Saw cutting to the right

[Big Edgar]

Hi all, here's another thread about a saw that's not cutting straight. I have a Stihl MS251 with an 18 inch Rollomatic bar. This saw is our family saw that is used by a bunch of people on our property (including reckless teenagers), mostly for bucking fallen trees and occasional felling. We got it new and it's been well loved over the ~7 years that we've had it.

Recently the saw started cutting at a curve, swooping to the right as you go through the cut. Here's what I've done to try to remedy this:

1. I flipped the bar - it still cut to the right
2. I swapped out the chain - still cuts to the right
3. I took off the bar and found that there was a raised rail, on both the bottom and the top of the bar. I could not stand the bar on edge due to the raised rails. I'm sure the saw had some significant use while in this situation, so not sure what else that may have contributed to. I filed the rails down with a file initially, and then ran it across a belt sander. The bar stands up nicely on the rails now (see picture below), so I think I have it in good shape.
4. I've sharpened the chains - I usually sharpen by hand, but have an electric sharpener that I'll use after a while to ensure the teeth are even. I haven't touched the rakers on my chains, but they seem ok (see pictures below). I could be wrong on this, but not sure that raised rakers would contribute to this problem.
5. I've checked the bar to see if it was bent - I put it up against a level and it seems straight to me, although I'll admit I've never dealt with a bent bar so I could be missing some telltale sign.
6. I looked at the nose sprocket and it seems to be in ok shape - turns easily and appears to be straight - but again, maybe there's something there that I'm missing.
7. I also checked the drive sprocket and there's some pitting on it (see picture below), but not sure if that would lead to this curved cutting.

I have three other saws and they are all cutting straight, so I can mostly rule out operator error .

What else could I be missing? Thanks for any thoughts.

 

[rupedoggy]

lean to the left
lean to the right
stand up, sit down
fight fight fight!

 

[rupedoggy]

Your bar is worn out inside of the groove where you can't see it. GET A NEW BAR!

 

[Big Edgar]

Thanks, Rupedoggy. I was a little afraid of that. Is it your guess that the grooves have been worn due to the teeth running at an angle, because one rail was higher than the other?

 

[rupedoggy]

yes

 

[Big Edgar]

Thanks very much. I called my local shop and they've got a replacement bar. Is there anything that can be done to the old bar to recondition it and keep it as a spare, or is it basically toast at this point?

 

[PV Hiker]

You have 3 of the above problems. You evened up the tops so they are square but over time the inside lost tolerances and pushes the chain to the side. As rupedoggy suggested buy a new bar and keep the chain sharp.

As far as the old bar, in worst case it could be used as a short term emergency. It could just be sitting in the garage forever.. things just wear out, especially a saw with multiple users.
.
.

 

[rupedoggy]

I will recommend one more thing. When you pick out your new bar look down the rails. If one side is slimmer than the other pass on it and pick another that is even. Look at your picture. One side is slimmer and wore out faster so the rails became uneven. Mike

 

[Deleted member 117362]

That one rail looks like it is rolled over. Have you ever dressed that bar? Bars need service also, just like saw and chain. Start with a new bar, square and clean that bar you will see a difference.

 

[Big Edgar]

Thanks for the feedback, guys - I really appreciate it. PV Hiker - that picture really helps clarify the issue, thanks for that. Duce - unfortunately I didn't check the bar frequently enough and the damage was done by the time I dressed it. This is a good lesson for me on bar maintenance .

 

[ammoaddict]

Thanks for the feedback, guys - I really appreciate it. PV Hiker - that picture really helps clarify the issue, thanks for that. Duce - unfortunately I didn't check the bar frequently enough and the damage was done by the time I dressed it. This is a good lesson for me on bar maintenance .

Turn your bar over everytime you sharpen your chain and check it for wear and file it if needed.

Sent from my moto g(7) power using Tapatalk

 

[buzz sawyer]

From the photo, the chain does not look sharp. Looks like the cutting edge is rounded over. Also, if the depth gauges are not set correctly, it could be cutting more with the teeth on one side than the other. Can we get a better shot of the teeth?

 

[Big Edgar]

Most definitely! I'd love to get your thoughts on the chain (all my chainsaw maintenance "skills" are self-taught, so I'm sure there's a bunch of stuff that I'm not doing right). Can you give me an idea of the angles that would be most helpful so I can take a helpful picture?

 

[buzz sawyer]

Get some better shots of the cutting edge from both sides and on top, something like this.

 

[buzz sawyer]

This is one of the teeth in your photo that I questioned. Looks like it's rounded a little.

 

[rd35]

No matter how badly the inside flats of your bar rails are worn...if to tops of the rails are flat (which you did with your maintenance work) and your chain is sharp it will cut straight! I'm with Buzz sawyer on this one. I think you need to concentrate on getting that chain sharp. I will admit that a worn bar with a dull chain will be worse for curving in the cut....but if the chain is sharp and the rail tops are flat it should cut straight. Pay close attention to the chrome plating on the tops of the cutters. You have to file or grind those cutters until you cannot see the edge of where the chrome is worn away. Otherwise the tooth will not bite into the wood.

 

[tug]

I know you said the saw was well loved. But that bar got way too hot at some point. Bars typically should not smoke or be much hotter then warm to the touch. If they are your saw is either not oiling or the chain is way to dull.

 

[lone wolf]

You rocked it and were unable to sharpen it well enough,either file it again a lot or get a new chain. I had this happen many times.

 

[Big Edgar]

Thanks, everyone. Yes, this bar definitely got too hot - I'm not sure when this happened as those scorch marks on the bar are fairly recent.

First off, here's a video of the chain in the groove - there's definitely more play than on my other saws, but I was expecting worse TBH.



Second, here are some photos of a tooth. Let me know what you think.

 

[rupedoggy]

Let me "splains" sumpin I think I knows, you may not agree, that's OK. That bar is a cheaper made unit. It is spot welded onto a piece. The fact that one side is more narrow than the other shows it is a cheaper bar. That part that some of you are saying is burned or got hot, is the induction hardening done to the rails to make them hard. If the bar gets real hot while using you will see paint burned off the bar. I don't see that. The wiggle in the chain, in the grove is the problem. New bar, new chain, problem goes away for awhile. If it was an expensive bar then it could be rebuilt with a bar shop. The owners of bar shops will not rebuilt these bars (spot welded) because they say the welds will come apart. I have actually pounded these but I know what I am doing. Mike