=======+=========================
Length | Diameter in
Inches | 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 | Equivalent
of Screw| in Decimals
Gauge | 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slotted heads so that they may be withdrawn by means of a screwdriver.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.
[Illustration: 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.
Many styles of expansion bolts are now manufactured under various
patents, and these may be procured in all sizes and made of iron,
steel, or brass.
In Fig. 7 are shown several makes of expansion bolts. The _McCabe
expansion bolt_, shown at (_a_), is constructed of a malleable,
cylindrical-shaped, slotted case, or shell, _a_, the aperture of which
reduces in size and engages with a bevel-shaped hexagon nut _b_. By
turning the bolt, the nut is drawn toward the head and thus expands the
outer case in its passage; this in turn binds against the sides of the
hole in the masonry into which the bolt is inserted. The shell, as the
outside case _a_ is called, can be procured in any length or diameter,
and can be used with any machine bolt having a standard thread. The
McCabe bolt is suitable for bolting any thickness of material, provided
the proper length of bolt is employed.
The _Brohard expansion bolt_ shown at (_b_), performs the same
functions as the bolt illustrated at (_a_). The case, or shell, _a_,
is composed of two or more parts riveted to a wrought circular plate,
near the head, as at _b_. These several parts are expanded by means of
the beveled nut, which approaches the head as the bolt is turned. The
principal feature of the Brohard expansion bolt is that the beveled nut
_c_ cannot be forced from the case on account of the lug _d_, which is
attached to the nut and travels in the slot _e_ when the bolt is turned.
[Illustration: FIG. 7]
The _Steward and Romaine double-expansion bolt_ is shown at (_c_). The
shell of this bolt is composed of two semicylindrical parts, as at _a,
a_, that are somewhat longer in diameter than the wedge-shaped nut and
the sleeve at _b_ and _c_, respectively. Each half of the shell is
held in place by light rubber bands. The wedge-shaped parts are caused
to approach each other by the turning of the bolt, and thereby expand
the split case at both ends simultaneously. From the fact that this
bolt is expanded at both ends, it is called a =double-expansion bolt=,
although it may be made single-expansion by omitting the wedge-shaped
sleeve at the head.
[Illustration: FIG. 8]
The _Star expansion bolt_, shown in Fig. 8 (_a_), performs exactly the
same duty as other expansion bolts, but its construction is radically
different. This bolt consists of only two parts, called _shields_.
Each shield is semicircular in form and interlocks at the joints.
The exterior of these shields has four rows of corrugated ridges, or
star-shaped projections, that prevent the shields from turning in the
hole. The interior of the shell is threaded and decreases in size
toward the farther end. Thus, by inserting a lag, or coach, screw of
any length, so as to engage with the thread, the shields are spread
apart at the farther end while the screw is entering the aperture.
The _Diamond expansion bolt_ shown at (_b_) is practically the same as
the one just described, as will be observed from the figure.
Expansion bolts are also made with all the parts entirely of brass or
bronze, with either plain, capped, or fancy heads, or nuts, and in any
finish desired.
=11. Screw Anchors.=—The device known as a _screw anchor_ can be used
in place of an expansion bolt for securing light materials. Several
kinds of screw anchors are in the market at present. The _star anchor_,
which is made in one piece of composition metal that is slotted about
seven-eighths of its length, may be obtained in various diameters
and lengths. The exterior has two star-like projections, to prevent
the anchor from turning, while the interior is constructed of ridges
projecting from the tube, with the hole reduced toward the slotted
end. This internal construction permits the star anchor to be used in
combination with trade wood or machine screws of any length. The screw
used engages with the ridges in the interior, cutting its own thread
and expanding the anchor in its passage. These composition anchors are
very cheap, the price ranging from 1 to 3 cents, according to the size.
They are made in different lengths, from ½ inch to 1½ inches, and for
Nos. 6, 10, 14, and 18 wood screws.
[Illustration: FIG. 9]
=12. Special Bolts.=—In Fig. 9 is shown a =toggle bolt=. This device
is a recent production for fastening materials to surfaces having a
hollow interior that will not admit the use of expansion or tap bolts
because of its frail character, as, for instance, sheet metal, hollow
fireproofing, etc. The toggle bolt shown in the figure is constructed
with long, fine-pitch threads cut nearly to the head, so as to allow
for securing thin materials. The =T=-shaped head _a_ is constructed
either hollow, as shown in the figure, or of flat strip metal, and is
riveted loosely to the end of the bolt, allowing the head to pivot and
fold over the bolt, and thus permitting the head to pass through a
small opening. The head is then tipped into its proper position, when
the bolt is ready for securing in place the work to be fastened. The
construction of the bolt is shown in Fig. 9 (_a_), while the process of
affixing it is illustrated at (_b_) and (_c_). These toggle bolts are
generally made with ³/₁₆-, ¼-, and ⁵/₁₆-inch bolts, from 2½ to 6 inches
long, and of either iron, steel, or brass.