Chapter

31. True or false? All answers can be found in the text or in the figures in Chapter 4.

■ There is no such thing as a 'non-functional dimension' since all dimensions are functional.

■ It doesn't matter if dimensions are given twice on a drawing.

■ There are six elements to any dimension.

■ It doesn't matter if dimension lines are crossed or separated by other lines.

■ With respect to dimensioning angles, it is common to have only one terminator.

■ It doesn't matter if the units used for the dimension value are different to the units used for the associated tolerance.

■ All dimension values, graphical symbols and annotations should be added to a drawing such that it can always be read from the bottom and the right-hand side.

■ Chain dimensioning should always be used wherever possible.

■ Projection lines should always touch the outside outline of a part.

■ The designation 'M8 8/10' means that the threaded 8mm diameter hole is to be 0.8mm deep.

■ The smallest tolerance should always be used because this means the part is always very accurate.

■ Unilateral tolerances are to be preferred to bilateral tolerances.

32. Draw the stepped shaft in Figure 4.3, add an end view using third angle projection and dimension the drawing correctly. Dimensions should be according to the convention in the latest ISO standard (Section 4.2).

33. With respect to the plate in Figure 4.7, if the maximum height is 10cm, draw the plate front view as shown using scaled measurements. Dimension the plate using correct rather than incorrect dimensioning practice (Section 4.2).

34. Draw the welding symbols for the following situations (Section 4.3):

a A single V butt weld with a backing run produced by manual metal-arc welding, reference number 111 in ISO 4063. The backing weld is to be ground flat, b A spot seam weld, 5mm wide, consisting of 3 runs of 10mm length with 10mm between them, c A'T' shaped fillet weld with fillet welds on with side.

35. Using the data in Figure 4.13, draw a graph of accuracy against cost. What do you conclude from this? Is the answer clearer if a log-log graph is used?

36. Identify the datum features, the functional and the non-functional dimensions of the movable jaw shown in Figure 3.2 and the hardened insert in Figure 3.3.

37. With reference to the table in Figure 4.13, the worst case is drilling which, if one simplistically adds the 36um and Hum errors together, makes almost 50um. Bearing in mind this applies to a 25mm diameter hole, it is equivalent to 0,2%. As a first order approach, one could use this proportion to define tolerance values. This 0,2% is the error one can expect from a machining process and we should add a 'factor of safety' if we are to translate it to a tolerance. Let's take a factor of, say, 5, which makes 1,0%. Thus, if we assumed dimensions and tolerances are linearly related, we could use the equation to calculate bilateral tolerance values:

Using this equation, add tolerances to your drawings from Questions 32 and 33. To help you, a 30mm diameter would be: >30 ± 0,15'.

38. Using the hole symbology of Section 4.3, draw the following holes (like the drawings in Figure 4.8) and add dimensions:

For'thick'sections: <¡>11 x 10 <|>22 x 3U

For a 30mm thick plate: 020 x 13U D20

013,5

In each case draw a section through the hole as well as a plan view (Section 4.3 and Figure 4.8).

39. Add the general tolerance ranges given in Section 4.5 (ie XX and XX,X and XX,XXX) to your template from Question 4 so that you can always refer to general tolerance values when you draw in future. You don't have to use the values I suggest. Why not explore what is said in other books and publications?

40. In the Figure 4.16 example, there are no out-of-roundness errors. Hence, the maximum and minimum hole centre spacings are 22,00 and 23,00 (as shown). In reality there must be some out-of-roundness, as shown in Figure 4.17. If the bolts and holes have out-of-roundness' of ±0.5% (Question 37 above), calculate the new maximum and minimum hole centre spacings which still permit assembly. There will be two sets of values corresponding to the <|>5 bolt shank in its <|)5,5 hole and the <j)8 bolt head in its <|)8,5 hole. Which one is the governing case?

Was this article helpful?

0 0
Pencil Drawing Beginners Guide

Pencil Drawing Beginners Guide

Easy Step-By-Step Lessons How Would You Like To Teach Yourself Some Of The Powerful Basic Techniques Of Pencil Drawing With Our Step-by-Step Tutorial. Learn the ABC of Pencil Drawing From the Experts.

Get My Free Ebook


Post a comment