South Bend 9A 9B 9C and 10K approximate metric conversion gear (14.5 PA, 18DP)

14.5 degrees pressure angle, diametral pitch of 18.

Converts your existing 80T idler gear to a 80/63 compound gear, offering a very good approximation to the 127/100 gear for cutting metric threads. The approximation error is 0.0125% or 1.5 thousands over a foot.

I have two versions. A whole gear, with holes for 10-32 screws, and a rim gear, whose inner diameter is 2.750". In the photos, I show the rim gear, printed in nylon with carbon fiber reinforcements, along with a 24T stud gear.