Punched Joint

A riveted joint in which the rivet holes are punched and not drilled. As already observed, there appears to be a diversity of opinion amongst those well entitled to judge as to whether drilling or punching is most injurious to plates, but it is established that both operations at all events weaken the metal between the rivet holes as much as 16 per cent. Punching, however, which is the cheapest and clumsiest method, is more than suspected of causing a much greater loss of strength and to a greater distance beyond the rivet holes, especially since the drift or rimer has to be constantly used to get the rivets in. Of this increased loss, however, much is supposed to be recovered by the rivet head obtaining a greater grip through the operation of punching, whilst on the other hand the rivet in the drilled hole is more easily sheared whether it be left clean or ragged with the burr. Confining the comparison simply to the scope of these peculiarities, the balance stands slightly in favour of the punched joint. Plates should be punched from the side which forms one of the surfaces brought into close contact by the riveting, for the diameter of the rivet hole being less on the side on which the punch enters, and becoming a little larger as the disc of metal is forced out, the rivet obtains a better hold from being swelled out towards its ends. For this reason some recommend the necks of rivets to be bevelled under the heads. The necessary pressure for punching a circular hole of 1 in. diameter in in. plate-iron is according to some experiments about 26 tons, and according to others about 36 tons. Within certain limits indicated by this difference, the pressure varies directly as the thickness of plate and diameter of hole. The holes for attaching sheets of galvanised iron to roofs are punched by hand.

Radial Joint

Radial Joint is a species of flange joint partaking of the nature of the ball and socket, explained in Section XIV., and allowing free motion within a conical space having a prescribed basal area. The contrivance has been taken advantage of in attaching columns to screw piles to allow for adjustment in case of the piles working out of position during the operation of screwing in.

Radiating Joint

This occurs between cast iron solid and perforated voussoirs, segments, etc, and the sections of wrought ribs, etc.

Rebated Joint

Rebated Joint is made when a rebate is formed on a casting in order that another piece may fit down into it to avoid an open joint, as is occasionally done, for example, in some kinds of cast iron sheet piling. Fig. 88 shows its application to lighter work where a continuous iron rail is rebated (or, perhaps, more correctly "halved in" and screwed together in lengths. Red Lead Joint is one stopped and made tight with a mixture of red lead and linseed oil, or white lead may be added in the proportion of two parts white to one of red, or otherwise as preferred. Its use has been previously alluded to in this Section, and is further noticed under Screw Joint.