source wingnut type bolt for mast track gate on a proctor mast

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steve yates

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It's a westerly longbow, and I think its a whitworth thread, whatever that is. The retaining bolt for my mast track gate, to hold the sliders in, has gone overboard. It's an old imperial one, any idea where I can source a replacement?

Thanks.
 
steve yates said:
It's a westerly longbow, and I think its a whitworth thread, whatever that is. The retaining bolt for my mast track gate, to hold the sliders in, has gone overboard. It's an old imperial one, any idea where I can source a replacement?

Thanks.
Click to expand...

Make one I guess is the answer

Start with a pan head machine screw with the correct thread and get a the butterfly wing welded onto the head.

You are very probably right about it being a Whitworth thread on something of that age. Simple enough to try a Whitworth bolt to see if it fits.
 
steve yates said:
It's a westerly longbow, and I think its a whitworth thread, whatever that is. The retaining bolt for my mast track gate, to hold the sliders in, has gone overboard. It's an old imperial one, any idea where I can source a replacement?

Thanks.
Click to expand...

Caution required here, Whitworth and Unified coarse share the same diameter and pitch, however, the Whitworth form has 60 degree to Unified 55 degree thread angle. The boat probably built in the 70's will be more than likely Unified thread. For the purist, yes, I know one size of thread does not conform to this "rule". Cannot remember if it is 11/16 or 7/16.
 
third engines said:
Caution required here, Whitworth and Unified coarse share the same diameter and pitch, however, the Whitworth form has 60 degree to Unified 55 degree thread angle. The boat probably built in the 70's will be more than likely Unified thread. For the purist, yes, I know one size of thread does not conform to this "rule". Cannot remember if it is 11/16 or 7/16.
Click to expand...

Other way round surely !

It's 1/2" where there is a difference in pitch between BSW and UNC (12 tpi vs 13 tpi)
 
Such a simple wee thing, it's amazing how complex sorting it is. Of course, I was daft enough to drop it overboard in the first place, which means I don't even have the original to get the size and thread dead right! A new hole maybe? and a wingnut araldited to the head of a new bolt?
Tho the camera baseplate screw is an inspired idea, I'm going to try the one from my tripod head base.
 
Can't you just thread the wingnut on to the bolt to the top then lock it in place with a nut? Loctite as well if you want belt and braces and much more robust and reliable than araldite
 
steve yates said:
Such a simple wee thing, it's amazing how complex sorting it is. Of course, I was daft enough to drop it overboard in the first place, which means I don't even have the original to get the size and thread dead right! A new hole maybe? and a wingnut araldited to the head of a new bolt?
Tho the camera baseplate screw is an inspired idea, I'm going to try the one from my tripod head base.
Click to expand...

A new hole is not a solution as you need that gate to fit in the original position for it to work properly. I suppose you could drill and tap it to take a larger sized coarse metric screw but you would also have to enlarge the slot in the gate

You have the threaded hole in the mast so you can determine the diameter of the screw required. The thread is very unlikely to be metric, given the age, which really only leaves Whitworth and UNC. 3rd enfgine thinks UNC more likely but I'd put my money on Whitworth as that was what was in common use in the UK before metric took over. Unified threads were use on cars but precious few other places on UK made stuff. When I built my boat in the '70s all the fixings supplied were Whitworth and its only newer stuff I've fitted that has used metric.

I would not rely on Araldite but what might be an alternative is a short length of studding ( you could cut the head of a machine screw or a set screw) and screw on a wing nut with some high strength Loctite ( eg Loctite 270) to secure it
 
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I had to do a similar thing on my mast gate - 1979 Moody 33 - from memory I just looked through my screw box, found a screw of the right length, does not matter if it's UNC or Whitworth, it'll work fine, no great stress on it. I just screwed a wing nut onto the screw up to the head and just graunched it up tight in the vice. Never come undone in 11yrs.
 
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