Replace sear screw

[Derby]

I have worked on the trigger mechanism, and bedding, of my No1 Mk3 Lee Enfield and the sear & trigger were very good (with minimal work required) but the sear pivot screw is a very tight fit and won't test-seat all the way. I think it should be replaced and maybe retap the housing thread.
Refitting the sear spring is also tricky ...is there an easy way? Any tricks?
The thread is very fine (not a BA or BSF thread) so any idea what it is?
Where can I buy these spare parts?

Information

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[Peter Laidler]

A real Armourer would identify the problem first. Is is a high thread or tight shaft or both. Then he'd fix what is wrong in a lathe or on the bench. There's no betting that a replacement will fit either. You won't tap out the s thread because it's what the engineering world call 'a bastard size'. Just clean the screw thread and polish the shaft and it might help.

Fitting a sear spring is simplicity itself. Insert a flat screwdriver blade in the U shape, sit the long arm in the slot, twist screwdriver blade until short arm fits in the other slot. When you've done one, the next zillion get easier!

[Derby]

Thank you for that advice as I looked at it from a different angle and guess what: "I'll be buttered on both sides!" ...the screw was far too tight in the bearing end opposite the thread, so I put it in my jeweller's lathe & polished it until it was a better interference fit. I was then able to screw it in albeit tight (I suppose as it should be).
Note that it was very hard to remove in the first place.
Then I fitted the sear & the spring as suggested. And, it worked! Simple really.
Now the trigger works a treat and it smooth to operate.
Thanks very much.