Stripped threads in plastic parts .....

[Stilli]

I would be interested to hear your fixes for dealing with stripped threads in plastic parts (when the metal screw is overtightened in the plastic part or just through general wear) other than replacing the plastic part.

[bbventovr6]

Not had to do this myself on plastic as yet but used helicoil/recoil kits many times with metal parts.

http://www.recoilshop.net/metric-m3-0-5-kit.html

[NeilRalph77]

Originally Posted by bbventovr6

Not had to do this myself on plastic as yet but used helicoil/recoil kits many times with metal parts.

http://www.recoilshop.net/metric-m3-0-5-kit.html

I carry a M3 helicoil kit in my hauler for just in case, it works a treat and makes for a stronger thread than the original but putting them in in the first place can be a little awkward.

[neil_p]

One thing I did, when I was tight on funds, and depending on application, was to plug the hole with new plastic. Get the old part spru, shave of thin slices of the plastic, cut them up so they were very small, put some inside the hole, heated up a piece of 3mm steel rod (which I think was an old 2.5mm Allen driver tip that had the tip ground off), and inserted the rod to fuse the plastic shavings and plastic part together and repeat untill the hole is plugged. Once plugged, drill with a 2.5mm bit and re thread with a new screw. I know it's not great but it worked for me, hope that helps.

[Stilli]

Great tips guys, thank you. Haven't seen the Helicoil kits before will give that a try.

Keep 'em coming.

[Cruise]

Take the middle layer of a paper towel ( AKA shock paper)
Rip off a small piece and stuff it in the hole using a 2mm allen key so it forms a layer of paper around the hole.
A small dab of Superglue followed by a very lightly oiled screw.
Keep the screw turning.

Actually if done proper you get very strong threads.

Cruise

[Ashlandchris]

depends how critical the part is (i.e. how much stress is it under?)

There are a few fixes I have used: -

a thin rubber band fed into the hole and then the screw retightened - the rubber allows the screw to bite and gives friction.
Likewise, sometimes a match or sliver of a match can do the same.
I've tried a small cable tie fed into the hole, but often the nylon doesn't "lock" as well when screwed against.

or superglue...

[bigalbi]

I have used araldite or a similar epoxy in the past. If you set the screw in araldite, let it go off then back the screw out it leaves a new thread. What was left of the old thread is usually a good enough key for araldite to key to.

[Allan1875]

Nothing if it's a non stress part.

[neallewis]

Replace plastic part. Take care next time.
Use hand tools, and don't overtighten.

Tried a longer screw? depends on part of course.

[Ashlandchris]

Originally Posted by neallewis

Replace plastic part. Take care next time.
Use hand tools, and don't overtighten.

Tried a longer screw? depends on part of course.

I was thinking back to my early days of RC (early 80s). I remember my old frog and hornet where most screws went into the plastic chassis and if I damaged something then my £1.25 a week paper-round often prevented my replacing it. Fixing things with matches, araldite, longer screws etc all came into play.
One of my proudest moments came when I broke the tub chassis on my Hotshot and discovered that the overall dimensions matched the 90mm square section drainpipes we were having replaced at the time. 1 * junior hacksaw later and I had a new chassis (that was easier to work on than the old Tamiya one).
Nowadays I can replace the part, but couldn't always...