Measuring Bar wear

[jeffpack1957]

I most likely have the terminology wrong, but the guide a chain follows on the bar. I read using the straight edge, but I'm a machinist, and I measure stuff

A chain (or this case my chain) is .050 nominal, what is the measurement for a worn guide? I searched but not finding, it, just the ruler trick. .055? or whatever.

 

[Philbert]

Obviously, there must be clearance for the drive links to move in the guide bar groove, even as they heat up during use. This clearance increases as both the drive link and the groove wear.

You can mic some new chains and bars and see how much clearance there is at the start, and which parts actually measure at specified gauges.

Common chain gauges are 0.043”, 0.050”, 0.058”, and 0.063”.

Some folks will run 0.058 gauge chain in a 0.050 gauge bar, when its worn, etc. Some will squeeze or hammer the worn bar rails together, to compensate for wear, but that can lead to a dovetail shaped bar groove.

Rule of thumb is more performance based.



Philbert

 

[jeffpack1957]

I found some sources, Oregon says .008, others basically .010 Max

 

[J D]

A new guide bar will usually measure 0.002‐0.004" over the nominal gauge. As Philbert mentioned, it has been common for many years to run a wider gauge chain on a (well dressed & evenly) worn bar. Your values of 0.008-0.010" tie in fairly well with that.

 

[jeffpack1957]

I think I'm just going to machine a no go gauge gauge at .060, but now depth is an interesting question from further reading

 

[Philbert]

but now depth is an interesting question

Yeah, I looked at groove depth a long time ago. But it seems that groove width / shape, and nose sprocket issues occur long before your drive links bottom out.

Some bars have replaceable nose tips or sprockets; some do not.

Philbert

 

[Sidecarflip]

Glad you are a machinist. I own and operate a short run machine and fabricating shop with 2 full time employees, myself and I've never given much of a thought to bar wear as I flip my bars over, every time I put on a new loop and so long as the bars have a visible rock in them, I'm good with that. Even my 45+ year old Stihl 028 has the original bar on it, but then I don't use it every day either.

 

[jeffpack1957]

My question on depth has more to do with bar depth, not sprocket, since that surface wears down too and why folks flip them

Maybe I'm overthinking it, and width go no go is more likely to occur first.

Now to think about sprocket

 

[Philbert]

why folks flip them

Top and bottom wear differently in use. Most cutting is done with the bottom of the bar, pressing against chain moving at 50 to 60 mph.

If you flip the bar each time you take it off, you balance the wear, and extend its useful life.

Philbert

 

[Sidecarflip]

Top and bottom wear differently in use. Most cutting is done with the bottom of the bar, pressing against chain moving at 50 to 60 mph.

If you flip the bar each time you take it off, you balance the wear, and extend its useful life.

Philbert

Exactly and using quality bar oil in a sufficient amount will really extend bar life and roller nose life as well. Having said that, all my guide bars have greaseable roller noses and they get greased prior to every use and in the last couple decades, I've never had one fail.

One thing I rarely do is I rarely bear down on a loop. I keep them sharp and the rakers set correctly and I let the chain self feed. My saws are much happier that way and so am I. My 'rule of thumb' if you want to call it that is, when I see pitch building up on the heels of the teeth, I change out the loop for a sharp one. Dull cutters just rob power and make sawdust.

 

[J D]

My question on depth has more to do with bar depth, not sprocket, since that surface wears down too and why folks flip them

Maybe I'm overthinking it, and width go no go is more likely to occur first.

Now to think about sprocket

The fact that you're thinking about it at all puts you well ahead of most chainsaw users out there.
I think with your engineering background it's unlikely you'll overlook any wear to the point it causes any sort of issue. Dress the bar, keep the chain sharp & the oil flowing & let the chips fly