Saw will not cut straight.

I put a used 20" bar on my Stihl 391. It will not cut straight. I'm Assuming the bar is warn out. All advise is welcome.

 

--I know very little about this but would take a guess--
Is the chain used as well? Put a straight edge along then bar to check for straightness and make sure that the chain is consistent on both cutting sides.


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Make sure your bar didn't have burs on it, your bar could be the wrong size for the chain, your cutting teeth could be sharpened unevenly. Bar and chains are not one size fits all deal, idk much about the different measurements but someone will be along shortly to help.

 

Pretty much both suggestions from jt will be where to look. If it just started with the swap to a different bar then dress it. Great info here - Chain Saw Guide Bar Maintenance

When I first learned to hand file, I started getting a crooked cut too. In my case it was from me having a little stronger file stroke on all of the cutters on one side of the chain. When one side gets shorter, the saw will cut a bit crooked.

 

Or is it more likely the chain. I just had it sharpened, but maybe they didn't do it right

 

That is most likely the case.

 

Use a vernier to compare the length of the left facing teeth to the right facing teeth. If they are not the same it is time to do some filing to fix it. I have never used a shop to sharpen a chain so I don't know what they do to maintain the saw as sharp as it should be and to make things match up right. Any bar wear that is causing the cut to curve to one side would have been a gradual change over a long time unless you ran without bar oil for a while and caused unusual wear quickly. If this just started happening with a newly sharpened chain I would suspect a bad sharpening.

 

That would be my guess. Throw a different chain on and see what happens.

 

As other said, put a new chain on first and see. Bar maintenance is something that gets overlooked a lot. Some will go so far to even think the saw is junk. Here are a few things to look for.



Bars wear most either at the base of the saw or at the tips. Especially if you are doing a lot of plunge cutting. Notice here how the bars slight bevel angle get a lot worse wear the saws body would be? Look close and you can even see a shiny rolled edge there.

[img}http://photos.imageevent.com/kevininohio/rugermini14/large/MVC-019S_22.JPG[/img]

This is a Stihl bar with a roller tip. I do a lot of end of the bar cutting too as this is off a trim saw.



Look at the end of the bar how the rails are angled in. They should be straight. When they start getting this bad you'll see scuffs/wear starting to wear up unto the chain. If you keep letting it go, it will start wearing on the rivets.



Here you can see how much wear this bar had. I had flattened out the bar so many times it finally was down to soft steel. Stihl only heat treates the edge so you have a max of 3/16" to work with. Once it gets to the soft/mild steel it wear again bad with a few tankfuls of fuel.



Here is a good shot of the angle. Most don't have the tools to recondition the bars but you can do it on a belt sander. I don't like wasting files as it takes a while and it dulls them fast.

Take a magic marker and red the whole edge up

I mount the belt sander in a vise and use it like a stand alone.

Lock the switch on and hold straight, sighting if you have to. You can mount a board or steel upright for truing guide if you wish.

Sand till the marker color is gone and try to start from one end and work down.

Flip over and repeat.

Sprocket tip are tricky but it can be done as I have.

Just keep moving the teeth out of the way and slowly make your way around.

If you know the bar needs attention you may as well keep running till your ready to switch chains. The reason is the chain has worn to the taper and you DON"T want to put that chain on any other bar as it'll wear it more than it should. Toss the chain is what I'm saying.

I've personally been given 2 saws that the owners claimed needed a new cylinder as they had no power. All it was, was the bars were wore like this and the chain was binding/dragging the rivets to the point of overworking it. Hope this helps if the bar was the issue but I'm guessing the chain too.

 

Three standard gauges for chain(thickness of the drive links) are .050", .058", and .063". You can measure the thickness of your drive links with a micrometer or a dial/Vernier caliper and the groove in the bar with a set of feeler gauges.

I have used a sanding disk on my table saw to dress bar rails but it was a nuisance to clean the saw every time so I bought the bar rail grinder from Baileys.





I also bought the bar rail closer from Baileys and use it from time to time to tighten up a used bar.



This is not a "set and forget" tool, you have to keep adjusting it and working over the bar but it does work. Others suggest a hammer and some shims in the bar but I find tool is pretty useful.

Once you know the bar is it good shape and the groove and chain match, you can focus on the chain.

Mark

 

Nice shop Heimannm. The advice I have looked at all makes sense. New chain with proper tension will be the tell tale. Try to hit up a woodsman/logging field days in the spring....great deals on bars and chains!!

 

Thanks for all the help guys. I took the chain back a second time to see if they could correct it, when I got it back I still had the same problem, pretty sure the rakers were not filed correct. I took it back again and they exchanged it for a new chain.

I put the new chain on and it cuts great! Glad you guys helped so I didn't buy a new bar!

I've been reading the chain sharpening tutorials and highly considering doing it myself. Hopefully it's as easy as it looks!

Firewood hoarders are the best!

 

Yep it sounds like the cutters are different lengths on the opposite sides and also the depth gauges all have to be equal height too.

 

IME, that's a "wives' tale" about cutter length. As long as they're not wildly different side-to-side, just cut. IME the big problem here comes when a chain is dulled/damaged on one side and you brute-force it to carry on. Then one bar rail gets worn, and the jig is up. Doesn't take much, a few thou on one rail will continue the damage, until you true the rails. That's hyper-easy with a bench-grinder that has a tool-rest.
Of course it's good to get your chains consistent side-to-side, but not worthy of obsessing, or removing perfectly good metal, to distract you.

 

If I am cuttin' to the left I just take off my right shoe, and vice versa. No fancy sharpening required.

 

It shouldn't make it pull to one side if the teeth are sharp but different heights, in my mind, make your chain become a skip chain if you will. Unless someone thinks a chains tooth will pull up into the wood. To me, the lower tooth on a larger cut where many are touching, is following a tooth that has all ready taken a lot of it's cut out. Maybe I'm over thinking it but I've noticed a lot less fines with a sharp, even toothed chain over a hand filed miss match one. Anyone else have thoughts or experience here?

On a side note. I had some loops of Oregon years back that evidently had weaker one side cutters. they broke off with about 1/2 sharpening. I ran several 18" loops till there were only 3 cutters on one side and all on the other. They still cut straight.

 

I agree, one cutter takes a big bite and the next is not doing much. The depth gauges can not be set properly if all the cutters are not the same length.

 

I disagree or maybe Im misunderstanding what you are saying. I have had numerous chains get damaged only on one side. Either the left or right cutters. I have had to remove substantial amount of material to get back to a clean edge but as long as those cutters where sharp and had the same height guages the chain cut straight.