Threading and Tapping

It is not possible to fabricate a practical anode such as that shown in Figs. 20 and 21. One approach is to drill and tap a hole in the carbon piece and screw a piece of threaded copper into the hole. This works fairly well for a hole 10 cm deep, perhaps 15 cm deep if one is careful, but not very much beyond that. There are two major problems (1) It is difficult to get a good... 

Fig. 29. The island of PBA brushes on mica was observed by tapping mode SFM. The phase image enabled clear resolution of the backbones (white threads) and the side chains (gray hairs) on the mica substrate (black background)...

Drill and tap the center of the aluminum disk to thread onto the barrel (%"x 24 tap). 

Thin wahed brass tubes are easily joined togs er with silver solder. Aluminum tubing can t be soldered but is easily held together with screws-because the wall thickness Is sufficient to hold threads. The holes can be drilled and tapped In the conventional manner or simply drilled with a hand drill and threaded with self tapping machine screws. 

Cut the sole leather into approximate sizes Drill or punch holes through the centers and slip them onto the tang. Drill and tap the end ferrule, and screw it lightly on the end of the shaft, which baSvpreviously been threaded. 

The electrolyzer body consists of a threaded stainless steel pipe nipple with drilled and tapped holes for positive electrodes. The top and bottom caps are stainless steel flanges (four flanges in total) with flange seals and bolts and nuts. 

Such oils are used in tough cutting operations such as tapping, threading and broaching. Lubricity and anti-weld characteristics are important characteristics of these cutting oils. These oils are derived from petroleum, vegetable and animal sources and usually contain various types of additives. 

Fig. 13. Ultramicro manometric gasometer (Nl). A, 0.5-nun bore Pyrex capillary tube joined to 1-nnn bore Pyrex capillary tube B, 10-ml syringe and side tube sealed on, as shown C, metal blank (from electric junction box) D, ball bearing for rotating screw without turning coupling E, machined screw tach diameter, 20 threads per inch, recessed and tapped at one end to receive machine screw F, vacuum stopcock G, ball and socket ground-glass joint.

The 14 and 1C threads uro not always adhered to. A house in Philadelphia say they usi laps of 13 threads, and a firm in Pittsburg advertise taps of 20 threads per inch. 

Piping fabricators are well aware of the problem, and will instead provide a steel boss 1-1/2-inches in diameter by 4 inches long, drilled and tapped for a 1-inch pipe thread. This boss is welded into the pipe elbow as shown in Figure 7-87b. It is a more expensive operation than using an elbow adapter. 

Thread cutting taps are suppi led in sets of three. Name each and state where each would be used. 

More rapid assembly can be achieved by self-piercing-and-tapping screws. These have a special piercing point and a twin-start thread, Fig. 12.4(c). Used in conjunction with a special gun, they will pierce their own pilot hole in the sheet metal (up to 18 SWG (1.2 mm) steel) or other thin materials and are then screwed home in a single operation. 

Figure 12.4. Self-tapping screws (a) thread-forming (b) threadcutting (c) self-piercing-and-tapping...

Some larger components are fitted with a drilled and tapped hole to accept an eyebolt to simplify lifting. Collar eyebolts, manufactured to BS4278 1984 are available with threads from 6 to 52mm with larger sizes available to order. Imperial threads are available for replacement on older equipment. Typical SWL of an eyebolt having an M45 thread is 8 tonnes. 

In cutting threads, either hy tapping with serial taps or threading with die and die stock, frequent stops should be made. The tap or die should be backed off occasionally to clear the thread and remove the chips. A coolant or lubricant is not essential, but, if available, its use is recommended to minimize heat and to flush away chips. 

More rapid assembly can be achieved by self-piercing-and-tapping screws. These have a special piercing point and a twin-start thread. 

---