ASME B18.29.1-2010 pdf free download.Helical Coil Screw Thread Inserts- Free Running andScrew
Locking (Inch Series).
1.4 Class of Fit
Since helical coil inserts are flexible, the class of fit of the final assembly is a function of the size of the tapped hole. Helical coil STI taps are available for both tolerance Classes 2B and 3B tapped holes. Tolerance Class 2B tapped holes provide maximum production tolerances, but result in lower locking torques when screw locking inserts are used. The higher and more consistent torques given in Table 5 are met by the screw locking inserts when assembled and tested in tolerance Class 3B tapped holes in accordance with section 2.
1.5 Compatibility
Assembled helical coil inserts will mate properly with items having UN external threads in accordance with ASME Bl.1. In addition, due to the radius on the crest of the insert at the minor diameter, the assembled insert will mate with UNJ profile external threaded parts with controlled radius root threads per SAE AS8879.
1.6 Types of Inserts
1.6.1 Free-Running. The free-running insert provides a smooth, hard, and free-running thread.
1.6.2 Screw-Locking. The screw-locking insert provides a resilient locking thread produced by a series of chords on one or more of the insert coils.
2 STI TAPPED HOLE
The tapped hole into which the insert is installed shall he in accordance with ASME 131 .1, except that diameters are larger to accommodate the wire cross-section of the insert. Dimensions of the STI tapped holes are shown in Table 1 and calculated per Note (3) of Table 1.
2.1 Screw Thread Designation
2.1.1 Designation for Tapped Hole. The drawing note for the STI threaded hole per Table I to accept the helical coil insert shall he in accordance with the following example:
EXAMPLE: /4-20 UNC-2[3 STI thread 0.430 mm. depth, per ASME 1318.29.1.
2.1.2 Designation for a Helical Coil Insert. Designation of the helical coil insert on parts lists, spares lists, purchase orders, etc., shall he in accordance with the following examples:
EXAMPLES:
(1) ASME B18.29.1, /4-20 UNC 0.375 long helical coil free-running insert.
(2) ASME B18.29.1, #10-32 UNF 0.380 long helical coil screw-locking insert.
2.1.3 Designation for STI Threaded Hole Including Installed Helical Coil Insert. The drawing note for the STI threaded hole per Table 1, having a helical coil insert installed, shall be in accordance with the following example:
EXAM PLES:
(1) %-20 UNC-2B STI thread 0.430 deep.
(2) ASME B18.29.1, /4-20 UNC 0.375 long helical coil free-running insert.
2.2 Gages and Gaging
Acceptance of the threaded hole is determined by gaging with STI GO, NOT GO (HI), and plain cylindrical gages designed and applied in accordance with System 21 of ASME 131.3 (see Nonmandatory Appendix C).
3 HELICAL COIL INSERT
3.1 Insert Material
Chemical composition of the inserts is austenitic corrosion resistant (stainless) steel within the limits of Table 2.
3.2 Properties
3.2.1 Tensile Strength. Wire, before coiling into inserts, shall have tensile strength not lower than 150,000 psi, determined in accordance with ASTM A 370.
3.2.2 Bending. Wire shall withstand, without cracking, bending in accordance with ASTM E 290 at room temperature through an angle of 180 deg around a diameter equal to twice the cross-sectional dimension of the wire in the plane of the bend.
3.2.3 Workmanship. The formed wire shall be of uniform quality and temper; smooth, clean, free from kinks, waviness, splits, cracks, laps, seams, scale, segregation, and other defects that may impair the serviceability of the insert.
3.3 Coatings
3.3.1 Red Dye Identification. Screw-locking inserts are dyed red for identification. The red dye may completely or partially cover the insert. However, it must be sufficient to identify the insert when it is installed in the tapped hole.
3.3.2 Dry Film Lubricant Coating. When specified, dry film lubricant coating can be applied to helical coil inserts. It shall meet the requirements of para. 3.3.2.1 and para. 3.3.2.2. Color of dry film lubricated insert is dark gray to black.
3.3.2.1 Dry Film Material. The lubricant shall meet the requirements of SAE AS5272, Type I.
3.3.2.2 Thickness. The coating shall be uniformly deposited on the insert with minimum thickness being complete coverage.