The 3/8" steel shaft of this motor is heat treated and supported by a needle roller bearing to handle better radial loads.

Features:

Rated Voltage: 27 VDC
Rated Current: 3 A
Rated Speed: 50 RPM
Rated Torque: 6 N-m (4.4 ft-lb)
Mounting: M6 screw holes
Shaft (Heat Treated): 3/8" shaft with 1 flat ("D" shaft)
Needle roller bearing for handling better radial loads

Documents:

Drawing of the motor is HERE
3D model can be obtained HERE
Torque Curve

Note on self-locking: This motor uses a worm gear drive, which provides a strong tendency to self-lock (the output shaft resists being back-driven) due to the high gear ratio and worm pitch. This is a gear-design characteristic, not a mechanical brake — the holding force is limited and is not a substitute for a brake in safety-critical or high-load hold-in-place applications.