blue tools OK?

Frank Fusco

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Mountain Home, Arkansas
The friend who sharpened my bowl gouge and showed me how to use it also does professional sharpening. He says he grew up in his fathers sharpening shop and has been doing this for about 60 years. But, to qualify, he once sharpened a carbide table saw blade for me. After sharpening it burned the wood being cut. Pretty awful results. I didn't complain, just took to another shop and it is fine now. Enneyhow....while at his shop I mentioned that I am very careful to not overheat my tools when sharpening. I have seen other members of my woodturning club whose fine tools are blue from the tip to over an inch up the steel. Makes me cringe believing they are pretty much ruined. Well, friend says that with high speed steel getting hot to the point of turning blue doesn't hurt it at all. Says it is OK. :eek: I'm dubious. Also doubtful and skeeptikal. What say the jury? :huh:
 
I'm no expert, but since I have been in these forums I have always heard that bluing high speed steel does not hurt it but bluing carbon steel completely ruins it and you might as well throw it away.
 
I have a friend who is a professional at sharpening. Been doing it for 62 yrs. He said HSS and Cryo tools that have turned blue are not ruined. He said it take a heck of a lot more heat than can be generated on a grinding wheel to ruin a piece. Carbon Steel like Rich said throw it away if you blue it because he told me you have to grind past the blue and by the time you get there it will be blued again. He said buy a new one.
 
All I can say is .....and I really hate to admit it in public...it's a good thing HSS turning tools....turning blue doesn't ruin them....:eek:
 
Everyone's on got this pretty much nailed - HSS has to go well beyond blue before any damage is done. To prove this, blue some HSS, then take some fine sandpaper to the blue - it's only on the surface. With carbon steel, bluing goes pretty deep.

All of this makes perfect sense given the name HSS - Back in the days when there weren't many choices from high-carbon steel, machinists were swapping out cutters VERY frequently or they cut really really slowly. Both cost businesses money in time. So a solution was found - HSS - it could take higher speeds (a direct relationship to temperature) for much longer periods without losing its edge. Slowly, this trickled down to other industries like woodworking. Now it's become carbide these days - for the same reasons - longer lasting edge which translates directly to higher temperature tolerance.
 
Got to turn it red before you can de-temper it. It is the surface that is blued, run it across a stone and the blue goes away and so does your concerns. The edges created when it was blued is of little use as it will dull quickly but it is only a few molecules deep... True it is not good to heat the HSS when grinding but it is more durable than some will say. Takes 1444 (Cherry Red) degrees to disarrange the crystals in steel.

Or at least that is what I remember from class back in the dark ages...
 
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