with a natural stone mined nearby. These were finer grit. Many years ago, these were replaced with the present manmade aluminum oxide SG stones. These are coarser, but could be modified with the stone grader to be finer. One stone could serve both purposes. In fact, when skillfully used, middle gradations are possible. Having several degrees of coarseness would require purchasing several CBN wheels.

Interchangeable wheels is a fairly new concept with Tormek, only since 2010. I believe Tormek may be moving in the direction of CBN wheels. The T2 uses diamond wheels. The diamond wheel is single grit; that's why there are two available. Several forum members, including me, have purchased third party CBN wheels. Mine are 80 and 180 grit. They work very well for heavier grinding, such as reshaping turning tools. For me, the SG is still my go to sharpening wheel.

I suspect that Tormek may eventually include CBN wheels as accessories, like the SB, SJ, and DWC-200 (the coarser diamond wheel for the T2). At this point, I do not believe there is adequate market demand to justify the cost of adding CBN wheels to the product line.

Incidently, adding Honerite Gold to the water takes care of rusting with steel wheels and reducing bushings.

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: cbwx34 on December 05, 2017, 03:40:32 pm
I'm kinda thinking like Ken... it may eventually be offered... at least as an option.  I don't grade my stone all that often, (although it is a nice feature to have)... so could maybe get away with just one.

Only things I would wonder about are longevity and cost vs. the "traditional" stone.  Also, one downside to diamond stones, and I'm thinking CBN might be similar, is if you damage them, for example using too much pressure can basically "strip" the stone... no recovery like a regular stone.

I really need to get one and experiment.  Maybe next year....  ::)
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Herman Trivilino on December 12, 2017, 01:53:25 am
CBN wheel has several advantages. No need truing, No wear out, Always same grit......

I think Tormek would not consider that last one to be an advantage. They market their premiere grindstone, the SG-250, as something whose grit can be changed.

And is it really true that there's no wear out of a CBN. Perhaps negligible wear when sharpening knives, but what about axes, lawn mower blades, and hedge clippers?
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: cbwx34 on December 15, 2018, 04:31:37 pm
Not directly Tormek related... but some interesting comments on CBN wheel use...

https://youtu.be/zI4wLWoZ9Vs
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 15, 2018, 06:08:46 pm
I think that Sharpco poses an excellent question.  It can be taken as “Are CBN wheels better for the Tormek?” and as “If CBN wheels are better, why hasn’t Tormek offered two CBNs as an alternative to the SG-250?”

On the first question, I and most of the dry-grinders I know (mostly turners) have gone over to CBN on dry grinders for tool shaping and sharpening purposes.  In dry grinding they have three important advantages (over stones): negligible heat, excellent balance and alignment, and constant diameter.

The first two of those are not an issue on the Tormek, so the main advantage on a Tormek would be the constant diameter.  This is not a big deal if you don’t mind adjusting as the stones shrink.
 
With that said, I recently got two CBN wheels for my T8 (from Woodturners Wonders; they have several Tormek-compatible 10” CBN wheels with 12mm arbors in various grits).  That is because, for one of my recent uses of the Tormek (repeatable grinds on scandi carving knives), the constant diameter is very important to me.  Also, though they can be used wet with an anti-rust agent, they are designed to be used dry, which is easier on my lovingly made custom knife handles.

While, as Herman notes, Tormek would not see having a constant grit as an advantage (relative to the variable grit SG-250 and SB-250), I don’t find swapping wheels to take any longer than re-grading the stones, so that factor is a wash for me.

And an advantage on the Tormek (that isn’t much different from stones in dry grinding) is speed: I have found that a coarse CBN is a lot faster than the SB-250 graded coarse.  Probably similar to the Tormek diamond stones.

Now on the second question, why Tormek doesn’t introduce CBN wheels, I agree that Tormek should (and probably will) come out with CBN wheels, but given the fairly narrow application, I can see that it would not be a priority for them.  They have just introduced the diamond wheels, and CBN might complicate their marketing. 

Which is to say, I sense that the main reason we don’t have CBN wheels from Tormek is Tormek’s general prioritization, for marketing reasons, of simplicity over optionality.  This might be good marketing.  They might be concerned that if they give people choices, people will perceive the Tormek system as too complicated. I think that they are slowly getting over that, as shown by the new wheels and other innovations in the past few years, but it does seem to be like a big slow-moving ship.  In the meantime, the option is there in the aftermarket.

Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: cbwx34 on December 15, 2018, 06:25:36 pm
One thing mentioned in the video I linked... he claims that "mild or high carbon steels will clog the CBN grit and cannot be removed, which will ruin the wheel"  (1:26)... and that only... quality high speed steel or carbide can be sharpened on them.  That true?

Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 15, 2018, 06:55:34 pm
I have seen this warning before, mostly in connection with high heat grinding with both diamond and CBN abrasives. 

I have also seen people report that it is not an issue.  Some confusion comes from the vagueness of the term "high carbon steel".  A fairly thorough review by Reed Gray (aka "robo hippy") seems to conclude that the culprit is not HCS per se, but non-hardened HCS.  So, for most cutting tools there should be no problem.  Gray also notes that a run over a clogged wheel with an HSS tool will clean it up.  Gray gives some comments at the following link, but his full report is available on his website.

https://sawmillcreek.org/showthread.php?246501-CBN-grinding-wheels-and-the-steels-they-are-suitable-for

It has not been an issue with me.  So far I only sharpen high carbon steel knives on my CBN wheels on the Tormek, and there is no clogging at all.

It might be that I haven't had a problem because I am only working with hardened steel and I don't grind on CBN at high speeds / temperatures.  I have CBNs on a slow speed dry grinder, and obviously speed is not an issue with the CBNs on my Tormek.  I wouldn't try to do serious shaping on non-HSS on a CBN wheel, that might cause clogging.

Gord
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 15, 2018, 07:03:58 pm
I think the real question with CBN wheels should be why are they not made for the Tormek.

CBN wheels are primarily designed and marketed for eight inch high speed dry grinders and woodturning tools. While they may also work with the Tormekto some extent, that is a marketing after thought. Even my three D-Way CBN wheels, which I have used successfully with my Tormek, are not really designed for the Tormek. They can be used wet (with a rust inhibitor) or dry with the Tormek. D-Way's reducing bushing works equally well with the T4 or T7/8. This works well, but would work better if made made from stainless steel. (Of course, it is designed for high speed dry grinders).

The last I knew, using the woodturnerswonders wheels wet would void the warranty. Has this changed?

The main argument for CBN vs diamond wheels seems to be problems with diamond at high grinding speeds (heat). The slow speed of the Tormek motor negates that constraint.

I believe the discussion about CBN wheels really began because Tormek has never offered a true coarse wheel. Many dry grinders use 46 and 80 grit wheels. These are much more coarse than the 220 grit of the SG or SB. I think the frustration which started the CBN desire was a product of the frustration from slow grinding of operations like turning tool reshaping or planer blade resharpening.

I would like to see Tormek offer a true coarse grit wheel. I would like to see Tormek realize how useful diamond wheels are with the T4. Looking ahead, I see Tormek with diamond and Original wheels. I would be surprised to see CBN wheels in the Tormek lineup. Keep in mind, I have no crystal ball......

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: cbwx34 on December 15, 2018, 07:11:51 pm
I have seen this warning before, mostly in connection with high heat grinding with both diamond and CBN abrasives. 

I have also seen people report that it is not an issue.  Some confusion comes from the vagueness of the term "high carbon steel".  A fairly thorough review by Reed Gray (aka "robo hippy") seems to conclude that the culprit is not HCS per se, but non-hardened HCS.  So, for most cutting tools there should be no problem.  Gray also notes that a run over a clogged wheel with an HSS tool will clean it up.  Gray gives some comments at the following link, but his full report is available on his website.

https://sawmillcreek.org/showthread.php?246501-CBN-grinding-wheels-and-the-steels-they-are-suitable-for

It has not been an issue with me.  So far I only sharpen high carbon steel knives on my CBN wheels on the Tormek, and there is no clogging at all.

It might be that I haven't had a problem because I am only working with hardened steel and I don't grind on CBN at high speeds / temperatures.  I have CBNs on a slow speed dry grinder, and obviously speed is not an issue with the CBNs on my Tormek.  I wouldn't try to do serious shaping on non-HSS on a CBN wheel, that might cause clogging.

Gord

Thanks for the reply.

I know some also feel that way about diamond stones (not necessarily Tormek wheels)... that lower end steels will destroy them for various reasons.  Hasn't been my experience... I'm sure there's a number of variables involved.

Good info!
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 15, 2018, 07:14:30 pm
Gord,

i don't think we have enough hard evidence about grinding non hss with CBN. I have ground my Carbon steel sharpening chisels with CBN wheels, and have not noticed any ill effects. I also recall Dave Schweitzer saying that clogged CBN wheels can be easily restored by grinding on a piece of hss.

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 15, 2018, 07:21:03 pm
CB and Gord.

I have a secret weapon for grinding carbon steel....my Original SG wheel!

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 15, 2018, 10:38:41 pm
The last I knew, using the woodturnerswonders wheels wet would void the warranty. Has this changed?

Ken

This has not changed, but when I bought mine I asked them why, and they said it was because the water could cause corrosion.  So, I see no reason why they couldn't be used wet with Honerite or Tormek ACC-150.  If I ever want to use mine wet, that is what I will do. (From his videos it looks like Vadim is using his wet, so I assume he is using some anti-corrosion compound.)

Gord
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 15, 2018, 11:40:18 pm
Gord,

I think you are correct. It is hard to get a straight answer on this. I think the vendors are reluctant to authorize wet use with anti corrosion for fear of complaints from those foolish or lazy enough to leave the wheels in the troughs between sessions. I question whether or not careful use would actually cause any damage. I would be interested in learning about manufacturer's test using the wheels wet with ACC.

I would also like to learn about these tests on the Tormek DWF-200 and DWC-200 diamond wheels. Although they are officially designed for only dry use with the T2, I have found that they work seamlessly with the T4.

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: RichColvin on December 16, 2018, 12:50:00 am
I seem to remember that CBN wheels work best at higher speeds than the Tormek (i.e., 1,500+ rpm).  I do know that certain grinding functions work best at high speeds and some work best at higher pressures (applied to the grindstone). 

In addition, diamond is significantly harder than CBN (like 2x as hard).  The reason CBN is used on grinders where high heat is generated in the grinding process is that diamonds can melt when used to grind steels at high temperatures.  CBN doesn’t do that, and that is why it gets used in many grinding operations.

In any regard, I’d tend to believe that Tormek have used research and good judgment to go with diamond stones in lieu of CBN.

Kind regards,
Rich
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 16, 2018, 03:55:23 am
Rich,

Both CBN and diamond wheels gravitate toward their optimal use. CBN, with its high speed heat tolerance, is used by turners with their high speed dry grinders and hss turning tools. If you watch Dave Schweitzer's videos, he prefers the 3450rpm eight inch grinders. With CBN and hss, heat is not really a problem.

The Tormek must work in several environments, from turning tools and planer blades to delicate carving tools. With its water cooled slow speed motor, it can handle the much harder diamond grinding wheels.

I started using CBN wheels with my Tormek before diamond wheels became available. If I was starting out today, after the SG-250, I would add one of the Tormek diamond wheels. In my case, I would start with the DC 360 grit coarse wheel. I have found it cuts more quickly than the 220 grit SG or SB wheel.
Eventual third and fourth wheels would be the other two diamond wheels. You pick the order depending on your needs. Frankly, I would not choose CBN or the SB today. I believe the Tormek diamond wheels have eclipsed them. Your thoughts may certainly differ; this is just my opinion.

I reshaped a new 3/4” spindle roughing gouge today. The bevel was steeper than I wanted. I reground it to 35°. That would have doable with the SG, but very time consuming. The DC did the job in a reasonable time. It was no speedster, however, it kept grinding. I could hear the grinding and watch the progress.

The SG can work with higher grinding pressure. The diamond wheels should always be used at low grinding pressure.

I think Tormek chose quite logically with diamond wheels.

For the record, I believe the Standard "Original" SG which comes with the Tormek is the ideal grinding wheel for most of us. For sharpening woodworking tools and kitchen knives, it does trooper service at minimum cost. For sharpening several kitchen knives occasionally or the home shop chisels and plane blades, I would find it difficult to justify the extra three dundred dollars US each for the three diamond wheels, unless one is a Tormek junkie.

Marie notified me that Tormek just placed more detailed information about the diamond wheels on the website. It is worth reading.

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 16, 2018, 07:48:41 am
I think Tormek chose quite logically with diamond wheels.
Ken

I quite agree.  Given that you don't have the melting-diamonds-at-high-heat problem, it would seem that harder diamonds are the way to go. 

It is worth noting that, if you do not need the flat sides of the Tormek diamond wheels, the 10"x2"x12mm CBN wheel that Woodturners Wonders sells in its "Spartan" line for the Tormek is $180, whereas the DC-250 is about $330. Also, the CBN wheel is available in 200 grit, which might be faster than the 360 grit of the DC-250 (it is difficult to say without trying them side by side).

Tormek recommends water with their diamond wheels but says that they can be used dry.  Woodturners Wonders says to use the CBN wheels dry, but it looks like they could probably be used wet (with a corrosion inhibitor).  If there are variations in the wet and dry cutting performance of the two abrasives, that too could be an interesting differentiator.

I have the CBN wheel and hope to get a DC-250 when Tormek gets the diamond wheels back onto the market, so I will be looking to see how they compare. 

(Ken, I think you have CBN and diamond wheels on hand, so perhaps you already have some views on whether you prefer one wet and the other dry, both wet, both dry etc.)

Gord
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: RichColvin on December 16, 2018, 01:38:03 pm
I like theses two charts from the new info that Marie mentions.

Kind regards,
Rich
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 16, 2018, 02:42:50 pm
Marie notified me that Tormek just placed more detailed information about the diamond wheels on the website. It is worth reading.
Ken

Like Rich, I found the new information on Tormek's site to be helpful--Ken, I think you have been asking for this for a while, perhaps you were heard.

I have made it into a pdf so that I could find it when off-line, attached.

Gord
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 16, 2018, 09:30:17 pm
I like theses two charts from the new info that Marie mentions.

Kind regards,
Rich

 Rich,
I like the tables, too. However, they don't tell the whole story. As noted, Diamond is the hardest substance by a wide margin. I have a DMT flattening plate specially designed for flattening sharpening stones. DMT has a reputation for quality, and I am sure my plate is no exception. It did a great job flattening my water stones and India oil stone. I made the mistake of trying to flatten my grandfather's two sided oilstone. I think the medium side is carborundum. The five dollar oilstone almost completely destroyed my two hundred dollar diamond flattening plate. The plate still works, however, most of its useful life is now gone.

Therefore, I would tread lightly with comparative hardness charts.

Ken
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on December 16, 2018, 10:26:16 pm
Ken's cautionary tale reminds me that an abrasive coating is only as effective as its bonding to the substrate.  CBN and diamond particles on a lapping plate or wheel will always be harder than steel (or sharpening stones) I target them at, but if I dislodge the particles, the target wins.  I would have expected the monocrystalline diamond particles on a DMT lapping plate to stay intact while flattening a silicon carbide stone, but evidently not. 

This makes me think about comments that CB and others have made about these "last forever" wheels: if you prong them with your tool, you might wish you had been working on a stone that you could restore.  Has anyone dinged one of their diamond stones yet?

Gord
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Ken S on December 16, 2018, 10:32:38 pm
Gord,

You are correct; I have been asking this question for a very long time. In fact, my question predates the diamond wheels by several years.

I keep a print copy of the handbook in my satchel. I often refer to it during quiet moments and have reread the entire handbook numerous times over the years. I have also loaded it onto my ipad.

Torgny Jansson did an outstanding job with the handbook. The SG grinding wheel is very well covered. Unfortunately, since his passing, almost nothing has been done to update the handbook. The SB and SJ wheels share only two paragraphs. The SB I purchased in 2010 has essentially remained in the box on my shelf. Whenever I have tried to use it, it quickly glazes and does not cut. The only reason I have kept it is because I know several experienced users who like it. I have found several alternative stones, the Norton 3X; CBN; and most recently the Tormek diamond stones. I freely admit that my problem with the SB is probably user ignorance rather than a defective product. Until Tormek decides to provide in depth information on the SB, it will continue to collect dust on my shelf.

I really like the new diamond stones, both the two 200mm and the three 250mm. Information has been lean, however, by using the ACC and a very light grinding touch, I have had very satisfying results. I welcome the new information referenced by Marie. The new Tormek diamond wheels are innovative; they deserve good support.

I would mention that Tormek has produced some outstanding videos. The pick of the litter is the turning DVD done years ago by Jeff Farris. I hope marketing will not "upgrade"it by only substituting a T8 and a new face. Jeff and the SuperGrind are as solid as ever, however, new grinding wheels and jigs have been introduced. Also, new questions have arisen, such as the 40-40 grind and the Alan Lacer skew. The turning DVD definitely needs a real revision.

Knife sharpening has also moved beyond the SuperGrind Jeff Farris stalwart you tubes.

I like the videos Alan Holtham has done, especially his outstanding DBS-22 video. We need more of them.

Yes, Gord, I have been asking this question for a long time. Actually, we seem to finally see some movement. I remain positive and hopeful.

Ken

ps I just read your last post. I have no expectations of any abrasive material lasting "forever". I do believe the Tormek diamond wheels to outlast the Original wheels long enough to be cost efficient. In my case, with a home shop and being 68 years old, I expect they will outlast me. I am happy with that, and consider them fairly priced.
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: Sigs on January 22, 2019, 09:01:37 am
Seems the only CBN wheels I have located are horribly expensive. Can buy 2 diamond wheels for the same price. We want the diamond wheels for certain HSS and ceramic knives.Why not just stick with What's available?
Title: Re: Why doesn't Tormek replace stone with a CBN wheel?
Post by: GKC on January 24, 2019, 02:30:07 pm
Sigs, I don't know where you have been looking, but there are certainly CBN wheels that are not twice the cost of the diamond wheels (try D-Way, Woodtuners Wonders).  But there are advantages to the Tormek diamond wheels, so they might be best for you.  There are supply chain issues, they are still out of stock in my part of the world.

Gord