Help finding a screw thread

[Gaz]

I want to put windage adjustment onto my .22" No.4 rifle. The rifle itself is set up as a C No.7, except for not having the windage knob as the Canadian rifle does. See here: http://www.rifleman.org.uk/Enfield_Rifle_No.7-C.html

I was going to order the parts from the Marstar website (here http://www.marstar.ca/dynamic/category.jsp?catid=78325) but they're sold out of the adjusting screws. Fair enough, thinks I, how hard can it be to find a similar screw in the UK?

Well, that's where I ran into problems.

I don't know the spec of the screw thread. The only information I can find on the screw thread spec comes from the Rifleman website's rip of the Canadian parts manual for the C No.7...

1005-21-106-8981 Screw, Special, Adjusting, Leaf. No 5 – 40NC – 2, 1.45 in. lg. 1 B1-801 35907

I know the 1005 number is the NSN, so useless to me. But does the 40NC figure mean anything? Obviously the screw's 1.45" long, but I don't know what the final figures mean.

The same document has slightly more info about the windage knob, which seems to give the thread spec - not that I can make head or tail of it:

5355-21-106-2129 Knob, Rear Sight Traversing. Knob, round, S, anti- rust fin, 0.410 in. (10.41 mm) thk, 0.500 in. 1 B1-1582 35907
(12.7 mm) OD, 1/4 - 40 UNC internal thread, grip aid surface. W/O skirt, straight shk, unmarked,
3 detent notches 0.020 in. (0.508 mm) dp on back of knob at 120° intervals.

Can anyone interpret that into something I can ask for from the screw shop round the corner?

[Demonic69]

It's 4-40 UNC thread Gaz
Specs Here
Quite common in PCs for DSUB connectors etc.

[Demonic69]

M3x.5 should be close but I'd stick to UNC if possible as the tolerances might be tight.

[ovenpaa]

It is a No 5 x40 UNC thread so you need a no5x40 screw. 5 refers to the gauge which is 1/8" and the 40 is threads per inch.

[ovenpaa]

Hmm... well I still read this as 5-40.

[rox]

It is a No 5 x40 UNC thread so you need a no5x40 screw. 5 refers to the gauge which is 1/8" and the 40 is threads per inch.

Which will give approx 1 MOA per click, if my fag packet calcs are in the ball park.

..

[ovenpaa]

From memory this is the same as on the Pattern 1914 fine vernier elevation screw.

[Gaz]

So I'm asking for a No.5x40 UNC screw? Thanks all. I'm expecting it to be 1MOA - fairly sure that's the elevation adjustment on the C No.7 rearsight.

[Demonic69]

Yeah sorry, TL;DR No5 it is

[ovenpaa]

I can put my hands on something to suit if you get stuck Gaz.