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Discussion Starter · #1 ·
My No. 4 MKI rear trigger guard screw is damaged on the end. The receiver hole is also damaged as if someone tried to hammer the screw in. I have a replacement screw but what size is the screw so I can tap the receiver hole. The new screw will start in from the outside so I'm hoping I can save it. Is the screw metric? Any help and info you can give is greatly appreciated.

Foxtrot351
 

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This list says it is 4BA size.

http://freespace.virgin.net/j.franklin/toys/thread-table.htm

The BA is a semi-obsolete set of British standards that mostly live on in the model making industry. Taps are available here in the US from various online shops, but I have not dealt with any so hesitate to recommend any. Search BA British taps.

Here's one -

http://www.icscuttingtools.com/catalog/page_212.pdf

By the way, if you go to a DIY Home Depot type store in the UK and ask for BA thread screws etc. they will have no idea what you are talking about.
 

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BA taps and dies are readily available over here in UK.

If there appears to be a demand we may stock them.

For a No4, etc. you need 2,3,4,5 and 6BA.

Some late production SMLE spares are made in BA and don't fit earlier components. The Inner Band being one in particular. This causes no end of problems when folk replace a shot out barrel with 1950s BSA made one with the Inner Band fitted.
 

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Foxtrot351, You may be able to chase the threads by cutting a slot lengthwise in the old screw and chasing from right to left the rear trigger-guard threads in the action-body. This worked for me on a '44 Long Branch that someone installed a front sight protector screw, which is shorter, into the rear trigger-guard screw's position.

Regards, Brad
 

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Have a related trouble with a front nose cap screw. The thread on the nose cap is completely stripped. Had to drive out the screw. Wonder if tapping is possible or have to drill out the nose cap, insert a sleave and then tap the sleave with the BA tap?

Jay
 

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Discussion Starter · #7 ·
Thanks for all the help. I will see if I can find a supplier for these taps locally. I tried to run a replacement screw from the right side last night and had some success but did not quite make it all the way through before the slot began to wear down.

Again, Thank you for the help, Foxtrot351
 

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Have a related trouble with a front nose cap screw. The thread on the nose cap is completely stripped. Had to drive out the screw. Wonder if tapping is possible or have to drill out the nose cap, insert a sleave and then tap the sleave with the BA tap?

Jay
I presume you are taling SMLE?

You will find not a tap to recreate the thread. The nearest is 2BA, but you will need to make a screw to match.

I suggest you get one of the "nuts" that the rear nose cap screw goes into (in the fore-end), and adapt that to fit into the front nosecap thread position. They are the same thread.

I don't know where you are. If you are in the USA, Brian Dick has the bits.
 

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Foxtrot351, You may be able to chase the threads by cutting a slot lengthwise in the old screw and chasing from right to left the rear trigger-guard threads in the action-body. This worked for me on a '44 Long Branch that someone installed a front sight protector screw, which is shorter, into the rear trigger-guard screw's position.

Regards, Brad
Brad, I was going to suggest that too. Although I was going to recommend buying a spare screw to modify and toss when finished. That's a pretty common gearhead trick. :)
 
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