CYLINDRICAL GRINDING MACHINES

The most common types of cylindrical grinding are external cylindrical grinding, also known as OD (outer diameter) grinding, and internal cylindrical grinding, also known as ID (internal diameter) grinding. 

External cylindrical grinding is the precision finishing of the external surface of a part. Both the workpiece and the grinding wheel are rotating during the operation. The workpiece is typically held between centers, but may be held on a single end in a collet or chuck for shorter workpieces, or in applications where the end of the part needs to be ground as well. 

Centerless grinding is a specific type of external cylindrical grinding where the part is not held between centers or in a collet. The part is placed between the grinding wheel and a regulating wheel, with a work rest or guide blade holding the part in place. 

Internal cylindrical grinding is the precision finishing of internal part features, including bores, radii, tapers and spheres. Both the workpiece and the grinding wheel are rotating during operation, and the grinding wheel must be smaller than the internal feature that is being finished.

Cylindrical grinding is one of the most precise machining processes available, and is widely used across a range of industries and applications. As consumers demand products that perform better and last longer, manufacturers often look to cylindrical grinding as a way to deliver individual components with better precision. 

Some industries and applications that use OD and ID cylindrical grinding include:

• Automotive: engine components, valve train components, transmission components, steering systems, turbocharger components
• Aerospace: Engine and turbine components, bearings, landing gear, hydraulic control valves
• Medical Devices: Surgical tools, knee prostheses, hip prostheses, dental equipment, surgical instrument motors
• Energy Industry: Rotor shafts, transmission components, compressor components

Machine manufacturing: Spindles, bearings, workholding, toolholding, pumps, motor shafts

The most obvious differences between cylindrical grinding and surface and profile grinding are in the part and workholding. Parts for cylindrical grinding applications have a central axis of rotation, and both the grinding wheel and parts are rotating during the grinding process. They are typically held between centers or on one end in a collet or chuck. 

Surface and profile grinding applications use a rotating grinding wheel to produce a precision flat, feature, or form into a non-rotating part. The parts are typically stationary during the grinding process, held in place by a magnetic chuck (for ferrous workpieces), vacuum chuck, rotary table or other workholding device. 

For more information on surface and profile grinding, please visit that section of our website. 

Cylindrical grinding is able to achieve impressive precision, with sub-micron tolerances possible under the right circumstances. But what tolerances are possible depend widely on the part, application and setup. For example, it is easier to maintain tighter diameter tolerances on a smaller diameter part compared to a large diameter part. 

Typical OD grinding tolerance ranges are:

• Diameter tolerances: from less than ±1µm to ±10µm (±0.00004” to ±0.00039”), depending on part diameter
• Roundness tolerances: from 0.25µm to 2.5µm (±0.00001” to ±0.0001”), depending on part diameter
• Finishes: from 0.10µm to 80µm (4 µin to 30 µin) 

Typical ID grinding tolerances ranges are:

• Diameter tolerances:  from 0.10µm to 80µm  (±0.00004” to ±0.00039”), depending on the diameter of the feature
• Roundness tolerances: from 0.25µm to 2.5µm (±0.00001” to ±0.0001”), depending on the diameter of the feature
• Finishes: from from 0.10µm to 80µm (4 µin to 30 µin)

At UNITED GRINDING North America, our applications engineering team works with customers to determine how best to achieve the tolerances that their individual parts require. 

Yes, a cylindrical grinding machine can grind non-cylindrical workpieces. On parts that have a central axis of rotation, an external cylindrical grinding machine can be used to create non-cylindrical shapes such as ellipses, cams and crankshafts. 

Additionally, certain cylindrical grinding machines can be used for form grinding to create shapes and features. This is useful for grinding polygons and flats onto otherwise cylindrical parts.

A universal cylindrical grinding machine is more versatile than a traditional cylindrical grinding machine. They feature multiple adjustable wheel heads, which offers increased flexibility over traditional machines with fixed wheel heads. 

Can ID grinding and OD grinding be completed in the same setup?

Yes, ID grinding and OD grinding are possible in a single setup, as long as you have a properly equipped machine. For example, STUDER ID/OD grinding machines from UNITED GRINDING hold up to four wheels with various combinations of ID and OD spindles, allowing for complex applications in one setup. 

There are many benefits to combining external and internal grinding operations in one machine. By eliminating multiple setups, the handling of parts during production is reduced, leading to improved part quality, reduced production time and lower overall costs.

Many job shops purchase a cylindrical grinding machine to increase their range of in-house capabilities. A cylindrical grinder allows manufacturers to achieve tight tolerances and precision surface finishes that are not typically possible through standard turning centers or lathes. Additionally, a high-end cylindrical grinding machine on a job shop’s equipment list can be a strong point of difference for customers looking for a new provider. 

For job shops that have outsourced grinding operations in the past, purchasing a cylindrical grinding machine allows them the opportunity to bring that critical process in-house. In addition to improved control over the final product, this gives them shorter lead times and increased profitability.