TM 9--2520--215--34
0018 00--6
GENERAL MAINTENANCE INSTRUCTIONS – CONTINUED
0018 00
SCREW THREAD INSERTS (ONE PIECE TYPE).
When determined feasible by inspection, damaged threads should be repaired by rethreading, use of thread
restorer, tap die, or by “chasing” on lathe.
Tapping holes for screw thread inserts that have mutilated threads may be repaired by drilling and tapping hole
oversize and installing larger inserts or by filling tapped hole by welding, redrilling and tapping hole to original size.
Refer to Table 1 for drill size and depth.
Table 1 Thread Inserts: Drill Size And Depth
THREAD INSERT
REMOVAL DRILL
Internal
Threads
External
Threads
TAP DRILL
Diameter
COUNTERSINK
Diameter
Diameter
Drilling Depth
10--24
10/32
3/8--16
Q
(0.332)
25/64
9/32
1/4
1/4--20
1/4--28
7/16--14
X
(0.397)
29/64
11/32
1/4
5/16--18
5/16--24
1/2--13
29/64
33/64
13/32
1/4
3/8--16
3/8--24
9/16--12
33/64
37/64
15/32
1/4
7/16--14
7/16--20
5/8--11
37/64
41/64
17/32
1/4
1/2--13
1/2--20
11/16--11
41/64
45/64
19/32
1/4
WARNING
Use the following procedure to remove and install screw thread inserts:
1. Drill thread insert. Refer to Table 1 for drill size and depth.
2. Deflect keys inward and break off.
3. Remove remainder of thread insert with a screw extractor.
4. Install screw thread insert until 0.010 to 0.030 in. (0.25 to 0.76 mm) below surface of plate.
5. Drive keys flush in with plate.
END OF TASK
