Stihl Working

8 Aug

The chainsaw we have, which was donated to us by Corinne’s Dad, has been out of commission for some time because the bolt that holds the bar on was stripped out. More specifically, it’s actually a stud and it was actually the aluminum casing of the saw itself that was stripped out. Aluminum is a great, lightweight material but it is relatively soft and therefor threaded holes are easily stripped out if over-torqued. I think this was the case due to the missing chain tension adjuster mentioned in an older post. I was a little nervous to tackle this repair for two reasons; first, if you screw up the repair you don’t really get a second chance and second, I didn’t have the necessary tool to do the job. OK… who are we kidding? I think everyone knows that I’d just see that as a reason to get another tool. I tried to resist, though and asked the mechanic next door to work to see if he could repair the threads. After about a month and a half of him being sorry he didn’t get around to it every time I stopped by I took it back and took matters into my own hands. I went and searched out a Heli-Coil kit to fix the threads. I wound up getting it at County Line Hardware in Huntington, which is right around the corner from my old apartment. As always they were very helpful and were able to determine what type of thread size I needed (Metric 8 x 1.25) and supply me with the needed kit to do the repair.
Follow along as I go through the repair step by step:

The first step is to drill out the damaged threads with a specific size drill bit that is called for by the tap. (I didn’t take a picture of this) It’s important to try to keep the drill bit as true to the direction of the original hole as possible. Then you take the tap in a tap wrench and basically screw it in to the hole you just drilled. Again, it is crucial to keep the tap aligned properly. I actually was a tiny bit off but luckily it was close enough to get away with.


The tap is essentially a hardened bolt which cuts new threads, it has recesses to catch the metal shavings as they come off.


Here is the newly tapped hole.


This is a look at the actual Heli-Coil itself, with the installation tool and the tap in the background, it is basically like a spring where the exterior fits perfectly into the cut thread and the inside fits the bolt that fits the original hole. The little tang sticking in to the middle is how the installation tool drives it in.


The installation tool has the same thread as the bolt that will go on with a little notch that engages the tang so it spins it in rather than just threading through it.


This is a view of the fully inserted Heli-Coil, the thread is now repaired. The tang is broken off by inserting a hardened punch and giving it a smart tap, it has a little notch in it so it breaks off easily.


The last step is to install the original bolt or stud into the repaired hole.


I actually wound up replacing the stud with a brand new one because the original nut was a bit stuck on and it was easier to get a new one for 85 cents rather than fight with the old one.

I’m happy to report that I was able to rebuild the chainsaw, install the bar and chain and actually start it. I gave it a test spin and then shut it down to tension the blade a little. Then I made my arm sore trying to get it started again, first because I had the cutoff switch in the Off position and then because it was out of gas! Once I put some gas in it and turned the switch On I was able to get it started and actually get it to idle and I even cut a small branch that had fallen in a few pieces. It seems like the chain could use sharpening or replacement to make it cut well and safely. A dull chain encourages you to push too hard, which can be dangerous, so, as with knives, sharper is safer than dull. Once I get that chain taken care of I think we are good to start chopping down a bunch of overgrown saplings and bushes on the side of the house, maybe even the berry tree by the deck, although I might solicit the services of Derek and his Stihl Farm Boss again if we decide to go for that.


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