scoop said:
Bentprop admits to using 26 t.p.i threads now and again.This is probably the old British brass thread which uses 26 t.p.i for all diameters of thread.Anybody else out there still using this thread system on a regular basis?
Yes, I admit to using it and other constant pitch threads on a regular basis.
The old British Model Engineer thread series used a constant pitch; the pitch depending upon the diameter.
The series consisted of 26 tpi, 32 tpi, 40 tpi and (rarely) 60 tpi.
The 26 tpi series is the same as the BSB (British Standard Brass) threads, and go from 1/8" up to 5/8".
32 tpi is partly BSW (British Standard Whitworth) and partly BSF (British Standard Fine). and goes from 1/8" up to 1/2".
The 40 tpi series is, again, partly BSW and BSF and normally goes from 1/8" up to 1/4".
These threads were developed pre WW2 when model engineering in the UK was geared towards 2-1/2" gauge and below railways where the normal range of commercial threads were deemed unsuitable.
BA threads are a different series, and were commonly used in the electrical industry.
Marv. The chart was drawn up just so that I could have a quick comparison between the various threads specified on drawings, particularly in my case, US to UK as most of my threading tackle is the old Imperials stuff, although I am widening my base reluctantly - cost, my boy.
Dave
The Emerald Isle
