Figure 85.—Machine Bolt and Carriage Bolt. The first is used against iron and the second against wood, but this rule is not arbitrary. The rounded side of the nuts are turned in against wood; the flat side against washers or heavier iron. Use square head bolts if you expect to take them out after the nuts have rusted on.
Figure 86.—Plow bolts and sickle bar bolts should be kept in stock. Standard sizes and shapes are made for several different makes of plows and machines.
Taps and dies are made to fit each size of rod. If the thread on the bolt is cut with a solid, or round, plate die, the corresponding tap is run clear through the nut. In that case the nut will screw on the bolt easily, possibly a little loose for some purposes. It is so intended by the manufacturers to give the workman a little leeway. If it is desirable to have the nut screw on the bolt very tight, then the tap is stopped before the last thread enters the nut. A little practice soon qualifies a workman to fit a nut according to the place the bolt is to occupy.
Figure 87.—Lag Screw. To set a lag screw in hardwood, bore a hole the size of the screw shank as calipered between the threads.