Restoring a damaged, dirty, painted or rusty thread by running a tool through it that follows the existing form. Chasing taps and dies are made to reform crests and push out debris rather than remove much metal, which matters on old threads where a cutting tap would loosen the fit. Galvanized and painted threads, head bolt holes and cut ends of threaded rod are routine chasing jobs.
Chase every head bolt hole before you torque, crud in the bottom will throw your clamp load way off.
Also heard as
- chase the threads
- thread chaser
Related terms
Cross-thread
To start a nut or screw crooked so its thread cuts across the mating thread instead of following it.
All-thread
Shop name for threaded rod: steel bar threaded end to end, cut to length for hangers, anchors and long studs.
Torque-tension
The relationship between the torque applied to a fastener and the preload it produces, dominated by friction.
HDG
Hot-dip galvanized: coated by dipping in molten zinc, leaving a thick, rugged layer for outdoor steel.