As I move into more intensive and detailed projects, I increasing need to fabricate custom parts. Normally, I get by with a 3D printer. It has allowed me to make objects far more complex than I can reliably make by hand. That being said, I’m beginning to run up against the limitations of plastic and FDM printing. Even with wondermaterials like PET and HIPS, there’s no easy way to build parts for more extreme applications – high wear or high temperature, for example. If a part is going to going to see temperatures in excess of 300C, few plastics are going to hold up, necessitating the use of other materials.
Thus, I’ve been trawling Craigslist for a few months looking for a mill. While I would have preferred a Bridgeport, there’s fairly few in Colorado to choose from, and I simply do not have the space. For this reason, small mills tend to hold their value quite well, insofar as there’s simply a larger market for them than a 8000lb VMC or 2500lb Bridgeport.
That being said, I still want a mill beefy enough to chew through steel and heavy enough so I can take more than a 100 thou cut in aluminum without destroying the machine. A desktop hobby mill, Sherline or X-Carve just wasn’t going to work for the work I envisioned.
Finally, I found a JET mill/drill from 1979 for sale on Craigslist for $800, negotiated down $100, and took it home. The machine was cast in Taiwan, and had seen remarkably little use. It’s marked “JET 16”, and has a 12 speed belt drive and Morse Taper 3 (MT3) spindle. While not as popular as the R8 taper for most Bridgeport and newer import machines, it’s still easy enough to find tooling for.
One of the most important factors for a machine tool is rigidity and dampening ability. Rigidity is obvious – good luck making straight parts when the machine is flexible and easily pushed around by the workpiece. On the other hand, dampening is a bit less obvious. People frequently use mass as a proxy for dampening ability, but this is only valid when talking about similar setups and identical materials.Here are the relative dampening abilities of cast iron, steel, and aluminum. For example, cast iron, even conservatively , is 2 orders of magnitude better than aluminum at absorbing vibrations. For machine tools, there is no simply substitute.
That being said, the JET is cast iron through and through. The gibs are, as far as I can tell, cast iron. The table base and column are all cast as well. Despite the mill’s superficial cleanliness, the ways were dirty with a mixture of old oil and old, never cleaned packing grease. I cleaned it all up with a bit of Brakekleen and relubricated the ways with Vactra #2 way oil. I also packed the leadscrews with lithium grease, as well as the thrust bearings.
Overall, I’m excited to use the mill in upcoming projects. It has immensely increased my ability to fabricate difficult pieces, as well as my ability to take on longer, more involved projects.