Deciding whether to use a turret or gang tooling is one of many topics that seems to engender religious fervor from one side to the other. Let’s start by providing a brief overview of each approach and then dive into the details.
Pure gang tooling is the simplest option for a CNC lathe. The tools sit in a row on the lathe’s cross-slide. To change a tool, an end user takes the following steps:
- Pulls the current tool from the workpiece with a Z-axis motion.
- Slides in the X-axis until the new tool is in position.
- Moves along the Z-axis to start cutting.
A tool turret is more complex than simple gang tooling. A turret holds a group of tools and rotates to bring a new cutting tool into position. Changing tools involves:
- Pulling the current tool back, typically with a Z-axis or combined X- and Z-axis motion.
- Rotating the turret until the correct tool is in position.
- Bringing the tool forward to begin cutting, again with a Z or XZ motion.
Lathe turrets are like the rotary toolchangers familiar to users of CNC milling machines.
Which one is better?
| Turret pros | Gang pros |
|---|---|
| More flexible | Faster tool changes |
| Handles longer, skinnier parts | Simpler |
| Handles larger diameter parts | Lower cost |
| Easier to program | Faster setup |
| Accommodates more tools | More accurate |
| More possible axes | More Reliable |
Here’s the top-level conclusion:
Choosing between gang tooling and a turret on a CNC lathe should be based on the kinds of parts being machined:
- Gang tooling is very hard to beat for small-diameter, short parts that do not need a tailstock.
- Turrets are more versatile. They are a must for long, skinny parts that need a tailstock for support.
Many machinists wish they could use their gang lathes for everything, but they have turret machines for parts that are too long and thin to be made with a gang lathe.
A CNC lathe with a turret (left) and gang tooling (right). Image courtesy of B. Warfield
For those kinds of parts, perhaps a better “competition” would be gang lathes vs. Swiss-style machines. Another possibility is to install small gang plates in some of the turret stations. This adjustment can make tool changes very fast for the tools on that station.
Turrets are also the norm on larger CNC lathes and multifunction machines. Turrets are preferred for large work because they don’t require clearance under the part. The turret can approach the part from behind, which allows more room for large-diameter parts.
Multifunction machines use multiple turrets and spindles to greatly enhance the speed and flexibility of the machine. The goal is to perform all operations in a single setup. With two spindles, the part can be transferred to a second spindle to allow machining of the back side. With multiple turrets, more tools can be accommodated, parts on two spindles can be machined simultaneously (one turret per spindle), and it’s even possible to increase the mrr by roughing an OD with two tools in one pass.
At the high end, the flexibility of turrets makes them the winner. At the lower end, the simplicity and speed of gang tooling makes them the winner.
An in-depth article about turrets vs. gang tooling is available on the CNCCookbook blog (tinyurl.com/y7372pe5).
Related Glossary Terms
- clearance
clearance
Space provided behind a tool’s land or relief to prevent rubbing and subsequent premature deterioration of the tool. See land; relief.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- lathe
lathe
Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- multifunction machines ( multitasking machines)
multifunction machines ( multitasking machines)
Machines and machining/turning centers capable of performing a variety of tasks, including milling, drilling, grinding boring, turning and cutoff, usually in just one setup.
- outer diameter ( OD)
outer diameter ( OD)
Dimension that defines the exterior diameter of a cylindrical or round part. See ID, inner diameter.
Author
Bob Warfield founded CNCCookbook.com and built it up to be one of the most popular CNC Blogs on the Internet. Thanks to his work with CNCCookbook and the G-Wizard software series, Warfield routinely receives questions from shops all over the world. For more information about the CNC Chef, visit his website here.
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