O1 HT issues

[cutter189]

Hello-I am very new to the knife making world and have a question or two regarding the HT of a O1 blade I HT’ed and tempered the other day.

I made an electric oven that is digitally controlled. Heated my oven to 1000 F. Put my blade in. Let it climb to 1500 F. Soak for 10-15min. Quenched in 130 F veterinary grade mineral oil. Cutting edge first. Then gradually lowered the rest of the blade in the oil(differential HT). Then it was in the oven @ 400 F for 2 hours X2.

I have a friend who has access to a Rockwell tester and he said basically my cutting edge is at 48 and my spine and handle are at 53. Needless to say I am confused by this.

My questions are.

What could I be doing wrong?

Does my process look ok?

I am a stock removal guy and I didn’t normalize my blade before I HT’ed. Is this Ok?

Any and all responses would be appreciated

 

[me2]

For accurate hardness testing, the surfaces under the indenter must be parallel. If the hardness tests were done on beveled surfaces, that can account for a percieved loss in hardness. If a differential treatment is what you're after, the 53 rating sounds ok for the handle and spine. Again, make sure you know the parts tested were flat and the sides were parallel.

A good way to test your edge hardness is with a coupon. Take a piece of O1 from the flat bar stock and harden it like you did your edge. Do the same with a piece representing your handle and spine areas. Most O1 I've seen is supplied in precision ground bar stock, the perfect shape for making coupons for hardness testing and verifiying you heat treatment procedure. Polish the coupons like you would your knives, or at least get all the scale and stuff off before hardness testing. I'd say a 220 grit finish is fine enough to get accurate readings, but I don't have the standard test method handy. My first and only O1 knife was "tested" using coupons from the same bar stock. I was within one point of the desired hardness. Consistency is another matter, however.

 

[Deweyknives]

Did you use anything to avoid decarb? [foil or coating to avoid burning up carbon]
Are your bevels ground in?

You will not get accurate Rockwell readings thru a layer of decarb or on an angled surface such as on a bevel.

Not normalizing should not be a problem as long as you grind evenly and did'nt get any one spot extremely hot.

Read the 'stickies' at the top of this page [2 or 3 times]. Also, fill out your profile so we know if you're 15 and a student or a 50 yr. old machinist. Your knowledge & experiences make a difference in how to answer & what you may understand.

 

[LRB]

You definately need decarb protection. I use the ATP coating from Brownells with very good success. You just paint it on, let dry. I go over the lower 1/3 of the blade and edge with a second coat. Comes out of the oven and quench with mottled colors and a shiney clean surface. Any decarb is .001, to none. I finish my blades with the edge right down to finished thickness. You don't want to use foil. Takes too long to get it off, and will not allow proper hardening if you leave it on.