Why should you consider the Hard Turning process? And why are Hardinge lathes ideal for Hard Turning?

Hard Turning on Hardinge QUEST Series Super-Precision CNC lathes provides many of the same capabilities as a cylindrical grinding machine. Although grinding does—and always will—have its place, there are compelling reasons to consider a Hardinge lathe for many of your operations.

Why Hard Turn instead of grind?

What makes Hardinge Quest Lathes ideal for Hard Turning?

On this page, we’ll investigate why you should consider Hard Turning instead of grinding, and point out some compelling reasons why a Hardinge QUEST Lathe is the perfect choice for Hard Turning.

Why Hard Turn instead of grind?

The major benefits of Hard Turning compared with cylindrical grinding come from:

Process Flexibility

Hard turning on a Hardinge lathe allows you to “soft turn” and Hard Turn on the same machine tool. You can achieve up to 4-1 and 6-1 higher metal removal rates, and even automate processes.

In addition, if your part configuration changes, it’s easier to make the appropriate changes on a lathe than on a grinder. Grinding is significantly more expensive due to cycle and setup times.

Lower Energy Costs, and Environmentally-friendly

Lathes often operate at a significantly lower cost than cylindrical grinding machines. In addition, the chips produced through the Hard Turning process are significantly more environmentally-friendly than the swarf produced by grinding. Coolant may not be necessary with Hard Turning, which further reduces increasingly-expensive disposal and recycling costs.

Lower Machine Investment

A Hardinge QUEST Lathe represents a significantly lower investment than a cylindrical grinding machine. Although higher-level grinding machines can cut multiple operations, the cost can be 3-4 times higher than the cost of a Lathe.

In addition, grinding machines require more support equipment such as balancers and dressers. Automation is quite difficult. Add it all up, and it’s simply more expensive to grind than Hard Turn. If you’re producing parts on a grinder that can successfully be cut on a Hardinge Lathe, you’re probably spending more than you should, and making less than you could.


Reduced Tool Inventory

Tooling is cheaper and takes up less physical space than grinding wheels. In addition, Hard turning provides Easier Chip Control and Faster Metal Removal Rates

Dramatically reduced setup times, fewer operations, faster cycle times

The chart below details machining operations on a typical part, and dramatically illustrates how significant time/cost savings can be achieved through Hard Turning versus grinding:

What makes Hardinge QUEST Super-Precision Lathes ideal for Hard Turning?

The same factors and considerations optimized in the design stage for Hardinge QUEST Super-Precision Lathes carry over to the successful implementation of Hard Turning. These lathes meet the demanding requirements necessary to successfully Hard Turn. Here are several key considerations that make Hardinge QUEST Series lathes ideal for Hard Turning:

Machine Rigidity
Workholding Rigidity
Outstanding Vibration Dampint
Rigid Tooling System
Unmatched Accuracy
Lower Cost


Machine Rigidity

The heavy-duty linear guideways of QUEST lathes are preloaded, similar to the double-nut ballscrews used on the axis drives, and thus have no assembly clearance.

The non-contact magnetic encoder design eliminates the need for belts and moving parts for enhanced positioning accuracy and feedback. This system provides noise/vibration-free operation, and is more reliable than belted encoder designs.

The wide set linear guides are typically 40-60% heavier-duty units than those of most competitive machine tools of the same size that utilize linear guides.

Linear guides on all QUEST Super-Precision machines are finished to a higher finish quality, resulting in minimum resistance to motion. The low-stress slide drive systems on QUEST machines have larger axis motors and shorter pitch ballscrews, providing high dynamic stiffness and significantly longer life.

Workholding Rigidity

The patented Hardinge direct-seating collet spindle ensures that the workpiece is as close as possible to the spindle bearings—the point of maximum rigidity and accuracy. This significantly improves the hard turning process compared to competitive workholding systems.

Roundness is a key requirement: Any projection from the spindle bearings multiplies the spindle runout (and therefore roundness errors) produced on a turned workpiece.

Hardinge is the largest manufacturer of lathe spindle tooling in the world. This means that the workholding systems made for our machines are designed specifically for our machines—without compromise.

Outstanding Vibration Damping

All Hardinge QUEST Series turreted lathes are built on a rigid cast iron base with our exclusive HARCRETE polymer composite reinforcement. Vibration damping is critical to the successful application of Hard Turning. HARCRETE is strategically located at key points in the base to assure maximum rigidity.

Hardinge QUEST GT27SP lathes are built on a solid HARCRETE Base, which also provides for superior Hard Turning capabilities.

FEA (finite element analysis) design techniques are used to ensure a balanced machine structure for optimum rigidity.

Rigid Tooling

Simple, rigid round shank tool holders locate “on center” and parallel to the spindle centerline.

The turret top plate on Hardinge QUEST machines is locked into position on a 3-piece curvic coupling to maintain accuracy and rigidity. The close proximity of the cutting tool to the coupling reduces the risk of vibration, thus improving the Hard Turning process.

Unmatched Accuracy

Hardinge QUEST machines also incorporate digital glass scales in both the X and Z axes for high machining performance over a large number of parts. Thermal growth is kept to a minimum. The spindle motor and collet closer assemblies are dynamically balanced. X and Z axis error compensation is performed to fine-tune positioning and compensate offset at the tool tip.

Lower Cost

Hard Turning provides an opportunity to achieve significant cost savings compared to traditional grinding methods. It’s faster, takes less setup time, is more flexible and takes fewer operations than grinding. The capital cost of Hardinge Super-Precision CNC turning machines is much less than that of grinding machines to accomplish the same work.

Summary

Of course, successful Hard Turning is dependent on the entire machining system, including the design integrity of the machine tool, efficient workholding devices, high-quality cutting edges, a rigid tool location, and appropriate machining parameters.

As experts in the field of Hard turning, Hardinge has the people, the products and the services necessary to ensure your success.