When to Choose Honing vs. Lapping for a Smooth Surface Finish

When your part needs an ultra-smooth surface finish, there are a few finishing operations precision machine shops use to get the job done.

Electropolishing, a common finishing process that removes a thin outer layer of metal to reduce roughness, might be sufficient. But if you need a surface finish finer than 16 Ra, honing or lapping are better alternatives.

What Are Honing and Lapping?

Honing and lapping both produce incredibly smooth, shiny finishes with exceptionally tight tolerances. These operations are ideal for high-precision parts commonly found in aerospace, medical, optical, and defense applications, such as:

• Bearings
• Matched sets (e.g., valve and sleeve or piston and sleeve sets)
• Firearm components
• Medical prosthetics

Despite their commonalities, honing and lapping are two distinct operations. Here’s what differentiates these services:

• Process. Often used in conjunction with grinding, honing is an abrading process that involves using a machine to remove material at a low cutting speed. Lapping is a sanding method used to correct minor imperfections and make mating parts more precise.
• Work area. Honing is specifically performed on the inner diameter (ID) of a cylindrical surface. Lapping is performed on both the ID and the outer diameter (OD) of a surface. We perform OD lapping on our roll lappers and ID lapping on our speed lathes. We can also perform manual lapping on some flat surfaces.
• Speed. Honing equipment can only handle one part at a time, but lapping plates are capable of holding hundreds of parts, allowing for a fast turnaround. At our precision machine shop, we have three in-house roll lappers that we can run simultaneously to optimize lead times even further for our customers.
• Tolerances. Honing is more precise than grinding, producing exceptionally tight finish tolerances of ±.00002” 8 Ra Finish. However, lapping is the go-to process if you need finish tolerances as tight as a millionth of an inch 2 Ra Finish.

Peerless Precision Is Your Trusted Source for Honing and Lapping

Peerless Precision is a tight tolerance machine shop specializing in honing and lapping. Here’s what makes us your trusted source for these services:

The right capabilities

We work with two different honing technologies at our precision machine shop: our newer Sunnen ML-4000 and an older piece of equipment. We generally use the Sunnen ML-4000 to perform most of the hard work, then finish the job with our faithful old machine.

We also have two types of lapping capabilities: match lapping machines and roll lapping machines. We typically use match lapping on our speed lathes for the inner diameter of a surface and roll lapping on the outer diameter of round parts.

An experienced team

Honing and lapping are complex processes, and ample training is required to perform them well. Only the most experienced machinists have the know-how to “feel” when a part is approaching the required tolerance.

At Peerless Precision, we’ve put in the work to master these techniques. We can hone and lap any metal you need, including tool steel, 400 series stainless steel, 300 series stainless steel, and titanium. We even work with glass-filled plastics!

The ability to scale

From prototyping to low-volume production, we hone and lap parts in a wide range of quantities depending on customers’ requirements.

If you know which finishing service you need, you can select our in-house finishing services à la carte. Just keep in mind that if your part’s surface finish needs to be finer than 16 Ra Finish, we may leverage grinding to perform the bulk of the work—ultimately, this decision will help optimize the cost and lead time of your project.

Still unsure which finishing operation is best for your part? We’re happy to help you make that determination. We’ll just need to know the surface finish or Ra requirements for optimum fit and functionality.

Request a quote from our tight tolerance machine shop today!