M2 HSS bowl gouges
There has been a lot of buzz recently about cryo treated woodturning tools. I have had numerous emails asking me about them and if I'm using any of these new tools. I have been using C-treated tools for the last few years, long before any of the major tools suppliers began offering them to woodturners. There are many advantages to deep cryo treatment of tool steels, including these many benefits:
Note: Tools that are cryogenically treated are exposed to nitrogen gas at temperatures of 300 degrees below zero for a specific period of time. This changes the structure of the metal, increasing its wear resistance.
As many of you know, I continually test tools and products that may benefit woodturners. As a part of this testing, I began a series of long term tests of cryo treated woodturning and carving tools. This testing ended last year and spanned more than three years. A professional Cryogenic treatment company called 300 Below, Inc treated all of the tools in my test.
The tools were shipped to the facility, treated and returned to me. Most of the tools were unhandled, but some retained their wooden handles. Leaving the wooden handles on does not present any problems for treatment. However, the handles will darken slightly as a result of the treatment, but will not loose any strength per the manufacturer.
Tools included in the testing were standard M2 HSS before treatment and included bowl gouges, spindle gouges, scrapers, parting tools, skews and micro turning tools. In addition, Kelton Center Saver knives, (Standard and Jumbo) were included for treatment with some Arbortech Industrial carbide carvers and standard Arbortech steel carving blades. A few homemade tools were also included made from shock absorber rods from automobiles.
As many of you know, I'm a professional production woodturner and I turn large quantities of wood regularly. To say my tools see brutal usage would be an understatement. After having turned thousands of bowls over the last few years, and several thousand different other items, I'm keenly aware of edge life in woodturning tools. I'm also a habitual sharpener of my tools, stopping to resharpen at the slightest hint of the edge starting to fail.
Through the years, I have always observed the wear rate on my tools, so incorporating this testing perfectly dovetailed with my existing protocols. I should mention that I have almost every alloy you can get in a woodturning tool, including M2 HSS, M4 HSS, ASP 2030, ASP 2060, A-10, A-11 and V-15, not to mention various homemade tools in different tool steels. I'm a big fan of some of the newer tool steels and use them regularly in my studio.
I approached the testing using this standardized protocol: Two identical tools from the same manufacturer were used for each test. One was cryogenically treated and one was unchanged from how the manufacturer supplied it when purchased. The tools were sharpened with the same profile and bevel and were sharpened on clean, freshly surfaced stones each time they were resharpened.
Primary testing was performed on 60-grit and 100-grit wheels on a dry grinder and 240-grit and 1000-grit on a Tormek wet grinder. An additional subtest was performed on the Tormek with the 1000-grit edge honed to a mirror finish on the leather buffing wheel to approximately 6000-grit.
My testing was necessarily subjective, but I think most woodturners would agree that it's quite easy to tell when you've lost the edge on your tool. Each tool was used for a specific period of time, and the resulting surfaces were examined under magnification. Care was taken to insure that each test closely matched the other, including using blanks from opposite sides of the same log for each tool.
The testing covered 500 bowls and several carving blanks for the carving tools. The carving tools were tested with blanks that were bark free and a few that still had the bark on. Results of the testing are as follows:
Cryogenically Treated M2 HSS turning tools in every tested category outperformed the standard HSS tools, averaging approximately 250% greater (longer) edge life. That means you can turn with your freshly sharpened edge much longer before it needs to be resharpened. In my testing, up to 2.5X longer, depending on the base tool steel.
Test results with the cryogenically treated Kelton Center Saver knives produced an average edge life increase of 200%, vs. untreated knives. The Arbortech carbide carvers produced a stunning 300% better edge life when treated, while the steel carvers averaged 200% better edge life.
Does this mean that you should run out and buy yourself some cryogenically treated woodturning, or carving tools? It depends. If you're looking to replace some worn out gouges or carving tools, I would consider getting a cryogenically treated tool, if one were available in the type and size you needed.
Currently, only a few manufacturers offer woodturning tools for sale that have been cryogenically treated. Cryogenically treated woodturning tools are more expensive than the non-treated versions of the same steel.
However, you are rewarded with an extended edge life, which makes your tool last longer in the final analysis. Cryogenically treated tools are not necessary to turn wood, but they're a nice thing to have around in the studio, especially when turning through bark, or when working with abrasive materials.
The main factor for me is the longer intervals I can go before needing to resharpen my tool. In a production studio, time is money. If you're turning for pleasure, saving a wee bit of time at the grinder may not be a benefit to you. There are several manufacturers offering Cryogenically treated woodturning tools, so give them a look the next time you need to buy a tool, or when you are replacing a worn out tool.
I still recommend the standard M2 HSS woodturning alloy for most of your woodturning tools. It is the least expensive tool steel in the HSS range and it works very well in most situations. Look at these Cryogenically treated steels and the other high-end alloys like the powder metals as "task specific" tools that offer the advantages of greater edge life in exchange for a higher initial cost.
Safety Note: Always follow all manufacturers safety instructions before working with your lathe, or any of the tools or products you may use. If you are unsure about any operation, obtain competent professional instruction before proceeding. Use and wear all necessary safety devices during turning and observe safe woodturning practices to prevent accident or injury.
Steven D. Russell is a professional studio woodturner, teacher and writer. He has written numerous articles for international woodturning magazines, which have been published in more than 78 countries around the world. Steve has demonstrated in numerous cities across the United States. His studio, Eurowood Werks, specializes in bowls, platters and hollow forms with unique visual and tactile treatments.
Steve is also the current and founding President of the Lone Star Woodturners Association, Inc., an AAW member chapter. The LSWA is a 501(c)3 non-profit educational organization dedicated to teaching and demonstrating the art and craft of woodturning.
Steve is also a featured writer for the Guild of Master Craftsman's "Woodturning" magazine, published in London England. Woodturning magazine is the world's leading magazine for woodturners. Look for his articles covering technical topics, or project based articles in an upcoming issue.