Rivets or Machine Screws When Splicing a Mast?

[s/v Jedi]

It is not 1/8”.

If you use a 12mm screw that I recommended, then it sticks out 1mm inside.

If you use a 16mm screw that someone else recommended then it sticks out 5mm inside.

If you use a 20mm screw that you ordered, then it sticks out 9mm inside. 9mm is almost 3/8” which is triple the 1/8” you talk about.

I started mentioning this because you had decided to limit the risk of damaging halyard and wiring by minimizing the length that sticks out and next thing you go from 1mm sticking out to 9mm sticking out

Also, a longer screw that sticks out more gives nothing extra, no additional safety by installing a longer screw. I don’t understand where that comes from?

You can not buy a M6 screw with flat socket head in 5/8” long, not in 3/4” not in 1/2”, none of that. Your choices are 12mm, 14mm, 16mm, 18mm and finally, “your” 20mm. You went up 4 sizes out of the blue.
The M6 screws have a 90 degree countersink.

You can get all metric taps with suiting drill bits as well as the countersink bits even from Amazon. I bet every hardware store has them on the shelf and for sure Fastenall etc.

[Chotu]

Oy…. The *difference* is 1/8. Not the total sticking out.

9mm stick out minis 5mm stick out is a 4mm stick out.l difference.

That’s around 1/8” difference

Those weren’t my posts talking about limiting the damage from the ends of the screws. That wasn’t me.

I didn’t even consider the possibility that there could be damage from tiny little screw ends sticking through.

[s/v Jedi]

Originally Posted by Chotu

Oy…. The *difference* is 1/8. Not the total sticking out.

9mm stick out minis 5mm stick out is 4mm stick out.

That’s around 1/8” difference

Those weren’t my posts talking about limiting the damage from the ends of the screws. That wasn’t me.

I didn’t even consider the possibility that there could be damage from tiny little screw ends sticking through.

1/8” is 3.2mm. The difference between 12mm and 20mm is 8mm, not 5mm nor 4mm

I give up, dam yanks can’t do metric

[Chotu]

Originally Posted by s/v Jedi

1/8” is 3.2mm. The difference between 12mm and 20mm is 8mm, not 5mm nor 4mm

I give up, dam yanks can’t do metric

I gave up too. Why do you have to break everything down to such small units? The smallest unit we have is an eighth of an inch.

We don’t do things in sixteenths of an inch. Not things like this. That’s for a micrometer or something.

This thread has turned absolutely crazy. 3.2 mm and 4 mm is the same exact thing. Why are you saying they are different?

You are making it sound like the 0.8 mm the difference in my conversion is huge or something. Why are you doing that?

There is no reason to be doing that.

There is a 4 mm difference between the two, which is an eighth of an inch difference which I have been saying all along but you somehow don’t agree with. Why?

And I also had to learn imperial units. At NASA I didn’t have any trouble with MKS. That’s what I was taught to start with. That’s what I used most of my early life. I had to learn this stuff for this project specifically. So I’m not wrong. An eighth of an inch and 4 mm is the same damn thing. 0.8 mm is not a big enough difference to be causing some kind of debate about.

Quoting your own post since you seem to have forgotten about it:

If you use a 16mm screw that someone else recommended then it sticks out 5mm inside.

If you use a 20mm screw that you ordered, then it sticks out 9mm inside. 9mm is almost 3/8” which is triple the 1/8” you talk about.

16mm sticks out 5mm. 20mm sticks out 9mm. For a grand difference of…..

4mm!!

4mm is 1/8”

So seriously…. What are you TALKING about??

It’s a difference of 1/8” as I’ve said all night long.

That’s directly from your numbers.

[JMB_40]

Originally Posted by Chotu

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

Hi. First time poster here - you took me out of the closet. I am helping a lad mending corrosion problems where his spreaders interface the mast. We are researching to decide on a solution, goolgle pointed us here and we've been following. We learnt a lot. We were all set on monel rivets and tefgel and it will now be stainless screws with loctite. So, thanks CF! Wonderful resource : professional riggers, engineers of all kinds, machinists, renowned blue water sailors, boatbuilders, a lot of knowledgeable people contributing here, despite all the noise.

The metric/imperial thing is too funny: were you involved in this? https://www.simscale.com/blog/nasa-m...rbiter-metric/

Trying to help you out:

Stop posting.

Are there going to be halyards inside the mast at this splice? If yes:

Get a piece of paper, a sharp pencil and a metric ruler.
Draw a cut of your situation at a scale of, for example, 2/1. Just like Dave_S post #265 did for your 1/2" $700 screw-up. Use mm only. It is not hard. each inch corresponds to 25.4 mm. Keep the decimals and centesimals. Do the drawings for the lenghts of 12mm, 16mm, 20mm screws. Everyone is telling you button head is better - you are not listening, so, consider the depth of the 90º countersunks on your drawings. See how much is protruding inside for every possibility and take a decision.
Order a couple of longer screws to bring the two pieces together at an adjacent hole and replace them after. This was taught you many posts before, repeated on this same page.

If no halyards will be travelling inside this section: length of the screw is basically irrelevant and the ones you ordered already will do.

You owe all the guys trying to help you through 200 plus posts a lot of pictures... of the splice insert, of the new inferior mast section, of the joining process.

But please stop running around asking for a poll to decide every mm of screw length on your vessel. Read with more attention, draw more, post less.

Good luck,

Jorge

[Chotu]

Originally Posted by JMB_40

Hi. First time poster here - you took me out of the closet. I am helping a lad mending corrosion problems where his spreaders interface the mast. We are researching to decide on a solution, goolgle pointed us here and we've been following. We learnt a lot. We were all set on monel rivets and tefgel and it will now be stainless screws with loctite. So, thanks CF! Wonderful resource : professional riggers, engineers of all kinds, machinists, renowned blue water sailors, boatbuilders, a lot of knowledgeable people contributing here, despite all the noise.

The metric/imperial thing is too funny: were you involved in this? https://www.simscale.com/blog/nasa-m...rbiter-metric/

Trying to help you out:

Stop posting.

Are there going to be halyards inside the mast at this splice? If yes:

Get a piece of paper, a sharp pencil and a metric ruler.
Draw a cut of your situation at a scale of, for example, 2/1. Just like Dave_S post #265 did for your 1/2" $700 screw-up. Use mm only. It is not hard. each inch corresponds to 25.4 mm. Keep the decimals and centesimals. Do the drawings for the lenghts of 12mm, 16mm, 20mm screws. Everyone is telling you button head is better - you are not listening, so, consider the depth of the 90º countersunks on your drawings. See how much is protruding inside for every possibility and take a decision.
Order a couple of longer screws to bring the two pieces together at an adjacent hole and replace them after. This was taught you many posts before, repeated on this same page.

If no halyards will be travelling inside this section: length of the screw is basically irrelevant and the ones you ordered already will do.

You owe all the guys trying to help you through 200 plus posts a lot of pictures... of the splice insert, of the new inferior mast section, of the joining process.

But please stop running around asking for a poll to decide every mm of screw length on your vessel. Read with more attention, draw more, post less.

Good luck,

Jorge

Fine. You want to be like that and you want me to stop posting?

You’ve got it.

[s/v Jedi]

Here’s two pictures of my handy small ruler: the front is for inches. It has a course 32nds scale and a fine 64ths. That is 8 times as small as 1/8”

The reverse side has metric. The course scale is 1mm and the fine scale is 1/2mm. See how course a mm is?

Look at 9mm, that’s huge, it is 1.5 times the diameter of your screws.

[stormalong]

Originally Posted by 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.

Metric taps, drill bits and Allen wrenches are common in the US now. Even my local hardware store stocks them.

[Dave_S]

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.

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.

You can't do that, especially with the bloody countersunk screws you are so determined to use.

IF you intend on pulling the 2 pieces of material together up to a 1/4', the holes won't line up.

It's because as you pull them together the hole will migrate, and your CS hole will no longer align, also the threads will no longer be colinear to each other so the screws will have to force/cut themselves into the material and the leverage will deform the threads and the small parallel section of the CS hole or it will weld/gaul the screw to the material at which point the screw will shear.

At best you will have used a much greater amount of the torque applied installing the screws to the friction in the thread and you will get a false reading on the clamp force, it is also much more likely that you will shear the fixing because they are only designed to take about 35% of the torque through the friction in the threads.

All this means if you manage to get this together, you will probably loose around 60% of your clamp force or worst case, shear the heads of screws where the CS meets the thread, hopefully during installation and not under sail.

[neilpride]

Originally Posted by Dave_S

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.

You can't do that, especially with the bloody countersunk screws you are so determined to use.

IF you intend on pulling the 2 pieces of material together up to a 1/4', the holes won't line up.

It's because as you pull them together the hole will migrate, and your CS hole will no longer align, also the threads will no longer be colinear to each other so the screws will have to force/cut themselves into the material and the leverage will deform the threads and the small parallel section of the CS hole or it will weld/gaul the screw to the material at which point the screw will shear.

At best you will have used a much greater amount of the torque applied installing the screws to the friction in the thread and you will get a false reading on the clamp force, it is also much more likely that you will shear the fixing because they are only designed to take about 35% of the torque through the friction in the threads.

All this means if you manage to get this together, you will probably loose around 60% of your clamp force or worst case, shear the heads of screws where the CS meets the thread, hopefully during installation and not under sail.

This is precisely why it is so imperative that the sleeve fits around its entire perimeter without gaps.

It is better to make a sleeve a little larger in diameter and cut it at the back, instead of the cut material you can adjust a single plate in the back area and put the sleeve in compression inside the mast, the objective is for the sleeve to make contact with the mast without gaps, and guide the other section to come together perfectly.

If the sleeve enters with gaps, you risk the integrity of the splice no matter if you use screws, rivets, or bubble gum.

The holes are not going to line up either way, you are right at that point, Jedi explain the process very well a few posts above.

[RaymondR]

The boom repair exploited a multi part sleeve with a wedging action accomplished by the screw tightening to achieve a tight fit.

[Bowdrie]

Originally Posted by neilpride

If the internal part dont match perfect the outer section then dont do it, sleeves fit evenly without gaps, let me know if im wrong ,but the whole question its to know if rivets or screws can help the sleeve to fit to the internal mast sidewalls?
Back to the question ,honestly try to fit a piece of small section in your current mast section its a risky bussines.

^ This from well over 200 posts ago is correct.
You cannot use fasteners, (rivet or machine screws,) to PULL inner and outer sections together when both are one piece.
They must fit perfect WITHOUT ANY GAPS.
Trying to line-up an internal "piece", (this thread is always using the singular,) is a fools errand unless the spar maker has furnished the factory part, made from his tooling that fits perfectly.
In the field, whether by external or internal sleeve, a "made up" sleeve is generally made in two lengthwise halves that are so shaped that when they are installed in the mast sections there is perhaps a 1/16 > 1/8th gap between the halves.
This allows continuous/intimate contact between the halves of the sleeve and the mast sections without stressing the metal or fasteners.
You can't pull gaps out of a smaller one-piece internal sleeve to fit a larger external part.
All this talk about "pulling gaps together" is highly misleading.

[Baby tug]

Originally Posted by Bowdrie

^ This from well over 200 posts ago is correct.
You cannot use fasteners, (rivet or machine screws,) to PULL inner and outer sections together when both are one piece.
They must fit perfect WITHOUT ANY GAPS.
Trying to line-up an internal "piece", (this thread is always using the singular,) is a fools errand unless the spar maker has furnished the factory part, made from his tooling that fits perfectly.
In the field, whether by external or internal sleeve, a "made up" sleeve is generally made in two lengthwise halves that are so shaped that when they are installed in the mast sections there is perhaps a 1/16 > 1/8th gap between the halves.
This allows continuous/intimate contact between the halves of the sleeve and the mast sections without stressing the metal or fasteners.
You can't pull gaps out of a smaller one-piece internal sleeve to fit a larger external part.
All this talk about "pulling gaps together" is highly misleading.

You can’t tell someone something they don’t want to hear

[Jim Cate]

You cannot use fasteners, (rivet or machine screws,) to PULL inner and outer sections together when both are one piece.
They must fit perfect WITHOUT ANY GAPS.

This is especially true when the internal bit is thicker than the mast itself: do you want the mast dimpled in around a screw?

I wonder if this is where use of a structural epoxy bog in the joint would help?

Jim

[col50]

Originally Posted by Bowdrie

^ This from well over 200 posts ago is correct.
You cannot use fasteners, (rivet or machine screws,) to PULL inner and outer sections together when both are one piece.
They must fit perfect WITHOUT ANY GAPS.
Trying to line-up an internal "piece", (this thread is always using the singular,) is a fools errand unless the spar maker has furnished the factory part, made from his tooling that fits perfectly.
In the field, whether by external or internal sleeve, a "made up" sleeve is generally made in two lengthwise halves that are so shaped that when they are installed in the mast sections there is perhaps a 1/16 > 1/8th gap between the halves.
This allows continuous/intimate contact between the halves of the sleeve and the mast sections without stressing the metal or fasteners.
You can't pull gaps out of a smaller one-piece internal sleeve to fit a larger external part.
All this talk about "pulling gaps together" is highly misleading.

I suggested the two part sleeve in post #118.
It seems that the fabricators don't understand the problem.