The Difference Between Honing and Lapping

When metal products are manufactured there are various surface imperfections caused by the cutting or shaping tools used in the manufacturing process. Often these surface imperfections, such as cutting burrs or tool marks, are of no consequence to the finished product and can be left as is. If, however, a more precise surface finish is required, then honing and lapping can be used to remove small amounts of metal to produce a smooth and precise finished surface.

What is Honing?

Honing is the process of removing metal from the inside surface of tube, pipe, holes or bores using a rotating abrasive stone. Honing is a final fine-tuning step in the manufacturing process as it is designed to remove approximately 0.005 mm of thickness, meaning the honing stage is a polishing or precision process rather than a shaping process.

Honing is completed using a stone, or hone, that is covered in a very fine abrasive grit and mounted to a mandrill to allow it to rotate. The rotation is typically slower than that of a normal grinding and cutting action to allow for more control and precision. The workpiece, a metal tube for example, is fixed in place in a such a way to allow it to float so the hone doesn’t exert too much pressure on the piece and distort the shape.

Depending on the workpiece and the type of machine being used, the process may require the rotating hone to move in a controlled path over the stationary workpiece, or the workpiece may move in a controlled path across the rotating hone. In both cases a cutting fluid is introduces to cool, clean and lubricate the surface being honed

What is Lapping?

Lapping is the process of removing metal from the surface of a material to achieve a smooth and precise finish. It is done by using an abrasive suspension. Lapping can be controlled by changing the variables such as speed, pressure, type of abrasive, and even the temperature, meaning the lapping process can be refined to make products within very tight tolerances.

There are two types of lapping:

• Flat lapping corrects surface irregularities in flat products
• Domed or ring lapping corrects surface irregularities in rounded products

The lapping process involves passing the material between very flat ‘lap’ plates while surrounded in a specialized liquid. The liquid contains a suspension of abrasive particles, and the friction generated between the loose abrasives and the moving workpiece creates the gentle surface polishing action.

The Difference Between Honing and Lapping

Aside the from the processes themselves, the primary difference between honing and lapping is that lapping is a gentler process. It is designed to remove less than 0.005 mm of metal from the surface and be the final precision step.