Sharpening

[David Heaf]

Thanks to all for very helpful suggestions! Yes, it was a case of the Oregon chain being harder than the new Oregon 7/32" file I am using. I suspected work hardening was the problem. The last ~90 min session yesterday on a 24" ash trunk may have caused it. It was not the sharpest of chains before that session, although I'd given each tooth two or three strokes of the file beforehand.

As it is a 52-teeth chain and they are still 5.5-6mm long I was reluctant to follow the 'throw it' advice. So, mindful of the work hardening possibility, I ground the hard teeth with a Lidl 'Florabest' chain sharpener. (I'm a bit skeptical as to whether that device gets the angles right, even when set up correctly. For example, my saw (Sachs Dolmar 123) manual says the leading edge if the tooth should be at 85 degrees to the bar.) To avoid the risk of overheating the teeth, I ground each one slowly, taking off only a small amount of metal.

The result is that the file bites again, and I was able to finish filing the teeth to the recommended 30 degrees angle with a 10 degrees tilt of the file relative to the horizontal.