4. INSPECT UNDERCUT DEPTH OF SEGMENT Check that the undercut depth is clean and free of foreign material. Smooth out the edge. Standard undercut depth: 0.6 mm (0.024 in.) Minimum undercut depth: 0.2 mm (0.008 in.) If the undercut depth is less than minimum, correct it with a hacksaw blade. Field Frame (Field Coil) 1. INSPECT FIELD COIL FOR OPEN CIRCUIT Using an ohmmeter, check that there is continuity between the lead wire and field coil brush lead. If there is no continuity, replace the field frame. 2. INSPECT THAT FIELD COIL IS NOT GROUNDED Using an ohmmeter, check that there is no continuity between the field coil and end field frame. If there is continuity, repair or replace the field frame. Brushes INSPECT BRUSH LENGTH Using vernier calipers, measure the brush length. Standard length: 15.5 mm (0.610 in.) Minimum length: 10.0 mm (0.394 in.) If the length is less than minimum, replace the brush holder and field frame. Brush Springs INSPECT BRUSH SPRING LOAD Take the pull scale reading the instant the brush spring separates from the brush. Standard installed load: 1.785 — 2.415 kg (3.9 — 5.3 lb, 18 — 24 N) Minimum installed load: 1.2 kg (2.6 lb, 12 N) If the installed load is less than minimum, replace the brush springs.