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[pipercub1772]

Hi I have a steam boiler that has been made by someone and one of the boiler bushes looks to be very slightly oval a 1/4 by  40 fitting is very tight fit so much so that i feel as though it could break the brass fitting by the time it is fully home the bush appears to be bronze would i be better better putting a 1/4 by 40 tap down the bush . so my question is will bronze tap easily and would you get a taper tap or what ,thanks for any replies ,Kind regards Allan.

[derekwarner]

If sufficient depth [in the boiler] is available, a taper or intermediate tap will be suitable.....engage by thumb & forefinger until restriction/tightness is felt......paste a little Rocol or Trefelex cutting compound in the flutes of the tap & rotate to cleanup. You will probably be surprised at how little material is removed in this thread cleanup process

Bronze technically does not require any cutting compound, however using it will decrease the cutting pressure and also aid in retaining any swarf in the flutes rather than falling into the boiler

Derek

[mrsgoggins]

Silly question, it's not a 32TPI bush is it?


Keith

[pipercub1772]

Thanks derek i will go with your suggestion it sounds good ,it is 40tpi Kieth,it will screw in but it is tight i can only think it got a bit distorted when it was silver soldered, kind regards Allan.

[steamboatmodel]

I always tapped the bushes after I soldered the boiler. Usually with the boiler upside down and the flutes filled with grease.
 Regards,
Gerald.