A rotary table on a milling machine is a precision indexing and positioning device primarily used to rotate a workpiece to a precise angular position or to mill circular features. It significantly expands the capabilities of a milling machine, allowing for complex machining operations that would otherwise be difficult or impossible.
What is a Rotary Table?
A rotary table, also known as a dividing head or indexing head, is a specialized accessory for a milling machine that allows for precise angular positioning of a workpiece. It consists of a circular table mounted on a base, which can be rotated manually or with a motor, often featuring a worm gear mechanism for fine adjustments and high accuracy.
Key Uses of a Rotary Table on a Milling Machine
The versatility of a rotary table makes it indispensable for various precision machining tasks:
1. Precision Indexing and Dividing
One of the most fundamental uses is to accurately divide a circle into specific, equal segments. This is crucial for:
- Gear Cutting: Creating teeth on gears, sprockets, and spline shafts.
- Bolt Hole Circles: Drilling or milling a pattern of holes equally spaced around a central point.
- Hexagons and Polygons: Machining precise flats on a round workpiece to create hexagonal or other polygonal shapes.
- Fluting: Adding grooves to tools like reamers or taps.
2. Circular Milling
Rotary tables enable the milling of arcs, radii, and full circles, which are beyond the capabilities of standard linear axis movements alone. This includes:
- Creating Large-Diameter Holes: For smaller milling machines that may lack the power to drive very large twist drills (e.g., over 0.500 inches or 13 mm), a rotary table allows for the creation of large-diameter holes by milling in a circular toolpath. This technique removes material progressively, putting less strain on the machine.
- Machining Radii and Curves: Producing precise convex or concave curves on a workpiece.
- Boring Circular Pockets: Creating circular recesses or pockets with high accuracy.
3. Helical Milling
When synchronized with the milling machine's linear axis movement, a rotary table can be used to mill helical features. This advanced application is vital for:
- Milling Helixes: Producing spiral flutes on tools like twist drills, end mills, or reamers.
- Cutting Lead Screws: Manufacturing precision lead screws or worm gears.
4. Cutting Complex Curves and Angles
With proper setup, a rotary table significantly enhances the machine's ability to create intricate geometries:
- Cutting Complex Curves: Skilled operators can utilize a rotary table to generate highly complex and non-standard curves on workpieces by coordinating rotary and linear movements.
- Cutting Straight Lines at Any Angle: While seeming counterintuitive, the ability to precisely rotate the workpiece allows the milling machine's linear axes to cut straight lines at any desired angle relative to a workpiece feature or datum, offering flexibility in angular machining operations.
5. Angular Positioning and Machining
Rotary tables are excellent for orienting a workpiece at precise angles for machining specific faces or features that are not parallel or perpendicular to the machine's primary axes. This is often done for:
- Angular Slots or Pockets: Milling features at a specific incline.
- Chamfering and Beveling: Creating angled edges on components.
Advantages of Using a Rotary Table
| Feature | Benefit |
|---|---|
| Precision | Allows for highly accurate angular positioning and indexing, crucial for repeatable results. |
| Versatility | Expands the range of machining operations possible on a standard milling machine. |
| Efficiency | Enables complex geometries to be machined in a single setup, reducing re-fixturing time. |
| Material Handling | Facilitates the machining of large or awkwardly shaped workpieces by allowing their rotation. |
| Surface Finish | Contributes to smoother, more consistent finishes on circular and contoured features. |
In essence, a rotary table transforms a standard milling machine into a more capable and versatile tool, enabling the creation of intricate and precise components across various industries, from mold making to aerospace.
