Need HELP - Blades Failing Brass Rod Test

T

tejas7

Joined
Sep 14, 1999
Messages
92
I really need a little technical advise. This past weekend I tempered some O-1 blades (hunters) in a new oven (old oven, new to me). As usual, I started out tempering the hardened blades at about 350 degrees. They were a yellowish color as expected.

I did the brass rod test with a 1/8" rod as opposed to the 1/4" rod I have read about. The edges chipped out very easily. Well, I kept going and tempering at progressively higher temps. I quit last night at about 410 degrees. The blades were just starting to look a little purple. The sharpened edge still chipped a little bit.(By the way, I left the knives in a pot of alcohol and dry ice in my freezer for 12 hours after the second temper.)

My questions are: 1)am I just not tempering the blades hot enough?

2) Am I using too small a brass rod?

3) What Rc is a 0-1 knife edge when tempered at 410 degrees+? I am afraid that I will get them too soft and not hold an edge well.

I could really use some practical feedback from some of you much more experienced blade makers and finger cutters!

P.S. - I need to get these things finished. I will sell them on consignment at a local gun store and the gift buying season is upon us.

[This message has been edited by tejas7 (edited 29 November 1999).]
 
Sounds to me like you've got the right idea on the brass rod test. I dont think the diameter of the brass rod makes a significant difference. The 1/8" rod just flexes a little smaller portion of the edge at one time than the 1/4" rod.

O-1 tends to be a little more brittle than steels like 5160 due to higher carbon content and other alloys. I think a draw temperature of at least 450 F will be needed to keep the edge from chipping out. If you haven't already done so, you need a good oven thermometer to gage your temp. Never rely on the oven setting to be accurate.

Any way you have the right principal in mind on the brass rod test. When the edge chips out you just keep raing the temp 25 F per session until the edge springs back instead of chipping.

Hope this helps,

GaryB
 
I temper my blades at 425dg (oven setting) 3 times, 2hrs each time. they pass the 1/4" brass rod test. Results back from a deer hunter, said the edge holding was excelent:-).
 
Thanks for the input. I will try running them at a higher temp tonight. Just out of curiosity, what color is O-1 at 425 degrees.
And, what Rockwell hardness does that work out to be?
 
I would try a 300 degree stress relieve for an hour, then the dry ice, then temper as usual. And as tejas says, if that dont help temper at a higher range.
 
Man, are you guys gonna get asked alot of heat treating questions in a couple weeks. I should have my oven by then. Hehehehe!!!!

------------------
"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!"
 
You must log in or register to reply here.
Back
Top