Looking for an oddball tap...

[x39]

Why do these things always land in my lap? I need a tap for some work I'm doing on a Rolls Royce V-12 intake manifold. It has studs in several places, all of them are 13/64" (.203) major dia.x28 tpi. I can't find any reference to a thread this size in Machinery's Handbook or any catalogs. Since the parts are obviously British, any guidance from across the pond would be greatly appreciated. Thanks in advance. BTW will be away from the computer for a couple of hours, please pardon if response is a bit slow.

[SDL]

It will be a special

Form as here

http://www.coventrygauge.co.uk/pdf%2...08-9bswbsf.pdf

What else do you want to know.

Steve Larner

[Ken_Shea]

This is as near as I found with ME Consultant Pro

[Russ H]

When was engine made? From Machinery's Handbook, 17th edition page 1189: B.A. #1 thread 5.30mm (0.2087") o.d., pitch = 0.90mm (about 28.2 TPI)
Russ H.

[Limy Sami]

AFAIK,

If it's a RR aero engine (or derivative) they used a lot of special threads on simple fasteners.

My RR diesel experience only goes to 1978, but IIRC they're nearly all standard, the (post 75-ish) have a metric / unified mix.

11mm manifold bolts come to mind??

[x39]

Russ and SDL I think you guys nailed it. I'm not quite sure what year the engine is as I'm only working on the components at hand. I would guess twenties or thirties. Thanks for taking the time to help me out. Limy Sami, the engine is from an automobile.

[Timleech]

When was engine made? From Machinery's Handbook, 17th edition page 1189: B.A. #1 thread 5.30mm (0.2087") o.d., pitch = 0.90mm (about 28.2 TPI)
Russ H.

Seems to me like the best bet. 1BA does sometimes crop up on engines from the 1930s.
AFAIR Gardners had 1BA tappings for the tacho drives.
7/32 also exists in the real world even if not in the main charts, I've got 7/32 Whit taps and a few screws, not personally seen it in BSF though.

Tim

[John Stevenson]

Tracy tools has 7/32" x 28 taps and dies.

http://www.tracytools.com/tapsanddiesbsf.htm

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