||Screwed stays and the holes
for these shall be screwed with a continuous thread.
||The screwed threads of the
stay shall be clean free from checks or imperfections,
of full depth, correct Whitworth form and a good fit in
the holes. The middle portion shall preferably be turned
down to the bottom of the thread.
||The stays shall be screwed
with fine threads of not less than 11 threads per inch.
||The diameter of the stay over
the threads shall not be less than ¾ inch or twice
the thickness of the firebox plate whichever is the greater.
||The pitch of the stays at the
furnace of vertical boilers shall not exceed 14 times
the thickness of the furnace plate.
||Where the stays are not fitted
with nuts, the ends shall be riveted over to form substantial
Alternatively stays may be screwed through the shell and
firebox plates and the projecting ends shall be substantially
fillet welded in an approved manner. The projection of
the end of the stay from the surface of the plate shall
be not less than one quarter of the diameter of the stay
but in no case less than ¼ inch. The full end of
the stay shall be visible on completion of the welding.
||Crown stays of Loco type boilers
shall either be fitted with nuts or riveted over on the