Countersink

Rounding of the edge is often employed to ensure absence of a burr. Pressure readings will be high it the tap is inclined upstream, is rounded excessively on the upstream side, has a burr on the downstream side, or has an excessive countersink or recess. Pressure readings will be low if the tap is inclined downstream, is rounded excessively on the downstream side, has a burr on the upstream side, or protrudes into the flow stream. Errors resulting from these faults can be large. 

T1-6A1-4V were superior in corrosion-fatigue performance to the type 316L devices even though some fretting and wear occurred in the countersinks. 

Figure 9.5 The can end. (A) curl diameter (B) countersink diameter (C) curl height (D) curl opening (E) countersink radius (F) countersink depth (G) nominal material thickness.

In addition, molded holes can be custom designed to aid in insertion of leaded components (entry radii or countersink) or to provide recessed mounting of hardware (counterbore). Furthermore, holes can be oblong, rectangular or parallel to the plane of the molded substrate. Possible hole geometries are illustrated in Figure 1. 

Countersink outer ends of tbe hole, insert the rivet, and rivet them together. Tbe perfection of the joint can bo ascertained by opening and dosing Uie mould a fevr times, removing the surface where the nibbing is apparent, with a fine-cut file. 

The countersink should fit the rim precisely in order that there may be no slipping. 

Twist drill Spade drill Trepanning cutter Center drill Combination drill Countersink Counterbore... 

To facilitate the secondary operations of drilling and tapping, cored-through holes should have countersinking on both ends of the holes. 

Standard data expressed at the predetermined motion-time level are too detailed for much cost-estimating work. But a typical TER is satisfactory for much cost-estimating work. A typical TER for a drill press operation of sheet metal parts is for setup 0.2 -I- 0.05/tool hr and for run time 0.015 H-0.003/tool + 0.001/hole hour per unit. Thus, if a sheet metal part requires two different countersinks for 22 holes, setup would be 0.3 hr and run time 0.043 hr/unit. 

FIGURE 8-18 Countersinking a hole and installing a flat-head screw. 

Countersink cutters, Fig. 8.13, made from high-speed steel, are used to cut a large chamfer of the correct angle, usually 90°, as a seating for countersink-head screws. Countersinks should be run at a fairly slow speed to avoid chatter. They are available with parallel and taper shanks. 

Pins of this type are now being used to replace solid hinge pins, split pins, rivets and screws, eliminating the need for reaming, tapping, counterboring and countersinking. They are... 

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