Machinery's Handbook, 31st Edition
1750
HELICAL COIL SCREW THREAD INSERTS Table 2. Screw Thread Insert Chemical Composition ANSI/ASME B18.29.2M-2005 (R2017)
Check Analysis
Element
Analysis, %
Under, Min.
Over, Max.
Carbon
0.15 max. 2.00 max. 1.00 max. 0.045 max. 0.035 max.
… … … … …
0.01 0.04 0.05 0.01
Manganese
Silicon
Phosphorous
Sulphur
0.005
Chromium
17.00 to 20.00 8.00 to 10.50
0.20 0.15
0.20 0.15 0.05 0.05
Nickel
Molybdenum
0.75 max. 0.75 max. Remainder
… … …
Copper
Iron
…
The accuracy of the finished thread when the insert is installed depends on the accuracy of the tapped hole. If the finished tapped hole gages satisfactorily, the installed insert will be within the thread tolerance when the insert meets the requirements of the Standard. It is, therefore, not necessary to gage the installed insert. After the insert is installed, the GO thread plug gage may not enter freely because the insert may not have been fully seated in the tapped hole. However, the insert should become seated after a bolt or screw is installed and tightened. Tang Removal Notch: The tang removal notch shall be located as shown in Fig. 2 and of such depth that the part may be installed without failure of the tang and that the tang may be removed, after assembly, without affecting the function of the installed insert. Torque Test Bolts: Assembled screw-locking inserts shall be torque tested with bolts in accordance with ANSI/ASME B1.13M or ANSI/ASME B1.21M, cadmium plated, or having other coating with a similar coefficient of friction and hardness of 36 to 44 RC (Rockwell C scale). The bolts selected for this test shall be of sufficient length so the thread runout does not enter the insert and that a minimum of one full thread extends past the end of the insert when the bolt is fully seated. Acceptability of bolt threads shall be determined based on System 22 of ANSI/ASME B1.3. Until a replacement for cadmium plating on the torque test bolts is found, and test data completed, an alternate coating/lubricant can be used to perform the torque test. Self-Locking Torque (Destructive).— The screw-locking insert, when assembled in threaded holes conforming to Table 1 and tested in accordance with the following para graphs, shall provide a frictional lock to retain the bolt threads within the torque limits specified in Table 5. Torque Test Block and Spacer: The insert to be tested shall be installed in a tolerance class 4H5H or 4H6H threaded hole conforming to Table 1 in a test block made from 2024- T4 (SAE AMS4120 or ASTM B209M) aluminum alloy. After installation, the tang shall be removed. The surface of the test block from which the insert is assembled shall be marked “TOP” and shall be marked to indicate the radial location where the assembled insert begins. A steel spacer meeting the requirements of Fig. 3 and Table 6 shall be used for developing the bolt load.
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