Tips for Machining with Tight Tolerances

If your part design requires tight-tolerance machining, plating can make or break your design. It’s important that you choose a machining shop who does their own plating or works with a high-quality plating vendor. While the overall process may take longer, you’re bound to get better results.

Here’s an overview of tight-tolerance machining and why plating needs to be taken into consideration.

How plating affects machining

When a part is machined, tolerances are always measured after the piece is plated. Plating creates dimensional changes, since it’s adding another layer of coating onto your part.

When you have exceptionally tight tolerances, even a thin layer of plating can disrupt the dimensions; therefore, the thickness of the plating needs to be taken into account, especially if you want to anodize or hard anodize your part.

When a part is anodized, the plates etch into the part to remove some material before anodizing the piece. This makes up about 10 percent of the tolerance. Hard anodizing, on the other hand, is a risky proposition. Hard anodizing adds a significant amount of material to the part. Your machine shop will need to account for hard anodization while machining the piece so that the tolerances are not affected.

Plating quality matters

Working with a quality plating shop is crucial to design success. Plating is an extremely complex process. Depending on how complex your design is, it can be difficult to calculate the right technique. Temperature, electricity and the consistency of both can affect how fast the plating process occurs.

When metal is plated, it’s cleaned and then placed in a tub of sulfuric acid. The plating grows on the surface of the part. The trick is to make sure that you can calculate growth rate properly, so the plating doesn’t become too thick. Similarly, if you remove the part too soon, the plating will be too thin.

A good plating shop will focus on your project to ensure the growth rate is just right. They need to have the manpower and the right tools available to complete the plating process properly. Some shops will do a haphazard job and push the parts through, so they can move on to the next project—that runs the risk of plating ruining your tolerances. To machine the part right the first time, whom you work with matters a great deal.

Plan in advance

If your parts need to be plated, that will add extra time onto your order. Knowing this ahead of time can help you plan for how long you’ll need before the parts are finished. Good plating jobs can add as much as six weeks to your order. That sounds like a lot—but when you consider how long it would take to wait for the parts to be plated poorly, then to have them redone, it’s not quite so bad.

If you have questions about machining with tight tolerances or why hard anodizing might not be a good idea, reach out to Evden Enterprises today.