Differential tempering

S

SDMatteson

Joined
Oct 3, 1998
Messages
94
I am in the habbit of cutting up 10 in.
circular blades into various blade shapes
for my personal use.I use a modified barbecue
grill to harden and my oven to temper.Only
problem is , the whole process is my best
guess.Should I oil or water quench?I try
to temper about an hour at 375 degrees F.
I would like diff. temper but don't know how.
As much help as you could give me would be
greatly appreciated Darrel.
 
Your saw blade is most generaly L6 material or
15n20 . Without a temp probe what I would do is get a good fire going, build the coal into the shape of the blade edge (mound one end if the blade curves). Then heat to red orange in the lighted dark just the edge and quench in 150 deg f or so trans fluid.
This is a good way to do an edge quench in your situation.. L6 is prone to cracking so make sure you pre heat your oil.. Let the blade set until you can just handle it bare handed. Then check it for hardness, Quench straight up and down. Keep it moving.. NOT SIDE WAYS! Another easy way is to heat the whole blade then quench,temper, hold the edge in water and heat the back with the heat going straight down playing the flame on the thickest part first . Preheat the riccasio area first because its thicker.. Bring the back to first blue.. This will give you a spring back hard edge. A dull file will skid on a hard edge about 60 rc..
There are many ways to do this . These are the less complicated ways I have seen..
You may want to change to truck spring. It is more forgiving in case of cracking...
 
Thanks Darrel , you told me exactly what I
needed to know. This information age of ours
is wonderful.If someone had told me 5 years
ago that I would someday sit in front of a
computer and get advice directly from a
maker of your caliber , I would have called
the boys in the white coats.
 
*blush*
ONE THING! Be careful - oils have a flash point and can burn you in a heartbeat.
Wear safty gear at all times

About the trans fluid. Its about a meduim quench speed and works great if you dont want to spend the money buying quench oil . Some use used motor oil. Its a slower quench oil.
I do recommend if you do this for a living that you buy quench oil.. But for playing and the budget minded person these will work fine.. Water will work on some carbons and water quench steel such as w2.. The water should have salt disolved into it until an egg or potato floats .. Hum sounds like a cookout eh! ALWAYS preheat you quench solution. I like mine at about 150 deg f.
If the quench is warmed it will bring the temp of the blade down faster and cause less of a shock to the blade also..



[This message has been edited by Darrel Ralph (edited 10-10-98).]
 
One other thing SD is if you are using the BBQ outside the natural light will not always be the same, therefore the red/orange color of the steel will look different almost every time. A good way to get aroung this is to have a magnet ready and when the steel gets to the right temp, the magnet will quit sticking. This is the temp that you quench in the way that Darrell explained. The magnet works the same every time on the carbon steels and gives you consistency. I started my knifemaking with saw blades also, and made many a good blade from them. Enjoy!
 
Thanks a bunch gentelmen.I grew up with a
cutting torch in one hand and the business
end of an arc welder in the other so at least
I know my way around hot objects a little.
I walked in our shop one day and saw my
Father dancing around on one foot trying
to pull the boot off the other.When I finally
got a hold of him we discovered a big drop
of molten steel had been blown onto his pant
leg by the torch , burned through, and fell
into his wellington right on top of his foot.
It made a crater you could drop a marble in.
I learned something that day .Never grab
daddy when his foot is on fire.Anyway , I
use circular saw blades because I wear them
out ever so often and cain't throw them away
because I see visions of Knife blades on
them.I have a big supply of red oak so that
is called on for handles . I have had problems with the steel cracking and now
know why.I will now try the magnet also.
I only try to make them for fun.I don't
think I would want to associate with anyone
who would want to buy one.Thanks again fellows!
 
Very good point Rob .I guess im used to the dark forge area I have. The color is second nature in the light there for me. Magnets do work very well .. and its consistant..


 
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