zero edge HT of oil quench blades

Knifemaker.ca

Dealer - Purveyor
Heat treated two today that were (inadvertantly) ground too thin - essentially zero edge - and both had an edge wiggle (warp) where the blade touched the blade rack. I'm thinking of dedicating a blade rack with short pns to such tasks. Any other suggestions most welcome.
 
As a rule in my shop, blades are left overly thick (especially at the edge) prior to heat treating. On blades 1/8" or less, I only profile prior to heat treating, and do ALL the bevel grinding AFTER heat treating. It's not uncommon for my blades to be 3/32"-1/8" at the edge prior to heat treating.
 
:) You can send me your blades for HT anytime Ed. (JK)

This maker knew he had ground too thin and asked me to try anyway. I guess I'm looking for hints for the tough ones. I managed to pull off a long thin carving knife a while ago without warping, but always learning from the helpful folk on this site. I have started turning down the agitation rate on the quench tank for 'at risk' blades. I am putting blades in the oven edge up. I use the evenheat blade rack - which I love - and I've now made some half height pins so they don't reach the edge if the blade leans over a bit.

I also had a maker recently explain the importance of North / South orientation of the quench tank - and he sounded like a physicist the way he explained why. It's a moot point because, as it turns out, my tank already faces magnetic north. :)

Really appreciate all the feedback. I'll keep offering here when I can and will sure keep reading.

Rob!
 
I place mine edge up in fire bricks that I sawed slots in.

Good idea.
I have a soft fire brick with grooves filed in it to hold the spine edge of the blades, cutting edge up.

This is my method as well, for for added security, like Ed mentions, I also try to leave them thick if possible. This also allows me to grind out any minimal decarb that may occur. In fact, I recently heat treated some small neckers where I didn't bevel the edge at all. Due to their small size, it really didn't take any longer to grind post heat treat, vs pre heat treat.
 
Turning the agitation down was a good call. There really aren't many places on most knife blades for vapor and bubbles to get trapped anyway. I think still quenching could also be a reasonable approach, especially with a vegetable oil quench, no vapors or boiling phases.

There's been a lot of debate on the magnetic north quenching, but it certainly couldn't hurt anything. I do it out of habit.
 
well yeah,... according to tradition, magnetic north is what to target for.. I built my whole shop aligned to magnetic north,.. forge, heat treat, even grind, sand, sharpen most of the time, (static charge, friction, electricity).... think shop alignment. Doing just about anything facing south is bad knife karma, unless you got a big magnet handy to pull things straight. LOL

... haven't had any serious problems with warping ever since.

"Knifemaking is an art - but there's a science to getting it right!" ;)
 
Last edited:
I wonder if the Knifemakers in the southern hemisphere should align to true south?:nothing:
Can anyone from Australia or South Africa help us out here?
 
I wonder if the electromagnetic field from the high tension power line adjacent to my shop might be causing my blades to warp during heat treat? :nothing:
 
Should the Coriolis effect also be considered when quenching?
 
What if I have a large neodymium magnet to the west of my quench tank?

Or what if I quench vertically? Then it's not facing north....

Or what if I turn my demagnetizer on before I quench....

so many questions!

:nothing:
 
All great questions. Don't stop now, KEEP GOING! Take something simple like lowering the temperature of an object and make is complicated!

...On a more serious note: The different "particles" which make up steel are not equally magnetic. I would reason that a degree of differential magnetic migration (Mm) occurs during heat treating. I have no interest in magnetic migration beyond that.

What if I have a large neodymium magnet to the west of my quench tank?

Or what if I quench vertically? Then it's not facing north....

Or what if I turn my demagnetizer on before I quench....

so many questions!

:nothing:
 
Last edited by a moderator:
Magnetic migration huh? So you're saying birds fly south for the winter because they have magnets in them?

Maybe I should quench in bird poop.

Will that make my blades light as a feather?



All great questions. Don't stop now, KEEP GOING! Take something simple like lowering the temperature of an object and make is complicated!

...On a more serious note: The different "particles" which make up steel are not equally magnetic. I would reason that a degree of differential magnetic migration (Mm) occurs during heat treating. I have no interest in magnetic migration beyond that.

What if I have a large neodymium magnet to the west of my quench tank?

Or what if I quench vertically? Then it's not facing north....

Or what if I turn my demagnetizer on before I quench....

so many questions!

:nothing:
 
Back
Top