Insert threaded mechanical

I o the Upper cap, forming the cover of the body, was soldered a striker clmralxT, externally threaded to hold the firing mechanism. The gaine was inserted through the striker-chamber cover and was soldered to the former. 

Machine Screws, Bolts. Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers (Fig. 7.6), especially if it is a very strong plastic. The threads used to engage the mechanical fastener may either be molded into the part (molded-in threads or molded-in inserts) or attached after the molding operation (post-molded inserts). 

Ultrasonic equipment can also be used for mechanical fastening operations. Ultrasonic energy can be used to apply threaded inserts to molded plastic parts and to heat stake plastic studs. 

Because of the lower ductility of the fluorocarhon materials (e.g., TFE, CTFE, FEP), snap-fit and press-fit joints are seldom nsed. Rivets or studs can be used in forming permanent mechanical joints. These can be provided with thermal techniques on the melt-processable grades. Self-tapping screws and threaded inserts are used for many mechanical joining operations. In holted connections, some stress relaxation may occur the first day after installation. In such cases, mechanical fasteners should he tightened thereafter, stress relaxation is negligible. 

Stripping torque n. (1) Of a self-tapping screw, the twisting moment in Nm required to strip the threads formed by the screw in a softer material. (2) Of a molded-in insert, the torque required to break the mechanical bond between the plastic and the insert s knurled surface. 

In order to visualize the development of pucker, a model (Figure 3.3(a) and (b)) is shown to understand the deformation of fabric stmcmre due to the insertion of a seam in it. This stitching line or a seam has to find a position on and in the plane of the fabric. In order to accommodate the bulk of stitch, the fabric yam in both directions gets displaced around this juncture. Depending on the physical and mechanical properties of the fabric, the sewing thread may have no resistance from the fabric and would manifest in different types of yam movements (distortions) in the fabric structure otherwise due to resistance from the fabric, only compression of the thread and fabric yam may take place. The former causes severe pucker and the latter causes little or no pucker. It is either the yams parallel to the seam, or the ones perpendicular to the seam, that absorb the longitudinal and lateral... 

---