Secret to hardening double edge blades

D

Doc Hollywood

Joined
Jan 24, 2003
Messages
341
What is the secret to hardening double edged blades like the Randall Toothpick style blades?

Do you want a softer center or temper it differently?
 
Doc, The simplest way is to leave it abit thick and heat it completely in the forge. It helps to pre-heat the riccaso area with the torch or turn it tang first in the forge to keep from over-heating the tip while the ricaaso warms up. Turn it tip first and bring it up to nonmagnetic at the edges at least and quench in warm oil completely. Temper as usual. I am going to do my next one in a steel pipe with one end welded shut so air cant circulate through it and cause scale. I can control my propane forge so it will hold nicely at 1550 deg. and the pipe will give me an even heat soak. Im also going to quench it in Nitre Blue Salts at 450 deg. This has the advantage of being able to straighten the blade for several minutes after it quenches. It can remain in the quench for an hour and will will tempered. The quench will be lowered to 375 -400 for that hour.

In both methods the blade will need to be reground to finished shape andd thickness. Hope this helps,
 
about the differential temper on a double edge blade
I just finished one today.
I full heat treat and temper as normal then
I water tube the edges and draw the middle out with acetylene and
oxygen. I made a special water tube to do the double edger's:)
 
that Bruce forgot to mention, though I have not doubt he does it, is you must let the blade cool to below martensite finish, though not necessarily all the way to room temp., before putting it back in the low temp salts. Otherwise, you may never get martensite. Of course, you will get martensite whenever you pull it out and cool it, but even after an hour in the salts it would be untempered martensite.

John
 
I did a double edged dagger a year ago, and this is what I did,I took masking tape and taped about 3/8" up from the cutting edge all the way around the blade both sides. then I took fireplace cement that comes in a tube and coated the inside of the blade over the tape edges
, I put the cement on about 1/8 to 3/16 thick, then peeled off the tape, this left 3/8" up from the cutting edge exposed all the way around and on both sides. I let it set and dry for a couple days and then with a hot forge heated the blade until the cutting edges were at critical temp, then quenched the whole blade, the cement came off easily and I had a great temper line all the way around.

It worked good, I've used the cement on several bowies and it makes for a real good temper line and helps keep the longer blades from trying to warp.

Hope this helps

Bill
 
This is my first attempt at a double edges blade. A buddy of mine has put in his "order" for a Randall style toothpick blade, and short of the heat treat I was not terribly afraid of the project. I just couldn't figure out how I was going to leave the center soft and the edges hard.

This is gonna be fun, and looking at the work that everyone here has posted I know I am amongst the right folks!!!

Doc
 
Doc, welcome to this great forum, you certainly are among the best folks! We're looking forward to your finished project!

Dave
 
I am planning on attending the Lonesome Pine Forge Hammerin in March (I think in march....will check site), and the Tannehill Hammerins (both the blacksmith and Batson bladesmith meets). I hope to meet some of you good people there!

I appreciate the information, and the welcome. Will be posting some stuff as I can get things done here. Trouble with a pinched nerve (neck) has slowed me down a bit, but persistence and plain ole meaness is getting me up off my rear end!

I have read posts back for about 150 pages and appreciate the information greatly. Looking forward to alot more good stuff from you fine people.

Doc
 
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