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Boss Counterbore Size
High tightening torques and large tensile stresses may cause a cone-shaped expansion and failure at the bottom of the boss. Designing the boss with the appropriate counterbore (CB) reduces edge stress and alleviates cracking.
CB depth£ºx=0.5d
CB width£ºw=1.08¡Ád
Length of Engagement
The length of engagement (L) should be 2 to 3 times the nominal screw diameter. This calculation should exclude counterbore depth.
Chip Space Depth
The depth of space (Lc) for chips removed during thread cutting operations should be between 0.8 and 1.2 the nominal screw diameter. |
The PT thread-cutting fastener is engineered to meet the demanding requirements of thermoset plastics, providing easy assembly and ensuring a strong.reliable joint to maximize assembly performance.
Key Advantages
¡ôCuts threads in stiffer plastics
¡ôMinimizes installation torque
¡ôMaximizes assembly performance
Features & Benefits
Asymmetrical 30¡ãthread profile,inclined towards load surface to increase friction (FR) between the application and the fastener
¡ôReduces radial stress
¡ôReduces back-out caused by relaxation
¡ôIncreases strip resistance
¡ôEliminates need for supplementary locking devices
Optimal thread pitch for deeper thread engagement
¡ôIncreases pull-out strength
¡ôIncreases resistance to vibration loosening
¡ôIncreases load-carrying capability
Recessed thread root provides space for displaced material
¡ôMinimizes installation torque
¡ôMinimizes risk of clogging and galling of threads during assembly
Shank slot minimizes chip production
Through hardened to HRc 33-39
Suggested Thread Engagement
Based on testing and past performance, a thread engagement of 50% to 60% is recommended. For optimal fastener performance,please contact a Cunjin applications specialist.
Boss Design Recommendations
Laboratory testing and service applications have produced the general recommendations shown. Specific applications may,however,require some modification in order to allow for:
¡ômolding conditions ¡ômold tool design
¡ôtype of resin ¡ômaterial density
¡ôtype of filler
Determining Optimum Boss & Hole Size
A hole diameter of .85d to .89d is permissible for most thermoset applications. In order to properly determine boss and hole sizes,it is recommended that testing be done on several different hold sizes. This will allow you to determine the optimun drive-strip ratio that is required for your application.
Model£ºPT Thread -Cutting Fasteners
