Sometimes, overtightening or putting excessive pressure on the thumbscrew of your shockmount can cause it to break. If you're in need of a replacement, use the following measurements to source the proper sized screw from a local hardware store.
T-shaped thumbscrew for MXL-70, MXL-90 and similar shockmounts:
M5 - 0.8 x 12.5 Thumb screw
(metric size, thread pitch and length)
Pan head bolt for USM-001 and USM-001:
M6 - 1.0 x 27 Pan Head Bolt
(metric size, thread pitch and length)
If you're unable to remove the broken thumbscrew from your shockmount, and it's covered under warranty, please submit a support ticket here.