John_Mc
Elite Member
- Joined
- Aug 11, 2001
- Messages
- 4,564
- Location
- Monkton, Vermont
- Tractor
- NH TC33D Modified with belly pan, limb risers & FOPS. Honda Pioneer 520 & antique Coot UTV
The idea of tapping the chain is to avoid overheating it. A light touch which doesn't heat it up much, then a pause to allow some cooling, then another light touch. The combination of the steel alloy used on most chain teeth and the small amount of mass (especially at the working edge) will allow the tooth to "Air harden": that is, if it gets heated up enough, it will "quench" in air, forming a martensitic structure in the steel. That structure is very hard - which is why you'll likely ruin a file if you try to hand file a tooth that this has been through this. It's also very brittle, so that thin working edge can break or chip easily. If the cutting edge of that tooth never gets above the critical temperature, the metal will not harden, no matter how quickly it is cooled.
I'm not saying it's impossible to avoid overheating with a very light continuous touch. It's just that the touch - pause - touch -pause technique was developed be cause its easier to avoid overheating with that technique.
I'm not saying it's impossible to avoid overheating with a very light continuous touch. It's just that the touch - pause - touch -pause technique was developed be cause its easier to avoid overheating with that technique.