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Tool sharpening - strange behavior?

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Tool sharpening - strange behavior?

#1

Tool sharpening - strange behavior?

GaryMc

>Fellow over on Woodnet suggested I post this here, in hope of an answer.

After 30 years of woodworking, I am finally getting into this lathe thing (at least the tool sharpening part) and finding a couple of unusual things. I have the Conover book and several book-length articles from the internet (mostly from Brits), a Woodcraft slow-speed grinder with dressed wheels, a homemade Wolverine-style jig for each wheel, and the Veritas tool rest. Tools include the HF carbon-steel set ($9.99) and the HF HSS set ($30).

I started practicing on the carbon-steel gouges, round-nose scrapers, and skews. Didn't have any trouble reshaping the nose angle (per the books) and sharpening to a knife-edge without burning. Used the 60-grit wheel only for initial shaping, 120-grit for sharpening, and used very light pressure with quenching after each pass. 1000-grit slipstone removed the burrs. Tools would smoothly cut an ash spindle used as a test piece, without tearing.

On to the HSS tools. I found it was far easier to burn the gouge edges than was the case with the CS using the same technique, although the books say the opposite should be true. Specifically, I tend to get a tiny bit of bluing at the edge, at the end of a "roll" in the jig. Also, the HSS edges did not seem to "feel" as sharp as the CS ones, nor were the cuts quite as smooth initially. Of course, the harder steel edge lasts longer as expected.

Are these observations normal? If not, do I have a bad batch of the "famous" HF tools, or what am I doing wrong? I hesitate to buy any good tools, or attack a fingernail gouge, until this is resolved.

Re: Tool sharpening - strange behavior?

#2

Re: Tool sharpening - strange behavior?

Dave Peebles Lyons, Ohio!

>Hi Gary,

I think your results closely follow mine.

It seems that you can get a better edge off the Carbon steel tools. It just doesn't last as long. I still use a Carbon steel tool for my shear scraper.

As for the blueing on the HSS, it should not be a problem. It happens, in my experience it will not hurt the steel.It is the lasting effect of the HSS that makes them the better tools for turning. But the Carbon tools are sharper right off the grinder, for a few seconds. :)

Dave

Re: Tool sharpening - strange behavior?

#3

Re: Tool sharpening - strange behavior?

Greg W. in NC

>Gary,

Yes, you can typically get a better edge on carbon tools, as they are softer and don't 'chip' on the very tip, like the harder steel tools do. Like Dave said, the carbon tools are sharper.....for a few seconds.

The bluing edges really shouldn't be much of an issue. I'm no metallurgist, but according to the 'experts', HSS is tempered at 1,000+ degrees, but the bluing occurs at about 600 degrees. Thus, if you're not getting the steel in excess of 1,000 degrees, it won't change the temper. Personally, I've not noticed any difference in my tools when I've blued the edges. I do only use HSS (2030 or harder, actually), at least for about 90% of my tools.

Re: Tool sharpening - strange behavior?

#4

Re: Tool sharpening - strange behavior?

GaryMc

>Thanks, Dave and Greg. Actually, your response was confirmed when I re-read some of the articles from the net. Guess I won't be afraid of going on to bigger and better things.

Re: Tool sharpening - strange behavior?

#5

Joe Fleming

Re: Tool sharpening - strange behavior?

Joe Fleming

>Gary,

The other Gary is correct. Steel color is an indicator of temperature. While heating a carbon steel tool to blue will ruin the temper, under normal sharpening conditions, you will not heat your HSS tools hot enough to draw the temper out. "Blue" is just not hot enough.

As for the "better edge" discussion. That is a red herring. If you are grinding on a 60 grit or 120 grit wheel, you are not going to get a sharper tool if the tool is carbon steel. If you get out your waterstones and hone the edge to a mirror shine, then you will see the difference. And don't forget, that for this honing to work, you have to hone the inside of the flute as will as the bevel.

Joe Fleming - San Diego

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