Metric threads on an Imperial lathe

[plongson]

Prolly beat to death but here's the question...
Is there a way to cut perfect Metric on Imperial or is using "close enough" good enough...sounds dumb but say, a M6x1 is 25.4/thou, if I chose 26 TPI, would that be "Close enough/good enough?
I'm thinking for a 1" long thread, probably but it would get progressively worse the longer the thread.
THANKS!! Just thinking out loud...LOL

 

[Jim F]

Need a 100/127 transposing gear

 

[rwm]

^^^This. 26 TPI would only work for a short length with sloppy fit. Even the 100/127 is an approximation but very close. See below
(I was thinking of the 47/37 transposing gear when I said approximation.)

 

[SLK001]

Yes, some kind of compound gear with a 127 tooth gear in it will allow you to cut perfect metric threads on an Imperial machine. The lowest factor between metric and Imperial is 127 (127 x 2 = 254). The compound gear with the 127 will bring the difference to easy fractions to gear like 1/10, 1/8, 1/6, etc, instead of fractions like 1/11.1334278128399445060133231.

^^^This. 26 TPI would only work for a short length with sloppy fit. Even the 100/127 is an approximation but very close.

No, the 100/127 is exact.

 

[rwm]

Learning everyday!

 

[plongson]

Heck yeah! I sure have more to learn... and I'm only 70!

 

[GeneT45]

In addition, check this out: https://conradhoffman.com/metricthreading.htm Works for me!

GsT

 

[FZR1KG]

Yes, some kind of compound gear with a 127 tooth gear in it will allow you to cut perfect metric threads on an Imperial machine. The lowest factor between metric and Imperial is 127 (127 x 2 = 254). The compound gear with the 127 will bring the difference to easy fractions to gear like 1/10, 1/8, 1/6, etc, instead of fractions like 1/11.1334278128399445060133231.



No, the 100/127 is exact.

Yep, the inch was defined some time ago to be exactly 25.4mm
So technically, the US is metric, but just using a different scale

Personally I would have chosen 25.5mm, then its a perfect 8 bit number for this digital world. Though I have been accused of binary thinking before...

 

[MrWhoopee]

My SB Heavy 10 came with an 80 tooth idler, so the obvious choice was 80/63 transposing gears. 80/63=1.26984126984. Close enough for government work.

 

[plongson]

GeneT45... GREAT READING! Thanks...