In article , Ed Huntress
wrote:

"JoanD'arcRoast" wrote in message
. ..
In article , Ed Huntress
wrote:

"Buerste" wrote in message
...

"JoanD'arcRoast" wrote in message
. ..
I shape my wood lathe tools by hand, and then heat treat in a campfire
and quench in used motor oil.

I have access to LN2, but wonder if it would make a noticeable
improvement of the O-1.

I know I will encounter inefficiencies due to Leidenfrost effect, even
if I pre-chill the steel to minus 80 C. (Perhaps I can roto-vac to
make
slush, I'll have to explore that.)

Opinions?

Do you think my methods are too primitive and hit-or-miss to achieve
better sharpness and edge retention on the lathe tool?

Am I barking up the wrong tree? Would the little extra hardness gained
not be desirable for this application?

Pointers? Links?

Thanks for taking the trouble to read this mess,
-j

I've heard from experts that cyro is smoke and mirrors. The best thing
said is cyro provides superb stress relief. Your application and your
level of correct heat treatment limits what you can do. Send stuff out
to
a heat treater. Your expectations are too high for home-brew.

Ah, guys, I think you're being trolled, if you haven't noticed.

JoanD'arcRoast is roasting you. d8-)

--
Ed Huntress


No Sir! Not trolling. Long-time lurker; I love this newsgroup! Probably
the widest range of practical, hands-on skills I've encountered in any
newsgroup, ever. Some folks with book knowledge, but a lot with long
hard-earned experience -- and I respect that.

I'm sorry if my questions are naive; (but dammit, Jim) I'm a 54 y.o.
carpenter and a woodturner, not a real toolmaker.

I was reading:
http://www.efunda.com/processes/heat_treat/matl_modify/cryogenic.cfm
and got the light-bulb over my head...

My wife runs a well-funded university lab, and offered to let me come
in over vacation some night and waste a buck or two of LN2. She's got
twenty years' experience, and her boss likes me... so I thought I'd
pick the group's brains about the O-1 steel hardening.

Cryogenic treatment of steel is well-accepted for certain applications;
I was simply asking whether it seemed feasible for my purposes...

-j

(If I was really trolling, I'd post OT political junk for Cliff and
Gunner to fight over!) :-)

For starters:

The first question that comes up is how you're reaching the transition
temperature (minimum 1475 deg. F) for O1 over a "campfire." You need a
strong, controlled natural draft or a forced draft, not an open campfire, to
heat treat using wood for fuel. So I don't understand how you're doing any
hardening at all.

More like under a six-foot diameter bonfire in the coals for two hours.
No earthly notion of the temperature, but it was glowing orange-red.


Second, if you know about the liedenfrost effect, you should know that used
motor oil is going to have enough contaminants in it to create a vapor
jacket around your workpiece when you quench it -- liedenfrost on steroids.
You could hardly choose a worse quenching medium.

Okay, I need to improve the quench oil. Besides, it caught on fire. Two
gallons is not enough... Pretty funny, at the time.


Third, the only rotovac I know of is a carpet vacuum. d8-)

Considering all of that, it looks to me like someone trying to troll up a
mess of time-consuming responses. If not, then we should start at the
beginning.

O1 is a fairly simple steel that doesn't, to my knowledge, have much
tendency to retain austenite. So the value of cryo treatment is likely to be
marginal. There are bigger problems with your process that could make a big
difference in tool performance, however.

First, improve your heat treating. Wood produces too much steam, which will
oxidize your tool surface and possibly decarburize it. For tools the size
you're talking about, you should be able to arrange firebricks into a
temporary furnace with two holes for a pair of propane torches. That's what
I use. And get some Tempilsticks, at least one for 1500 deg. F, so you can
tell when you've reached hardening temperature.

Thanks for the suggestion, I didn't know they existed! Very cool!

If you do a lot of this,
make or buy an electric furnace. One the size of a breadbox should do it.

Second, get a real quenching oil -- or use water, which shouldn't give you
any trouble with O1 shaped into wood-turning tools. The oil will last a long
time and you don't need much of it, so get some when you can. It will be
safer for your tools than water.

I'll look into this.


Third, if you're having problems with tools breaking, then double-temper
them. That's easier and should be tried before resorting to cryo treatment.

Make sure you have good instructions for hardening and tempering, because
O1, although not critical in the heat-treat department, will give the best
performance when it's heat treated properly. It is a steel grade that should
have some heat-soaking, at around 1200 deg. F, maybe for 10 minutes for
fairly thin lathe tools, before raising the temperature to 1475 - 1500 deg.
F.

Watch out for decarb. You can try covering the tools with soap, which I've
never tried but which some people say works very well.

Okay.


Temper IMMEDIATELY after quenching. It's best to use a kitchen oven, because
you'll want to temper for at least a half-hour to get best performance from
the tool. Preferably several hours for ultimate strengh.

I wouldn't waste my time with cryo treatment for an application such as
this, because there are other things that need attention. Concentrate on
getting the heat, quench, and temper within standard specs. Here's one set
of specs for O1. They sound familiar, but I can't swear to them:

http://buffaloprecision.com/data_sheets/DSO1TSbpp.pdf

Nice info there, thanks.


If your tools break or if the edges break down very quickly, and you know
you're heat treating within spec, then you should consider cryo treatment.
But it's unlikely to have nearly as much effect as getting your heat
treating procedures right.

Good luck. And if you really are trolling, you just roasted me, too. d8-)

--
Ed Huntress


Yeah, I see now why I look like a troll. My heat treatments are so
sloppy and slapdash that even thinking about cryogenic treatment
borders on the ludicrous.

Thanks for your trouble,
-j