Metalworking grinding machines
- Levelling and adjusting with metal grinders
- Surface planing
- Achieving the right dimensions
- Preparation for onward processing
- Grinding machine design
- Types of grinder machines
- Bore grinding machines
- Surface grinders
- Guideway grinding machines
- Double-disc grinding machines
- Internal grinding machines
- Jig grinders
- Knife grinding machines
- Cylindrical grinders & centreless grinding machines
- Bench grinders (one- and two-sided)
- Stylus grinding machines
- Crock grinding machines
- Roll grinding machines
- Tool grinding machines
- What do I need to know when buying a used grinding machine?
Grinding machines take over once the job of the cutting machine is complete. They remove tiny particles from the surface and can be used to achieve various objectives:
- Surface planing
- Achieving the right dimensions
- Preparation for onward processing
In the metalworking industry, dimensions need to be precise down to a thousandth of a millimetre. Even a surface that feels smooth to the touch may be far too rough for the intended application. Milling machines and lathes, for instance, can produce outstanding dimensional accuracy, but the ‘final touch’ can only be applied using an appropriate grinding machine.
This particularly applies to surfaces subject to narrow tolerances: piston tracks in combustion engine cylinders, for example. They need to precisely and securely guide the piston rings within a wide temperature and speed range without jamming, which can only be ensured through use of a metal grinder.
Achieving the right dimensions
Grinding machines work without tools: all they need is the corresponding abrasive medium, such as types of paper and textiles with an abrasive surface. Grinding stones are also used and consist of a pressed and fired abrasive medium – mostly quartz sand. The finer the abrasive medium, the less surface that will be removed per grinding cycle.
And if solid abrasive media are insufficient to achieve the desired dimensions, fluid abrasive agents are another alternative. Wet polishing machines and lapping machines facilitate this type of abrasion.
Preparation for onward processing
Polishing and lapping processes are used for achieving the best dimensional accuracy and a consistently smooth surface, which is ideal for galvanising applications, for example. A product can only be galvanised or chrome-plated if it has been polished to a very high sheen.
A smooth surface is also essential when using painting systems or powder-coating machines and grinding machines may be used for this purpose as well.
Grinding machine design
In contrast to cutting machines, such as lathes or mills, grinding machines are designed in a very simple way. They comprise:
- a work table
- a guide for the grinding media carrier
- a drive
The most widespread are round- and belt-shaped grinding media carriers, as well as roll-based grinding machines.
Round grinding media carriers are used in eccentric and plate grinders. They consist of a circular surface and the media are either moved radially or eccentrically. Radial grinding machines are designed very simply and are affordable.
Grinders with a belt-type abrasive medium carrier are called belt grinding machines. These types of grinder involve a grinding belt being tensioned between a drive roller and one or two tensioning rollers. They are used to remove outer layers from materials consistently and smoothly. Belt grinding machines remove a pre-defined quantity of material per work cycle, which makes it easy to maintain dimensional accuracy by spreading the abrasion process across different work cycles with varying grinding heights. Belt grinding machines are also designed to be simple and are thus easy to maintain.
Roll- or cylindrical grinding machines work using cylindrical abrasive media and are used to grind interior radii as well as surfaces.
A metal grinder always consists of cooling lubrication and powerful extraction. The particles removed from the workpiece need to be transported away as quickly as possible since fine metallic dust can quickly lead to heavy wear and tear. This particularly applies to iron-containing dusts, which increase in volume as they corrode and lead to further damage.
Types of grinder machines
There are many types of industrial grinders and CNC grinders available to metalworking operations of all sizes. See below for a selection of the most widely used types of metal grinding machines.
Bore grinding machines
Bore grinding machines are used to bore holes in metal, stone and wood. This type of machine is also offered by budget manufacturers and is designed for private use.
Professional bore grinding machines for industrial use are manufactured by FARMAN, FROEHLICH, KLINGEL, SCHANBACHER and SCHLUMBERGER.
Surface grinders are used when an extremely flat surface is needed. They work using a grinding disc that is consistently guided across a workpiece. These machines are key to the tool-building and mould construction industries and can be relied on to achieve the required dimensional accuracy.
Surface grinders are manufactured by ABA, BLOHM , ELB-SCHLIFF, JUNG and KUGELMÜLLER.
Guideway grinding machines
Guideway grinding machines, as the name suggests, are used to grind guideways and are deployed wherever very large cutting machines are being manufactured. Mechanical guideways need to be very precise and the guideway grinders on offer today can achieve tolerances of 1/1000 of a millimetre across seven metres of length.
Guideway grinding machines primarily operate using grinding stones. The abrasion caused by the stone is factored into the pressing force to ensure the results achieved are consistent.
Well-known manufacturers of guideway grinding machines include MEUSER MOL, SHW, SCHMALTZ, WALDRICH-COBURG and KRAFT.
Double-disc grinding machines
Double-disc grinding machines are highly efficient pieces of kit. They enable workpiece processing to be performed simultaneously on the front and back side per work cycle.
Popular manufacturers of double-disc grinding machines include: DISKUS, GIUSTINA, KOYO, BESLY, C+B MACHINERY and JUNKER.
Internal grinding machines
Internal (cylindrical) grinding machines are used to create consistent and accurate internal radii. They work using roll-shaped grinding bodies. The internal grinding machines available today feature computerised numerical control (CNC) and can thus achieve the strictest of tolerances.
Manufacturers of internal grinding machines include: DANOBAT, HANKOOK, TRIPET, JUNG and VOUMARD.
Jig grinders feature CN controls and a very small grinding body. They are used to grind away at specific points on a workpiece as required by the respective production process. As such, jig grinders feature a very similar design to CNC mills.
Jig grinders are some of the most expensive and complex grinding machines available and are produced by HAUSER, DECKEL, MOORE, MIKROMAT und KELLENBERGER.
Knife grinding machines
Knife grinding machines are used to sharpen blades, knives and scissors, as well as to grind chisels.
Knife grinding machines are made by BERNADO, KNECHT, GOWEIL, TORMEK and SCHEPPACH.
Cylindrical grinders & centreless grinding machines
Cylindrical grinders serve to grind profiles, pipes and round steels in a cylindrical manner. Tensioning cylindrical grinding machines use centre tips similar to the tail stocks of lathes. Centreless grinding machines, by contrast, can be used to indefinitely process profiles without any clamping process being required.
Major manufacturers of cylindrical grinders include STUDER, OMICRON, KARSTENS, SCHAUDT and HERMINGHAUSEN.
Bench grinders (one- and two-sided)
Bench grinders are standard grinding tools that are found in every workshop. A bench grinder can be used to sharpen, grind, plane, or deburr a workpiece by hand. They consist of a motor to which one or two grinding discs are attached. They are produced in single- and double-sided variants.
The best quality bench grinders can be acquired from ELEKTRA BECKUM, MAKITA, GREIF and REMA.
Stylus grinding machines
Stylus grinding machines are used to grind marking tools, such as styli. Their primary application, however, is to sharpen milling heads, which makes them very similar to bore grinding machines.
Popular manufacturers of stylus grinding machines include BERNARDO, DECKEL, HASBERG, KUHLMANN, PARPAS and SCRIPTA.
Crock grinding machines
A crock grinding machine
is a device used to grind pots, or ‘crocks’ in the US vernacular. Its name comes from the way the tool is guided: the grinding disc is mounted in a pot-shaped guide. The drive, guiding mechanism and grinding head are attached to a pivoting arm. Crock grinding machines are ideal for grinding and changing dimensions on small workpieces and are operated by hand.
Manufacturers of crock grinding machines include: DELTA, EDEL, KUGELMÜLLER, UNICUM and NYBERG.
Roll grinding machines
A Roll grinding machines serve to precisely grind press rollers to the desired dimensions. They can be used to grind new, used and freshly turned rollers to achieve the required tolerance. Precision rollers can only be created using a roll grinding machine.
These machines are produced by HARKOV, HERKULES, KELLENBERGER, SCHAUDT, WALDRICH and ZIMMERMANN.
Tool-grinding machines are the predecessors of the jig grinder. They are used to manufacture and repair crimping tools and casting tools.
The most well-known manufacturers of this machine are: AGATHON, CLARKSON, DECKEL, EWAG, HAHN & KOLB, TRUMPF and WALTER.
What do I need to know when buying a used grinding machine?
The wide variety of grinders for sale does not make it easy to choose the right device, but there are some general tips that any prospective buyer of a second-hand grinding machine should know. The first consideration is what applications the (used) device should perform – a simple bench grinder is incomparable to a complex jig grinder.
Cleanliness and condition
A good starting point is to look at the general condition and cleanliness of the machine. Even with comprehensive rinsing and extraction units, grinding machines require a great deal of cleaning – daily, thorough cleaning is essential for any frequently used grinder. If the first thing you notice about a second-hand grinding machine is that it is soiled, you should definitely take a very close look at the machine from all aspects.
Unless you buy a metal grinding machine from a trader in used machinery who has taken care of the maintenance and repair tasks, it will be necessary to completely dismantle and clean the equipment. If those intending to repair/maintain a used metal-grinding machine are lacking in qualifications to do so, a specialist service provider should be commissioned.
The weakest points in all used grinding machines are the bearings: the high speed experienced by the grinding spindles, the continual one-sided impact, and grinding heads that frequently lose their shape have a major effect on the bearings. It is therefore important that the bearings are inspected and, if there is the slightest amount of rattling, replaced. Once equipped with new bearings, a used metal grinder can continue operating for thousands of hours to come.
Those looking to buy a used grinding machine will find everything they need at Surplex. We regularly have second-hand grinders for sale. You can purchase machines via our portal where you will regularly find online auctions featuring a wide range of grinding machine types for a variety of needs and at attractive prices. The metal grinders for sale are generally in a good to very good condition.