Measurement & marking out
Graduated steel rule
Used for measuring lengths to a moderate degree of accuracy. Graduations on the ruler are usually millimetres and half millimetres. To be accurate, the rule must be in good condition with flat, straight and true edges.
- guide to scribe or draw a straight line
- straight edge to test the accuracy of a flat surface
- scale for setting dividers and other marking tools.
Consists of a metal blade set at 90 degrees to a solid metal block (the stock).
- to guide a scriber when marking out lines at right-angles to the edge of work
- guide to setting up or checking work for square.
Consists of a blade and moveable square head (including spirit level and 45 degree bevel).
Square head and blade for:
- depth gauge
- height gauge
- checking for level
- checking or marking out square
- marking out 45 degree angles.
Made from hardened steel with sharp points at each end. Lines drawn with a scribe are far more accurate than a line drawn with a pencil or pen.
- to make sharp, clearly defined lines on metal.
Using a scribe:
- Hold the straight edge (steel rule, square, etc) firmly in the required position.
- Incline the scriber away from the straight edge to bring the sharp tip as close to the straight edge as possible.
- Incline the scriber slightly toward you in the direction of the stroke.
- Draw the scriber toward you in one firm stroke.
- locating a centre position to start a drill point cutting accurately in that position
- iIndenting a centre position for scribing arcs or circles.
Note: A prick punch, a sharper pointer version of a centre punch, can be used to make light (witness) marks on scribed lines. This makes it easier to:
- see marking outlines
- check the accuracy of centre positions before centre punching
- locate the pivot points of dividers for scribing circles of arcs.
- transferring measurements from a ruler or drawing onto a piece of material
- scribing circles and arcs.
To scribe an arc:
- Lightly centre-punch the centre of the circle or arc.
- Hold the knurled stem on top with your thumb and forefinger.
- Place one point in the punch mark.
- Keep a balanced downward pressure on both legs.
- Twist the stem while you incline the dividers slightly in the direction of twist to draw the moving leg around in an arc.
Marking or scratch gauge
- to set distances from an edge or shoulder
- marking out lines parallel to an edge.
Using a marking gauge:
- Loosen the lock screw on the headstock.
- Hold the headstock with one hand against the end of the rule.
- Move the scriber point to the required graduation on the rule.
- Lock the screw on the headstock.
- Hold the headstock against the reference edge of the material.
- Draw the gauge along the edge to scribe a parallel line.