which imperial thread on 80s UK built boat stem fitting (1/2'')

D

DHV90

Well-Known Member
Joined
23 Aug 2013
Messages
325
Visit site
Hi all,

I need to source a dome nut or lifting eye nut to go on the end of a 1/2 inch bolt buried deep down in the stem of my boat, which is inside a small well in the foredeck. Due to the location access is absolutely terrible and I can barely get at it with verniers to measure and a thread gauge won't fit on. Im going to hedge my bets and order one or two to try. Is BSF most likely or could it be UNC/UNF? Any input much appreciated.

The boat is british built, around 1980 and the bolt is part of the rigging effectively, a series of glassed in bolts to which a channeled piece of stainless is secured to through which the forestay pin goes.

Lifting eyes seem to be non existent in imperial so the current plan is to drill the top of a dome nut and stick a shackle through, I need to run a short length of dyneema up to deck level to secure the tack of the sail and because of this weird shaped well there is no where else to connect it thats not either a few inches too far aft, where the deck starts, or infront of the forestay!
 
most likely BSW or perhaps BSF?
Once you identify the thead could you drill and tap a standard fitting
 
Last edited:
searj said:
Hi all,

I need to source a dome nut or lifting eye nut to go on the end of a 1/2 inch bolt buried deep down in the stem of my boat, which is inside a small well in the foredeck. Due to the location access is absolutely terrible and I can barely get at it with verniers to measure and a thread gauge won't fit on. Im going to hedge my bets and order one or two to try. Is BSF most likely or could it be UNC/UNF? Any input much appreciated.

The boat is british built, around 1980 and the bolt is part of the rigging effectively, a series of glassed in bolts to which a channeled piece of stainless is secured to through which the forestay pin goes.

Lifting eyes seem to be non existent in imperial so the current plan is to drill the top of a dome nut and stick a shackle through, I need to run a short length of dyneema up to deck level to secure the tack of the sail and because of this weird shaped well there is no where else to connect it thats not either a few inches too far aft, where the deck starts, or infront of the forestay!
Click to expand...

My money would be on it being a Whitworth thread if it is not metric. It was used extensively in the UK until the late 1970s / 1980 ish before metric threads took over. All the original fastenings on my boat are BSW.

Try a known BSW nut
 
Last edited:
VicS said:
My money would be on it being a Whitworth thread if it is not metric. It was used extensively in the UK until the late 1970s / 1980 ish before metric threads took over. All the original fastenings on my boat are BSW.

Try a known BSW nut
Click to expand...

I'd not normally dare to take issue with Vic but I did a marine engineering apprenticeship in the 60's and the only Whitworth stuff we came across was either just Post War or cases where chunky threads were required. By 1968, it we needed WW threads we usually had to cut them ourselves. My 66 Nicholson has BSF on all it's original fittings, replacements have either UNF or mm where I've replaced through deck fittings myself.
 
Funny thing about whitworth threads is that my boat uses them almost exclusively. My local chandler seems to have more ww stuff than any thing else. Despite Oz going metric in the early 80s. Another chandler nearby seems to be stuck with metric. Anyway yes my guess would be half inch ww. olewill
 
You must log in or register to reply here.

Share this page

Top