Fixing stripped nylon threading

[shorne]

To repair the hole, I have heard of people melting a plastic/nylon of the same type with a chemical- laquer thinner maybe?

I have been researching this and injection molding in general. The process you described is called solvent molding and it's a form of plastic welding.

http://en.wikipedia.org/wiki/Plastic_welding

From what can gather it seems our parts are molded with nylon-6 resin which needs to be extruded at a temperature between 250 and 290 degrees. It's pretty interesting stuff.

It seems a bit hard to buy small quantities of nylon resin pellets. I might have to use some doner parts.

http://en.wikipedia.org/wiki/Injection_molding

[klavy69]

It seems a bit hard to buy small quantities of nylon resin pellets. I might have to use some doner parts.

not trying to make fun of this but if you use a cheese grater you can take a junk nylon part and recycle the nylon instead of getting pellets. you have the correct nylon and color that way also

Todd

[shorne]

It seems a bit hard to buy small quantities of nylon resin pellets. I might have to use some doner parts.

not trying to make fun of this but if you use a cheese grater you can take a junk nylon part and recycle the nylon instead of getting pellets. you have the correct nylon and color that way also

Todd

Yup, that's what I meant by doner parts.

[vsefiream]

To repair the hole, I have heard of people melting a plastic/nylon of the same type with a chemical- laquer thinner maybe?

From what can gather it seems our parts are molded with nylon-6 resin which needs to be extruded at a temperature between 250 and 290 degrees. It's pretty interesting stuff.

That would be interesting if you could get nylon to flow at those temps It's much higher than that, IIRC it's ~450 for nylon, lower for styrene and slightly lower than styrene is ethylene. I can probably get some nylon pelets.

I did injection molding at Kodak from '95 - '03, in other shops from '03 through '07 until I swore it off for good! I still have a lot of friends in the industry and getting a handfull of resin would be a piece of cake, we used to fill each others tool boxes with the stuff!!

[shorne]

That would be interesting if you could get nylon to flow at those temps It's much higher than that, IIRC it's ~450 for nylon, lower for styrene and slightly lower than styrene is ethylene.

Sorry, I should have mentioned some units 250 - 290°C; which is about 480 - 550°F. I have been living over seas for a while.

[300D50]

I'll second heli coils for the best fix, if budget isn't an issue and there's enough wall thickness.

CA (krazy/super) works, but it will end up being a pain to remove.

Might want to use PTFE tape wrapped around the screw, if it still mostly threads in. Sort of like the toothpick in a wood screw hole. Could also try PTFE pipe goo, but not sure how well it will hold up.

Heatsink compound also tends to act like a thread locker, at least if I get it on fresh threads...

Hot glue may be useable depending on the stress imposed. Glop on threads, screw in, trim the excess.

Million ways to skin the cat and all.

[vsefiream]

Helicoils would probably be my weapon of choice. A close second would be brass inserts. They are knurled on the outside diameter for bite. You would heat stake them in place with a soldering iron. The brass insert heats up and melts the surounding plastic into the knurles. It's a process used for a lot of new parts as a second operation after molding. If you choose this method, leave the insert flush or slightly proud of the mating surface to avoid pulling it out.

[THE H.P FREAK]

HI1... The brass inserts I use from Tony's Screws don't need to be heated up. You drill the stripped hole out to the required size for the insert. Then you press it in. That's it. I usually put C/A glue on the insert before pushing it in. The brass insert is designed to expand and bite into the plastic has the screw goes in. I've never had any problems with any of them ever twisting or pulling out.