I have some wire shelving units that I would like to extend the poles on to make them taller. The shelves are composed of two vertical poles that are female threaded on one end. The poles are connected with a connector that is male threaded on both ends. Unfortunately, the poles are only threaded on one end, so I need to find a way to put threads on the unthreaded side of other poles I have. (the photo with the green arrow shows what I am trying to thread).
I don't have any experience doing taps, and I cannot figure out how to determine the size tap I need. I found a lot of charts for various drills required for a tap, but nothing that links them to the size of the 'hole' or pipe being drilled(someone needs to create a simple calculator!). I don't even know if it is metric or not; the ads for the shelves (they are all pretty standard) say "1 inch poles" but any tap I found at 1 inch was either 8 or 12 TPI, and these are closer to 16 (or they are metric). Even more confusing, the connectors say 'coarse' thread. The connectors also are described as having a pitch of 1.5 mm.
The closest I can figure is maybe a M23x1.5? Is the diameter of the tap the same as the interior pipe dimension?
Also, if I'm tapping by hand, would a 'plug' tap be the right one to get?
Thanks.
