Thread: broken chain......twice

I'd say it's a combination of lack of oil as the chain does look a bit dry and too much power

It does look a bit dry, but dunno what happened with it before taking the pic???

I agree with DJ.

Two additional contributing factors could be.

1) Raker height too low - what is it exactly?
and
2) The gullet needs cleaning out. Clean gullets help chips flow better and stop the cutter from tipping over too much,
The combination of these two could easily explain the break.

I use carlton/GB, Stihl and Oregon 3/8 chain, and never broken a chain like that.

Does my chain look like a quality brand? Can we definitely say its not Carlton, Oregon etc etc. Best not say where I got it.......

Cutter sharpened with a hook? Depth gauges a touch low? Tooth bites in and the chunk is too large to chip. Tooth jams – saw either stalls or breaks chain.
Suggest you check the appropriate size of your file. Almost looks (from the photo) that your file is a size or two on the small size.
Keep gullet clean.
Check the following website for details
http://www.sawchain.com/images/complete%20book.pdf

Good luck

Brosh

Originally Posted by timbertalk

Does my chain look like a quality brand? Can we definitely say its not Carlton, Oregon etc etc. Best not say where I got it.......

let's see - how about fleapay? If so - say no more.

If you type A363LM into Google the only thing that come up associated with chainsaw is a Belgian website that is also selling Sugihara (japanese) bars. These are actually very good but the chain does not come uyp anywhere else. I wouldn't put it past this to be chinese with a Made in USA sticker.

If A363LM was a common made is USA chain it would usually stick out like a Xmas Tree Lights on Google.

Do you want me to ask in the ArboristeSite?

By blowing up the photo of just the cutter and making a few measurements off your cutter details in photoshop here is what I see.



Your raker depth is nearly 0.050"
Your gullet width is only 0.36"
Thus using some basic trigonometry your cutting angle (Angle between raker, cutter top and wood) is ~7.8º (this has nothing to do with any of the usual cutter filing angles you see in chain filing manuals). This is just too much for ANY 3/8 chain except perhaps in really soft wood.

You could get away with this with 404 chain but the ideal cutting angle for 3/8 chain is about 6º which for a 0.36" gullet you should have a raker height of 0.036". Combine this with a gullet that is not clear, a bit more hook than ideal AND cheap chain, means tears before bedtime!

Thanks BobL, Brosh and others. I have to admit the rakers were not set very accurately - I have a little single-set gauge, but I deliberatly went a little further than this (two file strokes) in order to increase my 'chips' and reduce my 'dust'. This was because I was still getting a blocked oil hole in the bar from too much dust. This hasn't happened since I increased chip size. But there has been a down-side to it.... I think you are right - a combination of all these factors, plus cutting wattle which is tough stuff, has led to this. Feel free to ask on the other site about the chain, I didn't get it through fleapay, but the Aussie seller was 'getting rid of it cheap'. I intend to buy a 'file-o-plate' to help with setting rakers in future. Thanks again

Holy jeepers, that is some fancy work there Bob!!!

Originally Posted by Sigidi

Holy jeepers, that is some fancy work there Bob!!!

Thanks Sigidi,
It's very interesting what one can do with photos and a bit of basic maths.
BobL - aka - "the chainsaw chain detective"

Check this one out!

The cutters in the pic move 1.5"
The shutter speed is 1/640th of a second
This works out to be 54 mph which is 9000 rpm for an 8 pin 375 sprocket which is about right for the 076 powerhead used in the shot!

sure looks like its been run without much oil and been smoking not cutting??. will soften the steel if too hot. I bought some rebranded oregon chain off ebay and its good chain but arrived not sharpened , worked well when it was though . and cost about 40 o/o of local dealer price. cheers BOB

Impressive Detective Bob.
Are there any markings on the chain itself?
Also stretch and push the chain length-wise to see if there is any movement in the rivots. I there is a lot chuck it. I had a chain running between a 2100 Husky and a 084 Stihl the fella on the other end pushed hard I was wondering how many chips could come out of my saw before it blocked, then the chain broke. I cut it up to use in other saws and it broke again. The moral to the story; don't risk it.

The chain I have been using says "A3" on the drivelinks, but nothing else. Today I took 20 file strokes off every cutter, to reduce the cutting angle. Reassembled it all, got everything all lubed, got cutting again, and BANG, broke again. I think the damage has been done to this chain. If you have time Bob, could you analyse this photo - its the same cutter as last photo, but being a side-on profile will make it easier for you and more accurate. This has been a good learning process - the Carlton manual reckons full chisel chain should be filed at 10 degrees to the vertical bar, as well as whatever cutter angle you are using. I have not been doing this either.....

The chain still looks very dry and for that matter dirty too.

What oil are you running in your saw and have you adjusted the oil flow rate on your saw to get maximum oil?