Fabricating Curves

Since it is becoming increasingly difficult to find small machine shops that are willing to design and make parts for a single application or resto project, it makes sense to tackle making these parts with the tools that a home machinist can afford. Just about anything can be made with big-dollar, computer-controlled machines, but the processes reviewed here use older (and less costly) technology.

Making the Radius
Some of the features of the manufacturing process include holding the part in place with a vise or clamps, cutting angles and odd shapes, and using simple trigonometry to calculate the shapes. But let's not forget about how to make curves and radii (plural for radius).


That's because making curves is considerably more difficult. Why? Well, a manually operated milling machine is designed for straight-line operation. Remember the old Etch-A-Sketch toy for drawing? It really only moved in straight lines, right and left, and, fore and aft. When you tried to make a circle or a curve, things got complicated. It is nearly impossible to coordinate your right and left hands to make the right movements that a smooth arc requires.


The problem is exactly the same with a milling machine. The handles only move right and left, and, fore and aft.


So why bother making a curve, then? A simple radius can be a very important addition to a part. A curve can save weight and add strength to a part at the same time. That's why you see arches in old buildings. The curve of an arch distributes the weight more evenly, making it a great load-bearing shape.