Marking and Punch Marking - Course: Technique for manual working of materials. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 18 p.)
 (introduction...) 1. Purpose of marking and punch marking 2. Marking tools 3. Accessories 4. Preparation of the workpiece surface 5. Selected working techniques of marking and punch marking 6. Labour safety recommendations

### 5. Selected working techniques of marking and punch marking

5.1. Marking with steel scriber and steel straight edge

1. Prepare the surface to be scribed and a datum face.

Figure 20 Scribing with steel scriber and steel straight edge

2. Mark the parallel measures by dashes by means of steel gauge and scriber.

3. Put the steel straight edge to the dashes and connect the dashes by drawing the scriber directly along the edge of the steel straight edge (Draw the scriber to your body slightly inclined and with the scriber point trailing).

5.2. Marking with steel scriber and try square

1. Prepare the surface to be scribed and one or two datum faces.

Figure 21 Scribing with steel scriber and try square

2. Mark the measure by dashes from one datum face by means of steel gauge and steel scriber.

3. Put the try square to the other perpendicular datum face and draw the scriber directly along the edge of the long leg.

5.3. Marking with dividers

Prepare the surface to be scribed and:

1. Mark and prick-punch the centre as supporting point for the dividers.

Figure 22 Steps when scribing with dividers

2. Set the measure at the dividers by means of steel gauge.

3. Scribe check curvatures.

4. Check the radius or diameter.

5. Correct or finish-scribe the circular arc.

If straight connection lines between circular arcs are required, the arcs are to be scribed first and then the lines!

Figure 23 Correct connections between straight lines and circular arcs

5.4. Marking with height gauge scriber

1. Prepare the surface to be scribed and a datum face.

Figure 24 Scribing with height gauge scriber

2. Put the workpiece with the datum face onto the surface plate.

3. Set the scriber of the height gauge to the measure at the height scale.

4. Grip the height gauge at the base plate and draw it along towards your body with massive workplaces held directly and smaller workpieces pressed against the angle plate,

Notes

- Parallel scribing necessitates exactly machined datum faces or datum edges!

- For height gauge scribers without scale, the measure is to be set by means of special height scales or gauge blocks.

- For height gauge scribers which are not starting from the zero position of the scriber on the surface plate plane, a steel parallel is to be used as support for the workpiece. The height of the steel parallel is to be taken into account when setting the measure.

Figure 25

1 height of the steel parallel
2 measure to be marked on the workpiece
3 measure to be set at the height gauge

How is the scriber to be drawn along the steel straight edge or try square?

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What intermediate step is necessary for scribing with dividers?

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Which accessories are required for scribing with the height gauge scriber?

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5.5. Punch marking after scribing

Check punch marks are necessary after scribing if the scribed lines may be wiped out in the subsequent working process or would not be easily visible because of poor conditions of visibility during the manufacture or of bad workpiece surface.

Placing

The prick punch is placed onto the point in inclined position, then set to vertical position with a hand on it and blown!

Guidelines for check punch marks

- Spacing on straight sections: 7 - 10 mm
- Spacing on curved sections: 3 - 4 mm.

Figure 26 Placing of the prick punch

1 placing
2 setting to vertical position

Figure 27 Correct spacings for check punch marks

Figure 28 Producing a bore line

1 bore (D), 2 punch mark, 3 bore line,
4 scribed line - working line,
5 double-point punch width (y).
6 distance between bore line and scribed line (x)

The use of the double-point punch is necessary for prick-punching of bore lines to have a minimum of reworking for workpieces drilled. Scribing of the bore lines is to be done after scribing of working lines with the following requirements to be met:

D = y - 0.2 mm
x = D/2 + 0.5 mm

D = drill diameter
y = double-point punch width
x = distance between bore line and scribed line

Note

After the first blow, one point of the double-point punch is to be put into the last preceding punch mark, then the punch is set into vertical position and blown - a new punch mark is produced!

This will result in symmetrical punch mark spacing.

Then the punch marks are repunched with a powerful blow on the centre punch I

Figure 29 Correct placing of a double-point punch

What makes punch marking of scribed lines necessary?

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What size is of prime importance for bore line marks?

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