Pre-HT Edge Thickness

[Rick Marchand]

How much are you guys taking your edge down to, prior to HT? I have been keeping them at about .060". After HT, I bring it to about .020" then put my final bevel on. (usually micro convex) How thin can you go and still HT properly. I am using an LP forge.

Rick

 

[silver_pilate]

Rick, I take both stainless and carbon steels down to 0.03" to 0.02" pre-hardening. Probably most are at .03". This is using a digitally controlled oven. If I were heating in a forge, I'd likely leave my edges a bit on the positive of .03" so I'd have room to remove any decarb/scale.

I've found that as long as my grinds are even, I normalize prior to heat treating, and I go into the quench straight, I have had very little trouble with warping. This is with plate quenching steels (CPM154, 440C, ATS34), fast speed oil steels (W2, 1095, 1084), and medium speed oil steels (O-1). As I said before, if I were heat treating in a forge, I'd probably leave my edges thicker pre-HT.

Then again, maybe I've just been lucky . I have had a few warp. One warped in the plates at the tip because I accidentally overlapped the folded foil over the tip. Another two were ground by another member. They were long, very thin (1/16" stock) O-1 kitchen blades. They both took very gentle warps. I had to stress relieve, straighten, and re-heat treat.

--nathan

 

[Bruce Culberson]

Rick,
With 1080 & 1084 I go to 25 thou, and on O1 I go to 35 thou before heat treating. On blades < 6" I rarely get warped blades, and over 7" I get some. I grind the 1080 & 1084 thinner because they don't get a soak - just brought to temp then quenched. On the small blades (<6") I go to 5 thou before putting the edge bevel on, and on the bigger blades that will see heavier use I go to 10 thou.
On my original camp knife that was O1 I got a warp (but I just did two more that came out of the quench straight:thumbup. On the original camp knife I heated the spine in the area that needed staightened with a soldiering torch until the spine turned blue - then quickly put it into a vise that was open a bit wider then the thickness of the blade and give it a quick pull to striaghten - then quench into water so the heat doesn't travel to the edge.
As my grinding improves I get less ans less warped blades (due to the grinds being more even)

Anyway take what I say with a grain of salt as I'm a weekend warrior when it comes to knife making.

Bruce

Here is a pic of the camp knife clone and a tactical camp knife:

 

[69_knives]

When I was playing around with canola oil for quenching 1095 I ended up with 2 or 3 blades that were underhardened. I sharpened them and finished them out with rubber or cheap wood, etched, etc. for learning experience. Later on, once I had proper quenchant I busted the handles off and redid the HT, I didn't bother dulling the edges down at all and I barely had to take more than a couple thou off the edge. On the flats there is still some decarb that can be seen but I'm going to leave it there because it's already a pretty thin hunter style and once the decarb is gone from the edge it will never be a problem again.

 

[wnease]

I'm not finding edge thickness to be a major factor in gross blade warping, though too thin causes my edges to wrinkle during quench. Most other makers tell me to grind the bevels in the hardened state to avoid warpage... good luck, I make blades up to 40" and often 1/2" thick, yes they still exhibit warpage in the thick sections, not necessarily at the edge.