German Engineering, well known world wide for precision, has its secret in its innovative abrasive and grinding technology.

Krebs & Riedel was founded in 1895 have been manufacturing high quality standard, diamond and CBN abrasives for over 100 years and are able to count leading engineering companies such as Perkins Engines, Grundfos and Delphi Diesel Systems amongst their ever growing customer base. Krebs is constantly introducing new types of wheels with improved grain structures and novel bonding systems that enhance grinding wheel quality and optimise performance.

One area where Krebs & Riedel excels in is the supply of very special wheels for gear and thread grinding applications and special wheels are available to suit machines manufactured by Gleason-Pfauter, Oerlikon, Kapp- Niles, Hofler, Maag, Samputensili and Reishauer etc. Krebs are also a member of the “Gear Research Circle” at Aachen University and are heavily involved in developing advanced wheels for the latest production technologies employed by leaders in the field of gear manufacture. So successful have the Krebs & Riedel gear grinding wheels been they have become the major supplier to leading machine companies such as Kapp. For specially profiled wheels for gear production Krebs keeps customers blank wheels in stock and upon order will profile these to suit and then supply within just 2 days.

Diamond and CBN wheels that have been manufactured by Krebs & Riedel for more than 20 years are available from 3mm to over 900mm in diameter with peripheral grinding speeds of up to 160 m/s.

Another of Krebs & Riedel's specialities is wheels for the grinding of Camshafts and Crankshafts. Krebs have developed very special tri-zone large diameter CBN wheels that generate perfect geometry combined with very fine finishes on Crankshaft journals. These special wheels that are the result of long-term wheel development projects with major machine tool manufacturers such as Junker employ 3 different CBN grades on the same wheel without glue and avoid the problems of burning on the surfaces of Crankshafts that can sometimes occur when grinding at very high speeds.

Abrasive type

• Commonly found in nature are emery, corundum (alumina), quartz, garnet and diamond
• Abrasives that have been made
• synthetically:
• Aluminumoxide
• Seeded gel
• Silicon carbide
• Cubic boron nitride (CBN)
• Diamond

Manufacturing Program

Aluminium Oxide and silicon carbide wheels in vitrified and resin bond for most industrial applications:

Abrasive cut-off wheels with resin bond with or without fibre-glass reinforcement: outer diameters upto 600 mm:

Outer diameter upto 900 mms:

• Cylindrical grinding
• Surface grinding
• Tool grinding
• Centreless grinding
• Gear grinding
• Rough grinding
• Straight cutting
• Swing frame cutting
• Rotary cutting

Wheels for fettling and snagging, with or without fibreglass reinforcement, for use in contract fettling shops and foundries:

Vitrified diamond and CBN grinding wheels for peripheral speeds upto 160 m/s.

Outer diameter upto 900 mms:

• Grinding wheels for swing frame grinders
• Grinding wheels for floor stand grinders
• Grinding wheels for grinding manipulators
• Internal grinding
• Surface grinding
• Cylindrical grinding
• Tool grinding
• Special grinding processes

Grinding process

Grinding is defined as machining with geometrically undefined cutting edges. Advantages of grinding over other machining methods:

• Good machining of tough materials
• High degree of dimensional and geometric accuracy
• Defined surface finish

The below diagram shows the most common industrial grinding processes.

Centerless process

In contrast to external cylindrical grinding between centres, in centerless grinding the work piece rests on a work-rest blade. The work piece is driven and supported by a regulating wheel, which is usually rubber bonded. Centerless grinding is amongst the most complicated and difficult grinding processes.

The extremely precise set-up of the machine and the careful selection of the grinding tool require great knowledge and experience. We provide economical solutions with vitrified and resin-bonded grinding wheels for both plunge and through-feed grinding.

Centerless process

Typical components for internal cylindrical grinding are gearwheels, dies, perforated plates, pump rings, sleeves, etc. The targeted supply of cooling lubricant to the contact zone, especially to small holes, is a great challenge.

The trend in internal grinding is increasingly moving to dressable CBN and diamond grinding wheels.

Surface grinding

In surface grinding, flat, coplanar surfaces with defined surface qualities are created. There are different process variations. These differ in the arrangement of the grinding wheel axis to the work surface (peripheral or cup wheels), and in the feed rates (creep-feed or swing frame grinding).

Typical components are punching and blanking dies, guide tracks on machine beds, various knives, etc. In tool and die making, complex shapes are often created in profile cutting. For the most common machines, stocks a variety of proven grinding wheels.

Gear grinding

Gears are among the most important mechanical elements in the construction of transmissions, vehicles and machinery. The requirements placed on these products in terms of power transmission or running smoothness continue to rise steadily.

Grinding is therefore one of the most important methods for meeting these high demands. For this purpose, our principal provides proven grinding tools for virtually all types of machines.

Non-round grinding

Non-round grinding – for example, of camshafts, pump rings or pressing tools – is one of the most complex grinding applications. The non-round contour leads to changing contact and movement conditions in the contact zone.

The properties of the grinding tool must be appropriately matched to the process. Based on years of experience, can provide highly efficient solutions.

Crankshaft grinding

The grinding of crankshafts places high demands on the tools used. In the grinding of main and pin bearings on crankshafts, the use of dressable CBN grinding wheels has been widely adopted. Different grinding strategies require customised grinding tool specifications.

The machining of the flange and pin is usually performed with an angular infeed grinding process. Conventional grinding wheels in aluminium oxide or vitrified CBN grinding wheels are used. has in recent years established itself globally as an expert partner with innovative solutions for crankshaft machining.

Grinding wheels in vitrified bond

Vitrified bond (V)

Vitrified bond systems have largely prevailed in precision grinding. A major advantage of vitrified bonding is the controllable porosity. The appropriate micro structure is selected depending upon the size of the contact zone between the work piece and the grinding wheel.

Generally speaking, the larger the contact zone, the more open and porous the grinding wheel needs to be. Highly porous grinding wheels are in particularly needed for productive deep and creep-feed grinding processes to transport the cutting fluid directly into the contact zone and to optimally remove the generated grinding chips and heat. A product of this group is for example the successful KREBS MULTO grinding wheels.

• Diameter 30 mm to 900 mm
• Grinding segments
• Granular size from F20 to F400
• Precise finishing using CNC
• technology
• Optimal process adjustment through
• Customised grain types and combinations
• Modern bond systems
• Optimised pore space composition

Multo Series

The innovative bond systems MULTO Green (V86) and MULTO Yellow (V87) complement the already well-proven MULTO Classic (V84) and MULTO Blue (V85) range. Through selective bond modifications, the grinding properties are optimally tailored to the grinding task.

The Multo range features the following properties:

• Low bond content = cool grinding
• Increased porosity at optimal profile retention
• Operating speeds up to vc = 80 m/s
• Very good grain integration
• Increased service life

Multo Classic (V84)

The universal classic!

• Optimum grinding grain combinations for virtually all tasks
• Wide range for microstructure composition – depending on the size of the contact zone
• High cutting performance
• Optimal price performance ratio

Multo Blue (V85)

Sintered aluminium oxide provides for high removal

• rates at stable conditions
• Ceramic abrasive
• Higher stock-removal rate
• Good profile-holding
• More parts between dressing
• Improved life-time

Multo Green (V86)

The right choice for cylindrical grinding

• Very high cutting performance
• Optimal in angular in-feed grinding
• Cool grinding
• High service life

Multo Yellow (V87)

Optimum profile retention with increased porosity without sintered aluminium oxide

• Low wear of dressing tools
• Improved profile retention at increased porosity
• Increased dressing cycles
• Excellent price/performance ratio

Quasar Series

The new generation of innovative grinding wheels by KREBS & RIEDEL provides the end user with an economically appealing solution for precision grinding. A new, free-cutting ceramic grain is used as an abrasive. The excellent cutting performance is achieved through an optimal combination of toughness and break behaviour of the abrasive grains.

The innovative new low-fire V88 bond system is specially tailored to the new abrasive grain and thus ensures optimum bonding of the grain. With the optional addition of structured pore formers, the grinding properties can be customised to the process. The results of this grain-bond pore space optimisation is a very sleek grinding wheel with a higher removal rate, low thermal load

Gear shaft

Gear shafts must meet high demands in terms of roundness and surface finish. Due to its high precision, grinding is still an economical finishing process. The Multo bond systems provide highly efficient grinding tools which can be tailored to your individual requirements

Tool and dye making

Grinding plays a significant role in tool and dye making. Constantly increasing quality demands regarding dimensional and geometrical tolerances and exactly defined surface finishes pose a major challenge.

In recent years, the variety of materials to be machined has also grown

Roller bearings and linear technology

Roller bearings are used for supporting and guiding moving components. This includes mainly axles and shafts. They are used in gearboxes, pumps, pumping elements, motors, etc. Depending on the application, different basic shapes – e.g. ball, barrel and cone bearings – are used. Linear systems are used in many different areas.

The most diverse systems are used in areas ranging from handling technology to heavy machinery.

Tool grinding

We have wide range of grinding wheels for saw sharpening for the woodworking and steel industries. We stock proven grinding wheels in the most common dimensions.

Cutting and rough grinding applications

Cut-off wheels are the most widely used tool for removal of risers and runners. Depending on the application, stationary cut-off machines or swing frame cutters are used. They easily cut sanded or mineralised castings. High-alloy work pieces such as exhaust manifolds and turbine blades can be economically machined with cut-off wheels. For this purpose, we provide powerful cut-off wheels, reinforced with glass fibre offering maximum safety. Depending on the application, we provide straight discs or discs with a depressed centre.

When cutting (to length) linear guides, valves or pipes, for example, high demands are made on the quality of the cut. Neither blue cut nor burr formation should occur.. Such discs can be used on stationary cut-off machines in wet or dry cutting. We provide cut-off wheels with and without fabric reinforcement for these kinds of applications.

Stationary rough grinding wheels are used in foundries on stand grinders, swing frame grinders or manipulators. Stand grinders are used to machine smaller and lighter castings, which are held by hand. Swing frame grinders or manipulators are used for larger and heavier work pieces. Resinoid-bonded rough grinding wheels are distinguished by high safety and durability. We provide rough grinding wheels with and without fabric reinforcement.

Designation system

The grinding wheels are labeled according to ISO 6104 and ISO 525 standards. In addition to the labeling of the grinding wheel (see table below), a certificate (label) is included with each wheel containing the full specifications, dimensions, consignment number, product number and maximum approved operating speed.