Z-axis knob
thingiverse
This top knob is designed for your z-axis screws. It features M8 tap holes for easy installation. Purchase a Harbor Frieght tap kit ($12) to thread the part. Once printed, use the M8 tap and follow by adding a nut onto the Z-axis screw; then securely fasten the knob in place by tightening the nut against it.
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