Tamron Adaptall lens rear cap MKII

thingiverse

This is a minor tweak of John Beardon's original design (thanks for doing the heavy lifting, John!). It boasts thicker walls protruding upwards from the cap base (requiring a slightly reduced inner diameter) and wider, taller (but not thicker) bayonet lugs. These modifications ensure a tighter fit on the lenses and minimize the likelihood of caps coming loose in your camera bag if they get jostled around. The thicker inner wall seemed necessary to boost rigidity when printed with PETG, rather than PLA. This version of the cap still effortlessly fits over the rear element of the 2x teleconverter, which has the largest diameter and farthest projecting rear element of any Adaptall lens I own. Like the original version of this Thing, the caps don't lock onto the lens (the real Tamron ones do), but the longer lugs of the revised cap are securely held by the springs inside the lens bayonet socket, so they won't come off without a firm CCW twist. The more robust lugs are actually slightly manipulated parentheses from Tinkercad's text generator.