Fine or Coarse Threads

[islander28capt]

I'll second that motion! No matter how anyone get up a mast saftey should be the priority. That being said, a saftey line should always be used in conjunction with the steps so screw em, in rivet em in, glue em on. What ever gets you sailing safely!

[SailFastTri]

Originally Posted by cantxsailor

I am mounting some steps (1 1/2" x 1/8" flat stock) on my mast and want to use stainless machine screws.

Which thread holds better 10-24 or 10-32 when tapped into the fairly thin (1/8th?) aluminium?

I was going to avoid the problems with dissimilar metals but the 3/16"dia aluminium rivits just do not inspire confidence. I guess some sort of goop like Tefgel will be required if I use the screws...........m

I'd lean toward the rivets. Look up the shear strength -- it is more than adequate and the pull strength is also, maybe higher than screws held by just a few threads in thin metal.

When was the last time you saw an airplane that was held together by machine screws embedded in threaded aluminum?

[imagine2frolic]

The softer the metal the more threads needed for grip. so the finer the thread should be. I would check the shear strength of the rivets before I threaded something so thin without a back washing, and nut.......i2f

[cantxsailor]

Thanks for all the help. 4 screws at the top of the step and 4 at the bottom should hold even my fat self. I will of course use a bosuns chair for comfort and a safety line just in case. I decided to use the fine thread 10/32 mostly because the rivets just didn't make me feel confident although I'm sure if install correctly they would work just fine.

I'm the king of make it strong first and pretty second as anyone who gets closer than 10ft to my boat will attest.................m

[munkey906]

When was the last time you saw an airplane that was held together by machine screws embedded in threaded aluminum?

Exactly.... I've never put rivets in steps on a mast, but in the applications I've used them in they have always worked well... and they've been under very high loads... so cheap too... hard to pass up.

Actually last I checked I think the spreaders on my mast are held in with rivets... that ought to say something about their strength.