Precision Lapping Services: How We Achieve Superior Surface Finishes
Advances in automation have made many manufacturing processes easier but not always more effective. To ensure superior accuracy and precision, our shop still employs many traditional techniques.
One old-school method we swear by is hand lapping—not the mechanical lapping most shops prefer.
Read on to learn how United Centerless Grinding & Thread Rolling leverages hand lapping to polish a machined material’s surface down to an impressively smooth 1 Ra!
What Is Lapping?
Traditional lapping (or “hand lapping”) is performed similarly to hand sanding. But instead of using sandpaper, we apply a loose abrasive to a lapping plate and then manually rub the part’s exterior over the lapping plate until we achieve the desired surface roughness.
Mechanical lapping works the same way but with a lapping machine securing and abrading the workpiece instead of a person.
Hand Lapping vs. Centerless Grinding
Lapping is a logical complement to our shop’s precision centerless grinding services. Like lapping, centerless grinding is a subtractive process, but it’s a much harsher method that can’t always deliver the surface smoothness some parts require.
Centerless grinding
We can usually meet surface roughness requirements with centerless grinding, particularly with thru feed grinding. Using a soft wheel, dressing it slowly, and maintaining clean coolant, our experts can achieve 5 Ra surface roughness with this technique. To achieve even smoother surfaces, we follow up centerless grinding services with precision lapping services.
Hand lapping
When your surface roughness specifications call for 4 Ra or less, we use hand lapping to complete the job. We select the appropriate lap material, then apply a diamond lapping compound to the lapping plate and polish your part’s surface by hand. With a bit of “elbow grease” and an age-old surface finishing technique, we can polish most metal surfaces down to 1 Ra.
Which Parts Benefit from Precision Lapping Services?
Hand lapping isn’t well-suited for softer metals like aluminum, copper, and brass. Our metal lapping specialists commonly use the technique to abrade tool steels that we’ve machined into molding dies, metal molds, crush rolls, and other types of tooling. Low surface roughness is critical for tooling because any imperfections in the finish will transfer to the final product.
Can you imagine a part with 1 Ra surface roughness that has a couple of “surprise” 12 Ra spots? We can, because we’ve seen it—and it’s not pretty!
The crush rolls we produce for one medical customer’s forms must have an exceptionally smooth surface finish to ensure that the gel caps they use these forms to make are perfect.
3 Signs of Excellent Precision Lapping Services
Lapping is generally quite common, but hand lapping has largely been replaced by mechanical lapping. To fully benefit from the thorough, careful craftsmanship of hand lapping, you don’t want to trust your project to just anyone. Here’s what to look for in a manufacturing partner:
1. Metal lapping expertise
Professional hand lapping requires significant skill. Lapping begins with high-grit papers that smooth the roughest areas, then transitions to fine-grit lapping compounds. Our skilled technicians know how to apply exacting pressure—enough to remove high spots without inadvertently grinding down low spots that can’t be corrected later.
2. Careful inspections
Our quality assurance department verifies a part’s surface roughness using two methods. Inspection instruments are the first line of defense against inaccurate surfaces. Then, our experts examine each part closely to visually detect even the subtlest imperfections.
On a surface that’s 99.9% accurate, even a tiny patch of out-of-spec roughness is enough to make a big difference in the end results. That’s why we always perform visual inspections in addition to using specialty instruments.
3. Thoughtful handling and packing
The most skillfully executed precision lapping services are pointless if your parts are damaged in transit. We take extra care to prevent metal-to-metal contact during handling and packing, and we commonly wrap every individual part in paper. If the metal is at risk of rusting, we spray the parts with rust-proof oil and potentially wrap them in rust-preventive paper.
Get Smooth Surface Finishes from United CGTR
When you need precision lapping services, our experts have the training, experience, and commitment to quality to deliver exceptional results. We always welcome our customers’ questions, and we’re happy to provide guidance on design decisions, material selections, manufacturing processes, and more.
Ready to start your next project? Visit our online portal for a secure quote!
