Marking and Punch Marking - Course: Technique for Manual Working of Materials. Instruction Examples for Practical Vocational Training
 (introduction...) Introduction Instruction example 2.1. Door lock panel Instruction example 2.2. Holding Clamp Instruction example 2.3. Drill stand Instruction example 2.4. Angle gauge Instruction example 2.5. Bow for C clamp Instruction example 2.6. Open-end wrench 19/24 Instruction example 2.7. Base plate

### Instruction example 2.5. Bow for C clamp

To practise scribing of lines with height gauge and dividers, based on datum edges and one datum line and producing a bore line.

Material

Sheet steel (approx. 380 MPa)
Thickness: approx. 8 mm
Width: approx. 80 mm
Length: approx. 115 mm
(One longitudinal side and end side to be flat and at right angle)

Figure

Hand tools

Smooth-cut file 300 mm (flat), height gauge, steel scriber, dividers, marking-out punch, centre punch, double-point punch, engineers’ hammer.

Measuring and testing tools

Steel measuring tool, steel straight edge, bevelled edge square.

Accessories

Surface plate, angle plate, steel parallel as support (if height gauge cannot be started at zero level).

Required previous knowledge

Reading of drawings, measuring, use of the height gauge, application of simple mathematical equations.

 Sequence of operations Comments 1. Arrange the working place, prepare the working materials. - Check for completeness. 2. Check the two datum edges (one longitudinal side and one end side to be flat and at right angle). - File and check with bevelled edge square, if datum edges are not meeting the requirements. 3. Put the steel sheet on the worked end-side edge and set the scriber of the height gauge to “zero” level. - If the height gauge cannot be set to zero level because of foot height, an adequate steel parallel is to be used as support for the workpiece. 4. Scribe the centre line (size 55 mm above zero). Set the height gauge to the level of the centre line. - Choose an even number for reference. 5. Scribe the sizes from the datum line up and down. 6. Put the steel sheet on the worked longitudinal edge and set the height gauge to “zero” level. 7. Scribe the sizes in this plane. 8. Prick-punch the guide marks for the dividers. Scribe the radii according to specified size. 9. Scribe the oblique tines between radii and corner points by means of steel scriber and steel straight edge. 10. Scribe the check circles in the oblong hole by means of dividers (radius 5.0 mm). 11. Prick-punch check marks on all scribed lines. 12. Calculate the bore line based on specified width of double-point punch. - Equations:d = y - 0.2 mmx = d/2 + 0.5 mm 13. Scribe the bore line by means of steel scriber and steel measuring tool. Prick-punch by means of double-point punch. 14. Final inspection. - Dimensions and cleanness of scribing,

Completion

- Drill and chip the bow; file all edges.

- Weld threaded rings to it (Instruction example 9.5.).

- Insert a lead-screw (Instruction examples 9.5 and 8.2) into one threaded ring,