Eddie and Stacy, who are visiting from Prescott, were curious about the mill, or milling machine, so Kevin fills them in.
This is an old Bridgeport mill, not a drill press, although it can drill holes. It’s more for machining. You put metal into the machine’s vise or a turntable that fits in that same location so you can rotate the metal, but it’s more for cutting side to side or front to back – that’s X and Y, and Z, which is the height. Eddie turns the handle to raise the knee, which holds the table and the vise.
Next Kevin shows the chuck, which is similar to the chuck in a drill press. At the top of the machine is what is called the quill, which is a really long bolt that goes all the way down to the tapered shaft of the chuck. If you tighten the quill and put a drill in the chuck, you can use it as a drill press.
For milling, there are hundreds of types and sizes of threaded collets that fit up inside the quill to hold different styles of end mills. Kevin shows a grooved roughing mill that is used to cut more quickly. He then shows some other end mills including a large roughing mill. He explains that some have multiple flutes and some only have two flutes, which are used for softer metals like aluminum – the one he is showing is for steel.
Kevin shows how he’d use the roughing mill, clamping the steel pieces onto the table using the special clamps that fit into the slots on the table. Then he’d use the roughing end mill to cut away the excess metal. Then he’d switch to another end mill that smooths the rough surface. Eddie says that the roughing mill looks just like a tool he uses for hand carving wood. Kevin says that his metal mill has a much bigger motor, much stronger gears, but a much slower machine than a woodworker would use.
Eddie asks how often the end mills need sharpening. As long as you use cutting fluid on them as they are running, as long as you don’t try to force it through at a fast speed, they’ll last a long time. Kevin suggests you try not to run them into the table, which is really hard, or use the end mills with stone or anything similar. He’s sharpened maybe three of them in the several years he’s owned the mill.
The end mills are expensive – $25, $30, $50, $100, $200 each – depending upon the size. The high-speed steel ones are four to five times cheaper than solid caribide ones, which last much longer.
This machine was made in the mid 1970s, so it is entirely hand controlled except for a power feed that runs the quill up and down for drilling, but Kevin uses the manual handle instead. All of the table feeds are mechanical and hand-controlled.
The newer machines are all computer controlled. They have motors, so you just punch some buttons, put some metal in it, hit the “go” button, get a cup of coffee and come back to see chips fly.
Kevin bought this machine used for about $5,000. The new computer controlled mills cost $25,000 – $40,000 depending upon how many bells and whistles you get, but this will last his lifetime. It takes a lot of floor space and runs on three-phase power instead of single-phase. It’ll run on 220, which almost every house has, or 440 – you just have to change a little wiring on the top. It has a small rotary phase converter that takes single-phase 220 and turns it into three-phase 220.
The machine requires almost no maintenance. It has two oil ports into which you put a little drop every time you use it. You try to keep it clean by wiping down its surfaces, and it has a small oil tank on the side with a hand pump that you fill with light cutting fluid or light motor oil. Every time before you use the machine, you give it one pump, which applies oil on all the sliding parts. That’s pretty much it.
Stacy then asks what he uses the machine for. Kevin explains it’s for creating flat surfaces, channels, grooves, any kind of straight, square cut or hole you want to make in a piece of metal. Kevin uses it for making art, including MillKnot ( http://www.kevincaron.com/art_detail/millknot.html ). He then shows an aluminum billet and how he uses them to make a sculpture. He uses the mill to whittle, as well as to make standardized pieces for sculptures. It makes his job a lot easier.
Kevin explains that about 75% of the time you spend using the machine is set up, getting everything lined up, straight and clamped down. That’s why the new computer controlled ones are so much better. They’ll even feed in their own end mills!
Kevin is ready to go back to work, but before you go you might see Eddie risk his life ….