More Help for Engineers: People & Companies

In last month’s column, I discussed the value of communication between engineers and shop personnel. Here are some additional tips in that vein for engineers:

Avoid flippantly adding fillets, radii and chamfers on parts just because it is easy to do with a computer. Such features can substantially increase the time it takes to make parts, as special cutters and additional programming may be needed.

Square corners are nearly impossible to cut with a milling machine. Include radii on pockets and cutouts when possible. All images courtesy J. Harvey.

Avoid showing flat-bottomed holes in drawings unless you actually want the hole to be flat-bottomed. This can be confusing to a machinist, especially if it is not obvious how the hole will be used. Showing a drill tip angle at the
bottom of a hole will remove any doubt as to what you want and make it faster for the machinist to produce. Creating a flat bottom in a hole requires an extra tool or
operation.

Be aware that milled pockets must have a radius somewhere. If you submit a drawing of a part that has pockets or windows with square corners, the job may get sent out for wire EDMing at a substantial cost increase and/or delay to the project.

When designing and creating a drawing for a bracket that’s added to a machine after it is built, avoid holding a ruler to a machine and saying, “That looks about right.” I can almost guarantee you that approach won’t work. Instead, go to the machine where the bracket is going to be used and, with a pair of scissors and piece of cardboard, make a model of the bracket. Mark the hole locations on the cardboard—take your time. Then make a drawing of the bracket using the cardboard model as a reference.

I once had to remake a simple bracket a dozen times until it fit on a machine properly. Some machinists see this type of inefficiency as job security. Vendors may love it because they can charge for each revision. I see it as a waste of my time. As one of my respected mentors used to say, “It’s easy to make junk.”