Identify this bolt!

Iain C

Iain C

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Before I relaunch, I need to replace a bolt that has always been missing from the bronze skeg heel on my fin keeled Sabre 27. A quick session with the micrometer on one of the other bolts has given me the following measurements. I know that it must be an imperial bolt...I just need to know what to order!

Length overall-2.25"/57.2mm
Total shank length-2"/51.9mm
Length of threaded part of shank-1.25"/31.5mm
Number of threads on the threaded part-20 (yeah, I know it's only 1 but you know what I mean!)
Length of plain part of shank-0.71"/18mm (not that this matters, could be all threaded)
Diameter of plain part of shank-0.36"/9.3mm
A 14mm socket fits the bolt perfectly...no, not a bodge but the head mic'd up at exactly 14mm with a couple of coats of anti fouling over it!

Any thoughts, and even better any suppliers for a 316 grade version?

Thanks!
 
Presumably there is a nut on the end. Sounds like a 3/8" but don't know the thread bit if you get a matching nut, not a problem. For that job a bronze bolt would be better. Combwich - part of Anglia Stainless will sort you out one.
 
No nut unfortunately, it goes into a blind hole, vertically upwards, and either there's a nut glassed in there somewhere or the GRP has been tapped...
 
9.3mm is 3/8" ( But thats 0.375") 9.3 mm is not 0.36"!

20 threads in 1¼" = 16 tpi

So it could be 3/8 Whitworth or 3/8 UNC

14mm AF head size a bit of a puzzle but I reckon it will make it 3/8 UNC ( same size head as 3/8 UNF). If so a 9/16" AF spanner will fit. Mic it up in inches!

See http://www.sat.dundee.ac.uk/~psc/spanner_jaw.html

Obviously 2" long but i have not checked the thread length so confirm that it is standard. Info here somewhere but not to hand


Anglia stainless mentioned but also see A2A4 and Seascrew
 
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Guys

Many thanks for the response. I'll order a UNC and a Whit version just in case. Someone had told me it might be 3/8" but I'm much more confident now!

Need to get it right, as it will be a case of fit it, and crane it in!

Cheers
 
Iain C said:
Guys

Many thanks for the response. I'll order a UNC and a Whit version just in case. Someone had told me it might be 3/8" but I'm much more confident now!

Need to get it right, as it will be a case of fit it, and crane it in!

Cheers
Click to expand...

There is very little differnce between Whit and UNC just a small difference in the thread form.

The head size is the major difference. Cannot be whit, 14mm socket wont go on a whit head, so must be UNC . Check a 9/16" AF spanner on it.
 
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Iain C said:
Before I relaunch, I need to replace a bolt that has always been missing from the bronze skeg heel on my fin keeled Sabre 27. A quick session with the micrometer on one of the other bolts has given me the following measurements. I know that it must be an imperial bolt...I just need to know what to order!
Click to expand...

3/8 BSW or UNC. Might get UNC in a chandlers or from Classic marine

http://www.classicmarine.co.uk/

Although BSW and UNC are both 16 tpi the thread forms could be slightly different so the wrong bolt could be a wee bit tight and this could be corrected by getting a mechanic to run a die nut up it.
 
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