When we ran a full service chassis fab/turn-key hot rod shop a number of years ago, it was always useful to have threaded things around to weld into the frame for some kind of mount, etc.
Here’s a list of all our threaded things for your reference:
DOM Tubing; 5/8" OD - 1-3/8" OD, per foot
Product Details
Country/Region of Manufacture: Canada
Diameter: 5/8" - 1-3/8"
Available in 1 foot increments, 46" maximum length per tube.
If you order more than 4 feet, please specify how you would like it cut up with 46" being the maximum length for shipping. Does not come tapped.
Drill sizes:
7/8″ OD x .156: drill 37/64″ to tap 5/8-18.
1″ OD x .188: drill 11/16″ to tap 3/4-16.
1″ OD x .219: drill 37/64″ to tap 5/8-18.