Tramming the Vertical Milling Machine Head

Tramming the Vertical Milling Machine Head

• Tramming is the process of adjusting the head to ensure the spindle is perpendicular to the machine table's top surface.
• This is necessary to produce perpendicular machined surfaces when milling and to ensure machined holes are perpendicular to the table.

Preparing for Tramming

• Remove any workholding devices from the machine table to make tramming easier.
• Loosen both sets of clamping bolts and turn the adjusting screws to align each reference mark with its "0" on each protractor.

Initial Alignment

• Snug the clamping bolts just beyond finger-tight with a wrench.
• Move the quill to its lowest position and lock it in place using the quill lock.
• Place the beam of a solid square on the table and slide the blade against one side of the quill, ensuring the table and square are free of dirt and burrs.
• Use the adjusting screw to more closely align the quill with the square, repeating the process side to side and front to back on the quill.

Fine-Tuning Alignment

• Snug the clamping screws so that the head is not loose, but can still be easily moved when turning the adjusting screws.
• Position the table so that the spindle is in the middle of the table.
• Mount a dial test indicator in the spindle and position it to sweep a circle slightly smaller than the width of the table.
• Rotate the spindle to the front of the table at the 6 o'clock position and bring the indicator contact tip against the table, preloading it so the needle travels about one-fourth of a turn of the dial.

Checking Alignment

• Rotate the spindle 180 degrees to bring the indicator to the back of the table at the 12 o'clock position.
• Note the reading and adjust the head until both positions show readings within about 0.001 to 0.002 inches of each other.
• Repeat this process at the 3 o'clock and 9 o'clock positions, adjusting the head until these two indicator readings are within 0.001 to 0.002 inches of each other.
• Return to the 6 o'clock and 12 o'clock positions and adjust the head until these two indicator readings are within 0.001 to 0.002 inches of each other.

Alternative Methods

• Use a gage block, 1-2-3 block, or similar block to check indicator readings at each position instead of bringing the indicator into direct contact with the table.
• Sweep the indicator on a precision-ground flat disc, plate, or the base of a swivel vise, instead of directly on the table.