cbn wheels for knife sharpening

[bobl]

Happy New Year to you all.
So, Ken and all other gurus, I need to ask you this question.

What is the best cbn grit to use for --- Knife Sharpening ?
I know that many wood turners are happy using lots of low grits. The standard advertised is a 600 grit wheel.
I need to know which is the fastest to sharpen a knife.
Is it faster the lower grit you go?
OR
Is it faster the higher grit you go. I.E. 600 grit.
This I ask for my slow grinder, the Tormek T7.

I look forward to all your replies.
Cheers.
Bob
( The Knife Grinder )

[Ken S]

Bobi,

Please do not group me with the gurus. I am being honest, not humble. My experience with CBN wheels is limited to 80 and 180 grit wheels. Both of these grits seem too coarse, in my opinion, for knives. I believe the standard diamond wheel with the T2 is 600 grit. My guess, with no personal experience, would be that 600 grit will put you in the neighborhood for knives.

Until you have a strong sense about which CBN wheel best fits your need, I suggest you lightly use the fine side of the stone grader on your SG-250. That will simulate a 600 grit wheel. Keep studying. You will eventually get a feel for what grit you want.

Ken

[Stickan]

Hi all and a happy new year!

For knife sharpening our SG-250 is the best way to go, If you got some nasty nicks you can use 220 grid and finish with up to 1000 grid before honing.

A CBN wheel with 600 grid will not be faster than a 220 grid SG-250 and a CBN wheel 160 grid means you must use longer time to finish.

Our diamondwheel on the T-2 works great for knifes but if you are a little nerdy thats not enough. I still use our standard machines for my knifes because I have better control and the leather honingwheel gives me a finish on the knife that is better than on a new expensive knife.

If you are a experiensed Tormek user you sharpen as fast on the T-4/T-8 than on a T-2.
I have met knifesharpeners that has been using Tormek for years and are doing it freehand. When I sharpen a knife with the jig they admit that they have not learned how to use the jig correctly, and that its faster and gives a better looking edge than they doing it freehand. Now, we have some very experienced knifesharpeners on this forum that do sharpen freehand with very good result but also say that they use the jig on more expensive knives.

My suggestion is to learn to use the jig, it will be a bit slow the first days but when you got the speed up it takes less than 10 sec to attach the jig.
Use the stonegrader depending the knife you are sharpening, if the stone needs to be fine or coarse.
If it takes more than 3-4 minutes to sharpen a regular dull knife you are doing something wrong. Maybe you apply to little pressure when sharpening and also when honing.
It depends not only on the grid of the stone but also on the operator.

Best,
Stig

[Ken S]

Excellent advice, Stig.

Ken

[RichColvin]

I don't hone knives :   I use the Japanese waterstone (SJ-250).  It works magic !!

Kind regards,
Rich

[tonylumps]

I might be wrong but cbn is for HSS .Just for kicks I tried to sharpen a wood chisel on the 600 GI have and it kinda clogged the wheel a little.Isharpened  a HSS Gouge and it cleared out .Maybe it was my imagination

[Ken S]

Tonylumps,

It is not your imagination. There is no universal grindstone. CBN is designed for harder steels. How well it works with carbon steel depends on the amount of hardening of the tool being sharpened. I have successfully sharpened high carbon Irwin Blue Chip chisels with 80 and 180 grit CBN wheels. Both are adequate for these chisels, however, the Tormek SG wheel leaves a slightly sharper edge. It also has a feel I prefer while grinding.

I noticed a difference with the CBN wheel between grinding into and away from the edge. If you are grinding in the vertical position, try using your jig in horizontal. I found the process took longer in horizontal took longer, but left a sharper edge. I did not think of checking for clogging. Give it a try.

CBN transforms the Tormek into a much more efficient tool for reshaping high speed steel turning tools. I have not tried it, however, I believe CBN and Tormek is the answer to our planer blade frustrations. I believe a CBN wheel is a very useful second wheel for those working with harder steels. I still see the Tormek SG as our primary wheel.

Ken

[tonylumps]

Ken you are right.No one wheel does it all.I ended up getting a 180 Git for my dry grinder because the 600 grit on the slow speed Tormek was taking longer to sharpen my gouges.But if I want an exceptional edge then I go back to the Tormek 10" cbn wheel

[Ken S]

You won't go wrong with a 180 grit CBB wheel for your dry grinder.

One of the ideas I intend to try with my CBN testing is using my eight inch 180 grit CBN wheel on the T7/8. Ordering a second steel reducing, 5/8", would allow the wheel to work with either thr Tormek or a high speed dry grinder.

Please keep in mind my bias: I have nothing against dry grinders; at my age I just don't want another machine. This is not the case for most members. The CBN wheels do run cool. I like the option of using it on either machine.

Ken

[bobl]

GUYS,
Dont get me wrong here.
I love my Tormek
I Love the wheels SG250 etc
My only problem is that I have to use a water bath to make it work.
I have a small van ( Fiat Doblo ) converted behind the passenger seats ( Its also my family car, the wife wont let me get a proper van )
I do not have a sink or room to be using containers of water.
I only ask about the C.B.N. because it is a dry grind.
I am a knife sharpener only.
That is why I liked the idea of the T2

All said and done, I am happy with my T7 and I know it is a great machine, I just want a wheel that does not need a angle master, seperate jigs or a water bath.
I think what I need is a developed T2 for high volume knife sharpening.
I hope you have not taken my comments in a negative way. I believe that Tormek can produce such a machine and would click in to a massive market if they focus on a developed T2.

What do you think Stig?

[Ken S]

Bob,

Would you please describe your work routine? I get the impression that you actually work in your van, as opposed to carrying your Tormek on location. Is that correct?

You do not need to use the Anglemaster. Used efficiently, the separate jigs are fast to set up and give very uniform results.

A couple of quart or liter plastic bottles and a turkey baster are all you need for the water end. If you remove most of the water (not all), you won't have a spillage problem. You should be able to get through a day without having to change water.

Please speak up if I am missing something.

Ken

[OBR]

Bob,

I also sharpen knives. For me it's at our small local farmers' market using a T7 with a SB250 stone. I second Ken's suggestion to use knife jigs. I have 7 knife jigs on my cart; and when a customer brings knives, I put each knife in a jig and set the angle. Because I've found that the fine grit on the SB250 does a nice job of bringing the edge back, I never have to change grit on the SB250. I can grind them fairly quickly. On a typical busy summer market session  in our resort town I will sharpen 60-70 knives in four hours. Most customers get their knives back sharpened before they leave the market. You get to the point with knife jigs that you put the knife in the jig, and by eye you can see how much you need to adjust the jig to grind at the correct angle. I always check though; it helps give the customer confidence. If I had a convenient space on my cart, I'd probably add a couple more jigs.

Curt

[Ken S]

Well stated, Curt. As a hobby sharpener, I could easily get by with one knife jig. The fact that I have four knife jigs and a small blade holder is due to being fascinated with sharpening, not actual need.

If I was in your situation, sharpening many knives in a short amount of time, I would probably have seven jigs also (and be wanting more! )

Working with a totally manual large wooden camera for many years, I followed the discipline of setting the exposure before I looked at my light meter. One time I went to Rome and intentionally did not bring my meter with me. We can train ourselves to do many things quite well by eye.

I set the protrusion of my bench chisels in the square edge jig by eye. I am usually very close to the mark I have made on my TTS-100 setting tool. My eye settings are close enough to use without checking; a degree plus or minus is not critical for my use.

When you set bevel angles, do you usually follow the existing bevel or use standard angle(s)?

Using your SB-250 blackstone graded fine, how frequently do you use the fine side of the stone grader to maintain the fine grit?

Thanks.

Ken

[OBR]

Ken,

I set the angle according to the type of knife with the help of the Anglemaster.

Your second question brings up a concern I have about the SB250 stones. Yes I can sharpen every market day for 4 hours without having to change the grit or even resurface the blackstone with the fine grit of the stone grader. However, by the end of the market the stone will be significantly out of round. Knives sharpened at the end of the market on the oval stone do seem to be just as sharp as knives sharpened earlier after the stone has been trued.

When I re true at the end of a day's market, I am losing a lot of stone as I true back to round. I find that a stone will last for a season (June-Dec.), about 1000 knives. I've had 3 SB250 stones over 3 years. They all have gone out of round on a weekly basis, and end up about 7" in diameter by the end of December.

Now I'm ready to replace my current stone, and I'm seriously considering a 10" CBN. Even if a CBN only lasted 2 years, it would save some money and time. But I really like the fine grit on the SB250. Is it really a 1000 grit? Would a 1000 grit CBN wheel work as well as the SB250 does? I've been following the discussion on this strand of the forum with great interest.

I so appreciate hearing the experiences of you and others who have been experimenting with CBN wheels. I'm likely to join you.

Curt

[Elden]

   The old adage says, "Time is money." Thus the following idea might not work for one in OBR' s position.
   I know Ken is a proponent of light frequent truings of the wheel. Would a wheel last longer if it was carefully dressed often before it gets so out of round? One has to reset the US bar which takes time, but a second US bar set up for the truing tool could be utilized. From my position, the old adage "What is time to a hog?" applies to me!