Tim Edwards made a very nice and extremely useful attachment for the MakerGear Z-knob that drops on top and can function as both a crank for the Z-axis as well as a stop that automatically ejects if you forget to remove it when you start a print. It's a little bulky since it goes over the factory Z-knob. I combined the current MakerGear low-profile Z-knob with the ramp and post from Tim's cap to make a one-piece knob that's a little smaller and has fewer parts but retains all the great features.
The factory knob has a metal insert that was press-fit inside it. I simply sawed a little slit on each side of my factory knob then cracked it in-half with a screwdriver to remove the insert. I then re-used it in the new/improved knob. I used a socket from my tool set to allow me to squeeze it together in the vise without crushing the ramp and post. I also added a small chamfer to the top of the post so that the lever drops on more easily. Works great. This replacement knob uses the same crank handle from Tim's version: http://www.thingiverse.com/thing:934680
I recommend printing the crank in a color other than black so that you don't keep misplacing it like I do with mine.
Z_Knob_with_ramp.STL | 662.7KB |