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pugsrok
04-25-2010, 11:59 AM
I have been told that the edge of a knife needs to be no thinner than the edge of a dime at time of heat treat. Is this true?

And What is the cheapest way to start heat treating by my self?

Bennie Lovejoy
04-25-2010, 01:01 PM
A lot of that depends on what types of steel you will most likely be heat treating.
Myself since I use a coal forge(about $40 invested the coal is free)I tend to use the easier steels such as 1084 ,1095 and 5160. They dont need a lot of time at a certain temp so I can use a color chart and magnet. A taoster oven is a good investment as well to allow you to temper after quench. Or a household oven if you don't have a toaster oven. All of this is assuming you want to go cheapest . If you have the money then there are several online tutorials to help build your own heat treat oven. ( sorry I don't have links to them). Good luck

Bennie

SBuzek
04-25-2010, 02:27 PM
Depends on the steel you use.If you use on of the 10xx steels you can heat treat with a one brick forge and propane torch.
If your doing stainlees you need a kiln or send them out.
Stan

pugsrok
04-25-2010, 02:29 PM
I am using 5160. So should i take the edge down some?

SBuzek
04-25-2010, 03:47 PM
Using 5160 about the thickness of a nickle down to about a dime is about right.You will have decarb to remove after H/T so it's good to leave it a little thick.
Stan

pugsrok
04-25-2010, 04:12 PM
ok, so that means i have to take some off the edge, atleast that gives me a chance to fix any mistakes :)

Fred Rowe
04-25-2010, 05:12 PM
In this situation you should error on the side of excess. Too thin an edge and your inviting warpage. Where as to thick an edge just means a little more grinding after the blade is hardened.
Very thin blades such as for folding knives are usually hardened before grinding the bevels but after the profiling is done.
5160 requires a soak time at temperature, buy the way.

I prefer grinding a hardened steel blade it seems to come off cleaner/sharper
than a steel that is annealed.

The thickness of a dime, .45 is a safe bet on most blades.

Fred

JDW
04-25-2010, 05:59 PM
Thickness of a dime or a little more is good, just remember that while grinding after heat treat, to keep the edge of the blade below the temp that it was tempered at, basicly if you have a color change from shiny steel, you are to hot. Go light on the pressure and keep it moving across the belt, then dip in water after each pass. The cheapest way to heat treat is probably the one brick forge, but I would stick to 1084, not sure if 5160 requires a soak at temp, if not it should also be good.
Hope this helps
Dale

Doug Lester
04-25-2010, 09:49 PM
It also depends on the size of the blades. Smaller blades can use a smaller fire to heat treat. Look at what you already have. If you have an acetaline rig all you have to do is get a rosebud tip and that can heat treat smaller blades. You can also build a forge out of a coffee can or from one or two insulation bricks and power them with a propane hand torch. Go to www.elliscustomknifeworks.com and click on the forge gallery to see some really basic small forges or you can go to www.zoellerforge.com and search that site. A charcoal forge is not hard to build, look up Tim Lively's site to get an idea of how to put one together. I have one that is made from a three gallon bucket, a one foot length of 1" blackpipe and adobe made from clay kitty litter, sand, pearlite, and a fist full of grass clippings as a fiber reinforcement. 5160 should be easy to heat treat. Try to keep the forge a little on the "cool" side so that you don't over heat the steel, bring it up to a cherry red, confirm non-magnetic with a magnet, soak for about a minute, then quench in warm oil. Try tempering at 400 degrees in an oven, as measured with a thermometer, for three two hour cycles allowing the steel to cool to ambient temperature between cycles. Of course you will want to test the blade for proper edge holding. If the steel is too hard, increase the temperature by 25 degrees and run the blade through another cycle. If it is too soft, reharden and decrease the temperature by 25 degrees and repeat the three cycles.

As far as how thick to leave the edge before tempering goes I think that it is more important to control the temperature of the forge or other source of heat for austinization than the thickness of the edge. I've had to re-heat treat blades after putting a edge on them and did so without warping. It is nice to leave a little extra on the edge though because you will want to leave a little sacrificial steel for the finish grind. Marquenching can also reduce the stress on the steel at hardening. If you are feeling froggy and have a steel that lends itself to the technique you could also try austempering. I don't have access to an ITT diagram for 5160 so I can't say if the technique is practical or usable with austempering.

Doug Lester

pugsrok
04-26-2010, 08:12 PM
Another question, how should i put the edge on the blade when i lack a belt grinder? after heat treat that is.

Justin King
05-01-2010, 09:49 AM
Another question, how should i put the edge on the blade when i lack a belt grinder? after heat treat that is.

If your HT is done correctly then the blade will be too hard to file afterwards.
You will have to go to abrasives, either stones or paper. If you use paper you want to use something hard to back it so you can maintain nice flats.

pugsrok
05-01-2010, 10:34 AM
If your HT is done correctly then the blade will be too hard to file afterwards.
You will have to go to abrasives, either stones or paper. If you use paper you want to use something hard to back it so you can maintain nice flats.

this will take a long time to do right?

Justin King
05-01-2010, 10:50 AM
this will take a long time to do right?
Probably, depending on the specifics. Ideally you want to take the edge as thin as you can get away with before HT to avoid extra work afterwards, but when first starting you have to leave it a little thick and experiment, once you have a HT routine that works for you, you can experiment and find out just how thin you are comfortable going.
If doing stock removal and HT'ing in an oven you can generally go a little thinner than if you were forging the blade and HT'ing in a gas or coal forge. The latter methods will result in more decarb and generally have less precise control of temps during HT so some extra meat on the edge is a good idea.
If you are doing stock removal you are using fewer heat cycles so decarb should be less of an issue, and if HT'ing in a good oven the more accurate temps will help minimize warpage.
Some of the exotic alloys and stainless steels are pure hell on abrasives after HT and also pretty much require an oven or salt pot to HT correctly, so with these you might have a somewhat different strategy concerning edge thickness pre-HT than with the 5160 you are using now.
At any rate using good-quality abrasives and efficient techniques will make it much quicker. I have found that abrasives tend to be very sensitive to changes in pressure and the amount of surface area of the workpiece that you are presenting to the grit. If you use too much pressure you just break the abrasive down prematurely.