Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Is there a list of thread sizes for the different manufacturers boiler fittings such as Whistle, pressure relief valve and steam outlet?

I know a common thread used is 4-40, and I measured a Wilesco small boiler and it was 6mm.   Weeden used a standard 1/4" - 32 MPT (Model Pipe Thread) for all the boiler fittings.

I want to make a proper fitting to use compressor air to power some of my engines.

This may be of some help thanks to Jim:

https://www.officeofsteamforum.com/members-file-sharing-board/toy-model-steam-engine-thread-sizes/