I am restoring a Wyco 993 concrete vibrator. It was missing a cover, shaft, and switch. I had a matching switch in my parts pile. I bought this vibrator as a pile of parts from an auction (along with 5 working vibrators and a lot of shafts and other parts). It was broken due to physical impact (plastic cover broken). It is easy work, got the cover on ebay, have other parts etc. Vibrator runs fine after I put on the switch. No complaints.
My only problem is that in a certain place, they use 1/4-20 nylon plastic bolts, probably for electrical insulation purposes. The bolts are broken, they broke off as the cover, that they held, was hit and broke off. My question is how to remove their remains from holes.i