There is a fine line between over use and under use of the chain brake in my opinion. I’ve seen a lot of freshly qualified people using a saw all slamming the chain brake in at full chat. They say this is what they were taught, and another annoying habit is they all seem to run the saw at either tickover or full chat. Never in the middle, never using the throttle and feeling their way through stuff. I’ve always maintained that getting your chainsaw tickets is like passing your driving test. You learn how to do it properly after you pass!
Ive been working with some newish folks these last few years, and try to get them into good habits rather than bad. Using the chain brake correctly is on one of those habits. I say to folks, especially if they’re green, that they should be using it a fair deal. If they stop cutting for even a few seconds, put it on. They need to get into the habit of doing it, then once they are happy doing so, they will learn when it’s acceptable/sensible to leave it off. One lad I worked with recently, on two occasions, Had saw in hand and revved up then realised his visor wants down so took left hand off saw to flip visor down whilst chain was still running. He was someone else’s groundie but I told him straight it was very bad practice. He learned from it.
But the flip side of that is I often pick up a saw to use after someone who has years of experience with them, and find the chain brake off. I always put it on when finished, and the reason why was in case someone else came up to use it after me, as it was the safest way. But like leaving your car in gear with no handbrake on perhaps? If someone else came to use it they might be miffed to find it like that? I guess it boils down to personal choices at the end. I know what I am happy with, and what I deem safe and necessary. Others have different views.
I had a chain brake fail on my Mk2 550 after a few months also, so maybe some crap ones about. Prior to that, I’ve done about 2 in neck on 9 years.