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CNC Machining Precision and Tolerance

What Is the Tolerance for CNC Parts?

Tolerance is the acceptable range of variation of a manufactured parts geometry. CNC machined components are very precise and have been developed over the past decades to become the backbone of many critical industries who require high precision such as medical, aerospace, chemical, defense, gas and oil and others. Though no two parts are identical, it is the tolerance range that allows for some deviation and still functions within the intended design.

A common standard tolerance for many CNC precision machining parts is +/- 0.005 inches (0.13 millimeters). This means a part with a nominal length of 1 inch could be anywhere from 0.995 inches to 1.005 inches long and still be considered acceptable. As tolerance plays a vital role in all areas of manufacturing and is looked at with equal importance even if the tolerance is a +/- .020inches (0.5mm) or +/-  0.0005 inches (0.0127mm), the need and function of the desired part determines the tolerance required.

Examples of CNC precision machining parts tolerances are:

  • CNC technology: Under this umbrella, are CNC machining, CNC lathes, CNC Mills and others, can hold a tolerance of +/- 0.0254mm to +/- 0.0508mm.
  • CNC Micro Machining EDM: Can hold as tight as +/- 0.010mm to +/- 0.025mm.
  • CNC Fiber Laser machining: Holds a tight of +/- 0.0127mm to +/- 0.0254mm.
  • CNC Laser: UV Laser Machining: As tight as +/0 0.0127mm to +/- 0.0254mm.
  • CNC Femto Laser Machining: Can be as tight as a +/- 0.001mm to +/- 0.010mm.

Benefits to Having a Tolerance:

There are levels of tolerance to all industries and what is acceptable for one, may not be to the another. They do share in the need for having a tolerance applied to the parts requirements. Without this control and standardization to a level of quality, lives would be in jeopardy. Some examples of the benefits of tolerances for CNC machining manufacturing:

  • Uniformity: CNC precision parts manufactured under a tight tolerance can be replaced with confidence that the unit or device will continue to function properly.
  • Sustained function: A CNC machined components tolerance allows for a longer life cycle of the machined part. Industries such as medical, food, aerospace, automotive, nuclear science all require tolerance for the proper function of the implemented manufactured parts and public safety.
  • Business growth: Business goals are to create more business and opportunities. CNC machining parts manufacturers rely on their reputation by providing products that perform. Tolerance increases the quality of the product and integrity of the supplier.
  • Industry Certification: CNC machining parts manufacturers go through certifications such as ISO 9001-2015 or ASTM 9100 for example. Many companies will only do business with services providers who are certified. Being certified and having the capabilities to hold the tolerances required is essential to public safety.

Tolerance is vital element to not only to CNC precision parts, but to all industries supporting manufacturing. Without this range of acceptable deviations, there would be no level of confidence in the products or services we use. The stringent demands of the airline industry the medical industry, and so on have demanded these safeguards be embedded in manufacturing to save lives and to keep our critical needs and goods at the highest levels possible.

High Precision Machining Explained: Tight Tolerances for Demanding Parts

What is considered high precision machining?

High precision machining refers to a manufacturing process that utilizes computer numerical control (CNC) machines to create parts with exceptionally tight tolerances. These tolerances can be as close as ±0.0005 inches (0.0127 mm), which is roughly the thickness of a human hair. 

This level of accuracy ensures that the parts fit perfectly in their designated assemblies and function flawlessly in demanding applications. Precision CNC machining parts are essential in industries such as aerospace, medical devices, and automotive, where even the slightest deviation can lead to significant performance issues. 

Beyond tight tolerances, high precision machining often involves:

  • Advanced CNC machines: These machines use sophisticated software and controls to precisely maneuver cutting tools.
  • Specialized tooling: Custom-designed cutting tools may be required to achieve specific features or finishes.
  • Highly skilled machinists: Operating high precision machinery often requires experienced professionals with a keen eye for detail.

What is the precision of CNC machining?

In general, CNC machining can achieve tolerances of ±0.005 inches (0.127 mm) or better. However, high precision CNC machining can reach tolerances as low as ±0.0005 inches (0.0127 mm). The precision of CNC machining can vary depending on several factors, including:

  • The type of CNC machine: 3-axis machines offer good precision, while 5-axis machines can achieve even tighter tolerances.
  • The material being machined: Softer materials like aluminum are generally easier to machine precisely than harder materials like steel.
  • The complexity of the part: Parts with simple geometries are easier to machine precisely than parts with intricate features.

Do You Use Precision Machines to Build Custom Metal Parts?

Precision machines are used to build custom metal parts and are now instrumental in using this subtractive manufacturing process. Prior to CNC (Computer Numeric Control), there was manual machining, where skilled craftsmen used hand-operated versions of lathes, mills, drills, and other tools to produce custom parts. This process was slow and took time and a vast amount of experience to manufacture. There was some early NC (Numeric Control), systems that used punch card type of data that allowed for some automation. This was the groundwork for modern CNC technology. Today CNC precision machined parts are key in manufacturing metal parts for countless industries and uses. Imagine the products you take for granted every day and many will have been manufactured in part with CNC precision parts technology. Parts in your car, your washer, your stove, the instruments used in surgery, the hinges on your doors and the valves that control water flow or electrical hookups for EV vehicles. Precision CNC machining parts is a robust industry with thousands of suppliers supporting both critical and consumer applications.  Though the process is very detailed and controlled by industry standards such as ISO-9001-2015 and ASTM 9100 for example, it is straight forward in the general steps taken. Here is an overview:

  • Machine Program: CNC precision parts manufacturers use a CAD (Computer Aided Design) model to program the CNC machine using Computer-Aided Manufacturing (CAM) software. This software generates a program that specifies the toolpaths, cutting speeds, and other parameters the machine needs to follow.
  • Material Selection: The appropriate metal stock is chosen based on the part’s design and functionality. This can be aluminum, steel, tungsten, titanium, stainless steel, copper brass, and many other metal alloys depending on the final shape and parts function.
  • Machining Process: CNC machines are the star and take center stage. The metal stock is secured in place, and the machine follows the pre-programmed instructions. CNC precision machining parts manufacturers employ multiple cutting tools to remove material from the workpiece. It is a gradual process shaping to the desired form. There are two main CNC machining methods:
    • CNC Milling: A rotating spindle with a cutting tool at its tip removes material by moving across the workpiece on multiple axes. This allows for creating intricate features and complex geometries.
    • CNC Turning: The workpiece rotates on a central axis, while a stationary cutting tool removes material to create cylindrical or concentric features.
  • Finishing: Many CNC machined components require a post finishing process like deburring (removing sharp edges), polishing, or heat treatment for added strength or corrosion resistance.
  • Quality Control: From initial review of a project to final completion of the custom part that is ready to ship to the customer, quality is always part of the discussion and process. Precision measuring instruments are used to verify accuracy and that the tolerance required is within the acceptable range of the parts design and function. Examples of instruments that are used by CNC machining parts manufacturers:
    • Calipers: For internal and external dimensions
    • Micrometers: For highly accurate measurements of lengths, diameters, and thicknesses.
    • Dial Test Indicators: DTIs measure minute variations in runout, alignment, and flatness.
    • Gauge Blocks: These are precision-machined blocks with known, accurate dimensions. They are used to calibrate other measuring instruments and ensure their accuracy.
    • Machine Probes: CNC machines can use touch probes that automatically contact the workpiece. These probes verify dimensions and tool position during the machining process. This eliminates the need for manual measurement interruptions.
    • Laser Scanners: CNC Manufacturers may utilize laser scanners to create a 3D image of the machined part. This creates a detailed comparison between the manufactured part and the original CAD model.

Custom metal parts are manufactured daily by qualified and experienced CNC machining parts manufacturers. Backed by a long history of innovation in precision manufacturing, this industry has limitless opportunities to advancing technology in all critical industries including medical device, defense, oil and gas, energy, science, pharmaceutical, automotive and the list goes on. With CNC technology you can be assured many new advances in the mentioned industries will be due in part to the suppliers and individuals that manufacture always in mind with quality, pride, and workmanship.

Looking for High Precision CNC Machined Parts?

Leading CNC machining parts manufacturers utilize cutting-edge techniques and equipment to deliver high precision results, ensuring each CNC machined component meets stringent quality standards.

If your project requires parts with exceptional precision, look no further! As a leading CNC machining parts manufacturer BlueRing Machining offers high precision machining services to meet your unique needs. We utilize state-of-the-art CNC machines, top-quality materials, and a team of skilled machinists to deliver precise and reliable CNC machined components. Contact us today to discuss your project!