Originally Posted by
KeefeinVA
I've built several Tamiya cars in the past (just finished a TA-08 that runs great). I just ordered the TC-01. I want to run it in my local 21.5t TC club race. I have a question around replacing the kit JIS screws with hex head screws. Do I need to tap the holes with a M3 tap first or are the plastics soft enough that I can just build it with stainless steel or ti hex head screws? If I were to build it with kit JIS screws, could I move over to stainless/ti/aluminum screws later? I presume that would be fine but I don't know if the kit JIS screws are a different diameter than typical M3? Thanks!
So a few things here. First JIS is the screw head. Not the thread type. Most JIS screws from tamiya are self tapping, and like a .75mm thread pitch. The machine thread screws are 0.5mm thread pitch. Once you've built a car with the self tapping screws, it's a poor idea to do it with machine screws later. (you can get machine thread screws with JIS heads too, and you get a few from tamiya in most kits..)
If you're going to go with machine thread screws, do it from the beginning.
If you're going to do anything with machine screws, get a thread forming tap. They're about $7. They save you both time, and stop you from stripping the screw holes. Thread forming taps don't remove plastic, they just push it aside. With a thread formed, when your screw bottoms out, you know it, instead of kinda getting a "squish" when it bottoms out.
If you decide to stick with the self tapping screws. Use a little grease on the threads, for the same reason you'd tap the hole for machine screws.