To optimise machining processes, we provide free advice not only about grinding wheel specifications but also machine use parameters and all other aspects which combined with a good abrasive grinding wheel determine the result of grinding.
We continually aim to improve the performance of our grinding wheels by seeking new specifications, which are achieved by working together with suppliers and machine manufacturers.
By drawing on our database and experience, we can recommend the grinding wheel most suited to your needs.
Below you will find some of our recommendations. If you require any further information, please contact our technicians directly.
We can diamond dress a grinding wheel to restore it to its original profile or enhance its grinding capacity.
The shaft of the tool must be firmly locked in place and protrude as little as possible from its support, and never by more than double its diameter.
Single-diamond tools must not be used if the dressing face exceeds 1 mm2. The tool must be at a 10-15° angle and rotated frequently to prevent the formation of flat faces.
Plenty of coolant must be used and directed at the area of contact between grinding wheel and diamond. Dry dressing should be avoided, as it generates temperatures of up to 1200°C, causing damage to both the diamond and the grinding wheel.
There are no set parameters for dressing, as they depend on the grade of finish, type of diamond and machining process. However, by varying them we can change the behaviour of the grinding wheel.
For rough dressing or improved cutting, we can increase the speed of movement of the diamond over the grinding wheel (up to 500-800 mm per minute) and the depth of cut per pass. This creates a sort of threaded effect on the surface of the grinding wheel and spaces out the grains in contact with the piece, thus aiding the cutting action.
During finishing, the diamond must be moved more slowly (100-300 mm per minute), yet within certain limits to prevent problems of grinding burn or poor grinding on the workpiece. These variations in behaviour are more evident with single-diamond, chisel-type or wheel-based tools. Pad-based dressing tools are sometimes unable to produce the desired changes.
Sometimes just a few basic precautions are all that is needed to prevent unnecessary risks.
Here we list the main safety rules. For more detailed information, please consult the FEPA safety code available at https://abrasivessafety.com/en-us/.
DELIVERY, STORAGE AND HANDLING
On taking delivery of the grinding wheels, check with the transporter that the packaging and grinding wheels are intact. Never fit damaged wheels. Grinding wheels are fragile: they must never be dropped, knocked or rolled on the floor. Store them in a dry place at a constant temperature and keep them from freezing conditions. Never use them beyond their expiry date, where indicated.
SWITCHING OFF THE MACHINE
Before switching off the machine, cut off the flow of coolant and allow the grinding wheel to spin freely for a few minutes in order to expel the liquid it contains. Let the grinding wheel stop on its own, without applying pressure to its surface. When switching off the machine, make sure that the grinding wheel has completely stopped turning before leaving it unattended
SAFETY DURING MACHINING
Parameters of use and dressing change the behaviour of grinding wheels. By changing them, we can use the same grinding wheel for various machining processes or improve its performance.
These variables include:
The more rigid the machine, the more the grinding wheel loses its grains. In such cases, harder grinding wheels should be used than those fitted on less rigid machines or with play in the spindle.
GRINDING WHEEL/WORKPIECE SURFACE CONTACT AREA
If the workpiece surface is small, the grinding wheel cuts and does not become clogged. If we want the grinding wheel to cut more, we can make it smaller, for example by reducing the thickness of the cylindrical or surface grinding wheel. In grinding with vertical-axis wheels, we can round off the edge of cup grinding wheels or reduce the number of abrasive segments fitted to the machine.
PERIPHERAL GRINDING WHEEL SPEED
As a rule, the optimum speed of use is slightly lower than or the same as the speed indicated on the grinding wheel.
Decreasing the peripheral speed diminishes the hardness of the grinding wheel and improves its grinding capacity, at the expense of finish. Roughly, every 5-8 metres of speed reduction per second decreases the grinding wheel’s hardness by one grade. However, it is better not to reduce the speed too much, as a grinding wheel rotating too slowly loses its abrasive grains before they can work.
If, on the other hand, we want the grinding wheel to keep its profile or provide a better finish, we increase its speed without exceeding the maximum speed indicated, as it could explode.
PERIPHERAL WORKPIECE SPEED
If we decrease the speed of the workpiece, the wheel grinds better, as each of its grains has to remove a greater quantity of material and is therefore subjected to greater pressure. This is not a fixed rule, however; for medium-to-hard grinding wheels the greater pressure to which the grinding wheel is subjected cancels out the advantages of this expedient.
As a rule, the speed of the workpiece can range between 10 and 20 metres per minute. In surface grinding this corresponds to the bench speed.
The feed rate can vary between one third and one quarter of the grinding wheel thickness for each turn of the workpiece, or for surface grinding for each sideways movement of the bench. Increasing the feed rate means that the grinding wheel cuts better, although increasing it too much means that the grinding wheel tends to burn and to lose grinding capacity as its grains do not have the time to work as they should.
DEPTH OF CUT PER PASS
The depth of cut per pass depends on the grade of finish desired and the grain size of the grinding wheel; in other words, there are no fixed parameters. Increasing the depth of cut increases the force on the abrasive grains and the grinding wheel tends to lose its grains, improving its grinding capacity.
The speed of the workpiece, the feed rate and the depth of cut per pass must be correlated and balanced against each other depending on the machining process and the desired results.