2 Unit 1: Tramming the Head
Objective
After completing this unit, you should be able to:
- Describe how to tram the mill head.
- Explain how to indicate the vise.
- Explain the use of spring collets.
- Describe the difference between climb vs. conventional milling.
- Explain how to use an edge finder.
- Describe how to set the quick change gearbox correctly.
- Describe how to square the stock.
- Describe face milling.
- Describe advanced workholding.
Tools For Tramming
A dial indicator is a precision tool used to measure minute amounts of deflection between two surfaces.
When tramming, a dial indicator attached to the chuck is used to determine the orientation of the mill head to the mill table. The same wrench used to tighten and loosen the quill can be used to adjust the various bolts on the mill head.
Dial indicator used for tramming the head.
Tramming the Mill Head
Tramming ensures that the mill head is perpendicular to the mill table’s X and Y axis. This process ensures that cutting tools and the milling surfaces are perpendicular to the table. Proper tramming also prevents irregular patterns from forming when milling.
A dial indicator attached to the spindle for precise mill head alignment.
A vertical mill’s head is able to tilt from front to back and side to side. Occasionally these adjustments can drift. The mill head should be checked and adjusted periodically, ensuring that the spindle is perpendicular to the table.
- Remove the vice from the milling table.
- Attach a dial indicator to the spindle and offset the dial six inches from the spindle’s axis. Make sure the indicator probe is facing down.
- Raise the mill table so that when it contacts the indicator, the indicator reads between 0.005 inches to 0.010 inches. This reading is called the preload.
- Position the dial indicator so that it is visible, then set the bezel to zero.
- Hand-turn the spindle while watching the indicator.
- If the reading on the dial indicator stays at zero, the spindle is aligned.
- If the reading is not zero, continue tramming the head as shown below.
Tramming Process for the X-Axis
- To tram around the x-axis (the left-to-right direction of the mill bench when facing the front of the mill), loosen the six bolts (three on each side of the mill) using the mill wrench.
Location of the bolts to be loosened to allow the head to rotate about the X-axis.
- After loosening the bolts, re-tighten them by hand plus a ¼ of a turn using the mill wrench.
- The adjustment bolt that moves the mill head up and down around the x-axis is located at the back of the mill.
Adjustment bolt used to position the mill head vertically around the X-axis.
- Two protractors are used to indicate general alignment. The larger protractor on the mill head has a red indicating arrow that should align with the zero marker on the curved protractor on the body of the mill. This only provides a general guide, the dial indicator reading is required for precise alignment.
- Position the dial ind