hi, im new and could do with some advice on heat treating

N

Nath

Joined
Feb 4, 2009
Messages
3
Hi

This is my first post and i was wondering if you guys could give me some advice.

Okay basically a few years back i bought some 1080 carbon steel and fashioned my self a knife out of it using a hacksaw and files(yes it did take forever:rolleyes:). When i was researching how to heat treat it somebody told me that every knife makers first knife cracked during treatment, needless to say after spending the last few days hand filing the damn thing i got disheartned and put the project on hold.

however after being laid off recently i decided to get the thing finished while im not working, and here i am

so ive got the shape how i want it and ive filed the bevel the way i want it and as we speak im sanding it down

my questions for guys are

1. ive left a gap of about 1mm all the way along the cutting edge as somebody told me that if it filed to the final cutting edge before heat treatment i risk the blade cracking during treatment, is this true? should i leave the gap or should i have the edges meet? after heat treating it would it not be hard to file it down afterwards?

2. as ive said the knife was hand filed and thus has quite a few imperfections, e.g the odd deep scratch here and there(mainly on the handle area), could these scratches cause the blade to crack during heat treatment? if so is there any thing i can do to avoid this

3. heat treatment advise

now i did a lot of research on heat treatment, asked alot of different people and got alot of different answers

some people said use old motor oil, some said use pre-heated vegetable oil, and some said use brine

my question is could somebody advise a way that i can heat treat this blade with out any of the professional equipment, as i dont have a furnace what could i use as a substitute? should i just build a small fire or would a blow torch work?

what could i use as a quenching solution, it would have to be easily obtainable.

when i quench the blade do i do the whole thing? or just the blade?

how long would i hold the blade in the solution for?

4 tempering, would it be possible to temper the heat treated blade in a normal house oven? if so what sort of settings would i need to set it on?


well thats it:)

i know its alot of questions but if you could find your way to answering them it would be much appreciated

thanks for your time

Nath
 
I won't answer to the HTing aspect because I send mine to a professional service. However, in response to #2, get all the scratches out prior to HTing. It will make your life soooooo much easier afterward. Sand down to 220 and that will alleviate any chance of heat risers. The primary reason for the "first knives cracking" is usually due to overheating, quench fluid not pre-heated or improper (too fast) quench fluid. And yes, you can temper in a standard oven, but I would suggest using a thermometer (rated for baking) to verify the temp on the oven. The dials won't be accurate enough. I believe 1080 tempers at 400 for 2 or 3 cycles, 1 hour each, letting cool to room temperature in between.
 
I would go 425° for a bit more toughness. 400° could be just a tad brittle.
 
Before tempering MAKE SURE YOU CLEAN THE KNIFE. Personal experience taught me that 400 degree oil left on the knife from hardening really stinks up the house. Just juse a good scrub brush and dish soap to get all the oils off the knife.
 
I haven't HT'ed a darn thing but I have tempered some files down to make blades. I would start on the low end of the temp recommendations unless you know your oven is right, or you have a thermometer to check it, as TekSec said. If you temper at too low a temp, you can do it again at higher. If you temper too high to start with, the blade will be too soft and won't keep an edge as long.

The steel will turn a nice bronze color, this will polish right off. (which is kind of too bad, I think it looks cool!) Now sharpen it up and check the edge. If the edge is fairly thin, you can test it with a brass rod.

As for HT, get a copy of "$50 Knife Shop" by Wayne Goddard to learn some "home-grown" ways to HT high-carbon steel. Browse through the threads here for more information on "proper" HT; even if you do it in a charcoal grill and quench it in bacon grease, the sciency info will help you understand what's going on.
 
ok cheers guys, nobody got any advice on heat treating though

ive just ordered that book, is it anygood?

cheers

Nath
 
It's an excellent book, "The Wonder of Knifemaking" by Goddard is also highly recommended, although I haven't read it yet myself.
 
Nath,

Welcome to Bladeforums....:thumbup::)

Fill out your profile, who you are and little about your self?
And were your at? This helps some times to get better answers. ;):rolleyes::)

TA
 
Last edited:
My HTing book says to bring the steel up to 1575 to 1625 then quench in oil. The book from Wayne Goddard will be a good one for the basics. IMO (disclaimer to the purists), yes, you can HT this blade with an acetylene torch and temper in your oven. Will it be optimum, who knows. You may get lucky. The basic methodology is this. Heat your blade to the temp, how you know is guess work without the proper tools. You can use a handheld laser thermometer or look at the heat color (several charts on the web, I believe the color for this steel would be bright orange). Low tech quench for 1080 is automatic transmission fluid. Have enough to immerse the entire blade. Pre-heat the ATF to 140 to 160 degrees. Once your blade is up to temp, quickly quench. You go in tip first agitating the blade spine to edge, never side to side. Once quenched, wipe down (blade will still be hot enough to burn you) and place in a pre-heated oven at 400 degrees. James is correct, stay on the low side, you can always temper higher if need be. Heat for 60 min, let cool to room temp and heat again. Do this 2 or 3 times. That MAY get you a usable edge...
 
For my early knives I heated the cutting edge with a torch to where a magnet will not stick and then quench in warm oil. If you use propane you will need a couple to get the whole blade hot enough. The HT wont be perfect or ideal but will work. You need to get the blade thin enough where you can sand to finish because your files will not cut after ht. To test the HT just run a file over the edge (before you temper) and it should skate and not cut, this shows that the blade is hard and ready for temper.
 
Nath,

For HT, use any heat source available that will get to ~1500°F. A wood fire works, but you may need a leaf blower to get enough air in to get hot enough. Charcoal works, but it starts popping when you try to heat it with forced air. Since 1080 is a fairly simple steel, you can use a magnet to tell you when you are hot enough. It won't stick after the steel hits about 1420°F. Go a shade hotter than that, then quench. ATF works. Straight mineral oil is better. Dedicated quench oil is best, but mineral oil with a bit of silicon oil in it to cut surface tension is what I use.

Leave your knife in the quench oil long enough to get down to 140-150°F to let the hardening progress fully, then temper in your kitchen oven to at ~425-450. It will take you several knives to nail the tempering temperature, but this will be really close
 
Once you have the entire blade to temp (but not over temp) you quench it. okzj gave sound advice. Brine is faster than optimum, you'll run the risk of cracks or increased warping. Vegetable oil and automotive engine oil is too slow and you'll likely get some pearlite. ATF and mineral oil, preheated to 120-140 should work well.

If you pull the blade out of the oil while it is still above about 450 degrees you will be "under the nose" meaning the carbon isn't going to leak out of the martensite, but you'll still have austenite for a minute, which is ductile. This is the time to straighten any kinks with gloved hands. Once it starts to "set up" you need to stop. You'll never get it perfect.

25 degrees in temper makes a difference, and your oven can vary that much easily. I occasionally have overshoot on temper using my $3000+ PID controlled Lindbergh Blue HT oven, so you're really going to want to keep an eye on your kitchen stove. Two tempers, at an hour each is recommended.

Welcome to the forum. A number of fellows have now donated their time to your endeavor, we're entitled to picts when you're done....
 
thanks for the advice guys, its really is appreciated, I'll be sure to post some pics when its done, but ill probably wait and have a read through that book before a do anything just to get another point of view on the subject

thanks again

Nath
 
You must log in or register to reply here.
Back
Top