0.043" vs. 0.050" Lo Pro Comparison

[Chris-PA]

I decided do a comparison of Oregon 90S (0.043") and 91PX (0.050"). I had 2 16" bars with identical profiles and a good 56DL loop of each. The results were not what I expected.

The 91PX loop was pretty new and freshly filed with depth gauges set.

The 90S loop had not been run for a while but only had a couple of cuts on it and was sharp.

I ran them on my Husqvarna (Poulan) 142, which is one of my few stock engines although it had the cat replaced with a 141 muffler. The wood is fairly hard white ash, pretty much full bar. The first 2 cuts are 90S and the second 2 are 91PX:



Both chains cut identical times from what I could tell. Measuring the 2nd cut of each chain came out at 20sec, and the saw is running around 9500rpm on each cut. I expected the 90S to be faster as I've always found it to be very fast cutting chain before, but it didn't seem to have any advantage.

 

[Full Chisel]

The biggest gains from .050 over .043 is the cutter lifespan and durability....043 is some diminutive chain and they just don't last long. I would think the .050 cuts faster as long as the power head is strong enough to handle the wider kerf and keep the RPMs up in the cut.

 

[Franny K]

The smaller chain may not clear chips all that well. I found it to be slower than the 0.050 stuff with my Husqvarna battery saw. I was testing in pretty much bar buried but shorter bar. The advantage is primarily in smoothness of the finish and smoothness of the saw staying in one place.

I suspect that 142 uses the same drum as my 36. I got a rim drive kit for mine but have yet to use it. You could bump up to a 7 tooth small spline 3/8 sprocket and see how that effects the results, try oregon and Stihl 1/4 and the 0.325NK.

Another thing I noticed on my efco 132s 30cc top handle saw is after converting to the smaller chain the oil level is farther down when the fuel is used up.

 

[Chris-PA]

The biggest gains from .050 over .043 is the cutter lifespan and durability....043 is some diminutive chain and they just don't last long. I would think the .050 cuts faster as long as the power head is strong enough to handle the wider kerf and keep the RPMs up in the cut.

I've been running 0.043" on this saw for years and have not noticed any problems with cutter lifetime from wear. If you think of the cutter edge length as it is, add a bit more next to it to make it 0.050" would not change how much force is on the existing edge - the chain would just have to move more material. What effects wear on any unit length of cutter edge is the force on it and the chain speed.

I didn't end up with any greater chain speed here, but if I had the cut would have just finished sooner, which would not cause more wear.

The smaller chain may not clear chips all that well. I found it to be slower than the 0.050 stuff with my Husqvarna battery saw. I was testing in pretty much bar buried but shorter bar. The advantage is primarily in smoothness of the finish and smoothness of the saw staying in one place.

I suppose it may be a chip flow issue - this test was pretty much full bar. I have it in my head that this saw and chain combo was quite fast, but I have not been using it much of late and maybe my expectations have changed due to having more ported saws now.

 

[Termite]

Chris, thanks for posting the test. I have never tried and narrow kerf chain and see no reason to. My smallest saw is GZ4000.

 

[Chris-PA]

Chris, thanks for posting the test. I have never tried and narrow kerf chain and see no reason to. My smallest saw is GZ4000.

Funny about that - the last time I ran this chain I put the same 0.043" bar and chain on my ported GZ4000 clone to see how it did limbing:



It was turning over 12.5k rpm IIRC, which is part of the reason I expected it to be faster - but this was a much bigger piece of wood.

 

[SawTroll]

The biggest gains from .050 over .043 is the cutter lifespan and durability....043 is some diminutive chain and they just don't last long. I would think the .050 cuts faster as long as the power head is strong enough to handle the wider kerf and keep the RPMs up in the cut.

I agree - that saw likely is "too strong" for the 90 chain to have any advantage over the 91 chain.

 

[Philbert]

That is pretty big wood to be cutting with 3/8 low profile chain!

Type 90 chain is low profile. Type 90 chain is low profile and narrow kerf, which probably has more of an advantage for helping lower powered saws (especially powered pole saws and battery powered chainsaws) cut more efficiently, than cut faster (e.g. chain speed remains the same). I use it in a battery powered pole saw (Oregon PS250) and have had really good results with it.

What surprised me was that Oregon recommends different file sizes for these chains - 5/32" for Type 91 and 4.5mm (11/64") for Type 90. They said that they have different cutter profiles, so the 'smaller' chain uses a 'larger' file! Anyway, that is what I used and got great results.

It also appears that you compared a reduced-kickback chain (91PX) to a standard (90S) chain, without noticing an appreciable loss in cutting speed (something that I like!).

Philbert

 

[Chris-PA]

That is pretty big wood to be cutting with 3/8 low profile chain!

Type 90 chain is low profile. Type 90 chain is low profile and narrow kerf, which probably has more of an advantage for helping lower powered saws (especially powered pole saws and battery powered chainsaws) cut more efficiently, than cut faster (e.g. chain speed remains the same). I use it in a battery powered pole saw (Oregon PS250) and have had really good results with it.

What surprised me was that Oregon recommends different file sizes for these chains - 5/32" for Type 91 and 4.5mm (11/64") for Type 90. They said that they have different cutter profiles, so the 'smaller' chain uses a 'larger' file! Anyway, that is what I used and got great results.

It also appears that you compared a reduced-kickback chain (91PX) to a standard (90S) chain, without noticing an appreciable loss in cutting speed (something that I like!).

Philbert

I will try to measure it later, but if I recall correctly the cutters on 90 are actually taller than on 91 - it's only really "lo pro" in that it has the same chassis geometry. I use lo pro on wood that large and larger all the time. However long the bar is that's what I expect it to do.

As to the ramps on 91PX, I really don't think they have any negative effect at all in bucking cuts like this. I've modified a lot of chains to remove shark fins and such, in fact this "90S" started out as 90SG, but I fixed that, but I don't bother removing DL ramps. The ramps are really a help with brush cutting.

 

[Philbert]

I heard that the VG style (tie strap) bumpers were going to be discontinued (?), but apparently people still like them for cutting on small diameter wood, like with pole saws, where they provide a smoother cut. Otherwise, I prefer the PX (drive link) bumpers.

Philbert

 

[Chris-PA]

I heard that the VG style (tie strap) bumpers were going to be discontinued (?), but apparently people still like them for cutting on small diameter wood, like with pole saws, where they provide a smoother cut.

Philbert

I don't see 91VG in stores any more. Thankfully.

 

[Chris-PA]

That is pretty big wood to be cutting with 3/8 low profile chain!

I forgot to mention that I dropped that tree with 91VXL lo pro - it was a little bigger at the butt end.

 

[LegDeLimber]

Type 90 chain is low profile and narrow kerf, which probably has more of an advantage for helping lower powered saws (especially powered pole saws and battery powered chainsaws)
....
What surprised me was that Oregon recommends different file sizes for these chains - 5/32" for Type 91 and 4.5mm (11/64") for Type 90. They said that they have different cutter profiles, so the 'smaller' chain uses a 'larger' file! Anyway, that is what I used and got great results.

Philbert

I have to wonder if the cutter height is to help chip flow and reduce the drag a little bit more for the NK chain?

My Sis picked up a pole saw with a 6 amp motor.
Can't recall the bar length, probably 8"~10"
Something off of a shopping channel, a SunLong or LongSun or sumsuch sort of thing...
(of course the newer ones, now have an 8 amp motor. )
I haven't had the opportunity to measure what gauge chain it has.

But my point is about that mention of no more bumper-tie-strap chain.
You guys say the bumper link stuff is going away?

The pole saw came with a lo-pro skip cutter chain (roll eyes)
for extra jerkiness and carpel tunnel tweaking , I figure.
Don't understand what they where thinking by putting that skip chain on such a short bar, for cutting limbs with.

 

[CR888]

I use .043 for pole saws and top handles up to 28cc. More powerful units do better with 050. In the right circumstances the 043 chain can give you a speed advantage but not with big bars and saws above about 30cc. This is just my experience.

 

[Chris-PA]

I'm still surprised that the rpm was so close for both chains. The saw will free rev much higher. There really isn't any mechanism for regulating the rpm, unless perhaps the power band is such that it falls off very fast above that rpm. I'm wondering if maybe it was me subconsciously regulating the sound/rpm of the saw - when using small saws you get used to keeping them from bogging.

 

[LegDeLimber]

Hmm. What would you say to the difference in surface area between the bar and chain?
Would ya reckon that the difference in that area and the resulting difference drag of the chain lube is appreciable (outside of lab measurements)?
Would be kind of funny to find out something like the wind drag on the cutters was also influencing it.

 

[Philbert]

My Sis picked up a pole saw with a 6 amp motor. . . .The pole saw came with a lo-pro skip cutter chain (roll eyes)
for extra jerkiness and carpel tunnel tweaking , I figure.
Don't understand what they where thinking by putting that skip chain on such a short bar, for cutting limbs with.

The tie strap bumpers are still used to fill in the spaces between cutters for smoother cuts in small diameter wood.

The skip chain is often put on under powered saws, to reduce the number of teeth in the cut. This is common on the less expensive consumer pole pruners.

Philbert

 

[SawTroll]

I don't see 91VG in stores any more. Thankfully.

Husky has replaced 91VG (H36) with 91PX (H37) as their standard 3/8" lo-pro chain, and I believe they aren't alone about it.