Step (1)
Go to www.mcmaster.com order parts:
2 @ 40 mm Unthreaded Knobs Part # 62015K211 cost 9.02 each
2 @ 3/8" ID Set-Screw Couplings, Part # 6412K13 cost 5.33 each
Find 2 @ 3/8"-16 x 1.5" or longer bolts in your junk box.

Step (2)
Gather tools needed:
3/8"-16 Bottoming Hand Tap but a starting tap will work OK if that's all you got. A 12 MM Drill Bit or a 31/64" will do fine too. Drill Press, or Drill Motor, Hacksaw, File and a Bench Vise is helpful too.

CONTINUED NEXT PICTURE