Most conversations about centreless grinding tooling begin and end with workblades and grinding wheels. These are the visible, high-wear components that come up when quality problems arise or maintenance schedules are reviewed. Formers, cams and cam followers rarely get the same attention — yet in the machines where they are fitted, they are just as critical to part quality and process consistency.

Understanding what these components do, how wear affects their performance, and when to act on them can make the difference between a grinding process that runs reliably and one that produces intermittent, hard-to-diagnose defects.

The Role of Formers and Cams in Centreless Grinding

In standard centreless grinding of plain cylindrical parts, workblades and wheels do most of the work. But where components have non-cylindrical profiles — tapers, radii, stepped diameters or other geometric features — the machine needs additional mechanical control over part movement during the grinding cycle. This is where formers and cams come in.

A former is a profiled tool that guides the movement of either the workpiece or a grinding wheel, ensuring that the ground surface follows a precise predetermined shape throughout the cycle. In plunge or in-feed operations, the former effectively programs the shape that the grinding wheel produces by controlling the path of infeed movement.

A cam is a rotating or sliding mechanical element that converts rotational movement into a controlled linear or oscillating motion. In centreless grinding machines, cams work in conjunction with cam followers to govern the feed rate, dwell periods and retract motion during the grinding cycle. The accuracy and surface condition of the cam directly determines whether these movements happen consistently from one cycle to the next.

Cam followers — the components that ride against the cam surface — are subject to continuous contact stress. Over time, their surfaces wear, and as they do, the precision of the motion they transmit degrades.

How Wear Affects Process Quality

The effects of worn formers, cams and cam followers are not always immediately obvious. Because these components degrade gradually, the process tends to drift rather than fail suddenly. This makes it easy to attribute the symptoms to other causes.

Common indicators that former and cam wear may be contributing to quality problems include:

• Profile inconsistency - Parts that were previously ground to a correct taper or radius begin to show variation in profile geometry across a batch. The profile is still approximately correct but no longer within tolerance.
• Cycle time drift - The grinding cycle begins to take slightly longer or shorter than programmed, or dwell periods become inconsistent. This can affect stock removal and surface finish.
• Size variation at specific points in the cycle - Parts show dimensional errors that correspond to particular phases of the machine cycle, suggesting that a cam-controlled movement is no longer executing correctly.
• Chatter or vibration during plunge grinding - If a cam follower is worn or damaged, the motion it transmits to the grinding slide can become uneven, introducing vibration at the workpiece-wheel interface.
• Increased machine noise during the cycle - Worn cam followers or damaged cam surfaces generate noise as they work, which is often an early warning sign before dimensional problems become apparent.

Why These Components Are Often Left Too Long

Unlike a grinding wheel that visibly wears down or a workblade whose edge condition can be inspected and measured, formers and cams are usually enclosed within the machine and not routinely examined during production. They tend to be inspected only when a problem has already developed — by which point a significant volume of out-of-tolerance or borderline parts may already have been produced.

There is also a tendency to assume that because a former or cam was correct when the machine was last set up, it is still correct now. In practice, the cumulative effect of continuous cycling under load means that wear is inevitable, and the inspection interval should reflect the demands of the process rather than being indefinite.

Building former and cam condition checks into routine machine servicing — rather than treating them as emergency items — is a straightforward way to reduce the risk of unplanned quality failures.

Design, Manufacture and Reverse Engineering

One practical challenge with formers and cams is that they are machine- and application-specific. Unlike grinding wheels or standard workblades, they are not catalogue items. When a replacement is needed, the options are to source an original from the machine manufacturer — where that is still possible — or to have the component manufactured to the correct specification.

Workblades & Formers Ltd designs and manufactures formers, cams and cam followers in-house, both to customer-supplied drawings and by reverse engineering from worn parts. Where a component is worn but still retains enough geometry to be measured and referenced, this is often the most practical route — particularly for older machines where original drawings or spare parts are no longer available from the OEM.

The reverse engineering process involves precise measurement of the worn component, interpretation of the original intended geometry (accounting for material lost to wear), and manufacture of a replacement to restore correct machine function. This approach keeps older centreless grinding machines productive without the need for major capital investment in replacement equipment.

Regrinding and Refurbishment

Not every worn former or cam needs to be replaced outright. Where wear is limited to the working surface and the underlying geometry of the component is intact, regrinding can restore the surface to a condition close to new. This is generally a faster and more cost-effective route than full replacement manufacture, and it produces a component that will perform correctly for a further service period.

The decision between regrinding and replacement depends on the extent of wear, the condition of the base material, and whether the component geometry can be fully restored. Our technical team can assess worn parts and advise on the most appropriate route.

Getting the Right Support

Formers, cams and cam followers are not high-visibility components, but their condition has a direct bearing on the accuracy and repeatability of any centreless grinding process where profile control is required. Treating them as low-priority items until a problem develops is a false economy.

If you are running centreless grinding machines with cam-driven cycles, or grinding non-cylindrical profiles using formers, and have not recently reviewed the condition of these components, it is worth doing so — ideally as part of a planned service rather than in response to a quality problem.

To discuss former and cam manufacture, regrinding or inspection support, contact the team at Workblades & Formers Ltd. We support a wide range of centreless grinding machine brands and can advise on the right approach for your specific machine and application.