3" Burrell Traction Engine build.

 Screw cutting Acme Thread - Brake rod. Welcome to this month’s traction engine build update. With the weather not helping motivation, I decided to tackle some straightforward lathe work — the brake rod. The drawing specifies a 3/8" × 10 TPI left-hand square thread. While anticlockwise operation to apply the brake would justify a left-hand thread (as seen on some full-size engines such as those by Aveling & Porter and Burrell ), cutting an internal LH square thread at this size would be challenging. A right-hand thread will be perfectly adequate for the model. My plan is to screw cut a trial thread in silver steel, mill flutes to create a tap, harden it, and use it to thread the bronze nut. I’ll then cut the matching screw so both parts mesh correctly. Since the nut is bronze, machining should be manageable. Although the Boxford metric lathe is the easiest machine to set up for screw cutting, producing true 10 TPI would require imperial conversion gearing. Instead, cutting...