New guy heat treat question

[Pairomedicsfish]

Hi guys, I am very new to this! I have been consuming everything possible on making knives.....I made a trial/first blade from a circular saw blade, stock removal method.....when I wentto heat treat .....I used propane fired wood to heat.....my blade was affixed to a steel bar and placed into the swirling flame.....then my blade warped in several directions...what may have caused this? I will be putting together a proper forge, using brick and charcoal and forced air.....I want to continue with this hobby, but need some input

[Ray Rogers]

Do you mean a circular saw blade as in Skil-Saw? If so, there's no point in heat treating it at all as it will not harden. If you mean a saw blade from an old lumber mill then maybe/maybe not. The solution here is to buy a piece of blade stock from a knife supply house so that you know what you are dealing with. That way, you know exactly what is required to heat treat your blade because you'll know what type of steel you have and what condition it's in when you start (spheroid annealed).

Warpage is caused by unbalanced stresses in the steel. These stresses can be induced by welding (your blade was 'affixed to a steel bar') or by uneven grinding or uneven heating or by problems related to quenching (which you didn't do yet). To start with, you need to learn about annealing.

It's great to want to recycle old steel and keep the old skills alive like using a charcoal forge but without a teacher right there with you these things become something better put aside until you've mastered the basic skills. Buying some steel and using a propane forge will remove many of the problems you are now facing. Once you have mastered forming and heat treating your blades you will have learned enough to know how to evaluate a piece of salvaged steel so you can tell if it will be good blade material and have an idea of how it may be successfully heat treated. A propane forge will provide constant, even heat without all the intricacies that go with building and maintaining a truly hot fire with coal.

We generally recommend that new makers start with kit blades. There's less up front investment this way, you learn valuable skills like how to attach, shape, and finish a handle, and you're more likely to end up with a usable knife. Please give it some consideration ....

[C Craft]

It warped because of what the steel was. As Ray said it is much easier to work with a known steel as you will know how to handle the steel as far as the different operations you will preform in the making of a blade.

The steel that the body of the newer circular saw blade or even that of a larger bodied blade such as the of a table saw blades are made of are a composite of steel. They are of low quality steel. Most blades now day are carbide tipped and the body of the blade is the cheapest part. You can weld a strip of carbide to most anything and as long as the carbide is sharp the piece of steel it is welded to can be a cheap steel. It is not exposed to the same things such as wear and heat build up as the cutting areas are!

Take a skill saw blade on the saw and dull it and then you will begin to get heat build up, once the heat builds up the body will eventually warp and I have seen some that warped extremely bad.

Practicing on unknown steels for learning to grind blanks and bevels is OK but getting a quality finished product is basically a crap shoot.

Learn all you can about making a knife, and when you feel you are ready go buy some good steel. It is not nearly as expensive as most people think and you can order from your PC if you don't have a place to buy it and they deliver to your home!

I know when I first was told this I thought that everyone giving this advice was just steel snobs, (in other words they didn't appreciate that I was using a cheap piece of steel). Actually they are your friends and are trying to head off a lot of heart aches!

Here is a much simplified version of a list I made for myself when I first started to help keep myself on track when working with simple steels such as 1080. Read it and take it for what its worth. It's not meant to be gospel but a guide to keep you headed in the right direction.



1. Forge or grind to shape

2. Finish to preheat treat level
Shape and rough finish all components of the knife such as bolster, handle, etc., etc.
leave blade edge thicker than finished edge at this point

2a. When forgeing --- normalize X 3
Normalizing is done by heating to about 100*F above critical
(red-orange or non- magnetic) and air cooling
(to reduce stresses in metal created by hammering and deformation of steel)

Heat to (orange ? red) and allow cooling to air temp X 3

3. Heat treatment
Heat to non-magnetic approx 1450* and quench in appropriate quench medium.
(This depends highly on the metal you are using at the time)
Quench mediums and heat treatment ranges are sometimes supplied by the company
that supplies the steel, I.E. (Admiral Steel)

4. Temper
Take steel directly from quench medium to an already preheated oven, and heat at
400* for approx. 2hrs.
Making a clean patch on the tang will help you to be able to recognize the color
change from blue to light straw color more easily

5. Finish to final stages
sanding, polishing, and final fit for components

6. Final assembly


7. Final blade edge

[Doug Lester]

Another problem with mystery metal is that you can't know your steel. Different steels can require different handling. Lower carbon content can be heated above upper critical temperature, as long as it's not too much above, to assure that the carbon is completely disolved in the austinite without much worry about grain growth. You will also only have to hold at temperature long enough to heat evenly throughout In general, it could also require a slightly lower tempering temperature. The higher carbon steels, above 77 points, tend to have grain growth if heated above upper critical and also require a longer soak time to disolve the carbon between the upper and lower critical points. The alloy can also effect some of the above and that requres knowing the alloy. With mystery metal there is not way around a lot of testing, guessing, and hoping. With known steels you can refer to established data and be able to expect certain results from a certain heat treatment.

Doug

[Eli Jensen]

Don't feel bad though Pairomedicsfish! My first knife was a fillet/skinner (too thick to be a real fillet) out of mild steel. I think I ran that thing over a stone for hours frustrated that I couldn't cut squat.

[Pairomedicsfish]

Guys, thanks for all of the good information. I will start over.....first order of business is to order some steel....