Innovative Grinding Technology

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

KREBS Quasar facts:

  • New low-fire V88 bond system
  • New abrasive grain with great cutting performance
  • Customisable microstructure composition

KREBS Quasar application:

  • Gear grinding
  • Deep and profile grinding

KREBS - Quasar (V88)

Your benefits at a glance:

  • High removal rate
  • Low cutting forces
  • Very good profile retention
  • Less wear to dressing tool
  • High service life

Grinding wheels in resinoid bond

Resinoid bond (B/BF)

The resinoid bond is a bond type well tailored to the grinding task. In resinoid bonds, resins are used as binders, into which fillers are mixed in addition to the abrasive grains. Resinoid-bonded grinding wheels are characterised by having a good cutting performance and cool grinding. Compared with vitrified bonds, resinoid bonds are known as soft, fast and cool grinding bonds. They have a very wide range of applications.

Depending upon the application, the bonds can be used for either dry or wet grinding. Based on the production methods and the low curing temperatures, grinding tools with resinoid bond are usually the least expensive among the different bond systems. Due to the low curing temperature, they can easily be used for all types of abrasives.


  • Diameter 50 mm to 900 mm
  • Granular size from F12 to F400
  • Optimal process adjustment through:
  • Customised grain types and combinations 2. Modern synthetic resins 3. Optimised filler selection

Extensive product range

We provide a wide range of cutting and rough grinding wheels, ranging from a thin cutting discs to a foundry cutting discs. We produce rough grinding wheels in diameters from 50 mm up to 900 mm.This page shows you a selection of our product range:

Cut-off wheels up to 80 m/s

The cut-off wheels are special thin discs in resinoid bond without additional reinforcement for the cutting of all types of steel and cast iron as well as non-ferrous metals.

  • Diameter from 50 mm to 600 mm
  • Width from 0.5 mm
  • Narrow width tolerances possible
  • Available in all current drill holes
  • For dry and wet grinding

Cutting discs without reinforcement are used

  • For cutting and tool grinding
  • For cutting of low-tolerance grooves
  • For the tool industry and suppliers of semi-finished goods
  • For cutting (to length) linear guides (manufacturers and distributors)

Cut-off wheels with fabric reinforcement up to 100 m/s for use on stationary cut-off machines.

Cut-off wheels with fibre glass reinforcement can be used on stationary machines with operating speeds up to 100 m/s.

The fabric reinforcement makes these discs more durable and the risk of breaking is significantly reduced.

  • For fast cutting procedure (about 4 cm²/s)
  • For materials and tools that can not be sawn
  • For castings
  • For tempered parts
  • For geometry-related components
  • Diameter from 50 mm to 600 mm

Cut-off wheels with fabric reinforcement are used

• For stationary machines
- Feeding by hand
- Pneumatic feeding
- Hydraulic feeding

• On swing frame cut-off machines
- Attached to crane
- On boom mechanically guided by hand

• In foundries and contract fettling shops
• In the steel industry
• At suppliers of semi-finished goods

Rough grinding waheels without fabric reinforcement

  • Rough grinding waheels without fabric
  • reinforcement

Rough grinding wheels with fabric reinforcement / compact grinding wheels

  • Diameter from 300 mm to 600 mm
  • Width from 20 mm to 80 mm
  • Operating speeds up to 80 m/s

Rough grinding wheels are used

  • On hand-operated machines straight / two side tapered
  • On floor stand grinders
  • On swing frame grinding machines

Rough grinding wheels are used

  • On hand-operated machines straight / bi-conical
  • On floor stand grinders
  • On swing frame grinding machines

In these grinding wheels, normal aluminium oxide, semi-friable aluminium oxide, and silicon carbide as well as zirconium oxide are used as abrasive grain.

Compact grinding wheels have the following advantages:

  • High cutting capacity per unit of time
  • thus short grinding times
  • cool cutting and energy-saving work:
  • specially for grinding steel ingots, plates, slabs, billets
  • and as well as cleaning of steel and cast iron of all grades.

CBN and diamond tools in vitrified bond

The toughest abrasive in the world

Top high-precision grinding of hard iron and steel alloys or hard and brittle materials, the best removal rates and the longest service life are still provided by the hardest materials in the world: CBN and diamond.

Cubic boron nitride, CBN for short, is particularly suited to difficult to machine or high-alloyed hardened steels with a hardness of 54 HRC or more such as high-speed steel, tool or chrome steel, nickel-based alloys, powder metallurgy steels or white cast iron.


  • Diameter 3 mm to 900 mm
  • Operating speeds up to vc = 160 m/s
  • Granular size from 25 µm to 251 µm
  • Process adjustment through:
    • Various grain types
    • Targeted introduction of porosity
    • Tailored bond systems

Industrial Applications


The grinding of camshafts and crankshafts places very high demands on grinding wheels. Changing operation and movement conditions in the contact zone makes the feeding in of the cooling lubricant very difficult. For the best grinding results, it is necessary to customise the grinding wheel specifications.

Valve train components for valve actuators play a role in engine timing and determine the supply of fresh gas and the removal of old gas. These are generally components for series and mass production.

Injection technology plays a key role in today's engine construction. In recent years, tremendous advances have been made in terms of reduced fuel consumption and emissions reduction. Manufacturing tolerances of injection components must meet the highest standards. We have grinding solutions for the machining of injector needles/bodies and fuel injection pump components.

Engine turbocharging increases the performance of internal combustion engines. The current trend towards 'downsizing' – small engine capacity and few cylinders – makes supercharging by means of a turbocharger an attractive option again. It has long been standard in modern diesel engines, but for some time now the trend in petrol engines is also moving towards the exhaust gas turbocharger. With the MULTO bond systems, we provide you with general purpose solutions.

Gear components

Gear grinding

Gears are amongst 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, provides proven grinding tools for virtually all types of machines.

Bevel gear grinding

The grinding of bevel gears is a special process and takes place mainly with grinding rings on a specially designed grinding machine. For this purpose, we provide well-proven grinding tools for virtually all types of machines.

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.