Hi guys, I started working on a parring knife for the wife and I put a test piece of left over 1/8" thick 52100 in the forge and toaster oven when I tried to heat treat it and then temper.

sorry if the picture isn't as clear as it should be, I took about 20 and this was as close as I could get.  It kept wanting to focus on the vise instead of the blade.

I heat cycled them 3x, then went past critical and quenched.  Then I put them in the toaster oven at 350 for an hour.  After that I put them in the freezer overnight.  This morning I went out and put the test piece in the vise and put a crecent wrench on the end of it to flex test it and it broke very easily.  So Do I need to temper at a higher temp, or go longer?  Any thoughts would be appreciated.

Thanks

Glenn.

Tempering is a heat treatment.

What did you expect when you twist it with a wrench?

I was hoping that it would flex abit, then go back to straight.

 

52100 is not known as a flexible steel, its known for abrasion resistance

Thank you very much.  All of the different threads start to run together after awhile. I thought that I'd read somewhere about flexing it and having it spring back without breaking to test it.

Is 52100 suitable for making a pairing knife?

holds a nice edge for one, would be better for a shaving razor

what  is the  over night stay in a home freezer supposed to do ?

I would prefer a paring knife that is good and flexible.  I made one recently out of a bearing race that turned out to be very flexible and held a razor sharp edge very well.  I am planning on making a fillet knife the same way.  We'll see how well that turns out! 

7 hours ago, Steve Sells said:

what  is the  over night stay in a home freezer supposed to do ?

It is supposed to help the remaining austenite form into martensite.  At least that's what I've read a couple of different places.  Or is this one of those things that someone had an idea and then it got repeated around?...

that is NOT how you do cryogenic freezing, its about 130 degrees to warm for that

Try a web search for "cryogenic treatment of knives."

It takes some time and experience before you can sort through all the useless junk posted online and tell it from the real knowledge. There's a pretty extensive archive of blade making info here and a couple published authors are members. Steve being one of them. (Steve gives me a nice shiny wooden nickle for every 5 shameless plugs I make for him.) 

Frosty The Lucky.

 

What is he doing with his shameless that he needs to replace the plugs so often?

For a flexible paring knife I would look into L6 or perhaps a section of one of those 8"+ wide tree cutting bandsaw blades.

Giving me wooden nickle credits. No fair horning in my wooden nickle mine!

I was thinking 350 f. was too low. Make some test coupons and try drawing the temper farther. But, yeah a paring knife is pretty thin I'd try something more forgiving. Then again I'm not a bladesmith guy, my opinion is FWIW.

Frosty The Lucky.

Kevin Cashen gives some great info on heat tratment for 52110 (as usual) here: http://www.cashenblades.com/steel/52100.html , but does not specifically detail tempering temperatures, as these are variable depending on what ultimate hardness you are trying to achieve.  However, a quick 5 second google search has one supplier, specialty metals, recommending a minimum of two tempering cycles at a minimum of 400 deg. F.

As regards flexibility, a thin crossection will make your knife more flexible (1/8" thickness is very thick for a paring knife, IMHO).  Proper heat treatment and material selection will ensure that it doesn't either take a set after a bend or break while bending, but the actual amount of flex under a fixed load is proportional to the blade thickness for most steels, as far as I know.  Personally I don't know why you would want a paring knife to be flexible, but I"m sure we have different ideas regarding what an ideal paring knife will be used for.

Hi guys.  Thanks for the input, it is muchly appreciated.  I found the Dry Ice discussion from 2012, so I will skip the trip to the freezer.

I ended up bumping the toaster oven up to 400F and put the steel in for an hour, then tested with the crescent wrench.  It didn't break as easily, so I put them back in the oven for another hour at 400F.  This time I could lean on the wrench and it didn't break.  So I'll update my notes and call it good enough for now.

This is what I ended up with.  The handles are water buffalo horn.

 

Lar45,

A good source for a Dewer filled with liquid nitrogen can be found at hospitals and cryo-research  and / or medical and also bio-research laboratories. They are common at universities and hospitals.

Liquid nitrogen treatments take minutes instead of the hour or plus acetone-carbon dioxide  (a.k.a. dry ice) treatments.

A fellow would probably do it gratis or for a small consideration.

I am almost certain that they would not let you do it for yourself. 

It is very hazardous.

I remember us dipping a rose flower into the Dewer, for a second,  pulling it out and shattering it with one tap of a hammer.

The performance impressed the ladies no end.

AH,  gone are those good days!  Sigh.

SLAG.

p.s.  nice knife.

We got dewers of liquid nitrogen from our welding gas supplier.

In cattle country ask at your local feed store as it's used for AI (and that's not intelligence!) and they will probably know where to get it locally.

I broke down and bought "The Book"... Intro to knife making.  I sure hope they send the 2nd edition with the heat treat info.  I didn't see any option or info about which version the book was.

I've never handled liquid nitrogen, so I think I'll stay away from it, unless it looks like the blades need it, then I'll probably just go with a service.  Many years ago I built a 30-378 Weatherby on an  m1917 Enfield.  After all of the machine work was done, I sent just the barreled action to 300 Below for a cryo treatment.  They kept it for 30 days and said that the process helps to form tempered martinsite, and also releave any stress in the gun.  I should have shot it before and after, but I didn't think about it at the time and only shot it after.  It would shoot groups under the 1" mark and had several in the 5/8" zone.

the only differanse between first and second edition is the amount of typos, the second book is not available yet because I have not finished writing it

Also after 60 hours its just costing you money for the -300F cyro

Well I did manage to get an edge on it

It shaved the back of my hand very smoothly, so it should work on a tomato...

Must be some of those heirloom varieties---we don't shave the tomatoes we use out here!

I have never seen a harry tomato either, maybe they were already shaved when I got them ?

You chaps probably know that a kitchen knife can be sharpened too sharp.

Ideally the edge should some tooth  which helps cutting of vegetables etcetera.

I keep my paring and French knives to an 800 or 1,000 water stone grit and no finer. (1,200 or finer).

For people who are skeptical. Try cutting with a 2,000 knife edge versus an 800 blade edge.  The difference is noticeable.

Just Sayyin',

SLAG.