Thread: broken chain......twice

Either its a defective chain batch or you have a chain which is not matching the pitch you think it is, which would put the chain under a lot of stress going around the tip & drive sprockets. There is some of burring on the back of the drive link for some reason or damage from the break maybe ? Looks like plenty of oil & the drive link doesn't have much side plate wear which is a sign of low lubrication, depth gauge height shouldnt be a worry at all.

regards inter

what gauge chain is it 050 is too light ?also looks very dirty like its been really hot ,no oil on it either , its a big saw and bar and will break chains,if they are too small or not sharpened right . try some 404 for ripping with my mills 18hp motor no problems , Bob

This cutter . . .

has the following specs
Raker depth, 0.053"
Gullet width, 0.34"
Cutter length 0.32"

The previous cutter was
Raker depth 0.050"
Gullet width 0.36"
Cutter length 0.30"

Now I ask myself, how is it possible that you took 20 strokes off all cutters and that this appears to have made the cutter length longer and the raker depth deeper?
What this suggests is your cutters and rakers are possibly all over the place. You can't just take 20 strokes off, you have to measure the cutter lengths with a vernier and file them to the same length, and make sure the rakers are more or less the same depth although I personally wouldn't worry about a difference of up to 0.005" on a raker height or cutter length, this amount of difference is not really the cause of your problem. What concerns me more is that they are about the same AFTER you took off twenty strokes off this cutter since this means the cutter that broke last time had a much greater raker depth compared to this one (before filing). This means different cutters are grabbing different amounts of wood and some are grabbing too much.

This picture above also shows me something I could not see with the previous one, and that it the wear shown on the bottom of the cutter directly underneath the cutter. This has two diagnostics aspects.
Firstly, see the groove worn into the corner of the botton. See how it is angled backwards. That tells me immediately the cutter is bitting WAY too much or you are pushing it too hard or both. The wear should be flat or close to flat - any angled wear tells me there is too much force being applied either by the chain itself or the operator.

Next, cutter base wear not have any sort of corner groove wear, it should be dead flat, as it should be making contact with the top of the bar groove as shown in the left hand figure in this image.



What appears to be happening is as per the figure on the right, the cutter is not only biting too much vertically, it is also biting way too much sideways. This is twisting the cutter so that it comes back down at an angle into the bar groove and wears the cutter base in that way. This is also consistent with the shinier wear on the drive link pulling the cutter. It would be interesting to see the wear on the other side of the broken drive link.


If your bar is even a little worn or the groove a little too wide this will exacerbate the problem.

So, in summary, the excess raker height and uneven cutter lengths appears to be twisting the chain too much side to side in the kerf - no wonder the the thing breaks.

BTW - this is all explained in far greater detail in the Carlton and Oregon Chain manuals

Originally Posted by bobsreturn2003

what gauge chain is it 050 is too light ? . . . .

The label on the package says "63" which I suspect means it's 063.

Originally Posted by InterTD6

. . . There is some of burring on the back of the drive link for some reason or damage from the break maybe ? Looks like plenty of oil & the drive link doesn't have much side plate wear which is a sign of low lubrication, depth gauge height shouldnt be a worry at all.

I agree with inter - there is something also going on around the drive links, but I disagree that you can use 0.050" raker depths along with everything else that is going wrong with the way this chain is, and they way it is being used. It would be possible to do this on a quality 404 chain but not a 3/8. The damage on the back of the drive links suggests the sprocket is shot or on its way out.

I think the chain is a gonner. Combined with the fact that it has been subjected to far too much uneven wear and twisting and is probably riddled with cracks - time to throw it out, and just treat this as a learning experience. To complete the learning process, if you are game show us a close up picture of the state of your drive sprocket and your bar.

Oh yeah and one more thing, keep those gullets clean.

The A3 tells me that it is a Carlton chain. There are very few factories that make chain we will never get one in Australia as we don't use enough.

Thanks again guys, but a misunderstanding there somewhere - the most recent photo I posted is the SAME cutter as the original, NOT after 20 file strokes. Its just a better side-profile photo. I have not taken any photos of the most recent failure, the photos are all of the original break. My chain cutters are all very closely sized, after all the chain is quite new. To answer other questions, I use good quality NEW chain oil, and while my oiler is on max I have intermittent flow trouble at times. This may be the result of a blocked breather into the oil tank. Detective Bob, what do you think of my hook angle, and was the cutting angle in this photo much different? And all this talk about cleaning out the gullets - do you mean filing out the steel there, or just keeping it polished?

Originally Posted by timbertalk

Thanks again guys, but a misunderstanding there somewhere - the most recent photo I posted is the SAME cutter as the original, NOT after 20 file strokes. Its just a better side-profile photo. I have not taken any photos of the most recent failure, the photos are all of the original break. (

Ah ha, Now this makes sense because when I look at your first photo again it is at an angle compared to the second and this would explain why the raker depth measurement increases with a more side on photo and VV.

The hook angle is ok, the 0.053" raker height is not - well not for a 3/8 chain. This alone produces far too much top and side cutting action and is more than enough to explain the breaks.

Cleaning the gullet means removing the unnecessary steel so the chips flow well down away from the top of the cutter as shown here.



This reduces the back force at the top of the cutter and reduces raker penetration into the timber and puts less of a load on the cutter.

Once the chain has been work with these sorts of loads on it, it is probably stretched and microcracked beyond further use and the best thing you can do is to dump it.

I's still like to see a picture of the bar and sprocket.

Timber talk do you clean out the groove in your bar? And oil hole?

3/8" or 404" doesnt change in strength as the links are the same thickness in width & around the rivet hole so when my lucas mill is running 1.6mm depth gauges with 404" chain with 27 HP driving it, a 084 is nothing & shouldnt break the chain. If it was a bar groove problem then cutting a straight slab would be almost impossible plus there would be a lot of wear on the sides of the drive links, plus smoke & stretched chains.
regards inter

Originally Posted by InterTD6

3/8" or 404" doesnt change in strength as the links are the same thickness in width & around the rivet hole.

I agree, that's the theory, but I have measured a number of 404 and 3/8 chains, and quality 404 has ~10% more metal around the rivet holes than cheap 3/8. Whether that alone is enough to make the difference is another question. More importantly, 3/8 has more rivet holes, whereas 404 has more metal, per unit length, which makes it easier to stretch 3/8 as a chain. When a chain stretches it can take bigger sideways bite and eventually do what I reckon has happened.

If it was a bar groove problem then cutting a straight slab would be almost impossible plus there would be a lot of wear on the sides of the drive links, plus smoke & stretched chains.

Yep I agree straight slab cutting would be a problem but he could just be part of the way there which would cause extra sideways stresses on a chain and contribute to the problem. He could also be using a new chain on an old bar.

It's not just one thing doing this to Timbertalks chain. He's also got an oiling problem and probably a sprocket problem but it would be interesting to see his bar as well.

It could also just be a dud chain.

This has been interesting. I will indeed post photos of bar and sprocket, but have 4 visitors with me for the next 2 days, so you will need to be patient. I hope I didn't leave the 404 sproket on from last changeover! Yes Glenn k, I routinely clean out bar groove and oil hole.

[I hope I didn't leave the 404 sproket on from last changeover!
my money is on this one
regards inter

Originally Posted by InterTD6

[I hope I didn't leave the 404 sproket on from last changeover!
my money is on this one
regards inter

Very Interesting. . . . . that explains the damage on the back of the drive links and the shiny surfaces on the alternate faces of the drive links across the break. For those that don't know, what happens here is the sprocket goes around until it slips a drive link and then spreads the chain apart and causes cracks in the chain.

OK, here are photos of sprocket and bar. Thank God I haven't embarassed myself by finding a 404 sprocket. The sprocket looks OK to me, the bar obviously needs a 'recondition', but I have had no trouble cutting flat slabs at all. One thing which may be a little unusual is the fact that it is only a 7 tooth sprocket - I put this on in hope of getting a bit more torque when cutting wide slabs. May be relevant here as less drive links are being driven by the sproket at any time I guess.

Originally Posted by timbertalk

OK, here are photos of sprocket and bar. Thank God I haven't embarassed myself by finding a 404 sprocket. The sprocket looks OK to me, the bar obviously needs a 'recondition', but I have had no trouble cutting flat slabs at all. One thing which may be a little unusual is the fact that it is only a 7 tooth sprocket - I put this on in hope of getting a bit more torque when cutting wide slabs. May be relevant here as less drive links are being driven by the sproket at any time I guess.

Well the most obvious thing here is the bar needs seeeeerious dressing!

The amount of lip on the chain fully explains the little ledge cut into the side of the bottom of the cutter.

Putting a new chain on that bar with that much lip on it means the chain is gonna rock and jam in between the lips something chronic - and is more than enough to explain the breaks. That is one of many reasons for dressing the bar.