Amazon.com: M20 to 1/2" Inch NPT thread adapters. ($8.44 Each - Sold in 10 Packs) M20X1.5 threads on external side. 1/2" Inch NPT threads on internal side. Nickel plated brass adapter with
M20M12-6-0M | Jacob Reduction Adapter M20 x 1.5 - M12 x 1.5 Nickel-Plated Brass | Distrelec Norway
Record Power, 62112, Chuck Insert Adapter, M20 x 2 RH - The Woodturning Store