Squares and Bevels
Try Square
SIZE: Blade: 6 to 12in.; Stock: 4 to 8in.
MATERIAL: Blade: steel; Stock: cast iron, hardwood, plastic
USE: To mark out or check the work for square
Tools of this type remained in general use until about the middle of the eighteenth century, when the carpenters' tool makers of London and Sheffield introduced try squares with steel blades and ebony or rosewood stocks edged with brass and fancy inlaid riveting, borrowing the methods of their colleagues, the cutlers and pocket-knife makers.
The try square is used to mark a line at right angles to an edge and to check that the corners of a frame or joint are accurate.
The parallel sided metal blade is mounted at one end in the centre of a wider stock and secured by rivets. A superior try square has an L-shaped blade which extends down the length of the stock, which is riveted on either side. This type of square is always accurate, whereas the accuracy of those mounted at the top only can be affected by rivet wear.
The tool forms an accurate 90" both on the inside and outside edges and on some squares the top inside corner of the stock is cut to an angle of 45 for marking a 45 line. The effective length of the blade can be extended by resting a steel rule against the edge when the tool is in position.
You can also use a try square to check work being planed square. Before you begin, plane one face true, mark it as the "face side", so that all measurements can be taken from it. Once the edge is established as true mark it as the "face edge".
Testing accuracy
Mark a line at 90° to a true edge. Turn the stock over to see if the blade coincides with the line from the other side.
Measuring internal angle
Place the heel of the square into the angle. The edge of the blade should touch the other half of the joint along its entire length.
Checking angles
For 90° line hold stock against edge and mark along blade. For 45° line, align angled stock against edge.
Checking for square
Press stock against face side to see if inside edge of blade completely touches face being planed at right angles to it.
Carpenter's Steel Square
OTHER NAMES: Flat square, rafter square, framing square, roofing square
SIZE: Blade length: 12 to 24in.; Tongue length: 8 to 16in.
MATERIAL: Steel
USE: To mark out the work for squaring and to check the angles used in the construction of roof framing
A standard carpenter's steel square is marked out in inches or millimeters
and is used to set out a job on building boards or to check the squareness of
a large frame. Being made from one piece of steel, it is extremely accurate.
Standard metric and imperial numerical markings run outward from the right
angle. Many squares are also marked with various tables which enable the
carpenter to set out staircases or rafters and to calculate areas or, given
the other dimensions, the hypotenuse of a triangle.
Mitre Square
SIZE: Blade length: 8 to 12in.
MATERIAL: Blade: steel; Stock: hardwood
USE: To mark out both halves of a mitre joint at 45
A mitre square is constructed like a try square, but the blade projects from both sides of the stock to form internal angles of 45 and 135. A line can be marked to 45 to a true edge by pressing the stock against the edge and aligning the blade with the mark. In this way two halves of a mitre joint can be marked out. The mitre square can also be used to check the accuracy of the angle when the joint has been cut.
"T" Bevel
OTHER NAME: Sliding bevel
SIZE- Blade length: 71/2 to 13in.
MATERIAL: Blade: steel; Stock: hardwood, plastic
USE: To mark out or check angles on the work
The "T" bevel has a parallel sided steel blade, which can be adjusted to form any angle with the stock. Extending approximately half the length of the blade is a slot which enables the blade tc be projected or retracted to suit the circumstances. The locking lever secures the blade finger tight at any angle. Other patterns have a slot head screw, which must be tightened with a screwdriver.
Set the bevel to the required angle with the aid of a protractor. Alternatively, set up the required angle from a true edge of a board, ur a bench top and align the bevel to that.
Setting to a protractor
Slacken the locking lever just enough to allow the blade to be moved. Hold the stock against the base of the protractor, set the blade to the required angle and tighten the screw.
Centre Square
OTHER NAME: radial square
SIZE: For work up to 6in. in diameter
MATERIAL: Steel
USE: To mark the centre of round stock
The centre square is a simple tool which enables you to rapidly and accurately locate the centre of a round metal bar or turned wooden section. The tool has a 90 notch cut in one side, and a blade which bisects the notch with its straight edge. The centre square is rotated approximately one third of the circumference of the work and a second mark made, intersecting the first. For absolute accuracy the tool should be rotated once more and a third mark made. The centre of the work is indicated by the intersection of the lines.
Using the centre square
Push the stock into the notch, and mark a line across the end against the edge of the blade. Repeat if necessary.
Combination Square
SIZE: Blade length: 12in.; Head length: 4-1/2 in.
MATERIAL: Blade: steel; Head steel, cast iron
USE: To work as a steel rule, try square, mitre square and level
The combination square is a steel rule, securely clamped in a square head. A rounded groove runs along the centre of one side of the rule. When the rule slides into the head, the groove then engages a spring-loaded pin which is locked in place by tightening a knurled nut. The head can be adjusted to any position on the rule.
The tool can be used as a try square with a blade length of up to 10in. while the 45 face on the head transforms the tool into a mitre square. It can also be used as a depth gauge to measure the depth of a mortise for instance. (The measurement is read where the rule enters the head.)
The square head is also fitted vvith a level vial and a removable scriber may be provided with the square head.
Rest the tool on its square face to check a 90 angle and on its angled face to check 45.
Depth of mortise
Slacken the locking nut, rest the square face flat on the surface of the rail and push the rule into the mortise. Tighten the locking nut, remove the rule and read the depth.
Checking for level
Check for horizontal by resting the square face on the surface and for vertical by holding the attached rule against the vertical member.
Combination Set
SIZE: Blade length: 12 to 24in.
MATERIAL: Blade: steel; Heads: steel, cast iron
USE: To work as a try square, mitre square, protractor, centre square, level and rule
Although the combination square is commonly sold with a square head only, combination sets are available which clamp to the steel rule in the same way to form a centtr square or protractor.
The tool can also be placed over a beveled edge to measure the exact angle.
The centre head is slipped onto the rule and locked in any position. It can be used to find the centre of a disk of up to 18in. in diameter.
Centre head
Use the centre head like a centre square, wedging the round stock between the jaws and marking off with the ride, (above left).
Protractor
Press the fiat face of the protractor head against a true edge and mark off the angle. (above right).
The protractor head can be used to mark off or measure any angle through 180 .
When the protractor head is fitted with a level vial it can measure the level of any vertical or horizontal surface.
Engineer's Try Square
SIZE: Blade length: 3 to 42m.; Slock length: 2-1/2 to 21in.
MATERIAL: Steel
USE: To mark out or check metal for square
Engineer's try squares are made entirely from metal to guarantee constant accuracy. Although larger squares with long blades are used in engineering workshops, the smaller tools with blades up to 6in. in length are more common in home workshops.
A notch is cut in the stock in line with the inside edge of the blade for accurate measurement even when there is a burr on the edge of the work,
Engineer's Sliding Bevel
SIZE: Blade length: 3in.; Stock length: 3in.
MATERIAL: Steel
USE: To mark out or check angles on metal
The engineer's bevel is a small, accurately machined tool, which is used to mark out or measure various angles on metal work. Once the blade has been adjusted to e required angle it is locked in place by a knurled nut.
Dovetail Marker
OTHER NAME: Dovetail template
SIZE: As required
MATERIAL: Hardwood, brass
USE: To mark out dovetail joints
Dovetail markers, which are used to set out dovetail joints, are often homemade tools. The shoulder locates over the end of the wood and the sides of the tail are marked against the edge of the template.
Using the marker
Use the marker when you have a series of identical joints to cut to save repeated setting out.
Glazier's "T" Square
SIZE: 24 to 72in. MATERIAL: Boxwood USE: To guide a glass cutter square across a sheet of glass
The glazier's "T" square is in effect a wooden rule mortised at 90" into a stock. The stock is pressed against the edge of a sheet of glass and a glass cutter is used to score a line against the rule.
