The Goodhead manufacturing process Posted on 24 Apr 23:42 , 0 comments
Making a Goodhead starts with rods of 2.5” ultra-high molecular weight polyethylene (UHMWPE), ten feet long.
Step one cuts the rod on the band saw into pieces that are a little bit longer (0.2”) than finished heads will end up as. The saw leaves marks on the heads, and isn’t reliable enough to count on precise cuts; a CNC lathe will ‘face’ the pieces to make them exactly 5, 4.5 or 4 inches long.
Step two moves the will-be heads to said lathe for facing, along with ‘turning’ to get the pieces of rod to the right diameter. (When you buy 2.5” UHMW, it comes in pieces that are 2.6” thick.) This step has two steps -- I face and turn one end, then the lathe program pauses so I can flip the part to face and turn the other end. If you get one, you can look and see where the two passes overlap.
Step three drills out a big portion from the middle of the rod. Capped heads get drilled through most of the way to come out like cups. Open-ended heads get drilled right through and come out as tubes.
In step four the lathe bores out the contours of interior diameter, in three incrementally smaller passes. This step makes the awesome scooping chamfer and the internal ribs that give the heads their resilience. The open-ended heads get flipped for a subsequent pass to round off the heavy edge on the shooting end.
In step five, the lathe drills shaft holes and bolt holes into the heads.
Step six, on a plain old drill press, puts a chamfer (an angled edge) on the bolt holes. This way, the bolt displaces less plastic as you tighten it, for less warping in the head’s shape.