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scottnewcombe
19-06-03, 10:00
Help

I'm looking for a 3/4" whitworth nut in A4 stainless and can't find one.

I've triel local chandlers and local engineering firms. Tries A2A4.co.uk and they said that it could be done but it would have to be made special with associated tooling etc. Very expensive.

Basically I had to cut the nut from my propshaft and need a replacement.

Any ideas

Thanks

Scott

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Robin
19-06-03, 10:09
If it is a propshaft nut have you tried the marine engineers like Lake Engineering in Poole, T Norris in Isleworth or Lancing Marine etc. Maybe they have had a similar problem and have supplies.

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ccscott49
19-06-03, 10:32
A 3/4" UNC nut won't fit? It should. Mind you, try C&O engineering in newton abbot, they I'm sure would have one, you can also think on using a bronze nut, in whit or UNC.

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aztec
19-06-03, 11:00
why did you have to cut it off?

if it was due to corrosion, does it need to be stainless? can you not change the stud to metric or unf? if all else fails go to a commercial vehicle workshop (older ones are better) all the old leyland/ERF/fodens etc used whitworth stuff.

good luck, steve.

<hr width=100% size=1><A target="_blank" HREF=http://homepage.ntlworld.com/s.amos/index.html>http://homepage.ntlworld.com/s.amos/index.html</A>

scottnewcombe
19-06-03, 11:08
Thanks chaps,

The original one was bronze and I couldn't shift it. Hence the reason for me cutting it off. I decided that a sstl was probably easier to get than brass and that maybe it would be easier to get off next time.

I tried a 3/4 unc first and it wound on one thread and then jammed. UNC and whit are similar I agree but I guess that at 3/4" the root dimension and thread shape must make a difference. I will try out the lead mentioned.


Thanks


Scott

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19-06-03, 11:59
hey col
3/4 whit to 3/4 unc? i thought you were a knowledgeable old fart like me!
when i was a lad whit and bsf were the norm and them yanks started introducing funny threads, they didnt fit ours,
3/4 unc referred to the size of the shank, it was 3/4" across and the thread was coarse, i cant even remember now what the whit size was but i think it was bigger than 3/4".
call llangollen motor museum 01978 860324 http://www.llangollenmotormuseum.co.uk/ and see if he has got a 3/4" tap he will hire out

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ccscott49
19-06-03, 12:15
You are thinking of spanner size, my boy. 3/4" is the size of the threads/bar in both UNC and whit, Whit had 55 degree threads and UNC 60 degree, the spanner size was measured across the flats for a UNC nut and was some kind of formula for whit. But a 3/4" whit thread is virtually the same size/pitch as a UNC thread. I think the spanner size for 3/4" UNC is about 1 1/8" or slightly bigger. Anyway a 3/4" UNC nut will I think, fit 3/4" Whit threads. Unless of course he is talking british standard whitworth fine, shortened to BSF? It is of course best to fit the same type, I'm sure one will be available quite easily, from propshaft type peeps.

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ccscott49
19-06-03, 12:22
I wouldn't use a stainless nut, they have a tendency to sieze, when going on and crevice corrosion when on, thats why they tend to use bronze nuts, funnily enough I've never seen a bronze nut sieze on stainless, new one on me.

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dickh
19-06-03, 12:25
ccscott49 is correct, both UNC & Whit have the same 10 TPI - If you can get a "UNC, try running a "UNC die down the thread to clean it up. For the work it will do this will be OK. Are you sure it is Whitworth? If the nut you have only goes on a little it can't be UNC or Whit.
Is it Metric?(I suspect an M20-[10.16 TPI] might fit at a push...)
Alternatively, get a local engineering company who uses A4 stainless to make on for you from hexagonal bar - the actual Whit across flat size is not critical, just make it out of a suitable hex size available(just check you have a spanner to fit} - should not cost a lot. Or try boatyards on the Broads.

<hr width=100% size=1>dickh
I'd rather be sailing... :-) /forums/images/icons/smile.gif<P ID="edit"><FONT SIZE=-1>Edited by dickh on 19/06/2003 13:40 (server time).</FONT></P>

19-06-03, 12:27
my boy !!
havent been called that for ages, yup you are right on the spanner size, but the thread pitch am still not sure of, brains a bit rusty now, nearly 40 yrs since i used to split a 3/4" nut with a cold chisel down the pit. we used to have competitions with the face workers to see how many hits it took with a lump hammer, best i could do was 3. we used to have to split them when we were extending the panzer conveyor chain, the coal dust and water stuck em together better than loctite.
stu

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squidge
19-06-03, 12:46
Have you tried South Essex Fasteners (01702 615326)
or Essex Fasteners (01268 418911)
Both can supply good quality marine grade stainless fixings at a fraction of the chandlers prices.
Good luck
/forums/images/icons/smile.gif

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scottnewcombe
19-06-03, 12:55
My word there's some very knowledgeable gents out there.

Ok lets try to clarify it a bit. All I know is that I cut off the old nut. It has since been binned by an over enthusiastic helper.

Put my verniers accross the OD of the threads and it comes in at 19mm 3/4".

The best I could see was that there were about 10 TPI (actually 5 in 1/2").

Armed with this I looked in zeuss and guessed that it would be 3/4"UNC. I initially discounted whitworth as I knew it was much less common (especially on an american boat)

It could of course be 10.something TPI.

Is bronze favourite for a replacement? Maybe I was just feeling a bit weedy when I tried to remove the old one. A bit gung ho with the angle grinder being a might too handy.

Ta

Scott

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LeonF
19-06-03, 13:51
Have you tried Anglia Stainless? They seem to have everything including silicone bronze. I got a nut similar to the one you mention from my local supplier in Gravesend, Barnkets. It took them some three weeks and they then apologised for having to charge me 1.50. It fits on the bolt that goes through my tiller.

<hr width=100% size=1>L.A.R.Ferguson

ccscott49
19-06-03, 14:04
If it's an mercan boat, youcan almost bet it's UNC, not whit, they never used whitworth. It could of course be metric, but I doubt that very much. Even shaft manufacturers in UK use UNC nowadays. Most on the continent use metric. If the shaft is 3/4" then the thread is most probably UNC. Use Bronze.

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dickh
19-06-03, 14:57
Must be UNC if a USA boat.
Mine is a castellated Stainless and never have any trouble undoing it - as it is a coarse thread, and faily slack at that, there shouldn't be a problem. Make sure it is splitpinned though after tightening.

<hr width=100% size=1>dickh
I'd rather be sailing... :-) /forums/images/icons/smile.gif

richardandtracy
19-06-03, 15:40
The Americans never cottoned on to Whitworth. But then, neither have I.

It should be UNC or NC. These are basically the same, but some differences in the thread root & tips. If the nut won't go on, the thread may be NC, in which case the tips of the shaft thread should be pretty sharp. These sharp tips will be interfering with the rounded thread roots in the UNC nut. Answer - blunt the threads on the shaft, run a 3/4" die down the shaft or run a new tap through the nut. Final option, run a slightly oversize tapping drill through the centre of the nut to take some of the nut's thread off. A 75% thread shouldn't make a jot of difference to keeping the prop on.

I've had a problem with dies myself. I have been sold an 8-36 UNF die as an M4 x 0.7. Had me hopping mad yesterday when I found out. Shame it took me 15 years to notice - it's the first time I've used anything smaller than M6 in all that time.

Regards

Richard


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BarryH
19-06-03, 15:41
Have a look at these people. They carry nearly every concivable nut , screw, bolt in stock. Even non standard ones. They've never let me down in the past....cheap too<A target="_blank" HREF=http://www.dialengineering.co.uk/company-80106158.html>http://www.dialengineering.co.uk/company-80106158.html</A>

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