Top CNC Machining Hacks for Holding Tight Tolerances

by Norm Grimberg CNC Machining and Machine Shop

Tight tolerances are critical for high quality, high performing parts. Industries like Healthcare, Aerospace, & Military heavily rely on accurate precision parts to thrive. Some parts even need an accuracy of 0.0005”; a width comparable to the thickness of human hair. Achieving that tolerance is a challenging feat, but it is not entirely impossible.

If you are a machinist juggling with tight tolerances, these few hacks might help you achieve perfection with your CNC machined parts.

1. Tool Selection

The first hack on the list, obviously, is the tool selection. We cannot hope to reach absolute perfection with sloppy and ‘not-fit-for-occasion’ tools. Be wise with your choice of tools. For extremely tight tolerances, you’ll need to have a specific set of tools including separate ones for roughing and finishing. Work on over-dimension; hoping for absolute dimension and going under the set dimension can be an absolute horror for a machinist.

2. Spindle Warm Up

Warm up is not only important before a sprint or a long soccer match. Just like how soccer players do quick stretches to keep themselves from potential injuries, a CNC machine needs its own set of warm-up sessions to work at its maximum. While machinists do run substantial warm-ups on their spindles before working on a project, it’s not enough for parts with extremely tight tolerances. The former process only prevents premature bearing wear. Allowing your machine to run for around 15–20 minutes before you begin with the actual milling procedure. It would help you mitigate the risks of pre-processing thermal expansion while giving you the required dimensions.

Tip: Don’t forget to measure your tools post-warm up. Any discrepancies on the tool front can hinder you from achieving the desired results.

3. The Right Temperature

Believe it or not, the right temperature is one of the most crucial factors for holding tight tolerances. A slight diversion with the set temperature can impact your machine and parts in tones of ways. In fact, even innocent mistakes like not paying attention to where your machine is placed can harm the entire machining process. For example, if your machine is placed near the window and its cold outside; there is no guarantee that you’ll meet your desired dimension, no matter how many times you run the warm-up session on your milling machine. The best solution is to have your machines placed in the temperature controlled environment!

As you can see, holding tight tolerances is challenging but not impossible. Adopt the above-mentioned simple hacks to get the desired dimension at one go!

More interesting topics: 10 Ways to Ensure a Better Surface Finish For Your CNC Machined Parts

Do’s and Don’ts to get a Better Surface Finish For Your CNC Machined Parts