Measuring Rules
The standard Egyptian rule was a cubit (forearm) long, about 20.7in., divided into seven palms, each palm subdivided into four digits (fingers). It was a strip of wood about 2 x lin. in section wilh a 45 chamfer on one edge. The Romans used the foot as the unit for practical purposes, about 11.6in. long, divided into four palms and then into either three unciae (inches, originally the width of the thumb) or four digits. These were marked on flat strips of wood one or two feet long, the palms being indicated by circles or crosses. Apparently the Romans guessed anything smaller than a finger-width.
Medieval rules were graduated wooden strips. The earliest known two- fold rule is dated to 1613. The four fold pocket rule was developed in the late eighteenth century and the two foot length became the standard type.
Bench Rule
SIZE: 1 to 6 ft.
MATERIAL: Hardwood
USE: To measure a workpiece
Bench rules are straight wooden rules made in one piece. They normally have simple imperial or metric graduations. Stand the rule on its edge for accuracy. Laid flat, its thickness can lead to errors.
Straight Edge
SIZE: 1 to 6ft.
MATERIAL: Steel
USE: To test flathess and help cut a straight line
The straight edge is a parallel sided strip of heavy steel, which is beveled on one edge. The bevel is used to cut or scribe against while either edge can be used to test for flathess.
Check flathess by turning the edge to various angles. If there are gaps, the surface is not flat.
Steel Rule
OTHER NAME: Engineer's steel rule
SIZE: 6 to 72in.
MATERIAL: Steel
USE: To determine the size of a workpiece
A good quality steel rule is a very accurate tool for measuring and laying out work. Not only are the graduations very precise, but being steel the rule can be very thin and therefore reduce errors in marking out produced by parallax. A steel rule is essential for any kind of metal work and is also a useful too! in the woodwork shop.
Steel rules have metric or imperial graduations or a combination of both. The rules will usually be graduated on two edges and often on both Sides with increasingly smaller divisions of the basic measure. A combined metric and imperial rule is the most useful.
The steel rule can also be used as a straight edge.
Store steel rules carefully. If the edges and ends are damaged, there will be inaccuracies. Many rules have a hole in one end so they can be hung up out of harm's way.
Measuring diameters
The diameter of round stock can be measured with a steel rule. Rest the edge of the rule on the end of the workpiece and locate the squared end against your thumb to line it up with the circumference of the workpiece. Swing the rule backward and forward to obtain the exact diameter.
A reasonably accurate measurement of the bore of a tube can be made in the same way. Locate the squared end of the rule on the inside face of the tube. Swing the rule backward and forward to obtain the internal diameter.
Measuring from a corner
Measure from inside a 90 joint by butting the squared end of the rule against the right angle.
Measuring a diameter
Measure round stock (top) from the outer edge of the piece and bores from the inside face.
Circumference Rule
SIZE: 3 to 4ft.
MATERIAL: Steel
USE: To calculate the circumference of round stock
The circumference rule can be used as a standard steel rule, but it is also used to automatically calculate the circumference of a disk or cylinder. One edge of the rule has the standard numerical graduations, which are used to measure the diameter of the workpiece. The corresponding circumference measurement is shown on the other edge.
Using the rule
Measure the diameter then read off the circumference measure on the lower edge. A pipe with a diameter of 3/4 in. will have a circumference of 23/8 in.
Folding Rule
OTHER NAMES: Zig-zag rule, jointed rule, surveyor's rods SIZE: 1 to 6ft.
MATERIAL: Boxwood, alloy steel, plastic
USE: To determine the size of a workpiece, or survey an area
The folding rule can be used in a confined space where a long rule would be inconvenient. It also overcomes the problem of carrying a long measuring rod to the worksite. Both metric and imperial graduations are available on folding rules.
A single folding rule is made from two pieces, which overlap each other md are jointed at one end to swing apart, thus extending the rule. The four fold rule is the traditional carpenter's folding rule, it is made from hardwood and reinforced at the ends with brass. The rule is made from four strips, hinged in pairs to fold back on one another. These hinged sections are jointed at one end with a brass rule joint, made by a disk on one end locating between two disks on the other with a rivet passing thiough the centre of all three. This allows each section of the rule to lay side by side when the rale is closed.
The other common variety of folding rule is the zig-zag rule, which is really an extension of the single fold principle. In this case several sections of the rule are jointed together. Well-made rules have a catch which holds each unfolded section in line with the next.
A folding rule should be protected from damage. Once a joint hinge becomes
strained or loose the rule will be inaccurate.
Extension Rule
SIZE: 6 to 8ft.
MATERIAL: Hardwood
USE: To determine the size of a workpiece
The extension rule is a zig-zag rule which includes a brass slide for making internal measurements. The slide extends from the first section of the rule.
To measure the internal width of a frame, open the sections of the rule to fit the gap as closely as possible. Place one end of the rule against one side of the frame and extend the slide to touch the other side.
The slide can also be used as a depth gauge.
Mason's Rule
SIZE: 6ft.
MATERIAL: Hardwood, plastic
USE: To regulate the thickness of mortar joints between masonry units
Mason's rules are used to check accurate progress during wall-building. A wall must be exactly the same height at both ends and the brick covr -:i regulated to correspond with standard window and door frames. There are two types of mason's rule, the "modular" rule and the "spacing" rule. The modular rule determines how many courses of a modular brick or block, plus its mortar joint, will exactly reach a required height. The spacing rule gives the spacing of standard bricks to reach a required height with equal joints between. Both rules have standard numerical graduations on the reverse.
Improvised mason's rule
A home made gauge rod or story pole can be manufactured by calculating the number of courses required, plus the mortar joints, and transferring these calibrations on to a length of softwood. The rod is placed alongside the wall as the work progresses to insure the evenness of each course.
Add the measurement shown on the slide indicating the distance between the frame and the end of the rule to that shown on the rule itself.
Push-Pull Steel Tape
OTHER NAME: Flexible rule
SIZE: 3 to 16ft.
MATERIAL: Tape: steel, fiber glass; Case: steel, plastic
USE: To determine the size of a workpiece or survey an area
The push-pull steel tape measure is an extendable steel strip coiled into a container. The tape is spring-loaded, so that as soon as it is released it will automatically return to the case. On some cases a lock is provided to hold the tape when extended. A hook is riveted to the end of the tape to locate on the end of the workpiece so that even a long dimension can be measured single handed. This hook is loosely riveted to the tape and is free to move in and out for a fixed distance.
When hooked over an object, it extends by its own thickness so that the measurement can be accurately taken from the end of the tape itself. Similarly when taking an internal measurement the hook retracts so that the measurement is taken again from the end of the tape. Check periodically that the hook has not become too loose, or you will get a false reading. For external measurements, some cases are fitted with a device which indicates the exact measurement including the case.
Tapes are available with both metric and imperial graduations or a combination of both.
Taking an external measurement
Locate the hook over one end and pull the case to extend the tape, keeping it flat on the work. Read off against the other edge of the workpiece.
Taking an internal measurement
Measuring a cylinder
With the back of the case touching one surface, extend the tape. Read off the measurement where the tape enters the case and add 2in. for the case itself.
Wrap the tape around the workpiece and align the two meeting edges. Take the 2in. graduation as your reference point and read off the measurement alongside it. To calculate the circumference deduct 2in.
Wind-UpTape Measure
SIZE: 33 to 100ft.
MATERIAL: Tape: steel, linen; Case: steel, plastic, leather
USE: To determine the size of a workpiece or survey an area
The wind-up tape measure is primarily designed for measuring large dimensions, such as the size of a room.
It is a large circular case, or sometimes an open frame, containing a long coiled tape marked with imperial or metric graduations. The steel tapes are more accurate than the linen type which tend to stretch or shrink. A ring is attached to the end of tape, which can be hooked over a nail, so that long dimensions can be taken single handed.
Remember that the graduations measure from the outside of the ring and the nail should be positioned accordingly. There is also a hook which hinges out from the ring. This locates over a convenient edge and will automatically align the end of the ring with it. To retract the tape, hinge the winding handle to the open position and crank it clockwise.
Digital Rule
SIZE: Capacity: 999ft.
MATERIAL: Various
USE: To determine the size of the workpiece or survey an area
As the digital rule is run over a surface, the display will indicate the length. It measures curved surfaces as easily as flat. The display is returned to zero by depressing the reset button. By fitting an extension arm the rule can be used to measure ceilings and the height of walls. Digital rules are available with metric and imperial displays.
