Centerless grinding has become an indispensable part of countless manufacturers’ supply chains, providing precision, consistency, and quick turnarounds. Although the benefits of centerless grinding have been well documented, the process itself often goes undiscussed—but not today. In this blog, we’re putting the spotlight on the process that our team utilizes every day to achieve unmatched precision in ground round bars and blanks.
Types of Centerless Grinding
Centerless grinding is a process in which a work piece is supported by a blade housed between two rotating wheels: a grinding wheel, and a stabilizing wheel. The stabilizing wheel spins slowly to rotate the work piece as it rests on the blade, while the grinding wheel spins quickly to remove excess material. The 3 most popular types of centerless grinding are thru-feed grinding, in-feed grinding, and end-feed grinding.
In-Feed Grinding
In in-feed grinding, the workpiece is simply placed on the blade between the two wheels. The workpiece rotates in place on the blade and is removed once the desired diameter is achieved. It is also sometimes called plunge feeding, because the grinding wheel is plunged toward the workpiece as it rests on the blade and regulating wheel.
Thru-Feed Grinding
In thru-feed grinding, the workpiece is fed into the machine where it is supported by the blade and the regulating wheel. The regulating wheel pushes the workpiece through from one end to the other. This propulsion is achieved by fixing the regulating wheel at an angle to the workpiece. The angle can be adjusted to influence the workpiece’s travel speed.
End-Feed Grinding
In end-feed grinding, the workpiece is fed into the machine just like in thru-feed grinding. Before the piece can fully pass through the machine, it is stopped to create a tapered effect on the workpiece. This method is used for creating components that have multiple diameters. While in-feed and thru-feed grinding can be performed with the same equipment, end-feed grinding requires its own specialized machinery.
Looking for a centerless grinding specialist?
Boston Centerless has 65+ years of experience in in-feed and thru-feed grinding.
Centerless Grinding Process Variables
The centerless grinding process may seem simple at a glance, but there are many factors that go into achieving the right conditions for peak precision. A centerless grinding setup can be quite complex, with many variables which can drastically impact the outcome.
The most significant factors in the process are those which involve the wheels, although each wheel has its own parameters. The regulating wheel dictates the behavior and movement of the workpiece as it is being ground. A more intense angle will push the workpiece through the grinder more quickly, while the rotating speed and pressure determine the final surface finish. The grinding wheel naturally impacts material removal, but it also has an effect on surface finish too. With time and use, the grinding wheel eventually becomes dull and must be dressed to reveal new abrasive particles. Both wheels must also be precisely balanced in order to produce uniform results in both roundness and diameter. Many machines are equipped with coolers and vibration control mechanisms to avoid warping or otherwise damaging the workpiece as it’s being ground.
Challenges & Limitations
Although centerless grinding can achieve astounding results, those don’t simply come at the push of a button. One of the highest barriers to entry in centerless grinding is operator skill. Unlike many other modern manufacturing processes, centerless grinding relies heavily on highly skilled operators to properly set the machine for the type of material and the desired final diameter. That’s why at Boston Centerless, we invest heavily in personnel training for both new and experienced centerless grinding operators.
While centerless grinding may be an ideal solution for certain circumstances, it does have some limitations. Most notably, the process is limited to cylindrical parts of 3” diameter or less. The minimum diameter that can be processed will depend on the material length; 12ft. bars can be as small as 0.04” in diameter, while cut lengths can be as small as 0.005” in diameter.
The Precision Advantage
Now that we’ve gone over how it works, it’s important to understand why the centerless grinding process is preferred when prepping materials for precision manufacturing. Centerless grinding can shape cylindrical parts to near-perfect roundness, with consistent diameter and fine surface finish throughout. Unlike other reductive manufacturing methods, centerless grinding can be used to shape materials with extreme precision, easily meeting tolerances in the microns. These tight tolerances are not just met, but met quickly, making centerless grinding an ideal solution for high-volume or quick turnaround jobs.
For more information on the benefits of centerless grinding as it relates to precision manufacturing, visit these blogs:
- How AccuRod® Improves Manufacturability
- Scaling Precision: Solutions for High-Volume Manufacturing
- Effects of Straightness & Roundness on CNC Precision Machining
- Why Choose Us for Precision Grinding
Where does centerless grinding fit into your supply chain?
Contact Boston Centerless today to find out if our process is right for you.
Centerless Grinding FAQ
Q: What is centerless grinding, and how does it differ from other grinding?
A: Centerless grinding holds the workpiece between a grinding wheel and a regulating wheel, without spindle centers, enabling continuous, high‑precision cylindrical grinding.
Q: Which type of centerless grinding is best for tight tolerances?
A: Thru‑feed grinding is efficient for cylindrical parts, but in‑feed (plunge) or end‑feed methods are better for tighter tolerances or complex geometries.
Q: What tolerances can you achieve with centerless grinding?
A: With optimized setup and process control, centerless grinding can reach tolerances in the micrometer range (e.g., ±0.0001 in or better).
Q: Can centerless grinding handle small blanks?
A: It’s more challenging, but by using in‑feed grinding and precise fixturing, centerless grinding can work on shorter cylindrical blanks.