mushroomed

iTrader: (8)

I disagree with this if you're talking about the strength of the threads in the plastic holding the fastener in the hole. This is because sometimes self-tapping the screw leaves a worm of plastic that comes out when a screw is removed, or can get mashed into the threads in the plastic if removing and replacing the screw. This doesn't happen or matter enough for me to bother with using a tap set, but I think this does weaken threads in plastic where it happens. Generally less material meaning less strength, but mashed up threads are threads with less material doing its job.

OffRoadJunkie

iTrader: (9)

I wouldn't tap plastic. like mentioned before, it would weaken it. A little drill works nicely.

If hand threading plastic with a bolt is getting too hard, I would recommend not building a Kyosho kit. They use a really hard plastic that can cause some serious had cramps.

tomkatn

iTrader: (119)

I've had to drill out too many stripped heads of titanium and aluminum screws on used vehicles, where someone threaded the screw directly into Associated 'hard' plastic without any prep work ... if the application warrants it, tap the hole as a precaution ...

nitrodude

iTrader: (8)

I wouldn't tap. When you tap you remove material, and the screw will probably come lose.
The principle that is use on RC cars is that the screw forms the thread, moving the material towards it, therefore making the plastic "hold" the screw. The same principle is use in machining, its called roll tapping. The hole size is bigger than on a cut tap, what roll tapping does is it "rolls" the material towards the tap, forming the thread, not cutting it.

xlgraphicspro

iTrader: (5)

I tapped the holes on one kit and will never do it ever again, every screw that was tapped started to back out on it's own. I would have to check every screw after each run and re tighten them. Then I used thread lock and that helped a bit. Also the threaded holes stripped out easier because of the constant retightening. Maybe tap to get the holes started, but not all the way.

xlgraphicspro

iTrader: (5)

Double post whoops!

Milkdudd

iTrader: (13)

This is a screen capture from a website describing pros and cons of using roll (form) taps compared to cutting taps

I have never used a tap on any plastic mainly because I didn't think it was necessary. After reading the posts here, especially the one from the fella who did use a tap and the screws kept coming loose, I realize just what a bad idea it would be. Spinning a tap in for the first couple of threads or so would be a good compromise I think but only if it was extremely hard to get the screw started in extremely hard plastic

Milkdudd

iTrader: (13)

No argument here. When I'm assembling a part that uses more than one screw I'll turn one screw in two or three turns and switch to the other screws and back again until they're all tight. Gives my wrist a little bit of a break between screws. On a slightly different topic, what are your guys opinions of disassembling to put in Ti screws after initial assembly was complete. My opinion is taking screws out and putting new ones in probably doesn't have enough effect to decrease the hold of the screw but I also think nothing would be as good as the first time the screw goes into the plastic. Opinions?

Silverbullet555

iTrader: (16)

I can't speak to current materials as I haven't built a kit in 20 years that required regular maintenance and taking them down completely. Back in the day, we completely disassembled cars every week in between races. Didn't seem to create a problem with screws backing out. Perhaps because of what was discussed earlier. The threads forming vs cutting them perhaps.

OffRoadJunkie

iTrader: (9)

I haven't had an issue with it. They go back in pretty easy.

I'm referring to taping it with the original screw before inserting a Ti-screw. I would not tap plastic with a tap. I would, however, tap that... never mind.

the rc guy

never pre-tap plastic its designed to be used without tapping.

skife

I'll start threads with a tap, just to make sure everything starts straight. Then I'll use a screw with some grease in it.

AHR43

It's been my experience with Ti screws that they are slightly undersize from the CS (Carbon Steel) or AL (aluminum) screws they are replacing. Perhaps it was the Ti screw provider I used, but for that reason I tend to not use them. The miniscule saving in weight is not worth sacrificing the grip the previous screw provided.

Where possible, I try to put the same screw back into the hole it came out of. Not practical in a pit/race environment, obviously, but is doable on the workbench.

Oops. Dinner's ready. Gotta go. Cheers. 'AC'