Thread: Whitworth problem

I have a small metal work project that involves making a 1/2 inch BSW thread at the end of a 12mm steel rod.
Purchased a Sutton die ( 2in OD ) that has a small "adjusting" screw, from Bromac. I tried a couple of rods with the die but found that none of the nuts threaded nicely, binding quickly. I tried some more rods, with the adjusting screw at maximum, but the same thing happened. The nuts are definitely 1/2 inch Whitworth (12 threads per inch).

Went back and bought a smaller hexagonal die without the adjusting screw. This time the nuts threaded beautifully, no problems.

With very limited metalwork/engineering knowledge, what did I do wrong with the original die? Is it possible that the die was faulty?

Thanks.

Originally Posted by Sawmaster

I tried some more rods, with the adjusting screw at maximum, but the same thing happened. The nuts are definitely 1/2 inch Whitworth (12 threads per inch).

G'day Sawmaster, when using an adjustable die, you need to make adjustments expanding or crushing the die until the desired fit is obtained. There are a few designs of die, the little adjusting screw is usually for expanding it and to crush a die, you need to back the little screw off and then use the screws found around the die stock!

Originally Posted by Sawmaster

Went back and bought a smaller hexagonal die without the adjusting screw. This time the nuts threaded beautifully, no problems.

This one worked pefectly because it is called a die nut and is usually for cleaning up damaged threads. Of course a few of us as apprentices found these much quicker to use!

.5'' whitworth onto 12mm would have made for easy threading!

Like the spiked caddy design!

A couple of possibilities. Did the nut bind after about 1 1/2 turns of turning pretty freely? If it did the thread was wrong - in this case it looks like the expensive die was the wrong thread profile - it may have been AMF, UNC or metric, or something bizare. In most cases the difference is a couple of degrees in the angle of the "V".

I believe that the 'adjustment screw' is to allow you to cut the thread oversized on the first pass, then tighten it up on subsequent passes - this would also allow you to make over sized thread rods for loose/worn nuts.

Thanks guys!

Originally Posted by Tankstand

the little adjusting screw is usually for expanding it and to crush a die, you need to back the little screw off

Your right. I just had a better look at it. I thought by turning the small adjusting screw clockwise that the cutting diameter of the die was decreasing, but in fact it's increasing. Thanks!

Originally Posted by bsrlee

If it did the thread was wrong - in this case it looks like the expensive die was the wrong thread profile - it may have been AMF, UNC or metric, or something bizare. In most cases the difference is a couple of degrees in the angle of the "V".
I believe that the 'adjustment screw' is to allow you to cut the thread oversized on the first pass, then tighten it up on subsequent passes - this would also allow you to make over sized thread rods for loose/worn nuts.

Thanks! That makes sense. I've lost the packaging, all it says on the die is is "1/2 W 12."

Thanks again,
Graeme.

Sawmaster,

Just out of curiosity, was there a special reason why you did not go for an M12 thread?

Gotta know!

Ken

Originally Posted by neksmerj

Sawmaster,

Just out of curiosity, was there a special reason why you did not go for an M12 thread?

Gotta know!

Ken

Evening Ken. I never really thought about it actually, maybe this is my problem! The closest hardware store is Hudsons, where I buy all my nuts/bolts. The isle layout is arranged with imperial being the first offering and the 1/2 inch nuts/bolts are Whitworth (Which I learnt the hard way). Maybe I should walk further on into the Metric section in future?

Cheers,
Graeme.

1/2" is actually 12.7mm so you should have got a slightly under sized thread using 12mm rod.

Kev.

Originally Posted by Woodlee

1/2" is actually 12.7mm so you should have got a slightly under sized thread using 12mm rod.

Kev.

You're right Kev, but there's still plenty of thread to bite down hard on the wood with a nut and washer. It's only for a 18 hole grass 'Pitch and Put' course in town for me and the 12 yr old son to play on. You only need a putter and an iron of some description. Should help aerate the lawns...



Cheers,
Graeme