Basic shear pin know-how needed

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
How do you not have to tap it? Wouldn't the nylon be too weak to screw itself into even a paper tube? You don't have to tap machine screws going into wood, but this nylon can't gouge itself into the airframe, right?
I just ream the holes a little bit with the appropriate drill bit (5/64" for 2-56 pins) to get the fit loose enough where they can slide in with a bit of "zip" feeling (from the threads going into the tube). It's much easier to just push them in than fiddling with trying to thread them in with a screwdriver on a cold, windy launch day, and I've never had one fall out on the way up or down -- at least that I can tell.

Jason - on paper airframes I go with brass cutters (i.e., the thin brass strips from the hobby store) in the nose cone and inner airframe wall. To get things to fit, I cut out a small section on the airframe side with a hobby/razor knife, insert the brass strip, and then lay a very thin piece of fiberglass over it (the balloon trick helps to keep things flat and slippery after the cure) to hold it in place. On the nose cone side, I usually end up needing tape to adjust the fit anyway, so I'll just glue the strip to the nose cone and then wrap tape over it to make sure it doesn't go anywhere. Match drill and you're off to the races. On a 4" airframe, I use something like 2-3 2-56 pins.
 
Drats... now I need to go buy a 2-56 tap. LOL

I use a #50 wire gauge drill bit, then run a steel 2-56 screw through them. After this, the nylon screws go in just fine.
 
I just ream the holes a little bit with the appropriate drill bit (5/64" for 2-56 pins) to get the fit loose enough where they can slide in with a bit of "zip" feeling (from the threads going into the tube). It's much easier to just push them in than fiddling with trying to thread them in with a screwdriver on a cold, windy launch day, and I've never had one fall out on the way up or down -- at least that I can tell.

Jason - on paper airframes I go with brass cutters (i.e., the thin brass strips from the hobby store) in the nose cone and inner airframe wall. To get things to fit, I cut out a small section on the airframe side with a hobby/razor knife, insert the brass strip, and then lay a very thin piece of fiberglass over it (the balloon trick helps to keep things flat and slippery after the cure) to hold it in place. On the nose cone side, I usually end up needing tape to adjust the fit anyway, so I'll just glue the strip to the nose cone and then wrap tape over it to make sure it doesn't go anywhere. Match drill and you're off to the races. On a 4" airframe, I use something like 2-3 2-56 pins.

This ^

I tried threading them but having to screw those little limp screws in to get prepped for a launch is a pain in the butt. I like being able to just push them in.
 
Back
Top