Service Home How To Procedures Spindle - Drawbar - Force Measurement - VMC
Last updated: 04/25/2025

Spindle - Drawbar - Force Measurement - VMC

Introduction

This procedure will show how to measure the spindle's drawbar force. Once measured, compare the values with the recommended spindle drawbar force using the Spindle Drawbar Force - Reference Table for more information. 
 
Tools Required:
  • Drawbar force gage
  • All purpose machine oil
  • Clean cloth towel
  • Flashlight

This procedure applies to the following service kits:

Drawbar - Force Measurement

1

Remove the tool holder from the spindle.

Push [EMERGENCY STOP].

2

To prepare the spindle:

  • Clean the spindle taper with a clean cloth rag.
  • Add a coat of all-purpose machine oil to the spindle taper with a lightly oiled cloth rag.
  • Use a flashlight to visually inspect the spindle taper for signs of wear and damage.

3

Assemble the drawbar force gage according to the manufacturer’s instructions. Put the gage into the spindle.

Measure the drawbar force and compare it to the Drawbar Force Reference Table.

Drawbar Force Measurement DC-Series

The DC-series machines do not allow you to load tools directly into the spindle under normal conditions. Most tools for measuring drawbar force do not come with tool holder, making it impossible to load the tool into the DC tool carousel.

In order to load the clamp force gauge (included in the 93-2772 kit) into the spindle, the Z-axis needs to be jogged up and down while loading the tool. 

1

Start by moving the spindle to the orient position.

Press [Current Commands].

Go to the Devices > Mechanisms menu [1] and search for "Main Spindle" [2]. Press [F1] to search.

Press [F2] [3] to move the spindle to the orient position.

Note: When the spindle is oriented on DC machines the spindle drive dogs should be parallel with the Y-axis.

2

Press the [Recover] button.

On the recovery menu, press [Z] [1] to select the Zero Axes option.

Note: In order to jog the Z-axis above the zero position, you must be in recovery mode. The drawbar can only be released by the Z-axis moving up above the zero position.

Answer the questions about tools being in the spindle or carousel [2]. 

When on the "Zero Carousel" menu press [C] [3] to continue.

Once you get the the "Zero Z Axis" page [4] press [Handle Jog] and make sure to select the Z-axis. 

3

Jog the Z-axis up so that the carousel is fully pulled under the spindle as shown in the image. This is where the drawbar begins to unclamp.

Continue to jog the Z-axis up so that the drawbar is fully released. Jog to where the bottom face of the spindle [1] is 3 - 4 inches above the tool pocket [2] on the carousel.

Note: At this Z-axis position the drawbar is released and a tool can be inserted into the spindle.

4

DC-Series 30 Taper Machines

Assemble the clamp force tool with the correct spindle taper adapter and pullstuds.

Clean the tool taper.

Make a note of the starting force shown on the gauge.

Note: The gauge doesn't need to start at zero for accurate measurements. The clamp force is the difference from the initial reading, and the reading when clamped.

Hold the tool from the bottom [1] and insert it into the spindle. 

Note: In order to insert the tool into the spindle, physically pull the carousel towards the front of the machine. Pull the roller bearing [2] away from the guide rail [3] so that there is room to hold the tool in the spindle. Alternatively, you can remove the pocket that is inline with the spindle.

Keep holding the tool in the spindle and begin jogging the Z-axis down to the zero position. The carousel will need to be held pulled away while jogging. This will require 2 people.

When you get the Z-axis zero position the drawbar will be fully clamped on the tool. 

Record the value on the gauge when clamped, and compare it to the initial reading. Compare the result to the Drawbar Force Reference Table.

5

DC-Series 40 Taper Machines

Assemble the clamp force tool with the correct spindle taper adapter and pullstuds.

Clean the tool taper.

Make a note of the starting force shown on the gauge.

Note: The gauge doesn't need to start at zero for accurate measurements. The clamp force is the difference from the initial reading, and the reading when clamped.

Hold the tool from the bottom and insert it into the spindle. 

Keep holding the tool and begin jogging the Z-axis down to the zero position.

When you get the Z-axis zero position the drawbar will be fully clamped on the tool. 

Record the value on the gauge when clamped, and compare it to the initial reading. Compare the result to the Drawbar Force Reference Table.