Dear Shop Doc,
I have recently been asked if my shop does “micro” machining. I’ve done some work on small parts recently, but I’m not exactly sure what is meant by “micro.” Any thoughts?
Dear Small Beginnings,
One of the problems with the term “micro” is that it is often used to defne a very small portion of a wide array of categories. Maybe you’ve been to a microbrewery or have a computer that uses a microprocessor. In each case, the prefx or adjective “micro” defnes a small-scale or very small feature of the original term. To date, the term is loosely used in machining to refer either to the exact measurement of the parts, such as in microns, or to a small range of work, in the neighborhood of 1 mm or less.
In May 2010, I posed a similar question to exhibitors and attendees at MM Live—the Micro and Precision Manufacturing Event for North America, in Cincinnati, Ohio. As an exhibitor myself, I thought micro meant sizes under .050”, as this was the smallest tool in our catalog and very near to the 1 mm dimension. I often referred to parts from this diameter up to .500” diameter as Swiss, so everything smaller I considered micro. A large number of attendees defined micro as being smaller than a certain dimension.
Some said micro meant parts smaller than 8 mm or .250”, or 1 mm. Kyocera’s booth advertised a .250” dimension on their sign. However, when I asked them about it, they explained that although they make a wide variety of small tools, the ones they considered to be micro sized were really those .125” or smaller.
A few attendees believed the term “micro” referred to parts that were smaller than the human eye can see. The MM Live show had a wide of variety of these parts on display, and it seemed that every other booth had a microscope or magnifier of some type to help you see their wares. One of the most intriguing answers to define micro came from an exhibitor at Makuta Technics Inc. He said they use the term micro not to refer to a part’s size, but more exclusively to the feature’s size. You may have a part not considered to be a micro machined part, but if the features and tolerances are small enough, it may require what is commonly known as micro machining. This can lead to a lengthy discussion about tolerance, and if a part with +/-.001” variance can be classified the same as a part with +/-.000010”.
I believe micro machining refers to parts with an overall size or feature in the neighborhood of 1 mm. The features are not as large as common Swiss machined parts, nor as small as a nanometer (one billionth of a meter), but you will still need some form of glasses to make out the details. My suggestion is to not split hairs, but just state the size of the features you are comfortable making. The number of people who agree on the definition of the term “micro” is very small.