Duct crimping drill attachment - GIF

[rgsparber]

Seems to have no eccentrics, a mere 2 gears (with tapered ends?) and loose fit is rugged and "field expedient" enough,
as the manufacturer's own instruction tells you to enter/ exit at an angle:



2 cents
Johan

Ah, now I understand. The key is that you enter and exit at an angle. I didn't see that part of the process in the video.