125 MINSTAC Preparation and Installation Procedures

Boss Preparation


Boss Preparation Tools

Combination Boss Drill TTTA6201927A
Plug Tap TTTA6201627A
Bottoming Tap TTTA6201727A


  1. Drill a 0.062" (1.67 mm) diameter pilot hole in the desired boss location.
  2. Insert the front of the Lee Combination Boss Drill (Part Number TTTA6201927A) into the pilot hole and drill down until the 0.312" (7.90 mm) diameter spotface cleans up the surface of the boss. All diameters should be concentric within .006" (0.15 mm) T.I.R. The sealing face should be smooth with no burrs or tool marks.
  3. Tap the 0.250-28 unfinished threads using the Lee Plug Tap (Part Number TTTA6201627A) first and the Lee Bottoming Tap (Part Number TTTA6201727A) second. These taps incorporate stops to avoid damaging the sealing surface.


Unless otherwise specified, dimensions are in inches [mm].

NOTE: Care must be taken to ensure that the taps will follow true in hole produced by the Combination Drill.

125 MINSTAC Tubing Preparation and Coupling Assembly

Coupling Assembly Tools

125 MINSTAC TTTA6200143A *

125 MINSTAC TTTA6200343 (no ferrule) *


  1. Cut the tubing reasonably square to the desired length.
  2. Hold tubing with Tubing Grip. Slide the center drill end of Lee Coupling Assembly Tool* (Part Number TTTA6200143A) onto tubing. Hand twist the tool clockwise to form a chamfered lip seal. The resulting chamfer should leave a 0.002" to 0.004" (0.05 mm to 0.10 mm) flat on the end of the tube.

    * Use the Lee Coupling Assembly Tool (Part Number TTTA6200143A) for use with 0.062" (1.57 mm) I.D. tubing. Substitute the Lee Coupling Assembly Tool (Part Number TTTA6200243A) for use with 0.032" (0.81 mm) I.D. tubing.

  3. Slip the Ferrule (Part Number TMBA6201910Z) onto pin of the Coupling Assembly Tool. (Click here for 1/4-28 Flat Bottom Ferrule).
  4. Slide the flanged end of Collet Sleeve (Part Number TMCA6201920Z) over the Ferrule until it snaps in place.

  5. Thread the Coupling Screw (Part Number TMAA6201929Z) over the Collet Sleeve until it bottoms.

  6. Thread the tool/coupling assembly counterclockwise onto the chamfered tubing using the Tubing Grip, applying slight force until resistance is felt after approximately 5 turns.

  7. Unscrew the coupling from tool. The assembly is now ready for installation into a 125 MINSTAC boss.

125 MINSTAC Coupling Installation


Coupling Installation Tools

Torque Wrench TTTA6202227A
Wrench TTTA6200227C


  1. Start threading the coupling assembly into a 125 MINSTAC boss using Lee Wrench (Part Number TTTA6200227C).
  2. Tighten the fitting between 7 to 21 ozf•in (0.05 to 0.15 N-m) by slipping the Lee Torque Wrench (Part Number TTTA6202227A) onto the Coupling Screw hex. The minimum torque is achieved by pressing the shorter torque arm clockwise until it just contacts the longer arm. To check that maximum recommended torque is not exceeded, invert the Torque Wrench and press the longer torque arm clockwise until the Coupling Screw begins to move. This should occur before the torque arms make contact. After gaining a feel for the proper torque, use of the Torque Wrench may be discontinued.

Minimum recommended torque: 7 ozf•in (0.05 N-m)
Maximum recommended torque: 21 ozf•in (0.15 N-m)

Unless otherwise specified, dimensions are in inches [mm].