ASME B18.29.2M-2005 pdf – Helical Coil Screw Thread lnserts: Free Running and Screw Locking(Metric Series).
11.2.3 Torque Test Method. The torque test shall consist of a 15-cycle, room temperature test. A new bolt or screw and new tapped hole shall be used for each complete 15-cycle test. For each of the 15 cycles, bolts shall be assembled and seated to the assembly torque specified in Table 5. Bolts shall be completely disengaged from the locking coils of the insert at the end of each cycle. The test shall be run at less than 40 rpm to yield a dependable measure of torque and avoid heating of the bolt.
11.2.4 Maximum Locking Torque. Maximum locking torque shall be the highest torque value encountered on any installation or removal cycle and shall not exceed the values specified in Table 5. Maximum locking torque readings shall be taken on the first and seventh installation cycles before the assembly torque is applied and on the 15th removal cycle.
11.2.5 Minimum Breakaway Torque. Minimum breakaway torque shall be the torque required to overcome static friction when 100% of the locking feature is engaged and the bolt or screw is not seated (no axial load). It shall be recorded at the start of the 15th removal cycle. The torque value for any cycle shall be not less than the applicable value shown in Table 5.
11.2.6 Acceptance. The inserts shall be considered to have failed if, at the completion of any of the tests and inspection, any of the following conditions exist:
(a) any break or crack in the insert
(b) installation or removal torque exceeds the maximum locking torque value in Table 5
(c) breakaway torque less than the values in Table 5
(d) movement of the insert beyond ±90 deg relative to the TOP surface when installing or removing the test bolt
(e) seizure or galling of the insert or test bolt
(‘ tang not broken off, which interferes with the test bolt at installation
(g) tang breaks off during insert installation
Helical coil inserts are greater in diameter than the STI-tapped holes into which they are installed. The installation process applies torque to the tang to reduce the diameter of the leading coil and permit it to enter the tapped hole. The remaining coils are reduced in diameter as they, in turn, are screwed into the tapped hole, When the torque or rotation is stopped, the insert coil expands with a spring-like action to anchor the insert permanently in place against the threads of the tapped hole.
Finer pitch inserts are proportionally larger (before installation) than coarse pitch inserts and thus have to be “prewound” to a smaller diameter for installation. Large, coarse pitch inserts need only a threaded mandrel tool for installation.
Helical coil inserts are normally furnished in bulk containers. However, they are also normally available in feeding belts known as strip feed.
Strip feed consists of a belt or strip of pliable plastic such as polyethylene through which holes have been punched, and into which the helical coil inserts are positioned, the ends of the inserts protruding from each side of the strip. The strip is coiled on a reel or spool.
The purpose for, and advantage of strip feed is to ease handling of the insert and to increase installation rates.
Inserting tools are available for handling strip feed, wherein the strip passes through a slot in the prewinder thus locating each insert for engagement with the mandrel. After each insert has been driven through the tool and installed into the work, the strip indexes the next insert into position.
Helical coil inserts are normally available in strip feed in sizes up through 8 mm nominal diameter.
C-3.1 Manual Inserting Tools
Various types of manual inserting tools are available. Examples are shown in Table C-i. These manual inserting tools will install helical coil inserts up to 3 diameters long for thread sizes up through 22 mm. Tools for sizes 24 mm and larger will install inserts up to 2 diameters long.