Xtra Hard Teeth?

Ive noticed recently while sharpening my longer chains that some teeth seem harder than the others. File seems to glide over rather than take metal off. Has anyone else ever noticed this?
Im a strict freehand filer.

 

I have noticed similar on Oregon & some other "cheaper" brands of chain. I just chalked it up to mfg standards. Not real sure I'm right though.

 

Are the teeth individually hardened then attached to the chain loop?

 

I do get a few chains that the file just chatters over . It’s especially noticeable doing rakers . Rotary chain seems to be the worst offenders .

 

I think that's how they're made. Chain chassis is the assembled/riveted together. I would guess it's possible to get chain with cutters from different sources on the same chain.

 

I've experienced this also. Sometimes I think the files have QC issues too. I'm using files bought from the stihl dealer, and mostly Oregon chain. How many different companies make files?

 

The cutters get hardened when someone hogs too much too quickly with a grinder. It usually goes away after a couple proper sharpenings

 

I'm no metallurgist but I do have a theory. As someone that works with metal for a living, I wonder if what's happening is that the chain is "work hardening" due to heat buildup from the cutting process. Certain types of metal will do that. Heat can either anneal the metal making it softer, or harden it depending on the temperature and how long it's held there.

 

Teeth can get a different feel after hitting metal. Some teeth even have bits of metal left on. You were cutting on a tree with metal, so it crossed my mind.

 

I just bought a dozen of each 7/32 and 3/16 as i go though them. Same file and chain and a few teeth seen harder whereas others no issues with filing.

 

I have 1/4” round files that are good for filing out rock and metal dings in 3/8

 

For steel to change property's it needs to hit 800* +- the blue on bar rails is from the induction hardening process not from lack of oil, chain too tight or anything else. I'm no metalurgist either, but I did stay at a Holiday Inn and I did take a metallurgy course in college.

 

Funny buZZsaw BRAD , I’ve been having that same problem lately. Seemed like I was getting the angle wrong a little bit. If I got it just right I can get it to sharpen. It also seems to work if I take the guide off and run the file through the gullet a couple times then hit it a couple more times with the guide back on.

 

I just recently ran into this situation. I was touching up a loop I had a friend square grind. I simply couldn't get the file to bite at all on 2 cutters. Asked a couple friends and they told be to either hit it with a grinder (I have the round bits for my dremel) or heat it up to try and loose the temper. So I did both to see what worked better for me. The round stone in the dremel worked extremely quick. It took a lot of pressure but it got through the tough part, then the file allowed me to proceed. For the heat, I used what is called Hot Lips. It's a soldering tool I use at work that creates a lot of heat very quickly.
I snuck up on the heat because I didn't want to over do it. But after a couple cycles, the file started to bite in. Having this situation again, I'd just use the dremel to remove the real hard stuff just because it was quicker.

 

Can we ask what brand chain?
I feel it's just a temper issue. I've never run into this with Oregon, Stihl or Carlton. Only after it had been on a grinder.

 

I have a bunch of chains that have a few hard teeth...I've always assumed they were overheated at some point...either cutting or while being sharpened...although if it were from sharpening it wouldn't be from me, I mostly hand sharpen, and the few times I have used a grinder I was not pushing it at all...not terribly familiar with the machine...I think I could have hand sharpened faster

 

I have chains like that also I always thought that if a few teeth got dull they would overheat and harden making them hard to sharpen.

 

I've had it plenty of times. Stihl chain and save edge files, so good stuff. No idea what causes it. Seems to be ok once you finally bite through the surface hardness, maybe not quite right but better than the ceramic-hard surface.

 

Last year I finally got a grinder...and very rarely hand file now. It took me a while to get it right, but the grinder is much faster, and the teeth are much more evenly sized. When I hand filed, one side was always longer, I assume because of being right handed. Now I set up with the wheel just barely touching the face, and just barely move the handle over and when coming down it comes at the tooth from the side instead of the top. I keep my chains really sharp and normally just need to re-establish the correct angle, and they last longer this way. I always have 1-2 extra chains with me, and swap when the chips get small. I do my rakers with a dremel and like them aggressive, at least .030".

 

Even fresh factory made chain? Isnt it done by robot/computer at a factory?