Trying to fix curved cuts w/o new bar or chain

[muddy42]

If you do bar maintenance little and often with a flat file and a square you can keep bars going for ages. But I think that chain and bar are beyond rescue.

 

[Sidecarflip]

Make sure the sander table is dead on 90*. I use a quality machinist sq and re-check it often.
I’ve used a delta 1x30” belt sander for decades…60g Zircon belts.
I’ve redone dozens of bars the owners thought they’d squared up.

The problem with using a disc sander for bars is it will want to pull/push…up cut and down cut at the same time. A vertical belt sander is a lot better.

That depends entirely on the size of the abrasive disc, as well as the grit, the table (which has to be at 90 degrees to the disc and how you gold the bar when grinding it. I use a commercial 16" psa disc grinder and keep the bar securely held against the table at all times. How I re-rock a flat bar.

 

[Sidecarflip]

Problem with had filing versus machine grinding is... No matter how good you think you are at hand filing, you will never get all the cutters the same, an impossibility whereas with machine grinding. the grind depth is set mechanically and is totally repeatable across ALL cutters. Not only will the teeth vary but so will the rakers as well as the tooth angle.

 

[Kdavis2685]

Are you using a file guide? It may be worth mentioning that just because the top of the teeth are filed back the same distance, all the angles can still not match, causing crooked cuts. It can be a tendency to get the gullet deeper when sharpening from one side, vs the other. It is common to have one set of side cutters have a more aggressive chisel angle, not top plate angle, but actual chisel angle, ie like a razor blade vs axe. Check that. Or put a new chain on your tuned up old bar, and see what happens. That will tell you if it's your sharpening vs your bar.

 

[Gord404]

do you think that unless you take the burr off the edge of the bar brfore a 90 degree shapener would make a difference- otherwise you maybe out about 20 thou or more on your first pass to 90 degees

 

[singinwoodwackr]

do you think that unless you take the burr off the edge of the bar brfore a 90 degree shapener would make a difference- otherwise you maybe out about 20 thou or more on your first pass to 90 degees

Yes. Always file or grind any burr off first. Usually worse at each end, not so much the middle.

 

[mountainlake]

Who sharpened that chain, some links have good hook, some links have none. Show a pic of the other side of the bar and chain. Steve

 

[Kdavis2685]

Hi ,

Saw husky 3120
Bar 3/8. 0.058 84DL

Recently I’ve been challenged to correct a bar and chain that wouldn’t cut straight but without buying new chain or bar which would be the easiest and probably the best solution but I wanted to see if I could DIY cure the problem of very bad curved cutting.

I did all the following and it cut much straighter but still wasn’t perfect and still wanted to cut a bit to one side:

1. Filed All cutters same length

2. Filed all rakers same height

3. Filed Bar rails same height and square to side of bar

4. Squeezed and hammered the Bar rails snug against chain so that chain doesn’t move from side to side but still slides in bar.

A friend and I spent several hours trying to get the rails closed to the point of being snug against the chain but not too tight. We tried a roller , then hammering , then a large vise. None of these were the perfect solution to move the side rails in the thousandths of inch to the exact spot. In the end we got close but had some hot spots where it was too tight against the chain.

Couple of questions :

a) Does a straight and flat a bar sometimes become uneven and beyond correction ?

b) Does a chain that’s been run in a bar with uneven rails get worn to the point where it won’t cut straight even on a good bar ?

c) was I mistaken by thinking the curve cutting was caused by bar rails gauge that was too wide and my real problem was the chain’s drive links were worn and causing the chain to lean and not stand up straight on the bar ?

d) What’s the best easiest to use tool for closing the rails ?

Thanks
View attachment 1245037View attachment 1245038

Yeah based on the pictures, it is just not good sharpening. Little to no consistency. Some teeth have more hook from side view while others do not. Unless the sharpening gets consistent, the bar issues probably don't matter. Also, all the cutting corners are bent down at the tip, so it was in the dirt or ran far too hot / not enough bar oil.

 

[Bob Hedgecutter]

See when you get up there in the CC range- you can get away with blue murder regarding chains- sheer grunt gets you through- far from ideal, but big CC saws will pull a dull chain through timber until it gets real ugly and starts cutting curves.
From what I see in the photos above- chain is far from ideal in the cutter department- probably more dull one side than the other and therefore pulling to one side.

 

[JimR]

I do my bars on a belt sander also after removing any edge overhang. I normally hand file all my chains. If I have one pulling to the side. I will sharpen it on my grinding machine to make sure all the teeth are the same length and angle. Then I will grind down the rakers to all be the same height. If it still pulls, I swap out for a new chain. If it still cuts to the side, I'll replace the bar.

 

[Hermio]

Instead of a DIY method, I have a local machine shop that swages and grinds the bar true for about $18. That can be done 2-3 times before the groove is too shallow for the drive links. It helps, but the asymmetric weight of the saw itself will tend to make the cut veer to the right a little.

 

[ZeroJunk]

With all of the above the other little tid bit is operator. The weight of the saw itself hanging out on one side is a contributor if not paying very close attention. Once you get into 60cc and above that is a significant chunk hanging there.

That is my problem. It always leans the same way LOL.