In order to allow a short bolt to be turned and screwed along the entire length of its stem, it requires to be kept as far as convenient from the chuck by means of a comparative long centre-pivot, which belongs to the chuck, unless a special chuck is provided for such work. To adapt an ordinary disc-chuck to the turning of short bolts, the arrangement depicted in Figs. 1091 and 1092 are resorted to. In Fig. 1091 a gripper or carrier, consisting of two plates and bolts, is seen fastened to the bolt-head ; and one of these plates has a long cranked end, which is driven by the driver seen fastened in the chuck. This mode of driving is suited to any bolt which is more than an inch and a half thick. Smaller bolts may be rotated without any gripper, as indicated in Fig. 1092. By this mode a thick strong driver resembling an el-square is employed, which is bolted to the chuck with two or three bolts and nuts, the long arm of the driver having a slot to allow it to be fixed at any place on the chuck to suit the diameter of the bolt-head.

By either of these two appliances a short bolt can be turned and screwed to the head, if required, and the shoulder of the head can be also turned. It may be said that this mode especially suits bolts whose stems are to be turned, and perhaps screwed, but whose heads are to be left exactly as they were forged. Such a bolt is therefore centred with regard to the head and to the outer end of the stem. Every such bolt must be forged with superfluous metal on the stem ; the lining for centring can then be done with a calliper, with which four short lines are marked, similar to those in Fig. 1087, both ends being thus treated.

All comparative long bolts are rotated with ordinary carriers, because, while they are on the lathe-pivots, ample room exists between the mandril-frame and the poppet-head to allow the traverse of the carriage to and fro the required distance. Carriers or grippers are always preferable to el-shaped drivers, if the articles to be turned are long enough to allow the carriers room in which to rotate without coming into contact with the lathe-carriage.

Connecting-rod bolts and several others are furnished with stems having curved junctions resembling that shown in Fig. 1093. The formation of this curved portion is entirely effected by lathe-turning, unless it is to be extra large, in which case the bolt must be thickened at that place, to avoid using iron of large diameter, and thereby causing great reduction of the entire stem.