Guns - desperately need a screw

[Trenchard]

Ha, thought that'd get you looking.
The latest fun and games are fitting a steel dovetail rail to a gun to carry a telescopic sight.
The gun is a .22 calibre BSA Martini International Mk.II, which is effectively an approx half-size
version of the famous Martini Henry rifles used in the defence of Rorke's Drift in 1979 (see the
film 'Zulu').

The BSA version was originally invented by one Al Freeland, of Rock Island Illinois and BSA made
the design under license in the late 1950s. This explains why the pre-tapped holes I need to use
have an American thread and this is what's causing problems.

The screw needed is a 6 - 48, a number 5 screw with 48 threads per inch. The specs are...

Diameter: 9/64 inch (to nearest fraction), 0.135 inch, 3.3 mm.
Tapping drill: No. 31
Material: blued steel

Here's the rub. The screw holes were used to fit two steel blocks that took a spindly tube scope.
The steel blocks, ufortunately named the front and rear sight stools took very short screw. So
I can get any number of screws in 1/4, 3/8 ot 1/2 inch but I need eight 3/4 inch screws at least.

I also need countersunk screws and the drive type doesn't matter, I could use slotted, Allen hex or Torx.
Thing is, the 3/4" ones I'm chasing come from the US and have been missing from the suppliers for two months so the seller (Brownell's) won't take an order.

So, the right screws are in the rocking horse teeth/hen sh*t category and I need at least eight of them.

I know everyone (like me) who went through the Meccano/Hornby Dublo rite of passage has a bits box.
If anyone can help, I'll gladly pay.

Yours hopefully...

[Trenchard]

mikey_b

Thanks. Retapping is an option but not yet having a gun licence means I can't bring the barrel and receiver home or take it anywhere else. There's no kit at the club.

[Trenchard]

pequod said:

I have an assortment of old screws in various old 'baccy tins inherited from a relative who had a machining business, which may provide the parts you need? They can't be uncommon for that era?

I'll have a look tomorrow and let you know.

P

Thanks pequod, this is the kind of thing I'm hoping for. The gun's serial number dates it to 1957 and I understand 6-48s were often used in the States. However, , according to their gun forums, even they are struggling at present.

[Trenchard]

InitialDave said:

Would these suit if you took the length down slightly?

May not be the same countersink angle you need though?

https://www.kenfarrell.com/index.php?route=product...

Edit: nope, reading fail, you need 3/4", not 3/8"

Edited by InitialDave on Thursday 5th May 19:27

Thanks, InitialDave. Been there, I'm afraid but thanks for looking.

[Trenchard]

MKnight702 said:

Have you thought of looking on Ebay. I usually find them great for sourcing a few odd size screws etc.

I also have a BSA Model 12/15, oh, and I did have a Mk IV Martini Henry in 577/450 but I sold that.

Thanks, MKnight702,

eBay is the place for any number of screws uo to 3/8" long. They almost all in America and costly but too short for my task.

I've fired a 12/15 and a Mk.3 SA at the old club. I was fancying a Mk.3 but the alloy foreend hanger worries me. The one I'm working on and going to buy is a heavy barrel Mk.2 - I do benchrest shooting. I'm a big fan of the Martini action...looked afterr, they're practically bomb proof.

[Trenchard]

sociopath said:

Don't know if these guys will be able to help, but they're very friendly and have often sold me individual bolts when I've been stuck.

Even if they don't have any they may have an idea where you could get them

https://leytonfasteners.co.uk/

Thank you, sociopath. I've emailed them with my question.

[Trenchard]

Simpo Two said:

History appears to have changed!

Pedants' revolt? 'tis but a century out! Just wait 'til you mistype something.

[Trenchard]

No ideas for a name said:

You could try Non Standard Socket Screw Limited (yes, it really exists)

https://www.nssocketscrews.com/standard-products

Oddly enought they have 'standard products'???

Thanks, mate. E-mail sent to them.

[Trenchard]

smifffymoto said:

You could also try Threadfast in Congleton.

Thanks, smifffymoto,

Email sent to them.

[Trenchard]

dhutch said:

As another option, can you counter bore the new rail to a depth to allow use of shorter/existing screws?

Good idea, dhutch but I'm afraid not. As the new rail is steel, they're less than 3 mm thick where the screws go. Plenty of 'meat' to countersink but not enough to counterbore. I could use a thicker alloy 'riser' rail but I like my scope's centreline to be low.

[Trenchard]

Thanks, Bacon 'n' jonny.

Lathing some up might be a possibilty but I'm pursuing another. Because the added dovetail rail is going to be
long and held by four screws, shorter screws maight do the trick. Tonight's task, double check the depth
of the tapped holes in the barrel.

[Trenchard]

Thanks again, gents.

Major step forward this evening. I took my digital calipers to the club and carefully measured the depth of the four screw holes in question. They ranged from 5.01mm (max) to 4.89mm (min). I expect the lower figure could easily be down to muck in the holes. Given that the rail material is 2.5mm thick and that the holes will be countersunk, I'm thinking that 1/4 inch (6.35mm) screws will do the business. I believe I can get these.

In addition, I may use Weaver Oval Head screws like this.



Note two things. These are a sort of cross between countersunk and cheese head so some tweakery when drilling the clearance holes in the rail may be possible. Thing two is the note about their not being available on back order means no stock, even in the States, for two months or more.

Off searching now.

Found some!!


From Ant Hill at ANT Supplies in Swansea, at about £6 less than those not in the States with their £5.99 extra for carriage.
Only challenge, the shopping cart is 'Off 'til Saturday' perhaps to stop p*ss artists from ordering with a skinful?

Impending result.

Edited by Trenchard on Friday 6th May 23:52

[Trenchard]

NMNeil said:

Plenty available it seems
https://www.ebay.co.uk/sch/i.html?_from=R40&_t...

Yes, thanks. I'd seen such things but the postage scared me off! I've just ordered 8, which cost £7.50, including P&P, tax, the 'R' in the month of April and everything else. Job's reet, cracked it.

[Trenchard]

gazza285 said:

As an alternative, you could buy a die nut and rethread a slightly larger screw.

Thanks gazza285. I'd looked at this but some problems arose. The right die nuts are available but that's from the 'States with the consequent outrageous postage. I also spoke to a bloke who makes specials in S/S for a living and even he can't get blanks for threading in No,6 size. And then, larger screws tend to have a larger head than I could accommodate and the existing thread would have to be lathed off and I don't have a lathe.

As you see, I can do research but now I've found some suitable screws, I'm sorted.

Grateful thanks to all who contributed, I appreciate your input.

[Trenchard]

gazza285 said:

You would be surprised what can be achieved with a drill, a file and an angle grinder...

Well possibly. However, the club supremo who's letting me play with the gun pre-purchase is an MSc Eng. That'd be a hanging offence in his book!

Edited by Trenchard on Saturday 7th May 22:18