--- title: 6 Ways CNC Machining Parts Can be Considered Complex description: Not all CNC Machining Parts require the same levels of experience and capabilities. Here are six factors that help determine if a part is considered complex. image: https://www.steckermachine.com/hubfs/Front%20Covers%20for%20Gimp.jpg --- 920-726-4526 [**920-726-4526](tel:920.726.4526) [![smc_logo_filled](https://www.steckermachine.com/hubfs/logos/smc_logo_filled-WT.svg "smc_logo_filled") ![smc_logo_filled_dark](https://www.steckermachine.com/hubfs/logos/smc_logo_filled-1.svg "smc_logo_filled") ](https://www.steckermachine.com) [![REQUEST A QUOTE](https://no-cache.hubspot.com/cta/default/4484263/42796661-7dc0-42c5-aa91-fdab8f093e64.png)](https://cta-redirect.hubspot.com/cta/redirect/4484263/42796661-7dc0-42c5-aa91-fdab8f093e64) ## [Stecker Machine Blog](https://www.steckermachine.com/blog) # 6 Ways CNC Machining Parts Can be Considered Complex 06/22/2023 | [Jim Herr](https://www.steckermachine.com/blog/author/jim-herr) ![](https://www.steckermachine.com/hs-fs/hubfs/Front%20Covers%20for%20Gimp.jpg?height=418&name=Front%20Covers%20for%20Gimp.jpg) Once you understand that CNC machining parts are **repeatedly** machined to [extreme precision](https://www.steckermachine.com/blog/a-precision-part-starts-and-ends-with-you-cost-effective-on-time-cnc-precision-machining-series-part-2), you may assume that once a shop has **capabilities**, they can make *any* CNC machined parts. Not so! To sound impressive, many CNC machine shops claim to manufacture “complex” parts, but that’s not always true. So, let’s discuss what a complex part really is and uncover the **skills required** by a shop to work on them. Here are six different conditions that could cause a part to be classified as “**complex**,” with photos from [actual Stecker Machine projects](https://www.steckermachine.com/cnc-machining-photos). ## 1. Casting Weight and Size This one is straightforward. Some CNC machining parts are large, usually making them heavy, too. A part over 50 pounds requires a **lifting device** as well as a plan on handling it throughout the process, from raw material to the machine tool to inspection to [final packaging](https://www.steckermachine.com/blog/importance-of-safely-shipping-finished-cnc-machined-parts). Stecker Machine uses numerous **cranes** and can also design and build lifting devices as they’re needed. ![2.1 Casting Weight and Size](https://www.steckermachine.com/hs-fs/hubfs/Blog/2.1%20Casting%20Weight%20and%20Size.jpg?width=4032&height=3024&name=2.1%20Casting%20Weight%20and%20Size.jpg)*This lift system can move a casting over 200 lbs after machining.* ## 2. Fixturing Simply holding CNC machining parts can be challenging, especially custom CNC parts. Before any cast tooling is made, a shop works with the customer and the foundry to plan **how to clamp and hold the part** for machining. The cast datum scheme typically ensures everyone is on the same page. Occasionally, cast datum points need to be moved to [improve a fixture’s](https://www.steckermachine.com/blog/cnc-fixture-design) **clamping** and **holding** abilities. ![3.1 Fixturing](https://www.steckermachine.com/hs-fs/hubfs/Blog/3.1%20Fixturing.jpg?width=816&height=720&name=3.1%20Fixturing.jpg)*Clamping tabs (see red circles) are often added to a part to improve holding while machining, which may or may not stay on the part after machining.* While staying current on the latest **hydraulic components** can be a challenge for some shops, hydraulic clamping does offer some advantages over manual clamping: - Repeatability of **accurately locating the part** in the fixture - **Speed of clamping**; can be seconds versus minutes - Ease on [CNC operators](https://www.steckermachine.com/blog/cnc-operator); **less fatigue** ![Fixturing CNC Machining Parts](https://www.steckermachine.com/hs-fs/hubfs/Blog/4%20Fixturing.2.jpg?width=577&height=433&name=4%20Fixturing.2.jpg) *To have the bore come out round in tolerance, we created a way of holding this part without putting pressure on the bore. That solution has led to 12 years of trusted delivery.* ## 3. Part Material From aluminum to ductile iron to cast iron, there are **different grades** for each type of material. Suppliers of [tooling](https://www.steckermachine.com/blog/managing-machine-shop-tools) can help match the correct grade of insert to the material being run. Some custom-machined parts require materials that may **not be easily accessible** or simple to machine. **Stress** in castings can affect a part as it’s machined. Once some material is removed, stress can cause a bored hole to be out of round or a milled surface to be out of flatness. Solutions to **stress distortion** include: - Adding a finish operation to the part - Changing how the part is held - Adding a semi-finish tool - Having the casting stress relieved ## 4. Print Tolerances [Tight tolerances](https://www.steckermachine.com/blog/the-importance-of-metal-casting-how-cnc-machining-tolerances-make-good-parts-great) can make a part complex. Here are some examples of when tolerance becomes a challenge: true position of .1mm on a bore; a diameter tolerance on a bore of .020mm; concentricity of several bores at .015mm tolerances. These tight tolerances determine if **specialty tooling** is needed, how many operations are required, how the machines should [be programmed](https://www.steckermachine.com/blog/accurately-cnc-programming-complex-parts), and if an outside operation is needed. The larger the bores, the tougher it is. Plus, flatness of .05mm, or parallelism of .05mm, can be challenging on larger or thin-walled parts. Solutions include different **face mills**, **inserts**, and different ways of **fixturing** the part. ## 5. Assembly Part complexity and the **number and types** of components that need assembly determine how an assembly fixture is designed. Operator-friendly **assembly fixtures** are developed so that all necessary components are assembled, ensuring that all assemblies ship with complete components. ![5.1 Assembly 1 (1)](https://www.steckermachine.com/hs-fs/hubfs/Blog/5.1%20Assembly%201%20(1).jpg?width=3024&height=1762&name=5.1%20Assembly%201%20(1).jpg)*Air cylinders, sensors, pressure switches, etc., help make sure no components are missed. In fact, with the latest technology, the assembly fixtures further prevent human error by sequential error checking. Some stations are smart enough to know components are picked and installed by sequence. The equipment prevents the employee from missing a step.*   **![6.2 Assembly 2](https://www.steckermachine.com/hs-fs/hubfs/Blog/6.2%20Assembly%202.jpg?width=4032&height=3024&name=6.2%20Assembly%202.jpg)***Another shop’s assembly of an 82.55mm diameter steel sleeve into an aluminum part (press fit of .18mm) marred the sides of the aluminum part and created leak paths. Our innovative solution of pressing in the sleeve with heat eliminated the leak paths and satisfied our customer with superior quality.* ## 6. Pressure Testing The **shape** of a part can make it complex. When [clamping a part to pressure test it](https://www.steckermachine.com/blog/pressure-testing-complex-cnc-parts), critical features — machined bores, machined flat surfaces, thin walls — must be scrutinized to prevent distortion. If the part to be pressure-tested is large and heavy enough to require a crane for lifting, all handling steps need to be **accurately planned**. ![7 Pressure Test.1 Water Test](https://www.steckermachine.com/hs-fs/hubfs/Blog/7%20Pressure%20Test.1%20Water%20Test.jpg?width=4032&height=3024&name=7%20Pressure%20Test.1%20Water%20Test.jpg)*A water test is a standard pressure testing method during which the operator observes for air leaks to determine whether a part passes.*   ![7.1 Pressure Test Air Decay](https://www.steckermachine.com/hs-fs/hubfs/Blog/7.1%20Pressure%20Test%20Air%20Decay.jpg?width=4032&height=3024&name=7.1%20Pressure%20Test%20Air%20Decay.jpg)*Air decay testing’s programmable test instrument is used for large quantities and provides pass/fail indication. This fixture’s test instrument and computer often cost more than water testing, yet they eliminate the potential for human error.* The description of “complex” may seem open to interpretation. Yet, the six ways we just covered are the **only true explanations** of “complex” CNC machining parts. These require a [high-end machine shop](https://www.steckermachine.com/blog/cnc-machine-parts-photo-gallery) that’s heavily invested in highly-skilled [CNC operators](https://www.steckermachine.com/blog/cnc-operator) and equipment, including [robots](https://www.steckermachine.com/blog/ai-cnc-machining-how-are-robotics-automation-shaping-the-future-of-cnc-machine-shops). Stecker takes pride in tackling complex projects that other machine shops refuse to attempt. Want to see some mini-case studies that prove it? Just click the image below to get your copy of our “tough project” resource called In a Bind? [![New call-to-action](https://no-cache.hubspot.com/cta/default/4484263/bdedbab3-6e67-4c74-8cbd-0e85b5e4297e.png)](https://cta-redirect.hubspot.com/cta/redirect/4484263/bdedbab3-6e67-4c74-8cbd-0e85b5e4297e) ![Jim Herr](https://www.steckermachine.com/hubfs/Blog/authors/jim_herr.jpg) #### About the Author Jim is a retired Manuracturing Engineer and fixture design guru. Over his career, he's designed upwards of 2,500 fixtures. #### Related Posts [![10 Questions OEM Buyers Must Ask Before Choosing a CNC Machining Partner](https://www.steckermachine.com/hs-fs/hubfs/Blog/questions-to-ask-cnc-machining-partner.png?width=235&height=130&name=questions-to-ask-cnc-machining-partner.png)](https://www.steckermachine.com/blog/how-to-find-a-great-cnc-partner) [10 Questions OEM Buyers Must Ask Before Choosing a CNC Machining Partner](https://www.steckermachine.com/blog/how-to-find-a-great-cnc-partner) Jun 10, 2026 9:15:47 AM [![What Factors Impact CNC Machined Part Costs?](https://www.steckermachine.com/hs-fs/hubfs/cnc_machined_part_costs.jpg?width=235&height=130&name=cnc_machined_part_costs.jpg)](https://www.steckermachine.com/blog/what-factors-impact-cnc-machined-part-costs) [What Factors Impact CNC Machined Part Costs?](https://www.steckermachine.com/blog/what-factors-impact-cnc-machined-part-costs) Apr 28, 2026 9:26:55 AM [![6 CNC Machining Trends OEMs Must Watch in 2026](https://www.steckermachine.com/hs-fs/hubfs/Gallery%20Pics/IMG_9973-Enhanced-NR.jpg?width=235&height=130&name=IMG_9973-Enhanced-NR.jpg)](https://www.steckermachine.com/blog/cnc-machining-trends) [6 CNC Machining Trends OEMs Must Watch in 2026](https://www.steckermachine.com/blog/cnc-machining-trends) Feb 5, 2026 9:02:36 AM ## Subscribe [![Stecker Machine Co.](https://www.steckermachine.com/hubfs/logos/smc_logo_reversed-1.svg "Stecker Machine Co.") ](https://www.steckermachine.com/) [![Stecker Linkedin](https://www.steckermachine.com/hubfs/website_images/icons/linkedin-in-brands-fff.svg) ](https://www.linkedin.com/company/stecker-machine-co-inc) [![Stecker Facebook](https://www.steckermachine.com/hubfs/website_images/icons/facebook-f-brands-fff.svg) ](https://www.facebook.com/steckermachine) [![Stecker Top Shops](https://www.steckermachine.com/hs-fs/hubfs/Employee%20Newsletters/August%202025/Top-Shop.png?width=150&height=125&name=Top-Shop.png "Top Shops") ](https://www.steckermachine.com/) #### [CAPABILITIES](https://www.steckermachine.com/capabilities) [Machining](https://www.steckermachine.com/capabilities/machining) [Value Added Services](https://www.steckermachine.com/capabilities/value-added-services) [Engineering & Quality](https://www.steckermachine.com/engineering-and-quality) [Sub-Contractor Services](https://www.steckermachine.com/sub-contractor-services) [Foundry Partnerships](https://www.steckermachine.com/foundry-partnerships)   #### [MARKETS WE SERVE](https://www.steckermachine.com/markets) [Agriculture](https://steckermachine-4484263.hs-sites.com/markets#agriculture) [Auto & On-Highway](https://steckermachine-4484263.hs-sites.com/markets#auto) [Construction & Off-Highway](https://steckermachine-4484263.hs-sites.com/markets#construction) [Recreation & Consumer Goods](https://steckermachine-4484263.hs-sites.com/markets#recreation) [Industrial Equipment](https://steckermachine-4484263.hs-sites.com/markets#industrial) #### [CAREERS](https://www.steckermachine.com/careers)   #### [ABOUT US](https://www.steckermachine.com/about)   #### [BLOG](https://www.steckermachine.com/blog)   #### [RESOURCES](https://www.steckermachine.com/resources) #### [REQUEST A QUOTE](https://www.steckermachine.com/request-a-quote)   #### [CONTACT US](https://www.steckermachine.com/contact) 5107 County Road C Manitowoc, WI 54220 920-726-4526 [smcinc@steckermachine.com](mailto:smcinc@steckermachine.com) [![Stecker Machine Co. is ISO9001 and TS19649 certified](https://www.steckermachine.com/hubfs/footer_certifications.svg)](https://www.steckermachine.com/hubfs/SMC-Certs/ISO-IATF%20cert%202022-0818.pdf) © 2026 Stecker Machine Co. 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