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Unit of Measure

Insert Type

N/A Standard

Series

N/A RJ100

Material

N/A 4130 Steel

Finish

N/A Cadmium Plate per AMS-QQ-P-416, Type II, Class 3

Material Specification

N/A AMS-S-6758, COND F

Military Part Number

N/A MS51991-106

Lockring Part Number

N/A RLRR28SA8

Lockring Military Part Number

N/A MS51990-106P

Internal Thread Lock

N/A No

A - Internal Thread, Class 3B

N/A 0.2500-20 UNJC

B - External Thread

N/A 0.3750-16

B - External Thread - Pitch Diameter

N/A 0.3347-0.3372 in

B - External Thread - Minor Diameter

N/A 0.2906-0.3011 in

C ± .015

N/A 0.500 in

D ± .015

N/A 0.330 in

Heat Treat

N/A 125 KSI UTS min

E ± .015

N/A 0.170 in

F - Diameter

N/A 0.305 in

G - Diameter

N/A 0.291 in

H - Diameter

N/A 0.260-0.270 in

J - Number of Teeth

N/A 20.000

K +2º -1º

N/A 102.000 º

L - Diameter +.007 -.002

N/A 0.345 in

M - Diameter +.005 -.004

N/A 0.316 in

N ± .015

N/A 0.110 in
Aluminum Step Drill Part Number1 N/A RCDC28-312
Magnesium Step Drill Part Number2 N/A RCDAC28-312

Basic Tap Size

N/A 0.3750-16UNC

Wrench Part Number

N/A R1106W

Locking Drive Tool

N/A R106D
Removal Drill Size3 N/A 5/16

N/A

  • The external thread has a special pitch diameter and minor diameter which installs into a AS8879 class 3B, MIL-S-7742 class 3B, or National class 3 tapped hole.
  • Inserts are installed and removed in accordance with MS51995.
  • Insert lengths shown are based on installation in 2024-T4 Aluminum and in such materials will accommodate tension loads up to the strength of a mating bolt heat treated to 145,000 PSI UTS. If this design criteria is required in parent materials of lower mechanical properties, longer insert lengths should be specified. Mating bolts should have a thread engagement of 1.5 diameters or if insert has a thread lock, the bolt should extend through the insert 2 pitches including chamfer.
  • Mating lockring is not included with insert. It must be ordered separately.

  • 1 Step Drills are designed for thru hole drilling, when used to drill a blind hole, it may be necessary to grind the drill to suit the depth required.
  • 2 Step Drills are designed for thru hole drilling, when used to drill a blind hole, it may be necessary to grind the drill to suit the depth required.
  • 3 Removal Drills are not supplied by Howmet.