Running a milling machine involves the set up of raw material to be cut and the insertion of tools for cutting and proofing. With both a CNC (computer numerical control) mill and a manual mill, the setup and the way they are run are quite similar. The setup is the most crucial part of running a milling machine, as any mistakes during this process...
M/F Clean off the table of the mill. The table is where the raw material will be held by a fixture or vise and must be clear of metal chips from previous jobs and any debris buildup. Even the smallest metal chip will cause the fixture or vise to be slightly crooked, resulting in dimensional errors. Blow off the table with compressed air and use a fine grit sanding stone with oil to clean up rust and debris from the surface.
M/F Set up the fixture or vise. Place the fixture or vise on the table and loosely tighten the retaining screws that you will use. The milling table has slots to place T-bolts to secure vises and other work-holding fixtures. Place the vise as close to the end of the travel on a CNC mill or dead center of a manual mill. This will save time as the spindle will not have to travel far to start the cutting process. On a CNC, the spindle head moves, while on a manual milling machine, the table moves.
M/F Tram the fixture or vise. Tramming a fixture or vise is the process of assuring that the holder is perfectly straight. Use a dial indicator across a flat surface to make sure that it is dead straight within 0.001 inch. Tap on whichever side is off until the indicator reads straight and tighten the fixture or vise down on the table. Re-check with the indicator and loosen if it has moved and restart the process until it is straight after being tightened.
M/F Place the tools in the tool holder or spindle. Use a drill chuck for drills whenever possible and make sure you use tools that are sharp, as that will allow you to keep your dimension close to the print. Teach the tools in a CNC mill by entering the tool-teaching mode and indicating which tool needs to be taught. The spindle will bring the tool to a probe to measure its distance from the top of the table for accurate cutting. You must manually enter the other tool information, mostly its diameter.
M/F Cut the first piece, taking time to assure that the dimensions are correct. You want to go very slowly when cutting the first piece in a CNC mill to assure no mistakes in the program. A small error can result in major damage to the material, tool and machine. After you have proofed the first piece, you can make the other pieces quickly.