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Joinery: measurements and tracing

Tracing is an important step in metalworking. A plot error inevitably leads to a runtime error, which is often difficult to "catch up". Tracing is most often exactly reporting the indications provided by the drawing which, in scale or in full size, remains indispensable. It is therefore necessary to use appropriate tools, in good condition, and to use all your knowledge in geometry (plane or in space).

Necessary material

  • Metal ruler
  • Pencil
  • Carbide tip
  • Compass
  • Caliper

Steps

  1. plots
  2. Measures

plots

The mine rests between the ruler and the room

The mine rests between the ruler and the room

1. Many lines can be done with a hard pencil and a metal ruler. The pencil lead must rest on the line of intersection between the ruler and the work piece. Use the hard pencil for light alloy plots where the scribing tip leaves a groove, which may cause a break. The pencil is also used for preparatory layouts (marking and measurement) before the one made at the tip.

A tungsten carbide tip is ideal for profiles

A tungsten carbide tip is ideal for profiles

2. A trace on a profile (drawing of a line of cut to the square) is made with a tungsten carbide scribe. This must remain in contact with the line of intersection of the square (or ruler) and the profile, so that the layout is strictly straight. Always place the piece flat on a workbench.

The point compass is used on metal foil

The point compass is used on metal foil

3. To draw a circle on a metal sheet, use the spiked compass. The most common type of spike compass, this quick-action spring-loaded compass, allows for easy and precise adjustment. There are also compass points reported, with locking screws, ensuring greater accuracy. The compass is also used to record small lengths, from the drawing or the graduated ruler, and to realize the geometric constructions. For a tungsten carbide or tungsten carbide tip to be more visible, sprinkle the metal with chalk powder.

Measures

The sliding foot offers high precision

The sliding foot offers high precision

4. The vernier caliper, a very precise measuring instrument, is used here to accurately measure the inside diameter of a copper tube. It consists of a square with a fixed spout and a graduated ruler. A movable beak, sliding along the ruler, carries a small graduated ruler; this beak is called the vernier. The slider profile of the caliper allows internal measurements; in this case, the reading value must take into account the width of the spout and be increased by 1 cm.

It allows to measure the thicknesses

It allows to measure the thicknesses

5. The vernier caliper is used to check the thickness of a part during machining. The reading of the caliper presents no difficulty: the number of millimeters is read on the graduated scale, to the division situated immediately to the left of the zero of the vernier. The number of tenths of a millimeter is read on the vernier, the division which most coincides with one of those of the rule.

A graduated ruler is suitable for current plots

A graduated ruler is suitable for current plots

6. Current traces are made with a graduated ruler; it is a rigid or flexible steel blade carrying a millimetric scale (single or double). To find a point in a pencil on a flat surface, draw a V-shaped mark from the division of the ruler.

Joinery: measurements and tracing: ruler

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