IDEMI

Conventional drafting techniques are followed in tool design with the exception of a few practices that vary somewhat. The following section explains the differences and how they are used. No attempt is made to teach the basics of drafting. It is assumed that the student has a sound working knowledge of orthographic projection and is familiar with conventional drafting techniques.

Often tool drawings are used only once, when the tool is constructed. They are brought back into use only when changes become necessary, such as those caused by product redesign or changes made to improve tooling performance. They are used only by highly skilled toolmakers, tool room personnel, and tooling buyers. For this reason, many shortcuts can be used in tool drawings that would cause problems on product drawings. Product drawings have a greater circulation and are used more frequently and usually over a greater period of time; therefore, the shortcuts used in tool drawings are not permitted on product drawings.

 2.1    DRAFTING PRACTICE

            The following list of drafting rules generally applies to tool drawings and is intended as a guide to help maintain uniformity.

All lines must be dark enough to produce a clear and sharp print

All drawings should be on standard size that will allow the resulting prints to fold to standard A4 size.

All drawings should have a border line drawn 5 or 10 mm from each side of the paper, depending upon the size of the drawing.

The material and title block should be located in the lower right-hand corner of the drawing.

All dimensions should be expressed in mm, with the mm sign omitted.

Full-scale drawings should be used whenever possible. Otherwise, use half or as per IS: 696 standard.

Drawing and dimensioning must help the person who will use the drawing to make the item in the tool room. The toolmaker should not have to make calculations before he can begin producing the tool.

Only as many views as necessary to show all required detail should be given.

Use uppercase engineering lettering (3 mm high) throughout the drawing.

A name is always assigned to each tool and placed in the title block. The name usually is the tool name plus the name of the part as noted on the part drawing. For example, if the name in the title block of a part drawing is ‘Horizontal actuating rod’ the correct title of the drill jig is ‘Drill jig-horizontal actuating rod’.

Only critical dimensions, overall dimensions, and location dimensions should be shown on tool drawings. Dimensions of individual pieces can be indicated in the bill of materials and need not appear on the drawing.

Standard purchased tool components need not be dimensioned. These include die sets, screws, dowels, springs, knobs, and tooling specialty items. Dimensions are not necessary because the components come ready-made and are identified in the material list by number.

Standard purchased tool components that are to be altered by the toolmaker should have the altered portion dimensioned.

Special tooling components that have been standardized by a particular company do not need dimensions.

Dimensions that can be determined by or calculated from, dimensions on the part print need not be shown on the tool drawing. Examples would be the center of the nest, cutting edges on a punch, die clearance etc.

2.2    DRAWING LAYOUT

        There are two different methods of preparing tool-design drawings. One is to show all information, including the details, on one sheet. The tool is shown assembled with only the necessary views to give pertinent information. Detail drawings are included when necessary. The method is generally adopted by companies whose tool-making department is such that one toolmaker builds the entire tool or die and does most of the work on it.  This method will be explained in detail in the following section.

The other method of preparing tool-design drawings is similar to the method of preparing product-design drawings. The assembly is drawn on one sheet, and each component is detailed completely on a separate sheet.  In this case the tool is generally built by several people, each doing one operation on each component. Another person may complete the assembly. This allows the company to utilize different skill levels in the tool room. This method of drawing also ensures interchangeable components, which may be a real asset when repairing tools used on continuous production.

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