![]() The 'HRC' refers to the Rockwell 'C' hardness scale. With regard to the left-hand side elevation, the side is flame hardened to provide abrasion resistance. Note that the hardened insert is symmetrical as shown by the centre line and the 'equals' symbols at each end. This illustrates some other principles and applications of engineering drawing practice. Thus, the inverted plan is a part section.įigure 3.3 shows a detail drawing of the hardened insert (part number 2). The staggered section lines are shown by the dual thick and thin chain dotted lines terminating in arrows that give the direction of viewing. The inverted plan (lower left-hand drawing) is a staggered section projected from the front elevation. However, to illustrate the point, I have left it off the drawing. I would label its position as 10mm from the left-hand or the right-hand side. Not to scale.įigure 3.2 Detailed engineering drawing of the 'movable jaw', part number 3 Thus, if I were drawing this for real in a company inj I ![]() However, in product liability terms, all dimensions should be given and none left to chance. In such instances as this, the implication is that the hole is centrally placed and since its exact position is not critical for functional performance, it perhaps does not matter too much. On the side elevation sectioned view, the position of the M8 hole is not given. It is shown in outline by the double chain dotted thin line. The position of the hardened insert is shown on the sectioned right-hand elevation. The initial hole is 10mm diameter which is then counter-bored to 15mm diameter to a depth of 7.5mm with a flat bottom (given by the 'U'). The dimensions of this hole are shown in note form on the inverted plan. The right-hand side elevation section also indicates that the horizontal central hole is counter-bored. The 'xlO/12' means that the drilled hole is 12mm long and the thread is 10mm long. The designation 'M8' is all that needs to be stated since full details of the thread form and shape are given in ISO 68-1:1998. The 'M8' means that it is a metric standard 8mm diameter thread. The various line thicknesses of the threaded hole show that the initial hole is to be drilled (note the conical end) and then threaded to M8. The side elevation shows that there is a vertical threaded hole in the base. ![]() This is the designer's decision of how much to include in the drawing, called 'draughtsman's licence'. The right-hand elevation is a section through the centre of the jaw but nothing tells you this. Secondly, the counter-bored 5mm diameter holes are identical. Firstly, both underside surfaces that contact the body (as shown by thick chain dotted lines) are to be polished such that the average surface finish (Ra) is less than 0,2um. There are further outcomes from this symmetry. The 16mm wide tongue is thus centrally positioned in the front elevation and there is no need to dimension its position from either side. With regard to the front elevation, the 'equals' sign at either end of the centre line shows that it is symmetrical about that centre line. The thick lines are deliberately drawn so that shape and form 'jump' out of the picture. hidden detail or section hatching) is drawn in thin (or narrow) lines. The outline is drawn in thick (or wide) lines whereas additional information (e.g. ![]() It gives all the information necessary for the part to be manufactured. ![]() Such a parts list or item list is shown as part of the drawing in Figure 3.1.įigure 3.1 Assembly engineering drawing of a small hand viceįigure 3.2 is a third-angle orthographic projection 'detail' drawing of the movable jaw (part number 3). The assembly drawing is of little use on its own because it needs a list to identify each individual part within the assembly. The individual components making up the vice are numbered using a 'balloon' reference system, i.e., small circles with the part numbers in them. This is an assembly drawing and is not meant to provide any manufacturing details. This has been done by the use of different types of line thicknesses (thick and thin) and different types of line styles (continuous, discontinuous, dash, chain dotted). Although the drawing is 'busy', the different lines help to make the artefact jump out from the page. The movable jaw is actuated by a screw which is rotated by a small bar. The main body of the vice is a stubby 'U' shape in which a movable jaw is positioned between the two uprights. Such a small engineering vice is shown in Figure 3.1. A common artefact in any workshop is a small vice. ![]()
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