Re: Linear table actuator

via google:

http://www.williamsform.com/Threaded_Bars/C-
1045_Coil_Threaded_Bar/coil_threaded_bars.html

it is a threaded rod with round bottoms to the grooves, the bars look
a little like ballscrews. Nuts are available but are of course just
like normal nuts. You could probably use a length of the rod to make
a tap and tap delrin nuts that would be a tight fit as some have done
with acme bar to avoid the cost of a tap.

Graham