wind_dude
New Member
The top hole for mounting/adjusting the coil for my ms390 is stripped.
Any thoughts on how to repair the hole?
Any thoughts on how to repair the hole?
Holes for coil stripped Stihl MS390
- Thread starter wind_dude
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wind_dude
New Member
Crossed my mind, just so little plastic around the top hole, I'm scared of splitting it. I guess a the thinnest wall I can find and going down on screw diameter.
I forgot those were plastic fantastics.
Filling the hole with JB Weld then drilling and re- tapping might work
Maybe use these heat inserts with some plastic adhesive in the stripped holes. I did it on 2 Stihl TS420 concrete saws with great success for the air filter covers.
Just find the proper thread on the mounting screws and the length.
https://www.ebay.com/itm/3342171908...wb/UDGbHEM5vFappxfxiXrGz0=|tkp:Bk9SR-jTkf7BYQ
https://www.ebay.com/itm/2850519751...Av5E5FeQ2it4qFDdkTgvR8Ugk=|tkp:Bk9SR6zolv7BYQ
Just find the proper thread on the mounting screws and the length.
https://www.ebay.com/itm/3342171908...wb/UDGbHEM5vFappxfxiXrGz0=|tkp:Bk9SR-jTkf7BYQ
https://www.ebay.com/itm/2850519751...Av5E5FeQ2it4qFDdkTgvR8Ugk=|tkp:Bk9SR6zolv7BYQ
user 74409
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Low tech fix is to cut skinny end from smaller zip ties and stuff one or two in hole and screw down. If it works, you could add some Dirko or adhesive for a more permanent fix. It has worked for me with stripped starter screws in plastic cases.
Depending on type of plastic, one trick I use is put the screw in the hole and hold a hot soldering iron on the head until the plastic starts to melt. Carefully remove the iron without disturbing the screw. Let it cool then remove the screw. The melted plastic flows around the screw threads and hardens into good threads.
Sometimes I add slivers of similar plastic if the hole is really stripped out and the hole enlarged.
Works well on ABS and PVC, nylon may not flow depending on how old and moisture content.
Sometimes I add slivers of similar plastic if the hole is really stripped out and the hole enlarged.
Works well on ABS and PVC, nylon may not flow depending on how old and moisture content.
Anybody know what type of plastic is used on cases? That will make a big difference in how to fix it.
If anybody has access to a FT-IR spectrometer with ATR attachment, you could tell the type of plastic from a small (1mm X 1mm) shaving quickly with no sample prep.
If anybody has access to a FT-IR spectrometer with ATR attachment, you could tell the type of plastic from a small (1mm X 1mm) shaving quickly with no sample prep.
cut a piece of weedwhacker string, stuff it in the hole, run the screw home, sounds crazy but it does work, use it fairly often on stripped handle bar holes
but also...
Look over the plastic part carefully. There are often mold id marks and the type of plastic may be identified there. it might be by letters (PP, PET, ABS, PVC, etc) or by the use of the recycling symbol with a number inside.
Or just coat the screw with a thin coat of wax (thinning the wax with mineral spirits then painting it on the threads, then letting it dry generally works) degrease the hole, fill with epoxy then jam the screw in there and let it harden. After it hardens you should be able to remove the screw and have a threaded hole. If it gives you any trouble, heat the screw briefly with a soldering iron when you remove it.
OOps, now I see the hole is plastic. Epoxy generally won't adhere to plastic. I'd try something like what Northman suggested...or maybe some steel wool and Gorilla glue in the hole with a waxed screw...or melt some polyethylene (from strips of milk-jug plastic) into the hole and put the screw in...or use a screw with bigger threads...lots of ways to skin this cat, none of them very good, but probably will last if ya get lucky.
thenne1713
ArboristSite Guru
They do now make SEVERAL EPOXY FOR PLASTICS; have read, but not yet found a RELEASE AGENT FOR EPOXY, also, used to coat the threads on screw. TIP: TO PREVENT rethreading/ stripping plastic holes, gently turn screws in reverse first, until it feel it drop into hole/ thread, then screw in.
Dunno about the epoxies you say they make for plastics, but in my experience, paste wax works fine as a release agent. I've been coating screws and other stuff (like gun receivers) with wax and jamming them into wet epoxy for years, and it releases just fine, though you may need to use some elbow grease. Polishing/buffing the wax film after the wax dries helps. I've heard of using other things as release agents, as well, such as spray-on Pam, but those typically are a lot thicker than a film of buffed wax, and so they don't give as intimate a fit after the exoxy hardens. For more on epoxies and how to use them, see the West System publication "Epoxyworks."
I have posted many times what the Stihl cases are made of. Last time just a week or so ago. HERE IS A LINK SO i don`t have to type it out again,
https://www.techplasty.com/material/polyamid/pa66gf30-polyamide-66-glass-fiber-reinforced
As far as I know, "polyamide" is also known as nylon...so Tom's method (post 13 above) may also work with some heavy monofiliament fishing line, or a few pieces of thinner line. Worth a try if you don't have string trimmer line...
The plastic case as well as other plastic parts will be fiberglass reinforced nylon. Percentage of fiberglass may vary but generally it’s 30%.
Stripped out screw holes can be filled in with simple JB Weld, the hole sides are rather rough and the epoxy will fill in the groves and will hold when a screw is inserted. The screw can be initally inserted into the soft JB but don`t twist it much as it will pull too much of the JB up out of the hole. Better to just insert the screw and a small bit of wiggle will set it, I have coated the screw with spray on Pam, let dry before placing it, it will turn out easily a day later and the part being held down can be installed with the screw carefully threaded in, best to leave the JB to really set up before final torquing down.
Better page the husky boys, They’re experts in stripped bolts and bolts falling out.
