1095 - temper questions (lots)

[Daniel Koster]

1 - Why do they say to temper immediately with 1095?

2 - I've heard it said that with other steels you can wait a little bit. What about overnight?

3 - Jim Hrisoulas mentions that in some situations, you might not temper at all. What would be the advantage of this and why would you want to do it?

4 - Tim Lively tempers (in his video) by holding over low-temp coals and tempering by color (rather than temperature). He works with the spine down, careful to not heat the edge directly...until the edge is straw-brown and the rest of the knife is blue. Advantanges over oven-tempering?

5 - Re-tempering blades: let's say I've tempered too hard and the edge is chipping. Can I simply temper at a higher temp and expect it to soften accordingly? Even if a day or two has passed? In other words, does tempering still "work" even days after quenching?


Sorry for the philosophizing so early on a Sat. morning...but inquiring minds need to know. :foot:

 

[David Schott]

I am less of an expert than you, but i've heard the 1095 right to temper is to avoid cracking...1095 i know is a testy little steel....i'd like to know for sure though. I throw em in the oven as soon as i can hold the blade in my hand long enough to open the oven and place it in...my easy way of ensuring the balde has finished transformation and dropped below 500...

Not sure why anyone would not temper...ive seen some makers selling neckers and slim slicers at full hardness, but I always forsee a small knife being used more often for prying, picking, torqing that would be a no-no for a blade, especially a thin one....

Ive also always wondered about torch tempering....why do we do 2, 2 hour tempers at 400 degrees if it seems a short torch temper as you describe is enough? I can't imagine that edge that they get straw with the method you describe is at tempering temp for more than a minute or two.....

As far as re-temper, i do it all the time. If a blade chips out in testing, I re temper a little higher until testing will pass the brass rod test. I dont think tempering the next day or week will affect that....

I guess I've always had the same questions as you, so im interested to see what the metalurgy experts have to say...

 

[mete]

Warning I'm watching a Roberto Benigni movie as I answer !! You can retemper at any time at a higher temperature. Oven temper is more uniform and thorough. Remember we recommend at least 1 hour at temperature.It's safer to temper all steels immediately. You can at times get away with not tempering with a low carbon steel [lath martensite].There are some high tech applications for not tempering but normally I'd like a nice stable microstructure just in case.

 

[son_of_bluegrass]

1 - Why do they say to temper immediately with 1095?

2 - I've heard it said that with other steels you can wait a little bit. What about overnight?

3 - Jim Hrisoulas mentions that in some situations, you might not temper at all. What would be the advantage of this and why would you want to do it?

4 - Tim Lively tempers (in his video) by holding over low-temp coals and tempering by color (rather than temperature). He works with the spine down, careful to not heat the edge directly...until the edge is straw-brown and the rest of the knife is blue. Advantanges over oven-tempering?

5 - Re-tempering blades: let's say I've tempered too hard and the edge is chipping. Can I simply temper at a higher temp and expect it to soften accordingly? Even if a day or two has passed? In other words, does tempering still "work" even days after quenching?


Sorry for the philosophizing so early on a Sat. morning...but inquiring minds need to know. :foot:

1 & 2: Everyone else is afraid that the blade, when quenched but not tempered, will spontaniously crack or shatter. I've not had that happen and have waited days. I have even started leaving them in the freezer overnight (it does improve the blade) before tempering. The steel is under stress when quenched, but from my understanding, if you don't bang the blade around and it doesn't already have cracks or poor design with stress risers, you should be able to wait a bit. Try for yourself as YMMV.

4: The only real advantage I know of with oven tempering is heat control. An oven heats to within some tolerance of the set temperature. Once you know your ovens tolerance, you can set and forget. When fire tempering light conditions and a discerning eye are necessary.

5: in a word: yes.

philosiphize away.

ron

 

[Whit]

I can't believe Mete let TikTock get away with spelling it "metalurgy"!!!

Just kidding Mete. I too appreciate your input, as always.

 

[David Schott]

You will see annoying spelling mistakes in lots of my posts from home. My keyboard is currently dropping keys randomly as I type...every 6th or so key doesnt register. I do my best to correct it, but its gotten so annoying, I have given up spellchecking. Oh well....i was an english major, too.....

English major.....
Job in the tech sector.....
Make knives....Go figure!

 

[Kevin R. Cashen]

Steel that is eutectoid or below (at or less than .8% Carbon) can often got a long time without the stabilizing effects of tempering, even go untempered entirely for the reasons mete pointed out. Even high carbon stuff that was not soaked for an extended period, such as those done with a torch or a forge (not knocking it at all, I have done more than my share in the forge) , can survive some time without the temper. But if you truly reached maximum hardness with 1095, you will have plenty of plate martensite that will require tempering ASAP, plate martensite forms in such a manner that it is capable of forming microscopic fractures throughout the steel where the plates intersect. Leaving this stuff untempered leaves the atomic stacking forced in an arrangement that nature never intended and the stresses are unbelieveable.

Some say I am crazy because I allow O1 to get cold before tempering, but then I martemper, but I have never went longer than an hour before I got the stuff back up to 400F. I have seen my share of self destructing blades, and you want them that way because you have a most thorough heat treat when they are, the tempering is what brings things to workable levels. It is a very critical operation because blades that are too hard will fail to hold a proper edge as well due to micro-chipping.

 

[brash]

4 - Tim Lively tempers (in his video) by holding over low-temp coals and tempering by color (rather than temperature). He works with the spine down, careful to not heat the edge directly...until the edge is straw-brown and the rest of the knife is blue. Advantanges over oven-tempering?

Sounds like he is tempering in a way so as to leave the edge harder than the spine, making the knife tougher (like claying). Whether or not it works, and how well it works, I have no idea.