a C bar

[brianJ]

C could count as cutting but in this instance it is the shape I end up with when slicing firewood off the log.   I know that can happen from an uneven sharpening but mine is from a worn bar.    Seems like it should have lasted longer.   What are the factors that contribute to short bar life?      It slices a C either from the top or bottom.

[DelawhereJoe]

Any chance that there was a small rock in the bark from skidding the log that the points of the cutters just nicked on one side of the chain ? Also is the bar worn or opened up and have you been flipping the bar ? How cheap of a bar is it or how soft are the rails of the bar ?

[Ianab]

Lack of bar oil can cause that, maybe either running out or a blocked up oil hole in the bar.

If it's not too far gone the bar can be "dressed", which means filing or grinding it down even again. You can do that a couple of times before the groove gets to shallow for the chain links. Then the bar is well and truly worn out.

[mike_belben]

Put on a brand new chain and check again.  Ive only had it be the bar once and the chain a dozen times.  But ive chased my tail on the belt sander plenty over trying to resquare the rails when they were fine. 

You dont have a .050 gauge chain in a .058 bar do you?

[sablatnic]

Can come from running a dullish chain for too long. It will wear the sides of the bar unevenly, and eventually make the saw saw crooked.
You can check it by setting the bar on edge on a horizontal surface - it it falls over the sides are worn unevenly. 

[John Mc]

In addition to a lack of oil as Ianab mentioned, sometimes getting the bar partly pinched will cause a problem as well. As the rails start to get clamped down on the drivers, but you still keep going, you hit the limits of the oil and overheat the bar. Overheating softens the steel and you'll get lousy wear.

If the bar is discolored (blue or straw color) it has likely been overheated. Not much you can do at that point but get a new bar.

[Mountain_d]

I get that effect with a bent bar as a result of a pinch. I take the bar off and lay on a perfect flat surface ( my table saw deck) and if not perfectly flat then I replace it. The bar will look fine on the saw but a slight bend will give a curved cut. I never tried to straighten one but curious if anyone else has been able to straighten and get it back? Mountain.

[mike_belben]

You can straighten mild warp with a torch and a wet rag pretty easy.  Like aligning axle tubes or driveshafts

[Stoneyacrefarm]

You can also straighten them with a vise and an adjustable wrench.
I've done it a ton of times.  :D

[HolmenTree]

Best way to straighten a bar (not laminated) is a hammer, shim and anvil. Brings the "flat memory" right back.


 

[John Mc]

Best way to straighten a bar (not laminated) is a hammer, shim and anvil. Brings the "flat memory" right back.

I've seen someone do that. He made it look easy. So I grabbed one of the garbage bars from is junk pile and tried it. I found out pretty quickly that there was more to it than met the eye.

[HolmenTree]

Best way to straighten a bar (not laminated) is a hammer, shim and anvil. Brings the "flat memory" right back.

I've seen someone do that. He made it look easy. So I grabbed one of the garbage bars from is junk pile and tried it. I found out pretty quickly that there was more to it than met the eye.

You always lay the bent bar on the anvil with the hump up. Right in the middle of the peak of that hump you hammer. It don't have to be a brass or copper hammer like mine.
I use a bar cleaner hook tool like in my picture for a shim to avoid squishing the rails.
Keep eye balling down the length of the bar to check straightness
If you hammer too much the bend can go the other way so then you have to hammer the other side.
Just keep eye balling for straightness .

[John Mc]

Is the surface under the bar flat, or does something with a little dish or crown work better?

[HolmenTree]

Is the surface under the bar flat, or does something with a little dish or crown work better?

It has to be flat.
You can also close the rail gap up to factory specs too with the hammer.
Look at my picture again and you'll see my bar cleaner/shim inside the rails . As you hammer the rails where the shim is,  you pull the shim along by the exposed hook the length of the bar.
Don't hammer the detachable nose and don't hammer too hard or you may put cracks in the rails.

[HolmenTree]

Is the surface under the bar flat, or does something with a little dish or crown work better?

It has to be flat.
You can also close the rail gap up to factory specs too with the hammer.
Look at my picture again and you'll see my bar cleaner/shim inside the rails . As you hammer the rails where the shim is,  you pull the shim along by the exposed hook the length of the bar.
Don't hammer the detachable nose and don't hammer too hard or you may put cracks in the rails.

To add. When tightening the rail gap by hammering . Both sides of the bar has to be hammered to keep everything equal and squared up.
Again this hammering technique does not apply to laminated guide bars.

[brianJ]

Thanks everyone for your perspectives.   I guess the main thing is my next bar will last longer from your pointers.