This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
Combination tools are essentially American novelties, and those described here may all be obtained of Churchills, Finsbury.
Starrett's calliper-square is shown in Fig. 270; the jaws are hardened, and, being made independent and accurately ground, can be reversed for an inside calliper of larger scope, or used for depth gauge, etc. The beam is graduated to 64ths in. on one, and 100ths on the other. The 4-iu. size costs 18s. with adjusting screw, or lis. without.
The steel calliper-rule is shown in Fig. 271; when closed it is 3 in. long, and the calliper can be drawn out to measure 2 1/2 in. They are accurately graded, and durable; cost, 15s. 9d.
Starrett's combined try-square, level, plumb, rule, and mitre, is shown in Fig. 272; the various parts are: a, centre head forming centre square both inside and outside, one scale fitting both heads; b, square; c, mitre; d, rule; e, plumb level. As a try-square, it is a substitute for every size of the common kind, and more compact; as a centre square, it gives both inside and outside grades; as a mitre, it affords both long and short tongues; and it can be used as a marking gauge, mortice gauge, or T-square. The 4-iu. size without centre head or level costs 4s. 6d., and the complete tool may be had for l1s. 3d. for the 6-in. size to 15s. 9d. for the 12-in.
Ames's universal or centre square is shown in Fig. 273. For finding the centre of a circle, as in A, the instrument is placed with its arms b a e resting against the circumference, in which position one edge of the vertical rule a d will cross the centre. If a line be drawn here, and the instrument be similarly applied to another section of the circumference, and another line be drawn crossing the first, the point of crossing will be the centre of the circle. B illustrates its use as a try-square at n, and as an outside square at I. In C it is applied as a mitre, in D as a rule and T-square, in E as an outside square, and in F as a T-square for machinists. The prices range from l1s. 3d for the 4-in. size to 31s. 6d. for the 12-in.