CBN grinding wheels?

[Bill Boehme]

It is interesting to read all of the opinions about what is the best method of sharpening our lathe tools. Everyting so far has been subjective, no actual measurements of sharpness have been made or how long the edges last. The cutlery industry has a set of standardized tests for knives that measure, with numbers, how sharp an edge is and how it degrades with usage. Until we have an equivalent standardized set of tests for sharpness and durability, we will continue to express opinions and perferences. Without repeatable measurements yielding numbers that can be compared, this type of discussion will never estasblish the 'best' sharpening methods or types of tool steels. I will admit that reading about the different OPINIONS is interesting and instructive but this approach is unlikely to arrive at a solid defendable conclusion.

I'll have to agree with Odie. A good part of the time in my engineering career, I was involved with various types of qualification testing programs including writing test plans and specifications and there are two definite things that can be said regarding tests that attempt to quantify how well something will perform once it gets in the hands of the user:

1. The test methods are very rigorous structured processes that attempt to eliminate unknown variables and minimize uncertainties in the conduct of the tests -- and, because of that ...
2. The tests do not reflect reality in the way that something is actually used, but instead provide a quantifiable benchmark for the engineers and scientists designing a system.

Testing methods are not for the user community -- they are for the designers. Since you mentioned cutlery, the tests help refine manufacturing processes and selection of materials to achieve some specific level of performance. Presumably this translates to some degree into performance in the wild once the product is in the hands of the customer, but the customer isn't using the cutlery to conduct engineering tests -- what they are doing is using the cutlery in real world conditions where there is not somebody with a clipboard and wearing a white lab coat directing how the cutlery is being used. Because of this unending list of undefined parameters when used in the field, any comparison to the results of rigorously controlled tests becomes somewhat anecdotal to real world application.

Standardized testing methods has not led to things becoming cut and dried (excuse the pun) in the cutlery industry as far as the user is concerned. If it were, there would be no question about which particular product is best for some task regardless of the user's methods of using the product.

 

[Mark Mandell]

Good Explination

I'll have to agree with Odie. A good part of the time in my engineering career, I was involved with various types of qualification testing programs including writing test plans and specifications and there are two definite things that can be said regarding tests that attempt to quantify how well something will perform once it gets in the hands of the user:

1. The test methods are very rigorous structured processes that attempt to eliminate unknown variables and minimize uncertainties in the conduct of the tests -- and, because of that ...
2. The tests do not reflect reality in the way that something is actually used, but instead provide a quantifiable benchmark for the engineers and scientists designing a system.

Testing methods are not for the user community -- they are for the designers. Since you mentioned cutlery, the tests help refine manufacturing processes and selection of materials to achieve some specific level of performance. Presumably this translates to some degree into performance in the wild once the product is in the hands of the customer, but the customer isn't using the cutlery to conduct engineering tests -- what they are doing is using the cutlery in real world conditions where there is not somebody with a clipboard and wearing a white lab coat directing how the cutlery is being used. Because of this unending list of undefined parameters when used in the field, any comparison to the results of rigorously controlled tests becomes somewhat anecdotal to real world application.

Standardized testing methods has not led to things becoming cut and dried (excuse the pun) in the cutlery industry as far as the user is concerned. If it were, there would be no question about which particular product is best for some task regardless of the user's methods of using the product.

And now we can all understand the disclaimers in manufactures' warranty language [if you can read the engraving on the pin-head ] that relieves the company from liability for uses by the purchaser that were "unintended" or "outside the usual purpose" of the item. Darwin Award candidates are on their own.

 

[robo hippy]

Bill Nedow did an article within the last year or so for the AAW magazine on grinding wheels. We did chat a bit about the CBN wheels, and I believe I was the first woodturner to use them, but that doesn't really matter. They are a matrix type similar to the Woodcraft Green River diamond wheel. Our research with manufacturers of the wheels came to the same conclusion, that CBN is better for steel, and diamond is better for carbide. There is a You Tube video of Cindy Drozda showing it in use, and how she keeps the wheel clean by using an oil bath and brush to keep the wheel lubricated, and indicated that it does seem to work better that way, and does not load up. I should resurrect my old CBN wheels and give it a try.

Andre Martel (I think that is his name) sells diamond electroplated wheels up in Canada and has for years. He seems to think they work fine, but I have no experience with them, so no comment.

The electroplated wheels do break in. I can not explain it. Best attempt would be to say that the grit is friable, like standard wheels, but at a much slower rate, and after a time are broken into to the point that there is almost no more breaking in because of the hardness of the material. I have a friend who has been turning 6 inch myrtle wood bowls for 18 years, to the tune of about 700 or so a year. He has his process down to the second. He tried the CBN wheel, and didn't like it at first as it did not get as good/durable of an edge as his standard wheels (he does not hone). After having it for a few months, he said he liked it and was going to get another one.

Bottom line, they have huge advantages over standard grinding wheels, and in every category except cost. I will pick up one of the Optigrind wheels, and probably one of Andre's wheels at the Symposium to experiment with.

Dang, a curious mind can be expensive.

robo hippy

 

[Jim Carroll]

One thing to remember about the older guys who hone, started their turning career using carbon steel tools not HSS which are the norm today.

As Ian indicated the sharpening was done once a day and honing for the rest of the day, carbon steel is best honed and the habit of this has been brought through to the tools of today, Old habits die hard.

Carbon steel tools get a better sharper edge than HSS tools but lose that edge quicker so instead of wandering over to the grinder every couple of minutes to resharpen they got into the habit of honing

 

[AlanZ]

Jim said "Carbon steel tools get a better sharper edge than HSS tools... "

I'm wondering if this is also a holdover concept from times past.

With the modern steels (powdered metal, etc.) is Jim's statement correct, or out of date?

Inquiring minds want to know < s >

 

[Mark Mandell]

Simple Answer

Jim said "Carbon steel tools get a better sharper edge than HSS tools... "

I'm wondering if this is also a holdover concept from times past.

With the modern steels (powdered metal, etc.) is Jim's statement correct, or out of date?

Inquiring minds want to know < s >

Any and every steel that leaves a given abrasive surface will have the same edge scratch pattern and size, hence the same sharpness. It's the abrasive that determines the edge, not the metal. Softer steels may push up a "wire" or "false" edge that will quickly wear or break off. An 80 grit wheel will put an 80 grit edge on every steel it touches; no more, no less.

I suspect the myth come from someone noting that the crystalline structure of carbon steel is smaller than that in the "higher" alloys, thus inferring that it will take a finer edge.

 

[robo hippy]

While I am no metal science person, when this debate comes up about which steel can take the finest edge, the conclusion seems to be that they can all achieve the same edge, but some take more effort to get to that point. I would think that honing carbon steel would take less effort to keep the edge keen than honing V10 or V15 steel.

I do love my tantung tipped Big Ugly scraper. Almost as hard as carbide, and it can be sharpened. I did all the roughing on an 18 inch black locust crotch piece yesterday, and it didn't need to be sharpened once.

robo hippy