A quick print to assist threading NGK 14mm 5/8" hex plugs into the head. Sometimes they are just a bit too tight to thread by hand and too loose with a socket. The spline provides fingertip grip, especially around close fit headers. I used Polycarbonate for strength. ABS would be fine as long as they were not hot at the time. I suppose if it were totally cold you could use a PLA pro.
Plug_Grip_v7.stl | 183.8KB |