Stuart Twin Oscillator build

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Sarah

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Whilst I am literally waiting for the paint to dry on my Stuart Progress I thought I would make a start on a Stuart Twin Oscillator, along with a friend we are building the single and twin versions.

As I didn't want to get too far ahead I thought I would make the two steam unions first. Part way through the first one and I didn't understand how the drilling was supposed to go on the left hand end which is threaded 3/16" x 40. Picture attached. The drawing calls for 1/8" dia x 1/4" deep, should that be more like 1/16" instead?

Yes, I was dumb enough to try and put a 3/32" drill in it!
 

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I would say 1/16" dia x 1/4 deep eg to meet the 1/8" hole from the other side in the middle.

Then counterbore 3/32" x 1/16" deep
 
I would say 1/16" dia x 1/4 deep eg to meet the 1/8" hole from the other side in the middle.

Then counterbore 3/32" x 1/16" deep
Thank you Jason 😊

The one I've made may be okay but may be a bit thin around the under cut. I'll order some more brass .
 
I’d agree with Jason, but I’d also check the drawings to see what the unions are connecting to and make sure the counterbores match whatever goes into the union.
 
I was thinking about that yesterday, as the counterbore is not a common type of union in the UK for steam models. I wonder as this tends to be a beginners engine that it was felt it would be easier for them to just make and solder a simple ring onto the ends of the pipe rather than make the more common nipple/ferrule

I have a feeling the small end screws into the main casting so can't really see the need for any form of counterbore of 60deg conical bore.
 
I was thinking about that yesterday, as the counterbore is not a common type of union in the UK for steam models. I wonder as this tends to be a beginners engine that it was felt it would be easier for them to just make and solder a simple ring onto the ends of the pipe rather than make the more common nipple/ferrule

I have a feeling the small end screws into the main casting so can't really see the need for any form of counterbore of 60deg conical bore.
 
You are correct Jason, the small end does go into the main standard in a tapped hole. I don't think there is any need for the counterbore.
 
I reckon it is a 1/8 thru hole (1/8 x 1/4 x 2 = 1/2) and then either side is counterbored to the sizes indicated.

Bruce
Hi Bruce, if it was a 1/8" through hole then the undercut on the thread end could go completely through.

Sarah
 

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