thread gauge

[tyce]

hi,
i am trying to find out what type of thread is on the end of my prop shaft.
the shaft is sized imperially, and is 7/8 inch, i have tried unc, unf, metric, and none fit, imperial being a bit before my time could anyone suggest what thread it is likely to be.
thanks in anticipation

 

[Davolas]

Whitworth Has 9 threads per inch.

BSF has 11 on 7/8" diameter.

also important is angle of threads, which is 55 degrees in valley of thread. 60 degrees for metric and a lot of others.

Measure pitch as above by counting No of peaks over a 1" length then check against a nut to see it is a good fit. If you are still not sure cut a nut in half and use as a gauge to check fit visually.

Regards

Steve

 

[Claverock]

I had the a similar problem some time ago. I got round it by using a block of wax and casting a profile of the thread into it by constantly rubbing it around the shaft. I then took it down to our local marine machine shop, after measuring the dia. of the threaded part of the shaft. They made up a new nut from that and it fitted!
Hope this is of some help. It's not hi-tech but it worked
Regards