I'm taking a break from cutting wood this morning.

I was noodling through a log and came upon a "hollow" that seemed to be filled with something abrasive. The saw dulled quickly. I went to re-sharpen, and found four or five teeth, that the file could not touch.

When I go back out, I will try a new file and/or put the chain on the grinder.

Is it possible that I am right? Can sawchain become work hardened by abrasives or excess heat working hard in other ways?

Definitely. If you use a dull chain the metal hardens from the heat. Usually I have to use a new file and remove an excessive amount of metal to remedy.

Possibly hardened from a previous sharpening on the grinder, don't hit them for to long with a mechanical grinder.

Teeth and heat not a good combination.

WS

I would try a new file and make sure it is in a vice when you go to file so you can get good pressure on it

I have't had any I couldn't cut with a sharp file but have had some that a less than sharp file just seems to skidd off without biting

It's not "work hardening" per se but rather heating of high carbon steel and sufficiently rapid cooling (quenching) to resut in a hard crystal structure. It's the same effect a bladesmith gets from heating and quenching a blade the only difference being the quenching medium is air instead of oil or water. The bladesmith would then temper the steel to reduce the hardness to a workable level. As others have said, you may be able to grind off the part that has become excessively hard.

Or snow in this case.

I pulled the saw out of the kerf and set it down in the snow. It makes sense, now that I think about it. It also explains why the hardened teeth are all in one string...the bottom row when I set it down. It makes me think the entirety of the affected teeth would be hardened, at least the outside couple ten thousandths.

Thanks,

Lesson learned:

The next time I run into that abrasive stuff, I'll turn off the saw and leave it right in the kerf to let it cool on its own.

I'm back in after session two of cutting wood..

I clamped the saw into a vise and broke out the best of my discarded files. What have I got to loose? I used what I would consider excessive force to file down the hardened teeth. It actually worked. After a few very heavy strokes, they started to feel like a normal tooth would. After another tank of fuel, and another sharpening, I was back to a typical chain.

After the fact, I'm wondering how many good files I've thrown away over the years, when the problem may have been a work hardened chain.

Heat the tooth up with a bic lighter then file. I've seen some teeth hard to file right out of the box.

That was on my list or possible solutions, except I was going to use a propane/map gas torch. Like I said, didn't need to go that far, but, may have been a little easier. I'll definitely keep it in mind for the next time.