Buying a Grinder: Applications for Grinding Machines
How are grinding machines used in aerospace, medical, die/mold and other industries? Here is a rundown of some common applications.
This blog post was adapted from an article by Barry Rogers published in the Machine/Shop supplement to November 2018’s Modern Machine Shop magazine.
Common automotive applications for OD and ID grinding include brake cylinders, brake pistons, hydraulic steering pistons, selector shafts, spline and gear shafts, connecting rods, camshafts, and crank shafts. Precision grinding of outside shaft diameters provides near-perfect fit between gears, bearings and other mating components. OD grinding of these components enhances concentricity of the shaft to its centerline while ensuring that accompanying diameters are concentric to one another. Offset ODs for non-concentric diameters, such as crank pin journals and cam lobes, are also precision ground. For this application, special crank and camshaft grinders are required. They can be programmed to grind both on-center and offset diameters on the same shaft. Likewise, ID grinding is required for precise fitting of brake cylinders, connecting rods and other applications.
Here are some more specialized applications:
The medical industry uses grinding to produce surgical drills, dental drill bits, hip stems, hip balls, hip sockets, femoral knee joints and needles.
The aerospace industry is known for workpiece materials that are tough to machine with conventional cutting tools and processes. These high-strength, high-temperature materials enable components to survive in the severe environment of aerospace engines. However, the same attributes that make these materials difficult to machine are also likely to make them suitable for grinding. Turbine rings, turbine shafts, and inner and outer rings are a few of the aerospace components which are commonly precision ground.
Machine Tool Manufacturers
Machine tool manufacturers use ground components for spindles, linear guideways, ballscrews, Hirth couplings in indexers and rotary tables, roller bearings, cams, racks, valve spools, and pistons.
The die/mold industry uses grinding to produce thread dies, stamping dies, press brake tools, draw dies, thread rolling dies and mold inserts, along with many other die and mold components.
The tooling industry that supports the die/mold and machine tool industries uses precision grinding to produce three- and four-jaw chucks, profile inserts, step drills, drill points, reamers, taps, ring gages and collets. ISO and HSK adapters and shanks for toolholding also require grinding.
Note that when milling or turning with conventional machines and tooling, part tolerances and surface quality are degraded as tooling inserts wear. In contrast, a grinding wheel can be dressed frequently to keep the cutting edges of the abrasive sharp and the shape of the wheel constant, resulting in a consistent finish and close dimensional accuracy.
Roughing and finishing on a single machine, using a single setup, has appeal for most shops. The advantages in time savings and accuracy are obvious. Eliminating the transport of workpieces between machines, as well as the setup for those secondary operations, is a boon for throughput. Critical features that need to maintain dimensional relationships can be much more reliably produced if machined complete in one clamping.
In vertical grinding, the workpiece is held upright in a rotary chuck with the grinding spindle overhead. This configuration can improve roundness, facilitate single-setup processing and prolong the life of the machine. Loading and unloading may gets easier, too. Workpieces with relatively large diameters and short lengths benefit the most from vertical grinding.
If one must pick a manufacturing specialty, grinding carbide might not be the first choice because it’s perceived to be very difficult. RPM Carbide Die, however, has worked the material for nearly 40 years and, as specializing seems increasingly to be the order of the day, this northern Ohio shop is in a good position to thrive.