'74 Commando - Brake Master cylinder threaded hole question?

[74Norton920]

Hello,

I am trying to figure out exactly what the thread is on the hole for the Brake Master Cylinder. There is a threaded "blind" hole about 20mm long that I want to have an adapter made to fit a metric mirror. My 3/8" and 7/16" taps do not seem to fit. Can someone enlighten me? I have access to a lathe and would turn up an adapter and thread either end to suit.

Thanks Chris

 

[EstuaryBoy]

I recut some metric stems to fit my Mk3 with a 3/8 24 UNF die

 

[Dan1950]

Hello,

I am trying to figure out exactly what the thread is on the hole for the Brake Master Cylinder. There is a threaded "blind" hole about 20mm long that I want to have an adapter made to fit a metric mirror. My 3/8" and 7/16" taps do not seem to fit. Can someone enlighten me? I have access to a lathe and would turn up an adapter and thread either end to suit.

Thanks Chris

Tap it out for a 10mm 1.25 Helicoil. It is not a "blind hole", it goes through to the plunger. Use a copper coupling fitting inserted over the plunger to protect the plunger while drilling/tapping.

 

[Cuppy]

I tapped the hole on my clutch lever M10 X 1.25 for my metric mirror on a 72

Edit, the hole in my 72 Commando clutch lever was not tapped to begin with.

 

[Dan1950]

I tapped the hole on my clutch lever M10 X 1.25 for my metric mirror on a 72

I edited my post above to reflect 10mm 1.25. There didn't seem to be enough material to just tap the hole without the thread insert.

 

[Cuppy]

I edited my post above to reflect 10mm 1.25. There didn't seem to be enough material to just tap the hole without thevthread insert.

Also edited my post above.

 

[Dan1950]

Also edited my post above.

That explains why you had enough material for the 10mm 1.25 thread.

Mine were already threaded.