After quite a bit of measuring and head-scratching, I can't work-out what the thread is for the clutch/brake/air lever clamps. It seems to be 5mm, which I guess can't be right, with something like 28tpi. Any ideas as the slotted screws are past their best.

email (option): lee@twowheelstested.co.uk

You might find that the thread is 1BA.

Lee, most of this Smiths, Amal, Bowden stuff is BA threads. Your 5mm will be 2BA. The pivot screw is 0BA.

Ron

email (option): ronpier@talk21.com

0ba =bolt dia. 0.2362" 25.4tpi
1ba =bolt dia. 0.2087" 28.2tpi
2ba =bolt dia. 0.1850" 31.4tpi

Quite right Fred. The first lever I picked up has 2BA screws. The next one had 1BA screws. They are so blooming close to each other in size. Ron

Edit. What happened to the link you posted

email (option): ronpier@talk21.com

Ive even used 3/16 BSC in the past for 2ba holes & got away with it at 32tpi & negligible dia difference

Sorry the link didn't survive my edit it was these people, i use them all the time.
www.a2stainless.co.uk/

Yes Fred, I've a feeling that the primary case screws on an M20 are 3/16 BSC. But everyone uses 2BA which are more readily obtainable. Ron

email (option): ronpier@talk21.com

Thanks for that Fred. I use Dave Middleton. But always on the lookout for a cheaper option. Ron

email (option): ronpier@talk21.com

For some good value larger quantities of fixings i use Wye Vally supplies online shop aswel. They do some trade packs.

Thanks everyone. Just as I was getting used to cycle, BSW & UNC, a new thread came along to upset the balance.

email (option): lee@twowheelstested.co.uk