Need a little advice.

[Woodswalker]

OK
I made three knives yesterday two of them were smaller knives made of an old circular concrete cutting blade and one bigger one from a husky chainsaw bar. I hardened them with no problem but when I put them in the oven at 350 for an hour it didnt have any effect I then put it in at 375 for an hour and again no effect. I think the temp on the oven is incorrect and not heating to the right temp. So here is my question did the two times at the lower temperature effect the steel and if so do I need to aneal it and start over again or should I just go ahead and put it in another oven and temper as usual?

[NJStricker]

How do you know it didn't have any effect?

You don't know what kind of steel you are working with, and you don't know what temperature you tempered at. Lots of unknowns there.

[Woodswalker]

If I new the answer to those questions I wouldn't have started the thread. The reason I say it didn't have any effect is that the surface of the steel did not oxidize and a file still skates off of the blade. The larger blade I know is 6150 I know it has low carbon but as I said it is a larger knife. My problem is that since the oven didn't work right, and went to an unknown temp what effect could it have had on the steel that I wont see any sign of.

[Alan L]

If the file still skates, you didn't do anything to the blade except maybe a little stress relief. Find a better oven or use a propane torch.

Incidentally, how do you know Husky saw bars are 6150? Not trying to argue, just curious. It'd be a good thing to know if it's true, that's one tough steel.

[AcridSaint]

If you underheated the steel then it doesn't matter as far as re-tempering goes. If you over heated the steel I think that you would notice the file biting more. You'd have to be hitting below 300F to not change the steel hardness, you may want to pick up an oven thermometer.

[pipecrafter]

I'll just reiterate what Cap Hayes said - get an oven thermometer so that you know for sure what temp the oven is hitting.

If the steel is still hard, then chances are you didn't hurt anything, and only did a little stress relief (a good thing). If you find out that your oven didn't reach the temp you're looking for, then you can always adjust your oven to the right temp and do another cycle on the blades - it won't hurt anything.

The biggest problem is in not knowing what steel you're using. If you don't know what the steel is, proper heat treatment can be a hit-or-miss thing. Personally I'd be looking up what steel that circular sw blade is made from, and seeing if I could find a heat treatment method for that steel.

[Woodswalker]

Thanks for the advice, I put them back into my oven and it seemed to work a lot better this time. To answer your questions I made a mistake when I said it was a Husky chainsaw bar it is actually an Oregon bar, a friend told me the steel type a few months ago and since he is a higher ranking member in the Montana Knifemakers Assoc. and a good smith I am pretty sure I can trust that. I actually do have a thermometer in my oven but was at a friends house (I should have known better). I have been trying to find out the steel type, it was just a random piece I had on hand, but cant seem to find any info. Perhaps I should post a pic on here?

[WBE]

When you skate a file on a blade, it only tells you that the steel is harder than 58Rc. A common file will not cut steel harder than 58 Rc.

[Mike Krall]

If the blades were fully hardened... close to 100% martensite. 300F for 1-2hrs. will not change the 'as quenched' hardness... it is a "snap temper". (I just learned this from Mete a couple of weeks ago).

Got this off a really good cooking site that tests a lot of equipment... Cook's Illustrated. Their #1 choice for an oven thermometer is this: CDN Magnet Mounted Oven Thermometer, Model Number MOT1

Here's one place that has them... http://www.cheftools.com/prodinfo-ne...number=06-1505

Mike