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Indicating a Mill


When going on a milling machine for the first time, its always good practice to check the position of the machines head. The head can be adjusted in a angular fashion both forward and back from the user and  from the left and right. Therefor the cutting tool may not be perpendicular to the part when you first get on the machine.

To indicate the machine, a dial test indicator is generally used along with a Indi-Col holder to hold the indicator as its being indicated. Just as indicating the vice the indicator is attached to the spindle, however in this case the spindle is not locked as you need to rotate the indicator to hit the 4 points created by the way the head can be adjusted.

When indicating, some use a ground plate instead of the milling machine table, some use a large bearing race, while others take a honing stone to check the table for burrs and indicate directly off the table. What ever the method there are probably more different methods then I can write here. Myself I use the honing stone check and indicate the table to eliminate the possibility of compounding errors of other methods.


As you can see the indicator holder (Indi-Col) holds the indicator on the smaller part of the spindle while allowing you adjustment to indicate the table. Although the bolt loosening and tightening method to get the head to align seems to take a while when you first do it, over time the method becomes easier to do.

Indicating the head doesn't take a long time compared to the time it will take to rework or completely remake the work that was scrapped because the head was a couple of degrees off and you didn't see it.

Dimitrios Simitas

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