What am I missing?

David Sharp

David Sharp

Joined
May 23, 2008
Messages
954
My heat treat oven is due this week so I am getting myself ready for the big event.

In many posted shop pics there is a toaster oven or in many HT threads a reference is made to a toaster oven or the kitchen oven. Why can't the HT oven be used for tempering?

All help is greatly appreciated.
 
It can be used for tempering in most cases. The trouble is that when your oven is running at 1500 degrees to harden blades, you will have to wait several hours for it to cool down enough to run a tempering cycle at 400, and several hours is too long to delay between quench and temper, the sooner you can temper, the better. I usually do a tempering cycle in my toaster oven immediately after quenching, about 40 degrees cooler than I am intending for the final temper. After that I do the rest of my tempering in the HT oven because it is more reliable and precise.
 
What Justin wrote is dead on. I would add two things though.
When allowing tue kiln to cool, let it go about a hundred deg.
below your planned tempering temp. before reseting and powering
back up...( so as not to badly overshoot the programmed temp.).

Secondly, use an oven thermometer in the toaster oven.
 
Also do not try to get your kiln to cool faster by leaving the door open,it will shorten the life of your coils.
And whatJustin and Russ said.
Stan
 
SBuzek said:
Also do not try to get your kiln to cool faster by leaving the door open,it will shorten the life of your coils.

Stan
Click to expand...
That, I did not know, although it makes sense. That's 2 good reasons to have to coils baffled from the main chamber, I guess.
 
Thanks for asking the question David. I plan on getting a kiln this autumn and I did not know that. I am kind of bummed cause I am getting not so stable temps with my toaster oven and was looking forward to finally having a way to do it right. :(
 
Letting the kiln cool is not a real big deal for me as I do mostly Stainless steels.I try to do my heattreat late in the evening and after plate quenching I go into cryo overnite,then the next morning I do my tempering.
Stan
 
Patrice Lemée;8410769 said:
Thanks for asking the question David. I plan on getting a kiln this autumn and I did not know that. I am kind of bummed cause I am getting not so stable temps with my toaster oven and was looking forward to finally having a way to do it right. :(
Click to expand...

That's why the first temper (in the toaster oven) is done at a lower temp. than the intended temper. It is just a snap temper to keep anything untoward from happening between quenching and the real tempering cycles, which are done in the HT oven. After the toaster oven I do 2 full cycles in the HT oven, so a total of 3, but the first is pretty much disregarded and should have no real effect on the final outcome.
 
what about all the crap left on the blade after quench ?

If you don't take the time to clean it off and repolish the blade, will it just bake on and be much harder to remove after tempering ??
 
Angus McGunnigl said:
what about all the crap left on the blade after quench ?

If you don't take the time to clean it off and repolish the blade, will it just bake on and be much harder to remove after tempering ??
Click to expand...

If the blade is properly hardened (in oil) most of the hard scale should have popped off in the quench. I just wipe the remaining oil off with a rag and go to tempering, any leftover crud after this should not be dramatically affected by the tempering so I don't see why it matters if you clean it off before or after tempering, unless you are using oxidation colors to judge temp.
 
I just use my kitchen oven for tempering, I set it up with pizza stones on the bottom and top rack for thermal mass, I put the blades on a rack that holds them an inch over a cookie sheet on the middle rack. I let the oven equilibrate from the time I start the HT kiln so all temperatures are even, no hot spots, the blade is centered in the oven well in from the corners of the cookie sheet so there are no convection hotspots, and there is no direct infrared hotspotting

-Page
 
I'm with Page, I use my kitchen oven. My Evenheat temperature has up to a 25 degree fluctuation even after it comes to temperature and idles for a bit. This swing in temp is only at the lower tempering range. My kitchen oven stays very close to temp., I've never seen more than a 5 degree increase.
 
NY and NorCal must not have the same temps as the desert of SoCal. I can't imagine running the oven for a couple hrs during the summer. I may be able to temper by setting the blade out in the sun.:D
 
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