Keeping a chain on the bar, my saw keeps tossing it, what should I inspect?

[OuroborosDaybreak]

Has anyone dealt with a chain that derails even when you feel like you are doing the tension right? I’m still learning and this is making me hesitate because I don’t want to keep guessing and make it worse.

A specific moment was a couple days ago when I stopped, retensioned, and it still threw again later on the same log. That’s what made me think it’s not just me forgetting to tighten it. Would you start with looking at the bar rails for damage, the sprocket for wear, verifying the chain pitch and gauge match the bar, and making sure the bar nuts are tightened in a way that keeps the bar seated?

 

[rasawing]

Sounds like you are covering all the bases.....one additional thing I'd look at is: any bend to the bar. Sometimes I've seen a permanently bent bar throw chains.

A lot of times though: it is a burr you can't locate (or you see and don't think it is a issue). I had one bar some years back that was always a issue.....I get rid of it, and the problems go away. (And I still don't know why.)

 

[FuukaYamagishi]

I have seen this from three main things. Chain too loose after it warms up, worn drive sprocket, or a bar that is worn out. Check the sprocket for hooked teeth and check the chain drive links for damage.
When you tension, lift the bar tip up, then tighten the bar nuts. If you tension with the tip down, it can loosen right away once you start cutting.

 

[What]

Add to that bar twisted.
Bar to drive sprocket alignment.

 

[Alan]

If your saw is tossing the chain, stop running it until you find the cause. A thrown chain can hurt you fast. Let the saw cool, put on gloves, and inspect before the next cut. Check chain pitch and gauge match the bar, bar rails for spreading or a burr, and the drive sprocket for hooked teeth. Also confirm the bar nuts and tensioner are actually holding under load, not just on the bench.

 

[cjmac163]

Are you properly tensioning the chain? Different sawyers have different ideas for what "tight" means. Not an insult to you, I am just genuinely curious how tight you can get the chain (without overtensioning, obviously). Also what brand chain are you using? Is your chain sharpened properly? I've lost a couple chains off the bar after rushed (aka crappy) filing jobs, when the saw cuts in and the kerf starts curving. Also if you have a rim sprocket on your saw, check that for excessive wear, as that can really wear out the drive links and pins on your chain, and create slack you cant see at the nose of the bar.