Need oddball bolt: 1/2" x 12 TPI

Have you tried an M14x2 in it? Nominal inch dimensions .55 diameter and

12.7 tpi?

Anything "pre 1900, American-made" is vanishingly unlikely to have metric threads.

Unless, perhaps, it was built by a French family displaced by Royalists after the revolution.

My bet is on 1/2-12.

That's a British Standard Witworth or BSW thread. You can find the bolts in the USA here:

I was going to say "Not if it was pre-1900" -- but Whitworth was a standard by 1841!!!

Double-check the thread form, though -- just because the threads are pointy doesn't mean that they're 60 degree (or 55 degree, for that matter).

anorton wrote: ...

I thought flashing/blinking text was annoying, but the rotating bolts there are MUCH worse. I would have to be absolutely desperate to order anything there.

Bob

I didn't say I thought it was a metric thread, I said try an M14x2.0. Maybe it will fit, maybe it won't. If it won't, you're out

The idea was it might be close enough to work.

Which is of course a metric thread...

.. and if it fits, then the hole it fits into is *also* threaded with a metric thread -- which, as I said, is vanishingly unlikely for anything made in the United States in the 19th century.

When was the last time you succeeded in inserting a 0.55" bolt into a 0.50" hole?

The bolt's bigger than the hole.

Ive just looked up my Zeus thread chart, and as I thought, what your after is 1/2in B S whitworth threaded bolts. Ive plenty!! but of course the snag is im in te UK where BSW threads were used and still are on old machinery repair work. Im pretty sure I could find some to match your need , and they would be free to you apart from the postage from the UK. Any help? to you? The Chandler and Price guillotine may well be UK made tho. Frater In Dorset UK.

Actually, according to the Wikipedia article on Whitworth, it was used in the US until the early 1900's, when we adopted our own standard. IIRC, we changed the thread form from a pointy 55 degree to a flat-top

60 degree, but for the most part the 'merican coarse thread sizes match Whitworth -- with the exception of 1/2 inch, where we chose 1/2-13 instead of 1/2-12.

Mebbe someone on the committee had been beaten up by a lathe maker at some point, or just thought 13 tooth gears were lucky?

1/2"X 12 TPI is British Standard Whitworth. I have no idea where you could find them in the U.S. If you decide to turn them, note that the thread angle is 55 degrees not 60.

whitworth taps are commonly available - I happen to have some because of british cars, but they are not at all hard to find - and ebay is a source for them cheap -

They may not be Whitworth. I measured a tap I have here that's marked

1/2-12 USF and it's definitely a 60 degree thread. I've no idea what USF stands for -- perhaps it's related to the old USS (United States Standard) thread.

I repaired an old 36" bandsaw that used 1/2-12 fasteners and had to single point several replacement bolts. The saw was probably late 19th century. Old enough that the wheels had steel spokes and steam bent oak rims.

I see it in Machinery's Handbook - defined as :

Designating UNS Threads.=97UNS screw threads which have special combinati= ons of diameter and pitch with tolerance to Unified formulation have the basic f= orm=20 designation set out first followed always by the limits of size.

The pitch diameter tolerances used in Table 3 for all classes of the UNEF= ,=20

12-UN, 16-UN, 20-UN, 28-UN, and 32-UN series and the UNS series, are base= d on a=20 length of engagement of 9 pitches and are applicable for lengths of engag= ement=20 of from 5 to 15 pitches.

Martin

Mart> >