Peerless Centerless Grinding Capabilities

Centerless grinding has been part of our core machining capabilities for over 30 years, providing ultra-fine OD surface finishes and ultra-tight OD tolerances for our customers.  We provide production lead times as short as 24 hours for outside diameter centerless grinding, and can supply small volume runs and high volume requirements.

We offer a full complement of grinding services to satisfy the varied needs of our customers:

  • Infeed Grinding

  • Plunge Grinding

  • Profile Grinding

  • Thru Feed Grinding

Peerless Centerless Grinding Capabilities

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We combine flexibility with excellence in precision machining.
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Thru Feed Centerless Grinding

We offer Thru Feed centerless grinding for machined metal parts that require grinding of the major outside diameter. When there are no “centers” on the component, and only the outermost diameter needs to be ground, the parts can be fed down a chute and  between two grinding wheels that spin the part to remove material the surface.

Our Thru Feed centerless grinding services handle part diameters from .065″ (1.65 mm) to 1.5″ (38.1 mm) for a vast range of part lengths and offer maximum efficiency at minimal cost.

  • Part diameters from .065″ (1.65 mm) through 1.5″ (38.1 mm)

  • Part lengths .250” (6mm) to 144” (12’)

  • Maximum efficiency grinding

  • Minimum cost grinding

  • Grinding after heat treating eliminates distortion

Infeed Centerless Grinding

We also provide Infeed centerless grinding for parts with more complex profiles along their lengths. Infeed grinding differs from through-feed grinding because the part is pressed against the grinding wheel rather than being fed axially.

Infeed grinding is typically faster and more economical than multi-step grinding processes for parts with complex profiles, radii, and multiple outside diameters. It is also the best method for maintaining diametric relationships. This type of grinding can also produce more precise flats and slots than conventional milling.

Our In-Feed centerless grinding services handle part outside diameters from .065″ (1.65 mm) to 1.5” (38.1 mm) for a vast range of part lengths and offer maximum efficiency at minimal cost.

  • Part diameters from .065″ (1.65 mm) through 1.5″ (38.1 mm)

  • Parts with multiple outside diameters

  • Best method for maintaining diametric relationships

  • Complex profiles

  • Complex radii

  • Flats and slots ground with more precision than conventional milling

  • Grinding after heat treating eliminates distortion

Centerless Grinders for Making Precision Machined Parts

Providing exceptional finishes and tight OD tolerances often requires centerless grinding after CNC Swiss Turning of precision machined components. We continually invest in our equipment and capabilities to uphold this standard and adapt to meet our customers’ evolving needs.

Centerless Grinding Capabilities

Min Part Diameter 1.65 mm (.065″)
OD Tolerance +/- 2.5 µm (+/- .0001″)
Straightness 25 µm/mm (.0010″)
Concentricity 50 µm/mm (.002″)
Surface Finish .15 µm Ra (6 µ” Ra)


  • CNC Swiss Star Lathes with FANUC Controls, high pressure pumps and 12′ bar feeders

  • Centerless Grinding Equipment, both thru-feed and in-feed (plunge grinding) for precision tolerances and finishes

  • Various secondary operation equipment (Such as tumblers, deburring equipment, slotting)

  • Quality Inspection Equipment

Pioneering Quality Assurance

AS9100D and ISO9001:2015 certification (see our certification here) means we maintain quality standards worthy of the medical and aerospace industry requirements. Our modern non-contact inspection systems and software record detailed inspection results and provides Statistical Process Control (SPC) data for our customers. We use automated inspection equipment to measure both internal and external features, but no part leaves without a visual inspection.

Pioneer Service Inc Quality

Our Centerless Grinding Offerings

To modify the outside diameter (OD) of a precision machined component, there are two types of cylindrical surface grinding operations that can be used: centerless and centered.  Grinding the OD of a CNC Swiss turned component offers several benefits: a smoother surface finish (Ra), a tighter OD tolerance (up to +/.0001”) and elimination of the distortion that can happen during heat treatment.

  1. In Centered grinding, the part is held stationary and the grinding wheel moves up and down the part to remove material. To do this, there are using small indentations on the ends of the part (called centers) to aid the grinding machine in holding the part stationary
  2. In Centerless grinding, the grinding wheel is stationary. The part moves through the machine and past the grinding wheel, which removes the material from the part. This process is used when the part can not have centers added to the ends of the component.

Pioneer Service has in-house capabilities for centerless grinding. In addition, depending on the project requirements, lead time and capacity, we also use several highly qualified outside grinding service providers for components. Outside grinding partners are often used when the component requires the combination of OD and ID (Internal Diameter) grinding.

The work center blade supports the component (workpiece) as it moves through the machine. The grinding wheel, regulating wheel and work center blade are all stationary.  The component (workpiece) moves through the machine at a regulated speed to achieve the specified surface finish and size.

When grinding a component (workpiece) that has centers (see image right), the part is held stationary and the grinding wheel moves along the component to remove material to reach the specified tolerance and surface finish.

What We Offer… that Others Often Don’t

“Thanks you for the very prompt quote. The service you provided is just as your website says.”

Amy – Industrial industry


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