Screws are always measured for length from the point to the top of the head. The sizes in which screws can be obtained are given in [Table IV]. The diameter of screws is always measured directly under the head, and is always given in numbers of the screw makers’ gauge. The numbers vary from 0 to 30, going consecutively without skip from 0 to 18 and from then on using only the even numbers. In [Table IV] are also given the numbers of the screw makers’ gauge and their equivalents in decimals of an inch.
TABLE IV
SIZE OF WOOD SCREWS
| Length Inches | Diameter in Screw Makers’ Gauge | |
|---|---|---|
| ¼ | From | 0 to 4 inclusive |
| ⅜ | From | 0 to 9 inclusive |
| ½ | From | 1 to 12 inclusive |
| ⅝ | From | 1 to 14 inclusive |
| ¾ | From | 2 to 16 inclusive |
| ⅞ | From | 2 to 16 inclusive |
| 1 | From | 3 to 20 inclusive |
| 1¼ | From | 3 to 24 inclusive |
| 1½ | From | 3 to 24 inclusive |
| 1¾ | From | 5 to 24 inclusive |
| 2 | From | 5 to 24 inclusive |
| 2¼ | From | 5 to 24 inclusive |
| 2½ | From | 5 to 24 inclusive |
| 2¾ | From | 6 to 24 inclusive |
| 3 | From | 6 to 26 inclusive |
| 3½ | From | 8 to 26 inclusive |
| 4 | From | 8 to 30 inclusive |
| 4½ | From | 12 to 30 inclusive |
| 5 | From | 12 to 30 inclusive |
| 6 | From | 12 to 30 inclusive |
Screw Makers’ Gauge
| Number of Screw Gauge | Equivalent in Decimals of an Inch |
|---|---|
| 0 | .05784 |
| 1 | .07100 |
| 2 | .08416 |
| 3 | .09732 |
| 4 | .11048 |
| 5 | .12364 |
| 6 | .13680 |
| 7 | .14996 |
| 8 | .16312 |
| 9 | .17628 |
| 10 | .18944 |
| 11 | .20260 |
| 12 | .21576 |
| 13 | .22892 |
| 14 | .24208 |
| 15 | .25524 |
| 16 | .26840 |
| 17 | .28156 |
| 18 | .29472 |
| 20 | .32104 |
| 22 | .34736 |
| 24 | .37368 |
| 26 | .40000 |
| 28 | .42632 |
| 30 | .45264 |
9. Drive Screws.—A screw known as the drive screw is used mostly in the manufacture of various articles where cost is the controlling factor. These screws, shown in [Fig. 6], are made somewhat on the order of the wood screw, but without the deep-cut thread and gimlet point. Screws of this type are driven into the wood with a hammer and have slotted heads so that they may be withdrawn by means of a screwdriver. The thread is so constructed that the wood may be penetrated without breaking down its fiber when the screws are driven, and is shaped so as to engage with the wood while resisting a pulling stress. These screws are made with flat, round, or oval heads, as illustrated respectively at (a), (b), and (c), and may be had in sizes from ½ inch to 4 inches in length.
Fig. 6
10. Expansion Bolts.—The expansion bolt is a device that has proved extremely valuable in the building trades, as it provides a means of bolting to stone, brick, concrete, slate, or other materials of this nature. Expansion bolts are used principally in places where it is not desirable or practicable to drill through the material to which the fastenings are to be made. This type of bolt has also a great advantage over other fastenings in that it can be removed with as much ease and facility as it is applied, and also without injury either to the article fastened or the material to which it is fixed, the bolt likewise sustaining no injury.