The first purpose of a sketch is to give your draftsman a clear idea of the shape of the piece wanted with it’s dimensions. If you are hiring me to draw for you, I love having all the information I can get to give you back a quality drawing. While a well executed drawing with smooth lines and nice shading makes a pretty picture, it may not be nearly as useful to me as a rough sketch that has every dimension correct. A sketch may not have to show everything in its true proportion, but if the numbers are right, there should be no confusion, as there’s no excuse for measuring a drawing when all the dimensions are shown. One of the best things to do for practice is to sketch any tool or object around the shop, such as the anvil, a lathe dog, pair of calipers, a pulley or a hacksaw frame, so as to be able to make a new one just like the other. This shows how to be careful to put down all the changes of the shape and all dimensions, and to be careful that the figures are right.
Take a plain bolt or nut, sketch it so that you can put the dimensions on the right places and just about anyone can read them. For this purpose, some sort of a perspective or isometric view is usually the best. This can’t be done with complicated pieces, but for simple stuff, it’s easy to make something that’s often more understandable than a regular drawing.
In Fig. 1, there’s no need to make circles perfectly round or lines perfectly straight. We only need to give the idea of the general shape of the piece. Anyone who could make a mistake in making bolts from this type of sketch has no business being a drafter. This shows the bolt to be 4 inches long under the head with a 13-pitch, United States standard thread cut 1-1/2 inches on the end. The bolt is 1/2 inch rough, hexagon head, 1/2 inch thick and 1-1/8 inches across the flats, but not finished.
Don’t be afraid to put any information necessary on the sketch or on any drawing for that matter. It’s better than leaving a lot to the imagination as some drafters seem to like doing. There’s no need to not put the same dimension on twice in different places, because there’s a chance of getting one of them wrong, and that makes for confusion. Have the sketch tell all it can, either by figures or notes; there’s no such thing as too much information in this case.
Fig. 2 is a steel gauge, 1/4 inch thick all over, 2 inches long in the main part, with the end projection 1/2 inch each way, a 1/2 inch corner as shown and the round corner with a 3/4 inch radius. The fillet (rounded area) is not important as long as it’s rounded out enough to prevent cracking while it’s hardening.
Fig. 3 shows a small connecting rod, 24 inches center to center, which is the important dimension. The hole at the left is 2 inches in diameter and at the right it is 3 X 4 inches for an adjustable box. This opening is shown divided each side of the center so that the total length of the rod will be 24 + 2-1/2+ 3 = 29-1/2 inches. The ends are 2 inches thick and the central portion is round, 2 inches in diameter.
Making sketches is also great training in another way. It teaches us to observe small details. Most of us look at an object without seeing more than the basic outline. To test this, lay twenty common articles on a table or bench, ask someone to look at them for a full minute and then go away and make a list of what they saw. Seems easy, of course, but just try it yourself and see how much easier it is to forget from a quarter to one half of the items.
Once your sketch is done, it’s a simple matter to scan the sketch, and then email it to me. Don’t have a scanner? Go to Staples or any other larger office supply. They’ll be more than happy to scan it and save it as a PDF.