I need to make some jets for paraffin blowlamps. I can screw cut the threads but am totally baffled by what system they use, despite several hours going through various Machinerys Handbooks. The two in front of me now are max 0.320" by 28 tpi and max 0.176 by 48 (ish) tpi. I thought the former was Brass but its definitely 28 tpi. Can anyone shed any light on this puzzle please?
thanks