Rivets or Machine Screws?

[mherrcat]

In rebuilding my boom I have to replace/reinstall the internal boom bails. They are basically a curved metal plate with a 3/16" hole in each end and a small bail welded to the center. (See pic.) Originally held in place with pop rivets.

I was thinking that maybe replacing the rivets with 1/4" machine screws would be stronger. I would enlarge the mounting holes on the plates to 1/4" and weld a nut on the back.

Any thoughts?

 

[Guy Stevens]

Yes you are correct

The strength in all ways would be increased by using machine screws instead of pop rivets!

Go for it.

Guy

 

[Rhynie]

How far in are they from the ends of the boom? Can reach that deep in to get a nut on the inside?

 

[Rhynie]

I overlooked the 'weld nut on back', that would work. However, most of the load will be directly from the plate to the inside of the boom, I bet you would be OK with just tapping the plate. use a fine thread if you can find it.

 

[newpbs]

Pop Rivet

Since most of the force is not carried by the fastener, I would replace the bail with a pop rivet. The one advantage that a properly installed rivet has is that it will never vibrate loose.

Sometime it is good to keep it simple.

Paul

 

[treilley]

I would vote for the rivets over tapping. Tapping will invite corrosion into the threads and removing the machine screw will likely take the threads as well. You can paint the inside of a drilled hole for a rivet but you cannot paint the threads of a tapped hole. A good stainless rivet should be sufficient. You will need a good quality gun for this. Whichever way you go, use Tef-gel.

 

[tenders]

This is an interesting discussion. I had been taught that a tapped threaded fastener is always preferable to a rivet because rivets are less strong, not removable, and can and do work loose. Is this mistaken?

I would think drilling out a stainless rivet that's loose in its hole could be very frustrating.

 

[mherrcat]

The original rivets had become loose and were never replaced. The resulting corrosion was pretty bad. (See an earlier thread titled "How bad is it? Boom.")

My logic is that the screws would be at least as strong as the rivets, could be tightened easily if they became loose, and could be removed and checked for corrosion easily on occasion. I could use #10 screws and not have to enlarge the holes in the mounting plate, but I figured going to 1/4" (an extra 1/16") wouldn't compromise the mounting plate and might be just a little stronger.

I had to use a hack saw to cut off the heads of several of the rivets because, once they became loose, there was no way to drill them.