Thread pattern / size question

[pro-crastinator]

If I can get this right ahead of time - it will save me a 3 hour trip.
The exhaust cover bolts (12 of em) on a 1956 Evinrude Big twin 30.
Alas, my tap & die set starts at .25 inch.
I know they have 24 threads per inch
I know they are less than 1/4 inch dia
That leaves two possibilities. 10-24 or 12-24

ALSO, busted bolt drill, easy out or tap. Expect to have to drill/tap the hole to recover from the frozen bolt.

Will purchase new, cobalt drill bits to do the deed. Size to be determined.

Correct gaskets have arrived. (second times the charm)

Thanks everyone.

 

[pro-crastinator]

No Title

 

[bob johnson]

10-24

 

[bob johnson]

10-24 thread calls for a #25 drill...which is .1495" in dia...you will want to make sure you are dead on center when you drill....usually Ill try to get a point started with a larger drill.... then drill with something smaller than the final drill I want.... to make sure it is centered.....if it isn't centered, then I try to get the broken screw out with an easy out....if it is centered well, Ill go with the final drill size for that thread..and then re-tap slowly backing out 1/2 turn for every one turn in!!! lots of oil

bob

 

[pro-crastinator]

Thanks for the rescue Bob

-Bennett