Threaded insert

Screw Assembly. Self-tappiag screws are used for joining ETEE parts. Eor maximum hoi ding power, the boss diameter should be about double the screw diameter, and the engagement length about 2.5 times the screw diameter lubricants should be avoided. Threaded inserts can be molded ia place, pressed ia, or driven ia ultrasonicaHy. 

Mace prevented 3-methylcholanthrene (MCA)-induced carcinogenesis in the uterine cervix of Swiss albino mice (Hussain and Rao, 1991). Oral administration of mace at a dose of lOmg/mouse/day for 7 days before and 90 days following carcinogen thread insertion reduced cervical carcinoma incidence by 50%. 

Bellhouse, BJ, Costigan, G, Abhinava, K, and Merry, A, The performance of helical screw-thread inserts in tubular membranes, Sep. Purif. TechnoL, 22, 89, 2001. 

Moreover, phenol partially tightens the skin, and it may well be more worthwhile using Aptos threads as a second line of treatment, when the phenol has taken full effect, after at least three months. The presence of threads inserted in the skin several months previously is not a contraindication for a phenol peel, and it is possible to decide on the opposite course of action if the doctor thinks this is a better option for the patient Aptos threads can be inserted first and a phenol peel can be done afterwards. 

Threads cut directiy in plastics materials will not withstand high loads and win wear out if screw fasteners are removed and replaced several times. Where high strength and reliabitity are required, threaded inserts are used. 

Heat and ultrasonic inserts. Fig. 14.4(c), can only be used Figure 14.4. Threaded inserts for plastics materials in thermoplastics materials and are available in brass from M3... 

Machine screws are generally used with threaded inserts, nuts, and clips. They rarely are used in pretapped holes. Particular attention should be paid to the head of the fastener. Conical heads produce undesirable tensile stresses and should not be used. Bolt or screw heads with a flat underside, such as pan heads, round heads, and so forth (Fig. 7.7), are preferred, because the stress produced is more compressive. 

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. 

Polysulfone parts can be joined with aU the processes described in this chapter. Because of their inherent dimensional stability and creep resistance, polysulfone parts can be press fitted with ease. Generally, the amount of interference wUl be less than that required for other thermoplastics. Self-tapping screws and threaded inserts have also been used. 

Pull-out strength n. Of threaded inserts in plastics moldings, the force required to pull the insert out of the molding. It may be expressed as the force per unit area of the engaged outside surface. 

When two pieces of thermoset plastic must be joined together in service, but must also be suited to simple disassembly, threaded joints are possible. If metal screws are to be used, female threads can be molded in a plastic part to accept the metal screw. Metal female threaded inserts may also be molded into plastic parts to accept metal screws in a subsequent assembly operation. 

Bosses for threaded inserts. Bosses for threaded inserts are very similar to those for self-tapping screws. The inside diameter is determined by the diameter of the insert the exact size for heat, press-in, or ultrasonic postmolded inserts are those recommended by the insert manufacturer for a given plastic who will also provide the lead diameter. (For self-tapping inserts, follow the same inside diameter criteria as for self-tapping screws.) In this case, however, the lead is an 8° included angle instead of a step. The outside diameter of the boss is 2 to 3 times the diameter of the insert and the minimum depth of the hole is the insert length plus 0.030 in. 

The requirement for assembly of castings is limited since casting can make complex shapes. The most common methods are adhesives and fasteners. Self-tapping screws can be used with most of the materials used for casting. Threaded inserts can be molded in place, however they are difficult to salvage in the event of a reject moldment because the material is a thermoset and the inserts cannot be melted out. Threaded inserts can also be glued or tapped in place. 

Thermoformed decorative inserts and labels have been molded into cold-press molded parts however, threaded metal inserts cannot be molded-in. Threaded inserts can be glued or tapped in place, but not into bosses, which are impractical. Molded-in holes, core pulls, slides, undercuts, and ribs are, likewise, imfeasible. Holes need to be drilled and their location can be held to 0.030 in. The same assembly methods used for parts made firom compression molding can be used for those made from this process. 

It is possible to strip undercuts for parts molded of these processes in some cases and threads can be molded-in. However, side actions or split cavities, as would be required for details A and G, are more commonplace. Threaded inserts, like those at E and H, can also be molded-in. However, it may be more advantageous to emplace them after molding with adhesives since the molding cycle will be shorter and the risk of one misplaced insert ruining an entire moldment is ehminated. The other common methods of assembling compression, transfer, and thermoset injection-molded parts are self-tapping screws (holes can be tapped), adhesives, snap-fits, press-fits, and the usual screw and bolt techniques. None of the plastics welding techniques can be used with thermoset parts. 

The tooling is closed, but there is an uncontrolled internal space between the walls. Thus, all ribs and bosses must be hollow. Additional structural support can be attained by designing the walls or bosses from each side to meet. These contact surfaces will weld together and are known as tack-offs. Male and female threads and threaded inserts can be molded in from the outside surfaces. 

Machine screws and bolts. Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers (Fig. 9.8), especially if it is a very strong plastic. Machine screws are generally used with threaded inserts, nuts, and clips. They are rarely used in pretapped holes. Molded-in inserts provide very high-strength assemblies and relatively low unit cost. However, molded-in inserts could increase cycle time while the inserts are manually placed in the mold. When the application involves infrequent disassembly, molded-in threads can be used successfidly. Coarse threads can be molded into most materials. Threads of 32 or finer pitch should be avoided, along with tapered threads, because of... 

Parts molded of thermoplastic resin are sometimes assembled with machine screws or with bolts, nuts, and washers, especially if it is a very strong plastic. Machine strews are generally used with threaded inserts, nuts, and cups. They rarely... 

Ultraseal, Sealing threaded insert. Dodge, Emhart Fastening Teknologies... 

The method of preparation of sandwiched adsorption ca-pillary columns for gas chromatography is similar to that used for adsorbent layer formation during glass capillary drawing. Liberti, Nota, Goretti [8] use the term sandwiched capillary columns to describe columns made of any material, in which the separating medium is a thread inserted inside the capillary. Of course, any material which is available as thread can be used for preparation of sandwiched capillary columns. 

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