Broke first chain; could it be....

[Arky217]

I have a M7 with a Husky 395xp, 20" Forester bar and the low profile Stihl chain that comes from Logosol. I have the oiler set to max and also have a water drip at the end of the chain.
I ran probably 20-30 tanks of gas using this chain before its last sharpening. This last sharpening, I was careful to make sure all cutters were the same length and also the rakers. On this last sharpening, however, I changed the top angle from the original 10 degrees to 0 degrees to see if it seemed to make a difference in cutting. One difference I noticed right away was that the strong vibration I had been getting in the first couple feet of the cut was gone, and overall, the cutting seemed to go smoother.
After about 3 tanks of gas, I was about 1 foot into a 6" wide cut in green pine, no knots, when the chain broke.
The break occured at the rivet hole on a drive link.
The length of the cutters on this chain are still about 75% of the original.
The question: Could changing the angle have anything to do with the chain breaking ?
After all, the chain had made much wider cuts, sometimes even in large knots, for some time before the break, albeit at the 10 degree angle.
Or could it be that finally fatigue caused the break ?
What think ye ?

 

[Rodney Sinclair]

217, I got a M7 with a 385 husky and I don't know how you got by with going 20 tanks of fuel before sharpening. What part of Arkansas you in?

Rodney

 

[BobL]

For chain break diagnosis post a close up photos of

1. the break itself,
2. a drive link or two from the side
3. a tie strap or two from the side
4. a cutter or two from on top
5. the sprocket

Also what raker height were you using?

It could be just a "luck of the draw" or a fatigue thing but the danger with 0º top plate angle is how do you know you are at zero? You could be a -2º in which case the cutter will be pushed away from it's cutting side. Instead of cutting a proper width kerf the chain cuts a narrower kerf and the resulting sideways forces on the chain could be enough to break a weak rivet. BTW this will also wear the drive links quite severely.

All your ducks need lining up when using lo profile chain with a 395 since it is a powerful beast and you may not notice problems until the chain breaks.

If you were getting a lot of vibration at 10º that suggests something else is not right.

 

[Arky217]

What I meant was that the chain had run about 20 tanks of gas before I sharpened it from the 10 degrees to 0 degrees, not that I ran 20 tanks of gas without sharpening the chain.
The rakers came set at .025 and I always file them to that at every sharpening.
Yes, I suppose that instead of 0 degrees, the cutters could be plus or minus a few degrees (my eyes aren't what they use to be).
But I cut the full width of the bar quite a bit during the 3 tanks of gas before the 6" cut where the chain broke. As far as the vibration that it had before, it only lasted for the first foot or two at the beginning of the cut, and even then I could usually quell it by griping the saw more firmly; however after sharpening to '0 degrees, (more or less), it cut smooth even at the beginning of the cut.
After putting a new chain on, it cut good but the vibration at the beginning of the cut was back somewhat; (I suppose the vibration could be just the guide rail flexing out at the end from the torque of the saw).
I guess that when I repair the chain, I will try for about 5 degrees angle and see what that does.

 

[TedChristiansen]

Have you checked to confirm that the bar is parallel to the guide rail? Take a straight 3/4" thick stick about 3-4' long and place it on the bar parallel to the log and guide rail.

Now stand back at the log ramp side and look at the stick. It should be perfectly parallel to the guide rail. If it is not, then it can cause bar dipping and chain breakage. The cause of this problem is the chainsaw's clutch cover. The outer surface where the extender nuts mate is an as-cast surface, and may not be parallel to the machined inner surface of the clutch cover. This out of parallelism can force the bar out of parallel.

To correct this problem you will need to shim the saw sled where the plate is bolted to the extruded aluminum slides.

I have suggested several times that Logosol either include this troubleshooting info in their manuals and/or sell machined clutch covers with their new saws and as a replacement part for saws in the field. This problem caused me several months of frustration and a couple of broken chains with my Logosol Woodworkers Mill. Once corrected the mill works great.

Regards,

Ted

 

[SilverBox]

I think you just fatigued the chain till it broke..

with a 2 hp saw and cheepy 3/8 low pro (powercare) i broke a couple after 30-50% sharpened away. with a 3hp saw and cheepy 3/8 low pro (powercare) the chain snapped before the first sharpening..

Now you have a 7 hp 395.. and good quality 3/8 low pro.. same problem.. You could probably run that chain till its filed away to nubs on a 4hp saw..

 

[Arky217]

Yes Ted, I am very aware of the bar needing to be parallel to the guide rail, as well as many other parameters involved in tuning the M7.
Actually, I think SilverBox probably hit it on the nose; fatigue from a powerful saw coupled with a lightweight chain.
I will probably go to a heavier chain once I wear out the low profiles that I have.
Thanks for the responses,
Arky

 

[Brmorgan]

I have LP chain on my 660 w/ 25" bar with no problems so far. Probably not 20 tanks of gas on it, but pretty close. Running 0° vs. 10° does put more stress on the chain - it's gouging the wood out head-on rather than the slicing action that an angled top plate produces. Similar to how it's easier to push a hand plane when its angle is skewed to the grain rather than straight to the grain (or as a better comparison for this instance, across the grain). I run mine at 10° as I've found that to be the happy medium between smoothness and speed in the wood I work with.

 

[oldsaw]

Pics would help

 

[Stihl-in-Ky]

I quite using low profile milling chain after breaking 3 with my 441 in cherry I don't think they are made for the stress of more than 3-4 horse power saws.:greenchainsaw:

 

[Rockfarmer]

I run mine at 10° as I've found that to be the happy medium between smoothness and speed in the wood I work with.

Me too