I bought a VERY old heat treat oven quite a long while back...

I'd like to check that it is reasonably calibrated before heat
treating this part. Is there some sort of thermocouple and high temp
wire I can buy and take a voltage reading? I only know of this
concept, not any specifics.

I made a custom bolt out of 4340 for my 30 ton shop press. Looks like
I should heat to 1525 and quench in oil. Then temper to 450. correct?
I'll use SHMBO oven for tempering (when she goes shopping)

Karl

"Karl Townsend" wrote in message
...
I bought a VERY old heat treat oven quite a long while back...

I'd like to check that it is reasonably calibrated before heat
treating this part. Is there some sort of thermocouple and high
temp
wire I can buy and take a voltage reading? I only know of this
concept, not any specifics.

I made a custom bolt out of 4340 for my 30 ton shop press. Looks
like
I should heat to 1525 and quench in oil. Then temper to 450.
correct?
I'll use SHMBO oven for tempering (when she goes shopping)

Karl

The accurate, inexpensive way is to buy a second-hand temperature
controller and some high-temp Type K thermocouple wire.
http://www.omega.com/ppt/pptsc.asp?ref=XC
http://www.ia.omron.com/product/69.html

Be sure you can find the controller's operating manual on line. They
can be very tricky to set.

You could put a relay in a box with the controller and plug the oven
into it. The controller's PID function reduces power as the
temperature approaches the set point, so the oven doesn't overheat.

I have similar thermocouples from a different local supplier. Don't
try to cheat on the temperature rating. Cheaper 1200F glass braid
rapidly turns to dust in a candle flame at 1500F.

There are also hand-held battery powered thermocouple thermometers
like my Fluke 52 but they don't usually go cheap.

jsw

Also -- note that the dimensions of hardened steel are larger
than those of the annealed steel, so make sure that your thread and
shank diameters are made with this under consideration. You certainly
won't be able to use a die to fix the size after hardening. :-)

If this is an ordinary bolt in a reasonable size, what is wrong
with buying one of the proper size and strength off the shelf, instead
of going to all this work? Or do you want to get some experience at the
hardening process?

Enjoy,
Don.

Shoot, I didn't allow for it growing. The only way I had to test the
1.5 by 16TPI threads was to put the whole 30 ton cylinder in the lathe
and try to thread it on. I ended up a bit tight. Took fiddling with
the old triangle file but finnally got it to spin all the way in real
nice.

This bolt holds the block on the end of the cylinder to bolt press
beak and other dies to. I just wanted it as good as i could get it. I
guess "as is" is good enough. I've never trusted my old heat treat
oven, guess it won't get used again this time.

Karl

I literally have a clothes basket filled with thermocouples. Most are
brand new in various configureations..with the majority of them being
metal covered platinum K type

If Karl wants a few..simple drop me an email and tell me what style etc
he needs

Gunner

Thanks, I'll take you up on that. I'm pretty sure my good friend Don
Foreman can find a way to read temps with it.

Karl

On 20/05/2012 23:55, Karl Townsend wrote:

I literally have a clothes basket filled with thermocouples. Most are
brand new in various configureations..with the majority of them being
metal covered platinum K type

If Karl wants a few..simple drop me an email and tell me what style etc
he needs

Gunner

Thanks, I'll take you up on that. I'm pretty sure my good friend Don
Foreman can find a way to read temps with it.

Karl

At 2000F a type K is giving you about 50 millivolts and you can read
that on an ordinary DVM. But a chinese thermocouple meter from ebay is
cheap and easy and should be accurate enough for your needs.