Edge thickness for heat treating

S

sdw

Joined
Mar 28, 1999
Messages
246
How thick should the edge be for heat treating.Should it be at the desired thickness or should it be left a little thicker to help prevent warpage.I have taken mine down to the desired thiness and a 400 grit finish.I have had most of them warp,some worse than others and some not so bad at all.Thank you.
scott
 
If your doing your own heat treating, whether using a torch or heat treat oven, I would recommend leaving a fairly thick edge (about 1/8" or more)
I generally go to only about 2/3 finished dimensions before heat treating carbon steels. One of the real tricks to avoiding warpage during the heat treat is to run a normalizing cycle after you grind, and just prior to hardening. This will eliminate a great deal of warpage problems. It will require a bit more care when finish grinding, but the results are worth the extra effort.
Since I do a large portion of the grinding AFTER the heat treat, I only take the blades to 120 grit before the heat treat.

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ed just answered the qustion I was fixin to ask. Whew!! I was affraid I was leaving my edges too thick. Glad I'm doing something right! Thanks Ed!! Michael

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Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!http://www.nebsnow.com/L6steel
 
Ed, would you explain what you mean by a normalizing cycle?

Thanks,



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Hoodoo

The low, hoarse purr of the whirling stone—the light-press’d blade,
Diffusing, dropping, sideways-darting, in tiny showers of gold,
Sparkles from the wheel.

Walt Whitman
 
Normalizing is a stress relieving step, and should be accomplished anytime that stresses are introduced into the knifemaking process.
As it pretains to this thread....none of us can grind exactly the same on both sides of a blade. Many times when warpage occurs during the heat treat, it is a direct result of taking off more material on one side of a blade, or allowing one side to heat up more so than the other. The results often show up during hardending as warpage. Usually a blade will warp towards the side that had more material removed, or got hotter during grinding. For the steels I use, normailizing consists of bringing the blade to just critical, and allowing it to cool COMPLETELY in still air. This equals out the stresses, and will routinely cure the problem of warpage during the hardening step.
Take Care!

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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
 
Ed,
I did'nt do my own blades,they were done by an acomplished knife maker.I pretty much left them there and he did them.I do know though,that they were wrapped in stainless foil and they were placed flat and not on edge.I thought that maybe this had something to do with the warpage also.
Back to edge thickness,You say leave them fairly thick,1/8" or more.I am using 1/8" stock so I'm not sure I understand that.My edges were left at appx 1/64"to 1/32".Is that too thin for a 1/8"blade?
Also if the edge is left thick then hardened and tempered then back to the grinder,I guess extra care must be taken in order not to overheat the blade.Thanks.
scott
 
Thanks, Ed, for the great information.



------------------
Hoodoo

The low, hoarse purr of the whirling stone—the light-press’d blade,
Diffusing, dropping, sideways-darting, in tiny showers of gold,
Sparkles from the wheel.

Walt Whitman
 
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