Rivets or Machine Screws When Splicing a Mast?

[Chotu]

Originally Posted by s/v Jedi

Exactly, I’m flabbergasted over the decision to double the length which enables bridging gaps of almost 15mm, leading to a finished install with every fastener sticking 9mm (3/8”) into the mast after all the discussion to prevent exactly that.

A couple of longer screws to help if needed until they can be replaced with the short ones would have been enough.

16mm would allow bridging gaps up to 3/16”

Each layer is approximately 1/4 of an inch, with approximately 1/4” sticking out inside the mast. Flat tips. Not wood screws.

Is there really a big deal with that?

[RaymondR]

Originally Posted by s/v Jedi

Exactly, I’m flabbergasted over the decision to double the length which enables bridging gaps of almost 15mm, leading to a finished install with every fastener sticking 9mm (3/8”) into the mast after all the discussion to prevent exactly that.

A couple of longer screws to help if needed until they can be replaced with the short ones would have been enough.

16mm would allow bridging gaps up to 3/16”

Have to agree with you Jedi, and if internal halyards exit the mast below where the splice is situated there is a high possibility of damage to them from the screw ends.

[Chotu]

Originally Posted by RaymondR

Have to agree with you Jedi, and if internal halyards exit the mast below where the splice is situated there is a high possibility of damage to them from the screw ends.

From 1/4” nubs?

I mean, it’s not too late to change the order yet again.

But I’m going to have to talk to the metal guy before I can do that. Because what if he has gaps that are bigger? I don’t know. I have to see how he wants to work also.

[s/v Jedi]

Originally Posted by Chotu

From 1/4” nubs?

I mean, it’s not too late to change the order yet again.

But I’m going to have to talk to the metal guy before I can do that. Because what if he has gaps that are bigger? I don’t know. I have to see how he wants to work also.

I can’t follow you. The mast is 3/16”. The sleeve is 1/4”. That, together is 7/16” which is 11.11mm

When you put in a 20mm screw, you have 9mm sticking out inside, almost half the length of the screw. If you would use 12mm screws, you have 1mm sticking out inside and can start threading even across a 5-6mm gap.

1/4” is not 9mm… it is 6.3 iirc. I would use 12mm long screws and just buy some longer ones as helpers when the screw can reach the threaded insert. Pull it in with that screw, then replace with the 12mm screw.

[Chotu]

If we drop the metric you’ll understand.

7/16 of an inch is basically 8/16 of an inch. That’s half an inch. That’s basic how much material there is. Half an inch.

Now we have half an inch of material if they are absolutely perfectly mated. I’m getting 3/4 of an inch so that he can reach things that are 1/8” to almost 1/4” out of reach inside the mast and still thread them.

If the countersink goes all the way as far as possible, you have a 1/4” nub of a machine screw sticking into the mast.

Look at a tape measure. Take one out of you are here in the USA. Look at what 1/4” is in real life.

Do you really feel a 1/4” nub of a machine screw poses a big danger to anything inside the mast?

It’s a lot easier to drop the metric here. The numbers are more round.

[s/v Jedi]

Originally Posted by Chotu

If we drop the metric you’ll understand.

7/16 of an inch is basically 8/16 of an inch. That’s half an inch. That’s basic how much material there is. Half an inch.

Now we have half an inch of material if they are absolutely perfectly mated. I’m getting 3/4 of an inch so that he can reach things that are 1/8” to almost 1/4” out of reach inside the mast and still thread them.

If the countersink goes all the way as far as possible, you have a 1/4” nub of a machine screw sticking into the mast.

Look at a tape measure. Take one out of you are here in the USA. Look at what 1/4” is in real life.

Do you really feel a 1/4” nub of a machine screw poses a big danger to anything inside the mast?

It’s a lot easier to drop the metric here. The numbers are more round.

I give up. But just so you know: in the US half an inch is just as long as in the rest of the world. 7/16” is not 1/2”. Also, 3/4” is not 20mm, it is only 19mm. You can’t drop metric when you buy metric fasteners, it doesn’t work like that because it doesn’t translate to imperial sizes.

If you want to do that anyway to get the feeling for what it means to have 9mm sticking out inside: think 3/8”, not 1/4”.

I know exactly how much it is in both metric and imperial because I lived many years in both systems.

[Chotu]

Yeah but what’s really crazy is.. what’s the difference between an eighth of an inch?

That’s a rounding error.

How can you be really worked up about an eighth of an inch? That’s the only difference here.

I would submit that 2/8 and 3/8 is basically the same thing. And both present the same threat to whatever is in the mast.

[RaymondR]

Originally Posted by s/v Jedi

I can’t follow you. The mast is 3/16”. The sleeve is 1/4”. That, together is 7/16” which is 11.11mm

When you put in a 20mm screw, you have 9mm sticking out inside, almost half the length of the screw. If you would use 12mm screws, you have 1mm sticking out inside and can start threading even across a 5-6mm gap.

1/4” is not 9mm… it is 6.3 iirc. I would use 12mm long screws and just buy some longer ones as helpers when the screw can reach the threaded insert. Pull it in with that screw, then replace with the 12mm screw.

And if you get long enough screws you can put a nut and washer and pull by screwing the nut down and not risk rounding out the phillips head.

[Chotu]

OK, Can anyone else chime in? Because I feel like I’m going crazy here.

Does everybody think an eighth of an inch makes a big difference? On something that’s approximately a quarter of an inch hanging into the mast already?

Does everybody think I need to re-order these a third time now?

There are no Phillips head by the way. We went with sockets. Metric ones. My metal guy is probably going to have a fit anyway because he won’t be able to find the right tools and sizing for these things. I wasn’t even thinking of that side of things. I should probably re-order them in standard sizes anyway.

I could get 5/8 instead of 3/4.

Edit: There is no 90° head in the 5/8 at that site.

[Dave_S]

Originally Posted by Dave_S

I think we are miscommunicating, I'll draw it up tomorrow.

I know we have moved passed the 1/2 fixing but this is it drawn up.

[Wotname]

Originally Posted by Chotu

OK, Can anyone else chime in? Because I feel like I’m going crazy here.

Does everybody think an eighth of an inch makes a big difference? On something that’s approximately a quarter of an inch hanging into the mast already?

Does everybody think I need to re-order these a third time now?

There are no Phillips head by the way. We went with sockets. Metric ones. My metal guy is probably going to have a fit anyway because he won’t be able to find the right tools and sizing for these things. I wasn’t even thinking of that side of things. I should probably re-order them in standard sizes anyway.

I could get 5/8 instead of 3/4.

Edit: There is no 90° head in the 5/8 at that site.

See post #253.
16mm is the perfect size for your job
5/8" is the perfect size for your job.
Sockets is perfect, way better than Phillips.
5/8" and 16mm is the almost the same, the difference is 5 thou with the metric being the slightly longer.
If you can get 6mm x 16mm socket head countersunk screws - get them but if you can't, go second best which is 1/4" x 5/8" Phillip head countersunk screws.

Even in the USA, I am sure you can get metric socket drives, I know Snap On sell them

[Dave_S]

Originally Posted by Chotu

What about this factor? The button heads look kind of silly sticking out of the mast. I lean more toward the flat heads.

It is true button or pan heads will have a higher load contact at the centre point of the hole vertically than on the horizontal extremes. On a 7/16 diameter button head that doesn't translate to much on a 200mm radius, probably 2-3 thou when tightened. It will torque down to a better load bearing surface than the CS for your purpose. You could machine a flat for the screw, it would be nicer.

Another rule of thumb is the thread should protrude 1/2 diameter of the fixing thread diameter out of the hole, so a 1/4 fixing should protrude a minimum of 1/8". I like a little more so maybe 3/16th. So I'd go for a 5/8th screw length.

Note if you just order M6 you will get a finer thread by default. You should specify a course thread if you go metric it is not as course as imperial though. Metric come in 15, 16, and 18mm lengths, 16 is common and more than suitable.

Metric course thread for M6 is close to 25tpi, imperial course thread for 1/4" is 20tpi. 20tpi is better for your use.

I know you want CS for the appearance, but these will be better.

I would order these.
Cadmium plated 316 - 1/4"x20x 5/8" button head cap screws.

[smj]

Probably the last time you will think about whether your screws are 5/8” or 3/4” will be right before you step the mast.
If for some reason a year down the road you notice chafe in a halyard then one by one change them out for smaller screws. Otherwise feel good about the extra security the 1/8” will give you.

[Chotu]

Originally Posted by smj

Probably the last time you will think about whether your screws are 5/8” or 3/4” will be right before you step the mast.
If for some reason a year down the road you notice chafe in a halyard then one by one change them out for smaller screws. Otherwise feel good about the extra security the 1/8” will give you.

This is a really good answer. Thank you.

Everything will be nicely bent into place a year later.

A year out, It will easily accept a screw that is the exact thickness plus that extra 1/8 inch mentioned above.

Nothing has to be permanent here. I was thinking of it as permanent.

[Chotu]

Guys, he has to counter sink these things and tap out threads. That’s what I’m talking about having difficulty finding the tools.

It’s not about tightening the heads.

I’m going to talk to him first thing tomorrow morning and see what he thinks.