Wednesday, November 27, 2013

A better edge

A good number of spinners turn their own wooden spindles with wood turning tools.  And in wood turning, very sharp tools are essential.

A group such spinners on Raverly were advocating "grinding and burnishing" as a way of getting a good cut with tools made of high speed steel. I did research on the topic, concluded that grinding, sharpening, and honing produced a much superior edge.

I reported my research, and was promptly bashed by big bunch of the spinners.  I gave peer reviewed citations that they did not bother to check.  I cited names of engineers /spokesmen at the tool making companies that other spinners did not bother to contact.  The spinners just talked to each other and bashed me.  I find this a typical MO for spinners.

In the old days, wood turning chisels were made of carbon steel (CS), which has good ductility and a fine grain size. Think of CS as having a grain the size of peas.  Modern wood turning tools are made of high speed steel (HSS). If CS has a grain the size of a pea, then HSS has a grain the size of tennis balls.  HSS has been used for industrial purposes since 1910, and is very well understood.  It came to the retail market as the hones needed to sharpen HSS became available in the 1970s.

A fine edge on CS does not last long when used for wood turning, so a common practice was to grind an edge, and  burnish it over resulting in an edge the thickness of a pea with a known cutting depth.  This can produce a good quality cut.   HSS that is ground and burnished results in a cutting edge the thickness of a tennis ball, but which is brittle and tends to shatter, resulting in a (microscopically) rough edge  that produces a poor quality cut. However, even such a poor quality cut is much better than "dull" HSS  that has not been recently ground or sharpened.  Grinding and burnishing is better than nothing.  And this seems to be where the myth of the spindle makers come from.

However, when HSS is ground to shape, properly sharpened, and honed, the grains are cleaved resulting in a strong, uniform edge that is only a fraction of a pea in thickness, and which produces a superior cut compared to CS.  I often make temporary tools from inexpensive HSS.  Ground, sharpened, and honed,  these very cheap tools can produce excellent quality cuts.

When I use a freshly sharpened and honed a wood chisel for a final cut, mostly, I do not even bother to sand.  Sand paper coarser than 600 grit will just roughen the wood.  Mostly I use sand paper when I am  fitting a tenon or snug box cover.

I grew up sharpening tools on bench grinders. I have an industrial tool grinder. However, I grind and sharpen my wood turning chisels on a Sorby Pro-Edge. Then, they are honed with a diamond hone. Yes, it is expensive, but it saves my chisels, it saves the cost sand paper, and not sanding reduces dust in the shop.  Special tools are ground to shape on the industrial grinder, but they are sharpened on the Sorby.  Then, they are honed by hand.

I also have CS scrapers that I grind on the industrial grinder and burnish. It is technique that I understand and use -- just not on HSS.

Five of the 10 best spinners that I know are also expert wood turners.  These 5, all hone their HSS wood turning chisels.

So why did that thread on Raverly  need to bash me?   Yes, I challenged them, but they should have done their homework and gotten their facts correct before I got there.  They were telling me that they had 20 years of expedience, and that I had less, so I should defer to their expertise. Twenty years is plenty of time to do one's homework.  Experts do their homework.

I know a limited number of  spinners, and most of them are so talented, and so competent, and so nice, that I do not understand how there could be a bunch of readers on a spinning thread at Ravelry without somebody saying, "Hey guys, honing HSS works!" or somebody backing me up on where twist is inserted in a flyer/bobbin assembly.



Gordon said...

I'm sure it was just due to an accidental oversight rather than deliberate dishonesty that you omit the fact that it was a well-respected professional wood-turner and spindle-maker who challenged you, not just spinners.

Aaron said...

Well-respected by who? If he burnishes his HSS scraper edges, I do not respect him.

If he makes spindles without being an expert spinner and able to test them himself, I do not respect him.

I know a "well respected" chef who writes, does demonstrations, and TV appearances, but who falsifies the recipes that he gives out. For example, I have seen him hide stock base in the cavities of poultry being used to make stock in live demonstrations with subsequent tastings. If you use the recipe that he gives you, you will NOT get the dish that he makes.

The point is that a lot of spinners read the thread, and did not bother to go get the facts. Some of those folks had access to a good university library. Some of those folks had access to professors of engineering that teach tool design and maintenance. Almost every local library has old Navy machinist manuals that tell how to sharpen HSS tools. And, Chris Pouncy / Clive Brooks at Sorby are expert, and have always been responsive.

I respect folks who have their facts correct and are willing to tell the truth.

Gordon said...

All he actually said was that it's a matter of personal preference. So all this flailing about like Lady Catherine de Burgh is ridiculously out of proportion. If you're going to throw hysterical tantrums every time anybody disagrees or fails to accept your pronouncements without question, however wrong they are, no wonder you're mocked.

And that was months ago. the expression 'like a dog to its vomit' comes to mind.

Aaron said...


In that context;

"it's a matter of personal preference"


"Do your homework and find the answer yourself!!"

There are many, many good ways to sharpen/hone HSS. Selecting one of them is a matter of personal preference. Or rather, it is a compromise based on available capital, tools, skills, and schedule. Given a particular mix of capital, tools, skills, and schedule there will be one combination that yields the best cutting edge. This is about how the edge is formed. The good teacher helps the student find that optimum.

The shape and polish of that optimum cutting edge will depend on the turner's lathe, chisel, the material being cut, and the direction of the cut. This is about what shape of edge is required to be formed by the grinding/sharpening/ honing (or burnishing) process selected above.

The honest teacher helps the student find the optimum shape and polish of the chisel edge for the project.

In this context; "it's a matter of personal preference" really just means that it is complicated. Despite all that complexity, there is still one optimum edge for the next cut.

Dfferent materials demand different chisel angles. Sorby gives me chisel angles for some materials, and I test chisel angles for other materials and write them in my shop book. It is not a matter of personal preference, it is a matter of what cuts a particular material faster and more smoothly. That is an objective measure that can be determined by testing.

CdB, would point out that you seem to have a better command of your slurs than your facts.

I encourage you to go out to the shop and make a thousand oak pirns, with a HSS scraper. It is calming. Take your notebook and pen, so you will return wiser. All in all, it is as good as time in a Shoalin temple.

Gordon said...

How dare Neal Brand do things differently in a way that suits him, and say that your approach is stupidly dogmatic and unlikely to suit everybody. THE SHEER EFFRONTERY OF IT.

Aaron said...


What you miss is that I do not care how Neal Brand does anything.

My approach to do things better, cheaper, faster. However I do something today is NOT good enough for tomorrow. Tonight I need to find a better way. Every night I need to find a better way.

This means that I have to constantly look back; a day, a month, a decade, a century, or a millennium. History is a good teacher.

One thing I do care about is the way to get the very best cut from a scraper. I need to turn very accurate whorls. Neal Brand is just not concerned about 0.1 mm in the diameter of his whorls. I am. I want a cut that I do not have to sand. Neal sands - everything.

That is not my problem. my problem is how can I turn stuff that is better -- than any I have ever turned before.

How you spin is not my problem. My problem is how I can spin better -- than any I have ever spun before. When I have done that, I shall seek to spin better. This is a cycle to be repeated.

I report what I am doing in the hope that it can help somebody, and they will return the favor by reporting a better way. Then I will drop my way and use the better way. What you miss is that I am always looking for a better way to do things.

You are playing games here, getting a little jolt of joy in your brain every time you think you have zapped me. OK, that is not my problem either, it is between you and St. Peter. You only prove that at least a few spinners are incessantly rude.

Gordon said...

So if that's the case, why get so ridiculously bent out of shape over him disagreeing with you in a particularly mild way over the sharpening of tools? Nobody else showed much interest in the matter.

Aaron said...

I try to document the best way I know how to spin or make spinning tools.

Very often that is a reference to AA's Big Blue Book. He does so many things, so well.

When I find a better way, I cross out the old and write in the better.

And while I really do not care how anyone chooses to do something, I expect them to teach honestly. I hate it when professionals use one technique in their work, but tell amateur students another technique that produces a lower quality product.

I have expensive grinders for sharpening my tools, and those tools are sharper and give better results. I discuss the compromises with my students and show them how to get excellent results with only an inexpensive bench grinder and some jigs.

I get worked up over burnishing HSS cutting tools because it increases wear on the tool for the quality of the cut. Tools are expensive. I encourage my students to take care of their tools.

Badger said...

If I read your post correctly, I believe you said that HSS Stella was not availabe until 1910and not commercially available until 1970 or thereabouts. Might I point out that, prior to the invention of the spinning wheel, all spinning was done on spindles which were made without the use of HSS and were perfectly suited to, as you call it "production spinning." Even after the invention of the spinning wheel, with HSS still not yet in existence, spinning the kind of yarns you find so appealing was done with skill and speed - again without the use of HSS. As a spinner of nearly 30 years, I judge thhe quality of a spindle by its performance, not by the tools that made it. You are mistaking the menu for the meal.

Aaron said...


My point was that with the use of a thigh roll, a whorl is not required for production woolen spinning of short fiber. And, that simple metal (copper, bronze, iron, silver, steel) rods make very good spindles for production spinning. The metals that referenced were bronze and iron alloys.

I do not disparage wooden spindles, I only say that in an industrial setting, simple metal spindles have advantages for short fibers. I put this in the context that longer fibers are easier to spin using a spindle with a whorl.

HSS allow wood turners to work faster and more accurately. That means better and cheaper product, e.g., better and less expensive spindles.

I judge tools (e.g.,a spindle or a spinning wheel) by its cost, durability, ergonomics, speed of product production, quality of product, ease of maintenance, and residual value.I am just as critical of the tools that I make.

HSS became popular for industrial tools prior to WWI. However, both the tools and the diamond hones were expensive. In the 1970's, both the metal and the diamonds became cost feasible for craftsmen and hobbyists. I pointed out that there are still myths around on how to sharpen HSS.

I would say that "production spinning" was an industry during the Egyptian Old Kingdom, and perhaps before, at a time when metal of any kind was rare.

Those old spindles were not perfect for production spinning or folks would not have invented driven spindles, great wheels, flyer/bobbin assemblies, mule spinners, cap spinners, ring spinners . . . .