tempering--more than 2hours???? please advise

T

timfish

Joined
Jun 4, 2022
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Hey yall--i got a question----At the moment, I only have an old toaster oven that gets to 400deg max---I heat quench a little past non magnetic- then in 125 deg canola--
I read that 1095 might be too hard if tempered at 400deg for 2 hours--twice---
so what would happen if I tempered it longer than 2 hours since my little oven wont get that hot?????
I have been making chefs knives---and TRYING some 1095 Fillet knives--man they can be a pain--LOL---

Please advise and THANKS
 
You probably want to temper around 500F. Unfortunately, longer time won't make up for the wrong temperature.
 
Time and temperature control the change in the structure of the steel. Temperature is at least ten times as important than time. Tempering 20 degrees higher makes a measurable difference in hardness. Tempering for five hours won't change much at all.

Get a copy of Larrin's book "Knife Engineering" and the tables will help you plan the best HT regime for the use of the blade.

I generally find people putting far too much emphasis on high hardness, while ignoring the lower toughness. A properly HTed blade at Rc62 may easily outperform one at Rc 65 in real world use.
 
It seems that folks like higher hardness these days than 10 yrs or so ago. It "seems" like I remember 60 Rc was considered a good "high" hardness back then while these days it seems like at least 62 Rc is considered the desired hardness. Do I remember correctly?
 
Yes, if you read a post of mine from 2000 you will see I suggest Rc 59-60 as a good hardness. Better steel and allows and well as better equipment and studies by folks like Larrin have increased the usable hardness. The problem is that folks using a forge to do HT and a kitchen oven to do tempering are trying for Rc 65 blades. That takes a lot more precise control. Larrin's charts are done with lab equipment and a lot of skill and experience.
 
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