How to Operate a Rotary Table

Rotary tables extend the functionality of milling machines by providing circular tool paths and by giving an additional degree of freedom in positioning the workpiece. They enable operations where a circular arc is cut or where several operations are repeated along the arc. They provide the same precision and accuracy to angular measurements as the milling table provides to linear measurements.

Difficulty: Moderate

Instructions

Things You'll Need:

• Rotary Table
• Tailstock
• Index Plates
• Milling Machine

1. Mount the rotary table. This step is more nebulous as different rotary tables will mount to different milling machines in different ways. The bulk of this article is dedicated to describing how to perform the operations that a rotary table provides, but before that can happen the table must be mounted to the milling machine. This will typically involve accurately positioning the table on the milling machine and bolting it in place. Should the tailstock be required it must also accurately positioned and bolted.

2. Before the table can be used the workpiece must be mounted. Some rotary tables feature slots where bolts can be attached while others have vises or jaws mounted to grip the workpiece. Either way, the workpiece is carefully positioned on the rotary table so that the center of the arc is located at the center of the rotary table and is tightened into place.

3. Make an arced cut. This basic operation involves rotating the rotary table while the cutting tool is actively removing material. Once the start of the cut is located with the milling table, the table is locked into position, the cutting tool is engaged with the work and the rotary table is rotated through the cut until the last point is reached. This is repeated until the desired depth of cut is reached.

4. Perform indexed operations. This is where the workpiece is moved before the cutting tool meets the workpiece. Examples include drilling holes every five degrees or cutting the sides of a hexagon. Before every operation the workpiece is rotated by the predetermined amount using the rotary table's handle. Then the table is tightened in place for the cutting action.
   
   The standard rotary-table handle features angular divisions, but for accuracy in indexing, index plates can be used. These are metal disks with holes equidistant along a circular arc. This disk replaces the standard handle and uses instead a handle with a point that catches each hole. By counting the number of holes along each circle the rotary table is moved by a fixed and accurate amount.

5. Using the tailstock. Many operations on a rotary table involve circular arcs and indexed cuts on the face of a workpiece, but they can also be performed on the sides. For longer workpieces or pieces that require mounting away from the rotary table's surface, the tailstock is used to suspend the workpiece between the table and tailstock. The tailstock serves as a support that enables the rotary table to freely rotate the workpiece. An example of where this setup is required is cutting the teeth of a gear using a profiled end mill.

Tips & Warnings

• Take your time and plan each cut. It's always easier to remove material than add it. The best way to learn how to machine is to be taught by an expert.
• Any machine tool has the potential for great harm or death and should be used and treated with respect. Use safety gear, protective guards and common sense when operating any machine tool. This article assumes that the reader is familiar with how to use a milling machine.

References

• Machinery's Handbook. Industrial Press 28th edition