Wot size thread?

[Capt.Cadet]

Hi From a newbie...
I have a 310 Cadet and I am making a new eyepiece for it`s #8 BSA tang sight but I cannot fathom out what the thread is, I have tried metric, BA and unf-unc sized taps of approx size but NONE fit correctly. I would love to fit the new sight using the correct BSA thread.
Any help would be appreciated.
CC

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[jamie5070]

Try asking on the Lee-enfield board, you might get more responces to your question. If not there, try britishmilitaria.yuku.com. Someone there should be able to get you an answere.
I have a PH-7A with an ajustable eye piece on my cadet.
john

[Patrick Chadwick]

Get hold of a thread gauge and measure the pitch. Parker-Hale sights use 40 tpi for the eyepieces. My guess is that BSA might well have used the same.
If it is indeed a 40 tpi thread, then look for a model engineering supplier. 40 tpi fittings are (were?) common on live steam models, and taps/dies are available from such suppliers.

[Patrick Chadwick]

Get hold of a thread gauge and measure the pitch.

If you have not got a thread gauge, see if a 4BA bolt (which has 38.5 tpi) nearly fits the pitch. If so, that increases the likelihood that it is a 40 tpi thread.