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Access to rivet head in clam cleat


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I'm having a few problems reattaching a clam cleat to an aluminium dinghy mast.

The cleat was originally riveted on, but the rivets corroded and failed. I have a couple of suitable monel rivets I intended to apply copiouse duralac and bang it back on.  The problem is I can't get my riveter onto the rivet in the cleat.  I tried dropping a couple of nuts onto the rivet to give the riveter something to work against, but then there's not enough left for the riveter to grab.

Then I thought of bang in a couple of self tapers. However the #12 5.5mm countersinks are probably a little small for the existing 5mm holes in the mast, and the screws are too big for the cleat. They won't go through the holes. I don't really want to drill them out larger, and the heads don't fit anyway.

So I'm back to rivets, and I can't get my riveter into the rivets in the cleat. I've seen these cleats riveted before. How did they do that?

Had a photo, but I'm struggling to upload it...

 

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Rivnuts are ok but you are probably asking for a disssimaler metal mess. They depend on the outer knurled edge to bite so a little corrosion will let the whole thing spin later.  Not to say it can't work but careful prep is required.  Also requires more tooling and dies. Any chance you can move one way or the other to drill tap a new hole for a machine screw.

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1 hour ago, European Bloke said:

I tried that. There wasn't enough mandrel left for my riveter to grip.

try until pissed_off {
   Make the stack;
   clamp a visegrip or similar to the mandrel above the stack;
   put a pair of long screwdrivers between the stack and grips;
   lever a few mm;
   reset;
   repeat
}
 

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1 hour ago, SASSAFRASS said:

Rivnuts are ok but you are probably asking for a disssimaler metal mess. They depend on the outer knurled edge to bite so a little corrosion will let the whole thing spin later.  Not to say it can't work but careful prep is required.  Also requires more tooling and dies. Any chance you can move one way or the other to drill tap a new hole for a machine screw.

You can get them with internal and external machine threads and/or self tapping external threads rather than pop rivet style. That would allow drilling the existing holes a bit oversize while keeping the internal threads the required size.

That style usually installs with an Allen wrench.

https://www.mcmaster.com/threaded-inserts

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If you can get inside the mast, you could put in a backing plate with threaded holes for screws.

For a backing plate, a tube of the appropriate outer diameter to mostly match the curve of the inside of the mast can be used.  Cut a piece lengthwise to make a curved plate that fits nicely with a little bending.

You can glue the plate in place with epoxy.  To position and hold it, drill tiny holes where the screws will go and run a string through the holes in the mast, out the end (vacuum, small weight and gravity, etc.), and though the small holes in the plate.   Then pull it into place with the string.  After the epoxy sets, drill to the proper size and tap for machine screws.

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14 hours ago, SloopJonB said:

You can get them with internal and external machine threads and/or self tapping external threads rather than pop rivet style. That would allow drilling the existing holes a bit oversize while keeping the internal threads the required size.

That style usually installs with an Allen wrench.

https://www.mcmaster.com/threaded-inserts

That looks perfect thanks. I was worried that the riv nuts might be a bit soft to take the load.

Looks like a more professional version of sticking a plate inside the mast. In the past I've pulled bolts into holes from behind, put the nut on the outside, and cut the end off the bit. But that wasn't going to work here.

I also considered moving the cleat, but that really would be a last resort.

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19 hours ago, ctutmark said:

Slide a nut or two (same size as the rivet head) onto the rivet mandrel to act as a spacer between the rivet the rivet gun.  

another trick I've found works pretty well is to take a beefier rivet (like a larger mild steel one), pull the mandrel from it, and use it as a spacer.

 

Still the issue of 'the mandrel's not long enough' - but I haven't found a cleat deep and narrow enough that this is an issue.

 

You could always use a bolt - getting the nut on is always fun, but not impossible with a stick, a ring spanner and some tape. You could even cut an access hole under the cleat if you felt like it,

 

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That looks like an Oppy mast... I've used the stacked washers up the mandrel technique on these but it does depend on the right combination of rivet, washers and gun... mine was marginal and I felt lucky to have made it work... if you can get it started then it gets easier...

 I assume there are rivet guns with narrow ends for this job- might be possible to take it to a specialist and see if they can help?

Good luck!

Cheers,

              W.

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I have assembled hardware onto spars by taking a box-end wrench, taping it onto a stick long enough to get to the hole(s) from the nearest end, adding another piece of tape over the back side of the wrench box, putting a standard nylok nut in the front side, inserting this assembly into the spar to the marked depth of the farthest hole until visible, installing machine screw through hardware into nut from outside and torquing.  This is permanent and secure. Using this method on Clamcleats that wear out might be marginal ...

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I'm going to try the nuts inside the mast on a spanner with a stick first, because it doesn't need any kit I don't already have and it will be very strong.

After that I'll try the ss machine thread inserts.

I'm not sure I can pop a monel rivet with a Heath Robinson approach, but I might try that in some scrap to see what I can do.  Aluminium fastenings won't take the load, so I'm not going there.

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