Rivets or Machine Screws When Splicing a Mast?

[singlespeed]

Do a simple test yourself. Take two scrap pieces of aluminum plate and join with a rivet and a machine screw. Run your hand over the back side. Which one is likely to snag your halyard? The one with a sharp point and sharp threads or the one with the button? I have never had a properly sized monel rivet, in a properly drilled hole, fail.

[Cwens]

Originally Posted by Benz

The exterior part could be drilled and countersunk before the inner sleeve is put in, then the sleeve drilled at each hole to the right tapping diameter.

Once you drill and countersink the holes in the mast sections and then put in the sleeve and reassemble, precisely drilling each (slightly smaller) tap-sized hole in the exact center of the existing (slightly larger) clearance hole might be a bit of a challenge.

[s/v Jedi]

Electronics/software/networking pro here (so only diy mechanical knowledge) After reading this thread and thinking that machine screws is the way, here is what I know:

Fasteners shown in that picture from the pro are A4-70 grade. This means it is metric and equivalent to 316 stainless steel, but afaik the countersink will be 90 degrees, not 82 or 100 like used for imperial sizes. I think they are 6mm or 8mm… hard to say without a reference. 6mm is like 1/4” and 8mm is 5/16”. With 1/4” thick sleeve I would think 8mm would be great but this is something a mechanical engineer should know immediately.

So it is important that the mast is drilled to a close fit. This means no play in the hole for the fastener. Then the countersink. Make sure you buy the best type to make a smooth cut (or is the workshop doing this?). I use these butmake sure to get the correct angle to match the fastener: https://www.amazon.com/KEO-Cobalt-Si.../dp/B00948QUCG

For tapping you get all kinds of info regarding thread engagement, which is about which drill size to use. Aluminium is different than steel. I would think it’s very important to get this right, or it may lead to loose threading. I use one of those little machinist almanac cheat books to look that up. It will also tell you which torque with threadlocker etc.

On procedure for drilling and tapping it would seem to me that a test fit, alignment, then mark and drill for tap, then disassemble, tap the sleeve and drill the mast for close fit, then countersink the mast. I would use a depth stop to get every countersink right.

On epoxy: our gooseneck and boomvang fittings are all epoxied and bolted to the mast, but the splices are not I think.

[s/v Jedi]

Originally Posted by ChrisOwens

Once you drill and countersink the holes in the mast sections and then put in the sleeve and reassemble, precisely drilling each (slightly smaller) tap-sized hole in the exact center of the existing (slightly larger) clearance hole might be a bit of a challenge.

Exactly, but there are special drill bits for that. They work very well, centering the drill in the bigger hole.

[Training Wheels]

[ATTACH]267534

These work great.

[Lodesman]

Originally Posted by Chotu

I don’t feel comfortable just calling someone and using them like that. That guy is in business.

You can just read his website - look at 'mechanical splice assembly': https://ballengerspars.com/guides/6-...y-instructions

He uses screws, apparently.

[Chotu]

Originally Posted by Training Wheels

[ATTACH]267534

These work great.

Perfect! And kind of funny with your user name. They are kind of like training wheels. For drill bits.

I’ll pass this info along to my metal guy.

Although, it seems like I could save a fortune drilling these out myself. Not really a big deal to do.

[Wotname]

Originally Posted by Chotu

..........
Although, it seems like I could save a fortune drilling these out myself. Not really a big deal to do.

Nah. IMO this is not good thing to do unless you are willing to take the rap if the job goes sideways.

If it goes south, there will always be a disagreement as to who caused the problem, the driller or the bolt-er. Tradesman says "I best my best with the holes I was given..." etc.

[thinwater]

Originally Posted by Benz

The exterior part could be drilled and countersunk before the inner sleeve is put in, then the sleeve drilled at each hole to the right tapping diameter.

Yes, that would do it. Centering the tap holes just requires the right tapered punch (that will self-center).


Centering bits work, but not for a size difference this small. But grinding a punch to the correct taper would take only a few minutes. Or the centering bit might work fine, resting in the countersink taper, which is centered.

[Baby tug]

I vote for welding

[Chotu]

Originally Posted by Wotname

Nah. IMO this is not good thing to do unless you are willing to take the rap if the job goes sideways.

If it goes south, there will always be a disagreement as to who caused the problem, the driller or the bolt-er. Tradesman says "I best my best with the holes I was given..." etc.

That’s a pretty good point. I guess I will have to just pay for the simple stuff along with the complicated stuff. Just to make sure it comes out as one whole project.

[RaymondR]

I drilled and countersunk and tapped to fasten a sleeve in my boom and decided that it I was doing another I would drill and tap without countersink and then screw a measured length of thread and it cut off with about 1 mm sticking up and then peen it flush.

I would even consider using largish diameter, threaded, aluminium round bar and glueing it in to seal out water and put more fastenings in to compensate for the lesser strength.

[neilpride]

Originally Posted by s/v Jedi

Electronics/software/networking pro here (so only diy mechanical knowledge) After reading this thread and thinking that machine screws is the way, here is what I know:

Fasteners shown in that picture from the pro are A4-70 grade. This means it is metric and equivalent to 316 stainless steel, but afaik the countersink will be 90 degrees, not 82 or 100 like used for imperial sizes. I think they are 6mm or 8mm… hard to say without a reference. 6mm is like 1/4” and 8mm is 5/16”. With 1/4” thick sleeve I would think 8mm would be great but this is something a mechanical engineer should know immediately.

So it is important that the mast is drilled to a close fit. This means no play in the hole for the fastener. Then the countersink. Make sure you buy the best type to make a smooth cut (or is the workshop doing this?). I use these butmake sure to get the correct angle to match the fastener: https://www.amazon.com/KEO-Cobalt-Si.../dp/B00948QUCG

For tapping you get all kinds of info regarding thread engagement, which is about which drill size to use. Aluminium is different than steel. I would think it’s very important to get this right, or it may lead to loose threading. I use one of those little machinist almanac cheat books to look that up. It will also tell you which torque with threadlocker etc.

On procedure for drilling and tapping it would seem to me that a test fit, alignment, then mark and drill for tap, then disassemble, tap the sleeve and drill the mast for close fit, then countersink the mast. I would use a depth stop to get every countersink right.

On epoxy: our gooseneck and boomvang fittings are all epoxied and bolted to the mast, but the splices are not I think.

I couldn't have explained it better.

[s/v Jedi]

Originally Posted by neilpride

I couldn't have explained it better.

Thank you

I spent significant time studying all this, especially the details for practical application and it’s good to hear I got that right

[Chotu]

Originally Posted by s/v Jedi

Thank you

I spent significant time studying all this, especially the details for practical application and it’s good to hear I got that right

And thank YOU.

Another good post.