Tips for Improved Surface Grinding

Tips for Improved Surface Grinding Article Header Image


Arianna Smith, Application Engineer III, Norton | Saint-Gobain Abrasives


grinding Wheel Selection and Parameter Recommendations



urface grinding is a very typical grinding process which is done in many industries, especially general industrial and job shop type locations. While some facilities are set up with optimized machines, coolant, and dressing capabilities for high volume manufacturing, some smaller facilities do not have the same luxury. Many job shops with lower volume parts, and even some larger manufacturers, struggle with older machinery, as well as a lack of coolant and wheel dressing capabilities, which can lead to inefficient grinding processes and poor part quality. This article includes some recommendations for wheel selection and tips for grinding parameters, which may help to improve part quality and take some of the complication out of surface grinding.


choose a more friable abrasive grain


One of the most common mistakes in surface grinding is using a grinding wheel with an abrasive grain that is too durable. If a durable abrasive grain is used, a significant amount of force is required to fracture the grain in order to expose new sharp points and allow for continued cutting. Otherwise, under low pressures, durable grains will not fracture; instead, they become dull and rub against the metal instead of cutting it. This causes friction, and as a result, chatter, burn, or poor surface finish due to heat can occur.


Often times, in surface grinding, the depths of cut are smaller, sometimes under 0.001”, which may not create enough force to efficiently fracture a duller grain. In this scenario, where forces are too low to effectively fracture the grain, dressing is needed to re-sharpen the wheel and sufficient coolant is required to cool down the grind zone. However, if dressing and/or coolant are not available, it is critical to use a grinding wheel with a more friable grain.


A more friable grain fractures with lower forces and lower depths of cut, which are typically found in surface grinding. If heat generation is a large problem in a surface grinding operation, it is important to know if the abrasive is a more durable grain or a friable grain and to change to a wheel with more friability. This will create a cooler cut and allow the grains to fracture and provide more sharp points that cut instead of rub the metal.


opt for an Aluminum Oxide Grinding Wheel


While ceramic grinding wheels are considered superior technology and provide excellent material removal rates, they are not always ideal for surface grinding applications for several reasons.


Ceramic grains can be slightly more durable in general compared to conventional aluminum oxide grains. Even a highly friable ceramic grain will be stronger and harder to fracture than a highly friable aluminum oxide grain. While this is one reason that ceramic is an upgrade (because the stronger ceramic grains allow them to last longer and not break down too quickly), ceramic wheels can actually be too durable for surface grinding applications due to the reasons discussed above.


This does not necessarily apply to all types of surface grinding/materials/parts, but if a grind process using a ceramic wheel is incurring heat, a more friable ceramic grain may be required, or possibly switching to a friable conventional grain altogether may solve the issue.


It is also important for coolant and/or dressing to be used in processes using ceramic wheels to keep the cut cool and to re-sharpen any durable ceramic grains that are dulling. If a process has either or both of these elements, then ceramic may be an option. Otherwise, conventional aluminum oxide abrasives will be a better choice.


decrease the step over amount


Many parts that are surface ground have a large surface area which is wider than the grinding wheel. For example, a part could be a 3’ x 3’ slab being ground with a 2” wide grinding wheel. In order to grind the entire surface, the wheel will need to do multiple traversing passes or cuts. These cuts can all be in the same direction, or it may grind in both directions, alternating between upcuts and downcuts.


Grinding wheel step over diagram

When doing these traversing passes, it is necessary to have a slight step over from one grind pass to the next, meaning that the second cut slightly overlaps the first cut to ensure that the grind is continuous. Without a step over, some material in between passes may be left unground if the grind passes do not align perfectly.


For traverse surface grinding that alternates between upcuts and downcuts, a large step over: 50% or more, for example, may induce heat generation. A 50% step over means that 50% of the first will be ground again in the second pass, and so on. For example, if the wheel is 2” wide, the second pass will regrind 1” of the previous pass and 1” of the new pass.


If the section being ground does not have time to cool down before the step over regrinds it (which is typical in a traversing cut in both directions since there is very little time in between each pass), then it is very possible that this section will still be hot when the next grind pass occurs. This is especially true if there is a lot of heat generated during the initial grind pass from using a durable grain, lack of coolant, etc. This heat can generate internal damage to a material and poor surface finish in the form of chatter, burn, etc. In this scenario, it is better to have a smaller step over amount, for example 20% or less, to minimize the amount of part that is reground. In addition, decreasing the step over amount will require less passes to grind the entire part, decreasing overall cycle time, which is an added bonus!


sharpen the wheel with these dressing tips


In a surface grinding process where dressing is used, there are multiple ways to manipulate the dresser to ensure that it is sharpening the wheel most effectively. These tips are not just for surface grinding but can also be used for many types of grinding wheels. While they may warrant an article of their own, for a quick reference, the following parameters can be used to improve sharpness for wheels being dressed by a traverse dresser, which is the most common dresser type for surface grinding:

  • Increasing the dress traverse rate will improve the aspect ratio of the dresser to allow for a more open wheel face.
  • Increasing the dress depth can ensure that all grains are being conditioned enough to induce fracturing for a sharp wheel face. Shallow dress compensation can just knock off the tips of sharp grains, dulling them, instead of sharpening them.
  • Switching from a multipoint tool to a single point tool. Like a slow traverse rate, a multipoint tool can close off the wheel face. A single point tool simulates an improved aspect ratio and can assist with improving the sharpness of a grinding wheel during dress.


Norton dressing disc

While there may be other ways to alter machine, wheel, or dress parameters to improve the efficiency and quality of surface grinding, these recommendations can help alleviate common issues and can be a simple fix to help create the most productive surface grinding process.