The scribing block shown in the accompanying illustrations is made from a rod of mild steel 10 in. long and 1/2 in. in diameter. This is turned down to 7/16 in., finished smooth, and quite parallel throughout its length. The top is finished off as at A (Fig. 1), and the other end, for rather more than 1 in., is turned and threaded 3/8 in. A collar IS is then screwed on tightly. The bottom disc of iron or gunmetal C, with the bottom dished out, is tapped to suit the post. The hole in the sliding block (Fig. 2) should be a sliding fit on the post, the saw cut meeting the large hole; this will enable the block to grip the rod and scribing point when the nut (Fig. 3) is tightened. The steel pin (Fig. 4) should be turned, drilled, and threaded to fit the nut. Two washers (Fig. 5) are required, one being grooved diameterwise for the scriber to bed into; they are placed one at each side of the block (Fig. 2). The ends of the scriber (Fig. 6) should be hardened and tempered.

How To Make a Scribing Block.