Chain configuration & "Bite" at different chain speeds

[weimedog]

An observation. And resultant confusion:

I stuck together a little Jonsered 2051. It was a little low on compression...and had other issues. Make a long story short, now it runs well and is building compression with time to the point its running really well now.

So the issue. A week or two ago I ran it with a reasonable looking chain...it created dust and wouldn't bite. A "sharpening" later, it was better. Less dust but still no "bite" so the saw just made rpms and noise with dust & small chips. So a new chain was put on (borrowed from a member dealer at a GTG)..same results and actually the "timed" run thru the test log was virtually idential to the touched up old chain...still didn't really feel like it was right. So I put the saw on the back burner. Disappointed.

This week I took another "run" at the saw. Put a 16 inch bar with 3/8 chain along with removing the limiters on the carb and re-tuning the saw. Much better...but still that feeling like the chain wasn't biting and forming a good chip. Too much dust and on the oak test log...smoke/burn. Sharpened..the same. BUT the saw was running better. So I rummaged thru my pile of used chains and came up with a lightly used chain. Kind of curved on the edge vs. a sharp angle. Actually this chain didn't look as good as the prior one....but now that little 2051 cuts like crazy! Just from a chain "shape' change. No more feeling that the chain wasn't getting bite. It chewed thru my oak test log and made a nice chip while dragging the saw RPM's right into its sweet spot for power.

So back to the "newer" chain...sharpened..and back to no bite.

So the question is. Does one tooth design work better at higher chain speeds than another? Should I try and find a 6 tooth sprocket to drop the chain speed when using those oregan "chisle" chains I have?

 

[timberwolf]

Have you adjusted the raker height?

If you file a chain back sooner or later the rakers will need to be taken down to get it to bite.

Also a real worn bar can cause a chain to bite inconsistantly though the cut.

 

[JasonBmac]

The way you describe things, the first 2 chains were chisel chains (sharp point), and the third one that cut well was a chipper chain (rounded or chamfered cutter).... the first 2 should have cut faster....

I'd question your raker heights too.

Lay a flat edge across the tops of the cutters. Use feeler gauges to see what the raker heights are. I'm betting they're well under .020". Most chains work best with .025-.030" rakers...

Use a flat file to lower them (not more than .025" or so below the cutters), and then try again...

J

 

[mtngun]

Have you adjusted the raker height?

:agree2: See the FOP sticky thread at the top of the forum.

I've had good luck using the FOP with 3/8" crosscut chain.

0.325" I still haven't figured out yet -- the FOP does not seem to be aggressive enough.

 

[weimedog]

Have you adjusted the raker height?

If you file a chain back sooner or later the rakers will need to be taken down to get it to bite.

Also a real worn bar can cause a chain to bite inconsistantly though the cut.

On the one I touched up I just eye balled the rakers, so I honestly don't know. The bar was fairly new. Still had the paint completely on and the second chain was out of the box new.

Actually the 3/8 was used and the bar was a reconditioned bar. The rounded cutter was in good shape and the rakers were around .020inch..it worked best.