Surface Grinding Machines

Grinding machines come into their own once cutting is complete. By removing tiny particles from a workpiece surface, they serve several key purposes in metalworking:

• Surface planing and finishing

• Achieving precise dimensions

• Preparing workpieces for further processing

Surface Planing

In the metalworking industry, dimensions must be accurate to within a thousandth of a millimetre. Even a surface that feels smooth to the touch may be far too rough for its intended application. Milling machines and lathes can deliver outstanding dimensional accuracy, but the final finish can only be achieved with the right grinding machine.

This is especially true for surfaces subject to tight tolerances – such as piston tracks in combustion engine cylinders. These must guide piston rings precisely and reliably across a wide range of temperatures and speeds without jamming, a level of accuracy that only a metal grinder can consistently deliver.

Achieving the Right Dimensions

Grinding machines rely not on cutting tools but on abrasive media. These include abrasive papers and textiles, as well as grinding stones made from pressed and fired materials – most commonly quartz sand. The finer the abrasive medium, the less material is removed per grinding cycle, allowing for highly controlled stock removal.

Where solid abrasive media cannot achieve the required finish, fluid abrasive agents offer an effective alternative. Wet polishing machines and lapping machines are designed specifically for this type of precision abrasion.

Preparation for Further Processing

Polishing and lapping processes are used to achieve the highest levels of dimensional accuracy and a consistently smooth surface finish – a prerequisite for processes such as galvanising. A component can only be galvanised or chrome-plated if it has first been polished to a high sheen.

A smooth surface is equally essential for painting systems and powder-coating applications, making grinding machines a valuable step in many finishing workflows.

Understanding grinding machine design begins with a fundamental distinction: unlike cutting machines such as lathes or mills, grinders are built around a relatively straightforward mechanical principle. Every grinding machine comprises a work table, a guide for the abrasive media carrier, and a drive unit.

The most widespread configurations use round or belt-shaped abrasive media carriers, alongside roll-based designs.

Round abrasive media carriers are found in eccentric and plate grinders. The circular grinding surface moves either radially or eccentrically – radial grinders in particular are simple in construction and cost-effective to acquire.

Belt grinders tension an abrasive belt between a drive roller and one or two tensioning rollers. This design excels at removing outer material layers consistently and evenly. Because each work cycle removes a defined quantity of material, dimensional accuracy is straightforward to maintain by distributing the abrasion across multiple passes at varying grinding heights. The uncomplicated mechanics also make belt grinders easy to service and maintain.

Roll or cylindrical grinders use cylindrical abrasive media and are suited to grinding interior radii as well as flat surfaces.

Any metal grinding machine must incorporate cooling lubrication and effective extraction. Particles removed from the workpiece need to be cleared away promptly, as fine metallic dust accelerates wear on machine components. This is especially true of iron-containing dust, which expands in volume as it oxidises and can cause progressive damage if left unmanaged.

There are many types of industrial grinders and CNC grinders available to metalworking operations of all sizes. Below is an overview of the most widely used metal grinding machines, along with their applications and leading manufacturers.

Bore Grinding Machines

Bore grinding machines are used to create precise holes in metal, stone and wood. While budget models exist for private use, professional-grade machines for industrial applications are manufactured by FARMAN, FROEHLICH, KLINGEL, SCHANBACHER and SCHLUMBERGER.

Surface Grinders

Surface grinders are used wherever an extremely flat finish is required. A grinding disc is guided consistently across the workpiece to achieve the necessary dimensional accuracy – making these machines essential in tool-building and mould construction. Leading manufacturers include ABA, BLOHM, ELB-SCHLIFF, JUNG and KUGELMÜLLER.

Guideway Grinding Machines

Guideway grinding machines are designed to grind the guideways used in large cutting machine manufacture. Today's models can achieve tolerances of 1/1000 of a millimetre across seven metres of length – a level of precision that mechanical guideways demand. These machines primarily operate using grinding stones, with abrasion factored into the pressing force to ensure consistent results. Well-known manufacturers include MEUSER MOL, SHW, SCHMALTZ, WALDRICH-COBURG and KRAFT.

Double-Disc Grinding Machines

Double-disc grinding machines deliver high efficiency by processing both the front and back of a workpiece simultaneously within a single work cycle. Popular manufacturers include DISKUS, GIUSTINA, KOYO, BESLY, C+B MACHINERY and JUNKER.

Internal Grinding Machines

Internal cylindrical grinding machines are used to produce consistent and accurate internal radii using roll-shaped grinding bodies. Modern machines feature computerised numerical control (CNC), enabling them to hold the strictest of tolerances. Manufacturers include DANOBAT, HANKOOK, TRIPET, JUNG and VOUMARD.

Jig Grinders

Jig grinders feature CNC controls and a very small grinding body, allowing precise material removal at specific points on a workpiece – a design that closely resembles that of a CNC mill. Among the most complex and high-value grinding machines available, jig grinders are produced by HAUSER, DECKEL, MOORE, MIKROMAT and KELLENBERGER.

Knife Grinding Machines

Knife grinding machines are used to sharpen blades, knives and scissors, as well as to grind chisels. Manufacturers in this category include BERNADO, KNECHT, GOWEIL, TORMEK and SCHEPPACH.

Cylindrical Grinders & Centreless Grinding Machines

Cylindrical grinders are used to grind profiles, pipes and round steels. Tensioning variants use centre tips similar to lathe tailstocks, while centreless grinding machines can process profiles continuously without any clamping. Major manufacturers include STUDER, OMICRON, KARSTENS, SCHAUDT and HERMINGHAUSEN.

Bench Grinders

Bench grinders are standard workshop tools used to sharpen, grind, plane or deburr a workpiece by hand. They consist of a motor fitted with one or two grinding discs and are available in single- and double-sided variants. High-quality bench grinders are produced by ELEKTRA BECKUM, MAKITA, GREIF and REMA.

Stylus Grinding Machines

Stylus grinding machines are used to grind marking tools such as styli, though their primary application is sharpening milling heads – a function that places them close in design to bore grinding machines. Popular manufacturers include BERNARDO, DECKEL, HASBERG, KUHLMANN, PARPAS and SCRIPTA.

Crock Grinding Machines

A crock grinding machine takes its name from its pot-shaped guide, in which the grinding disc is mounted. The drive, guiding mechanism and grinding head are all attached to a pivoting arm. Operated by hand, crock grinders are well suited to grinding and resizing small workpieces. Manufacturers include DELTA, EDEL, KUGELMÜLLER, UNICUM and NYBERG.

Roll Grinding Machines

Roll grinding machines are designed to grind press rollers – whether new, used or freshly turned – to precise dimensional tolerances. They are the only means by which precision rollers can be produced to the required specification. These machines are manufactured by HARKOV, HERKULES, KELLENBERGER, SCHAUDT, WALDRICH and ZIMMERMANN.

Tool-Grinding Machines

Tool-grinding machines are the forerunners of the modern jig grinder and are used to manufacture and repair crimping and casting tools. The most recognised manufacturers in this category include AGATHON, CLARKSON, DECKEL, EWAG, HAHN & KOLB, TRUMPF and WALTER.

Choosing the right used grinding machine can be challenging given the wide variety available, but a few key considerations will help any prospective buyer make a confident decision. The first question to ask is what applications the machine needs to perform – a simple bench grinder is incomparable in scope and complexity to a precision jig grinder.

Cleanliness and condition

A good starting point is the general condition and cleanliness of the machine. Even with comprehensive rinsing and extraction units, grinding machines require significant upkeep – daily, thorough cleaning is essential for any frequently used grinder. If a second-hand machine appears visibly soiled on first inspection, this warrants a much closer look at every aspect of its condition.

Unless purchased from a reputable used machinery dealer who has already carried out maintenance and repairs, it will likely be necessary to fully dismantle and clean the equipment. If those responsible for the work lack the relevant qualifications, commissioning a specialist service provider is strongly advisable.

Weak point: bearings

The bearings are the most vulnerable component in any used grinding machine. High spindle speeds, continual one-sided impact, and grinding heads that frequently lose their shape all place considerable strain on the bearings. A thorough inspection is essential, and even the slightest rattling should be treated as a signal to replace them. Once fitted with new bearings, a used metal grinder can continue operating reliably for thousands of hours.

When evaluating a second-hand grinding machine, also consider the availability of spare parts, the machine's service history, and whether the manufacturer still provides technical support – all factors that significantly affect the long-term value of your investment.