How to Bend Plastic Stems

[Sobrbiker]

I tried to bend a cheap mini-meer plastic stem this morning with a heat gun. I’m pretty sure it’s a polycarbonate type plastic.

Is there a trick to getting it to bend straight instead of wiggly?

 

[Hillcrest]

If its cheap plastic wouldn't boiling water for a few seconds be better as in less heat than a heat gun ? I don't know as I've never done it but i would think to go up in increments heat wise. And put a pipe cleaner or two down it to keep draft open. Maybe check with @RustiePyles CPG or @georged ???

 

[Sobrbiker]

If its cheap plastic wouldn't boiling water for a few seconds be better as in less heat than a heat gun ? I don't know as I've never done it but i would think to go up in increments heat wise. And put a pipe cleaner or two down it to keep draft open. Maybe check with @RustiePyles CPG or @georged ???

Damnit! I should’ve had more coffee and I’d have remembered the stems I’ve done for my cobs using boiling water, but the heat gun was right there.
And I use a spray nozzle (the tubes taped to side of brake cleaner cans) to not collapse airways.

 

[Sobrbiker]

Definitely more of a polycarbonate than the plastic MM stems. Boiling water didn’t soften it the same as plain plastic.
Gonna go with heat gun and rubbing out with leather gloves…

 

[Hillcrest]

Definitely more of a polycarbonate than the plastic MM stems. Boiling water didn’t soften it the same as plain plastic.
Gonna go with heat gun and rubbing out with leather gloves…

I think there's a youtube video of someone bending vulcanite with a tea candle. Good Luck !

 

[Non-Mentholated Black Man]

Definitely more of a polycarbonate than the plastic MM stems. Boiling water didn’t soften it the same as plain plastic.
Gonna go with heat gun and rubbing out with leather gloves…

Have you considered using an electric toaster (bread)?

You should not have to actually insert the stem into the unit.

 

[ssjones]

I've never tried to bend straight, I can see how that might be challenging.
The trick is to get it warm enough to bend, but not too hot to deform. It's a fine line. (my only experience is with vulcanite)

 

[Chasing Embers]

The ripples look like you've burned the plastic.

 

[Chasing Embers]

Straightening a stem isn't difficult. Heat it just to the point of being pliable then insert a straight metal bar or wire into the bore and allow it to cool.

 

[georged]

Straightening a stem isn't difficult. Heat it just to the point of being pliable then insert a straight metal bar or wire into the bore and allow it to cool.

If the stem has been heated enough to bend, that means the walls of the airway will be soft as well, so the end of the rod would have to be VERY smoothly rounded and polished or it will dig into the plastic when inserted.

Unless the rod is an exactly-right slip fit, it couldn't straighten the outside any more accurately than the looseness of the fit.

But if it's TOO close, the rod will be locked in place when the stem cools.

Also, airways taper at some point, meaning the rod-end would have to be ground to match.

Hardly kitchen table stuff, and "a solution to a non-existent problem" in any event... Just put on some leather gloves thick enough to keep your fingers from getting burned, and tweak it until straight.

 

[Sobrbiker]

Just put on some leather gloves thick enough to keep your fingers from getting burned, and tweak it until straight.

Huh, that’s what I was just doing before I saw the new posts on this thread
Not perfect, but good enough for a $25 mini meer, and a lesson that’ll stick.

 

[Sobrbiker]

I've never tried to bend straight, I can see how that might be challenging.
The trick is to get it warm enough to bend, but not too hot to deform. It's a fine line. (my only experience is with vulcanite)

This stuff (whatever Paykok uses in their mini replacement sets) is somewhere between cob plastic and acrylic. So far I’ve had good results with the former in boiling water and the latter with a heat gun.
Plastic/acrylic don’t give the extra indicator of smell that vulcanite does. I’ve taken a little bit of the bend out of these before (just enough to change angle), but trying to get a bent to a straight line requires more patience and focus than I estimated for sure.

 

[Chasing Embers]

Ah, okay. I've only worked in plastics since the mid '90s so what do I know?

Looks good.