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How to Level a Milling Machine

The first thing to do when installing a milling machine is to level it. Mills produce the best accuracy when properly leveled. Mills last longer when properly leveled; if a mill is operated while it is not level, moving parts wear unevenly, causing premature malfunctions.

Use the most precise level available.

Mills have four leveling screws through the base of the machine. The screws are adjusted to compensate for an uneven floor. Each screw seats into a leveling pad, which sits on the floor.

  1. Remove fixtures and clamps from the mill table. Remove oil and shavings from the mill table. If the table has any nicks or dents, stone them flat with a flat machinist's stone.

  2. Position the mill table to the center of its range of motion in both directions. Lock the slide clamps. As you face the front of the mill, place the level longways, (left-to-right) in the center of the table.

  3. Adjust the leveling screws on the left or right edges of the base until the bubble in the level is centered. Keep equal pressure on the screws as you adjust them; when you adjust a screw on one edge of the mill, turn the other screw on that edge the same direction until the pressure is equalized on both screws for that edge.

  4. Turn the level 90 degrees. As you face the front of the mill the level will be placed longways toward and away from you.

  5. Adjust the screws in the front and rear edges of the base until the bubble in the level is centered. Keep equal pressure on the screws as you adjust them; when you adjust a screw on one edge of the mill, turn the other screw on that edge the same direction until the pressure is equalized on both screws for that edge.

  6. Rotate the level 90 degrees. Check the bubble. If it does not read zero, repeat steps 2 through 6. Repeat steps 2 through 6 until the level reads within allowable range in both directions.

  7. Tighten the lock nuts on the leveling screws if your mill is so equipped.

  8. Tip

    This will require patience. Each time you level the machine in one direction, you must go back and check the other direction. The adjustments are smaller each time. This job goes faster with two people. One person watches the bubble level and communicates with the person turning the leveling screws. The machine builder specifies an allowable range of accuracy of levelness. The bubble level you use should be capable of reading in the appropriate resolution.

    Warning

    Do not attempt to level your machine on an unstable surface.