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chas045

FYI: Chainsaw Chain Pitch is Different if Low Profile.

chas045
8 years ago

I just learned something this afternoon that my generally very good local tool and parts and repair place had misinformed me on. I have a perhaps 15 year old McCulloch chainsaw. It has always run well except when I got confused while changing gas lines and needed help from loger who set me straight on primer bulb routing. It is a far better saw than one might expect from Mcculloch's reputation.

However, I just found that my local dealer has been selling me the wrong stuff for years which explains why my saw chain has been acting up. My saw is quite powerful, but it is a consumer saw that was/is designed for 'low profile' (lp) chain; specifically 3/8 lp 050 chain. Low profile chain is supposed to be safer because it doesn't kick back as easily as regular chain, and being a little smaller, does not require so much torque.

A good number of years ago, I ran over the bar with the car or a lawn tractor wheel or something and had to replace it and at the same time I was grousing about how my cutting was inefficient. So my nice dealer said he would make up some more aggressive 3/8 pitch chain for me. Yes, they did cut more aggressively and the saw could keep up, but the chains seemed to loosen up all the time.

I finally decided to figure this out after I noticed while sharpening that my chain was moving out of the bar with each sprocket pass; so I went online where, not surprisingly, I got conflicting results that did suggest that maybe not all 3/8" pitch are the same. So I called Oregon directly (who has a help line where they actually talk to you!!), and they confirmed absolutely that 3/8 and 3/8lp are not the same. I suppose it should have been obvious since the lp version was specifically listed for my saw, but I had assumed that it was just for safety and lower saw stress that my saw seemed to handle well. I gather my dealer thought the same.

It turns out that the dealer sold me the wrong pitch sprocket tip bar (my bent bar didn't have Any) too. So looking back, The pitches, (which is the distance between a couple of links divided by 2) are essentially, although not exactly, the same, but that is not the problem over the short sprocket distances. The issue is that the chain pins or rivets are slightly smaller with the lp chain and the sprocket teeth are therefore made slightly bigger to take up the extra space between pins. When fatter pins rest on a too wide tooth, the chain gets pushed up.

Who knew? Well, not me or my repair shop.

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