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Experts classify machining based upon the way a machinist extracts excess material from a workpiece. Three key machine processes stand out: single point cutting, multi-point cutting and abrasive techniques. A machine process called “lapping” falls into the third category. It holds value in numerous industrial metal parts manufacturing environments today.

Lapping has become one of the most important abrasive machining processes. Essentially, it involves a manufacturer interposing freely moving abrasive grit particles between the workpiece and a rotating lap wheel. A manufacturer uses this hard abrading material to help shape, facet and smooth metal surfaces. Lapping differs from grinding because it relies upon loose abrading material, not abrasives bonded into a rotating wheel.


Lapping Process

During the lapping process in a metal parts manufacturing setting, a machinist relies upon loose abrasive material placed between a moving lap plate and a work piece to remove tiny particles of excess metal. Both manual and machine lapping occur widely in industrial parts production settings.

For example, a machinist may rely upon a firm rotating lap wheel composed of iron or glass to support a hard gritty abrasive material, such as diamond, silicon carbide or aluminum oxide, set inside viscous material on a rotating plate moved by the wheel. By rubbing a metal workpiece against the rotating lap and its associated abrasive, the machinist produces microscopic fractures and indentations in the surface. This process gradually helps to shape and facet the exterior of the metal workpiece. 

Sometimes the heat of this process requires the application of a coolant material, such as water. The size of abrading particles utilized during lapping will determine the texture of the resulting surface on a metal work piece. A machinist may progressively decrease the abrasive particle size to successively finer sizes by changing the abrasive during a succession of laps in order to polish a metal surface.


Lapping Equipment

Since lapping has become one of the most important industrial machining processes, a wide variety of lapping machinery exists on the marketplace today. Machinists creating a prototype sometimes turn a lapping plate manually. However, in mechanized mass-production settings, large automated lap machines typically predominate. Multiple machine parts rotate in unison to generate high volumes of machined components.

Manufacturers can select computerized lapping software programs to complete the machining of a variety of metal parts. These programs may control the speed and number of lap rotations and the patterns and various sizes and types of abrasive materials utilized in lap plates. Since abrading material will eventually wear out, it may become necessary to reintroduce lap abrasives on a regular schedule.

Basic Lap Machine Components

Most lap machines consist of a fixture containing a round rotating lap wheel and several spinning constraining rings to hold plates containing different layers and sizes of abrasive materials. Operators can control both the size of the abrasive grain and the speed and direction of rotation.

Two Important Types

Lapping machines typically involve two varieties. Lapping may occur with abrasive material contained within patterns formed on a plate made of cast iron or copper. Alternatively, (and more commonly), the rotating plate holds loose abrading particles suspended within a viscous material, such as grease or mineral oil. For example, manufacturers may coat finely patterned lap plates with abrasive pastes before using them to machine parts.



Manufacturers who utilize a machine process can rely upon lapping in order to obtain smooth, flat surfaces on work pieces. This process can generate metal parts, as well as an array of other in-demand consumer items, such as rounded stone cabochons or faceted gemstones used in jewelry making or watch making.

Today, lapping applications enable the production of metal parts in large quantities. Aeronautical and aviation firms, oil and gas industry equipment manufacturers, the optical industry, and watch and toolmaking sectors depend heavily upon this process. Manufacturers rely on lapping to help machine engine components, slip gauges, hydraulic valves, and testing equipment, for instance.

Consider using lapping to help create flat, smooth, faceted or gently sloping metal components. BuntyLLC’s machining department can assist you in evaluating the utility of lapping for a variety of popular applications.


Lapping Advantages

As a machining process, lapping offers a number of advantages:

Lapping can help modify the shape and appearance of parts. (The size of components undergoing lapping appears limited only by the capacity and dimensions of individual lapping machines, for instance.) Additionally, it can assist with the machining of an incredible variety of materials. Perhaps for this reason, manufacturers sometimes choose lapping as a preferred process for removing thin metal burrs from cast parts.

Depending upon the available equipment, automated lapping may assist in the production of machined parts within high tolerance ranges. It enables product designers to realize dimensional accuracy when used in conjunction with rigorous quality control protocols. “Precision lapping” helps achieve desired part thickness and dimensional uniformity in the production of lenses, for example. It can ensure a tight fit between mated components in an assembly.

Manufacturers frequently employ lapping as a way to create a designated surface roughness. This process may help prepare a metal part to accept further finishing more readily, for instance.

Finally, lapping sometimes helps correct minor appearance imperfections, creating parts displaying a more polished, smoother surface finish. An industrial manufacturer may choose to use lapping in lieu of some other finishing techniques in certain situations, or to rely on it in conjunction with other machining and finishing processes.


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From a contract manufacturing firm, BuntyLLC evolved into a full service custom machined, forged and cast metal parts fabrication enterprise. We supply global solutions from our headquarters in Greenville, South Carolina.

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