6 replies to this topic

[Sam-underscore]

Hello NerfHaven!
I have made 2 homemades in my days(yes im a bit of a nub), but I have recently noticed that every writeup ive seen calls for a tap(or even more than one) to use on your drilled holes. However, when gathering parts, of course a tap was present, but my dad (who is a mechanical engineer) said that a tap is not really necessary as PVC is soft enough that simply putting a screw in will cut threads. So what are the benefits of using one? There is probably a very simple and obvious reason that I am not seeing, and I hope you will be easy on my n00biness...

Thanks
Sam_

[Langley]

Which write-up was this? All of the PVC based designs I've seen use pilot holes and sheet metal screws. Only designs that use polycarbonate generally call for tapping the plastic and using machine screws.

[Sam-underscore]

Which write-up was this? All of the PVC based designs I've seen use pilot holes and sheet metal screws. Only designs that use polycarbonate generally call for tapping the plastic and using machine screws.

I guess the only SNAP tutorial Ive seen with tap required was NoM's SNAPbow one. And I realize now the reason I probably was thinking about this topic is because I've mainly been looking at rainbows and plusbows as I am about to make one. So is a tap necessary to put screws in polycarb?

Thanks a ton,
Sam_

[KaneTheMediocre]

I use 6-32 machine screws for pretty much everything out of convenience. When using anything softer than aluminum, I only tap if it's a screw I plan on repeatedly taking in and out, or I need to be able to take it in and out with low torque for some reason.

[Daniel Beaver]

I only tap if it's a screw I plan on repeatedly taking in and out

Yep, that's the criterion that should be used for PVC. Taps create nice reusable threads, which may or may not be useful.

Edited by Daniel Beaver, 16 October 2013 - 06:26 PM.

[Mully]

Don't worry about tapping if you're only using PVC. What your dad said was right, it's a weak material; what I do when I'm tapping, is I find a drill-bit that's a little smaller than the screw I'm placing (1/8" for a 6/32 screw), I drill the hole, and then just simply drive the screw through it. (I recommend an electric screwdriver) The first time through it's a little tight, but it threads the PVC by itself, so the next time you insert the screw, it has the same feeling as if you tapped it.
Polycarb is a different story, I'd recommend tapping that as it's a harder material.

Edited by Mully, 16 October 2013 - 07:02 PM.

[Ryan201821]

Another reason is if you're using set screws. If they have a hex-based drive, you'll need to tap the hole before forcing the screw in.