Thread of Screw for Steering Column Nacelle?

[Edin Dundee]

Part number PX557P or 153517, pozi pan head 1" long - does anyone know what thread this is?
It's the short screw for the middle of the steering column covers.
I'm not paying shipping of £4.50 for a bloody screw

[MIG Wielder]

Edit 5/5/15.
Hi Bill, I reckon 3/16 BSF 32tpi. for the 2 screws either side (PX512P Qty 2-off ).
Interestingly M5 x 0.8 is very close.
Tony.

[tractor boy]

M5 x .o8 will go if you are careful. Tractor boy

[xvivalve]

I'm sure I can find one of those for you Bill...

[Edin Dundee]

5/16" UNC - that's big!
Alun if you would pop one in the post sometime I'll ping you a fiver, much rather pay you than £4.50 shipping for a 74 pence screw.

[BobM]

This will be 3/16 UNF.

Bob

[Mad Mart]

5/16" UNC - that's big!

Who said that?

I've just checked Bill. Number 10 x 32 TPI UNF.

[Edin Dundee]

It's the screw in the middle - not the side ones. 10-32 is way too small.

[Mad Mart]

That's weird! I'm pretty certain they are the same thread, just shorter.

[MIG Wielder]

Yes, sorry about that. There are 2 x PX512P and the centre one is different.
The part no for this one is PX557P and is 0.1855 O.D. and 24 tpi.
So my trusty Zeus manual reckons this is ....
3/16 Whitworth ( 0.1875 O.D. x 24 tpi ) or ....
10 - 24 UNC ( 0.190 O.D. ,24 tpi ) or ... ( Non-preferred size)
No 10 A.N.C (0.190 O.D. x 24 tpi.) ( Unlikely for B.L. )
Tony.

[1300_2door]

99.9% of threads on our Triumphs are American, namely the UNF/UNC series with the pipe threads being NPT. The only Metric threads I can think of would be the spark plugs.

The British motor industry stopped using Whitworth and BSF/BSP threads during WW2 when we standardized with our friends across the Atlantic.

[Edin Dundee]

IMG_3901 by edindundee, on Flickr

Well, here goes - above is the photo from the steering column - the hole on the left would appear to be for a different type of steering lock, and the thread above THAT is 5/16" UNC - same as the shear bolts! My bad. (I also found one of the shear bolts loose, removed that, cut a slot and refitted).
The hole on the right is for the centre securing screw.
Going by Tony's investigations it must be 10-24 UNC.
The screws for the two side holes are definitely 10-32 UNF, as per Mart's post.

Incidentally, if anyone ever needs an 0BA screw - use 6mm, it's absolutely spot on!
I found a ba screw kit at work and one of the old fitters showed me that 0ba and 6mm are pretty much identical.

I'm off to the lock-up again, I have a 10-24 tap I want to try........

10-24 it is The tap dressed the first couple of damaged threads and then ran in and out no problem, it's obviously had an incorrect screw fitted in the past. Come to think of it.......old age memory is a fickle thing. We have 10-24 in stock at work, albeit A4 stainless and hex head socket, but that'll do.

Thanks to everyone for their help - if anyone ever needs one of those screws in stainless, give me a shout.