Lapping: How Many Types Exist and How to Choose the Right One

Today we dedicate ourselves to high-quality metal machining: lapping. That is, that step after grinding that activates when even greater precision is needed. If you need to work on a block, you can drill a hole in metal and obtain a rough hole. Further processing of boring, reaming, and mechanical grinding allow you to enlarge and refine everything.

We are improving millimeter by millimeter a machining. But lapping goes beyond and allows you to achieve those tolerances that in very demanding sectors - such as aerospace and medical - can make the difference. Want to learn more about the topic? Read this guide dedicated to lapping and the improvement you can achieve through precision mechanical machining.

What is Lapping and What Is It For?

Lapping is a mechanical machining process that is used to finish metal surfaces and more to obtain extremely homogeneous surfaces free of defects or roughness. We also speak of operations that go beyond the order of millimeters.

The movement necessary to apply lapping on metals (and not only) to optimize includes a combination of pressure and rotation of the grinding wheel that acts on flat surfaces and holes. In other words, if you need maximum surface finishing to remove defects and roughness of the material in question, you must turn to a machine shop dedicated to lapping.

Difference Between Lapping and Grinding

Let's move on immediately to comparing with an activity that is often confused: grinding. In this case we are talking about a job capable of eliminating rather consistent layers of material, for example to increase the displacement of an engine or reduce scratches caused by seizing of rings and pistons. With lapping, on the other hand, we operate with minimal dimensions, almost invisible to the naked eye.

How Does This Principle Work?

It is performed with a combination of abrasive pastes and specific movements of the grinding wheel designed specifically to move small amounts of material. It is a very slow and expensive operation, so you reserve it only for parts that truly require it. As happens, for example, in the aerospace sector, in the manufacture of surgical equipment, in precision optics, and in the production of critical hydraulic components or gauges. Lapping - from the term lap, light pressure - involves the use of more or less strong abrasives.

Here the choice depends on the type of material to be optimized. The active element exploits structures such as silicon carbide or diamond powder combined with oil or water that act as abrasive paste. The result is achieved through equipment consisting of a grinding wheel - which can be flat or cylindrical - and a precision machine that performs a slow rotation and oscillation movement.

How Is Lapping Carried Out?

Starting from the clear assumption that lapping is an activity carried out only in specialized machine shops, and that possess all the tools to minimize roughness through the lapping process, we can say that there is a basic path to know. At least to have an idea of how to work. It starts with a phase of careful cleaning of the support on which you need to operate.

Any residue, dust grain, or other element can compromise the final result. The abrasive paste useful for the operation is applied - which can also be diamond to operate on hard materials such as hardened steels or non-ferrous metals - and the parameters of the lapping machine are defined. That is, the machine that applies the rotation and oscillation movement. The parameters:

• Rotation speed.
• Contact pressure.
• Temperature.

The fundamental characteristic of lapping is that it has minimal adjustments, with low speeds and minimal pressures. This is because we are talking about a precision process, if we increase the values we have greater mechanical stress that does not meet the needs of the operation. Following, cleaning operations and verification of the obtained result are carried out.

Advantages and Disadvantages of Lapping

Actually, it's wrong to talk about pros and cons of the process analyzed because lapping is a necessary step in certain cases, regardless of advantages and disadvantages. Certainly, if we want to talk about the negative aspects, it is a slow process and economically costly, with the risk of obtaining defective products if you don't work optimally with the ideal settings.

On the other hand, lapping is the only way if you want to achieve certain results in terms of micron tolerances and minimal roughness for surfaces that must adhere perfectly. So burrs and defects, even invisible to the naked eye, are banned. But it is precisely in these circumstances that lapping can make the difference.