5 Things to Consider When Choosing a Metal CNC Service.

With various metal CNC services available in the market, your knowledge about the things to consider when choosing your service provider is vital.


The utilization of modern technologies is inducing a revolution by increasing speed and efficiency in the manufacturing process industry. While additive manufacturing is taking the prototyping industry by storm, the large-scale manufacturing industry still heavily relies on CNC (Computer Numerical Control) machining.

The precision and versatility of CNC machining make it a unique offering. With every CNC machining service provider progressing with the introduction of new technology, understanding which aspects matter for your business is vital. This article will comprehensively walk you through the process of choosing your next metal CNC service. So, without further ado, let’s just dive right into it.

Considerations 1: Material Characteristics

Material properties play a vital role in the selection of the right machining service. As a customer, you need to understand which CNC machining materials are appropriate for matching your needs.

Some common criteria include:

  1. Corrosion resistance
  2. Strength of material
  3. Hardness
  4. Ductility and Malleability

CNC machining techniques will depend on the type of material and so will the surface finish.

These parameters are also of paramount importance in choosing types of cutters and their metallurgy.

To make understanding easier, let us classify each of these parameters into quantifiable terms.

Tensile Strength <100 MPa Nylon, Polycarbonate, Thermoplastics
<500 MPa Aluminum
>500 MPa Stainless Steel, Alloy Steel, Tool Steel
Hardness <90 HRB Stainless Steel, Alloy Steel
>50 RC Tool Steel
Thermal Stability <250 °C Teflon, Brass, Thermoplastics
<400 °C Aluminum
>500 °C Stainless Steel, Alloy Steel, Tool Steel
Chemical Resistivity High Stainless Steel, Thermoplastics, Teflon
Volume of Machinability High Volume Production Aluminum, Brass, Polyacetal (POM)
Low Volume Production Stainless Steel, Alloy Steel

For a common reader, let us discuss range of materials in the CNC industry and their typical applications:

Material Grades Common Applications
Aluminum 6061 Automotive parts Aviation components Bicycle frames
6082 Automotive parts Food containers
7075 Aerospace and aviation Marine Engineering Sporting goods
5083 Pressure vessels Marine Engineering
Stainless Steel 303 Aviation components Industrial grade fasteners Gears, Bushings
304 Medical equipment Chemical industry Marine Engineering
316 Surgical goods and Medical Devices Prosthetics Architecture
Duplex (2205) Oil and Gas Industry Industrial Pumps Heat Exchangers
17-4 Turbine Blades Nuclear Engineering Chemical vessels for the Oil and Gas Industry
Alloy Steel 4140 Machinery components Conventional tooling
4340 Aviation landing gear systems Power transmission systems CNC tooling
Mild Steel 1018 & 1045 Machinery parts, jigs, and fixtures

Considerations 2 :Machining Processes Involved in CNC Components Production

With an in-depth discussion of the material aspects covered above, now let us have a look at the various types of machining processes in CNC machining and how you can realize the types of operations required for your parts. The main types of machining processes in the CNC industry include:

  • Milling: The workpiece remains stationary while the tool rotates and performs machining
  • Drilling: Cutting of holes in the workpiece using a rotating tool
  • Turning: The workpiece rotates in a chuck while the tool remains stationary during machining
  • Grinding: Using an abrasive rotating wheel to remove material at a very gradual rate from the surface
  • Sawing: Cutting of blanks into pieces using a blade
  • Deburring: Removal of excess metal, sharp edges and ridges leftover from main machining operations
  • Polishing and Brushing: Improving the aesthetical look of the finished product by using a slightly abrasive machining process.

Typical machines used in the CNC industry are:

  • 3, 4, and 5 axis CNC milling machine. 5 axis machining provides the most versatility.
  • CNC Turning Machine
  • Universal machining center
  • Grinding machine

At the start of the article, technological innovation in the CNC industry was discussed. These conventional CNC machining processes combine with IoT (Internet of Things) concepts to breed new life into operations and achieve tight tolerances.

The role of IoT in machining processes is very important in rapid prototyping especially when customers are dealing with development of assemblies comprising several machined parts. Want to know why?

The answer is simple: The parameters on a machine shop floor are so diverse that identification of human-caused errors or inefficiencies in the CNC machines will be impossible to track. IoT enables transparency for top machining service providers. It highlights deficiencies in tolerancing of individual CNC machined parts so that stacked-up machining tolerances in entire assemblies might not be affected for the end-customer.

Now as a customer, you should not only know the types of machining operations but also be able to evaluate a service provider about the latest technologies in practice at their facility. After COVID-19, online CNC machining services offer pre-evaluation of the types of machining operations and the maximum achievable finish for your parts. Usually, seasoned high precision machining service providers have a diverse set of offerings.

Considerations 3: Surface Finish

While the aspects of material selection and machining processes are important, aesthetics of a part still play a major role in value-addition. What we can achieve from surface finish includes:

  • Rust protection
  • Exterior Decoration
  • Surface strengthening

As the name describes that surface finish is the process that follows the machining of metal parts. In some cases, the surface finish is purely for aesthetics while in other cases, it is important for the proper mating of parts in an assembly.

Some of the surface finish methods are as follows:

  • Nickel plating
  • Carburizing
  • Powder coating
  • Grinding

Nickel Plating:

Metal parts become corrosion resistant and wear resistance is enhanced. This can be done by using the electroplating technique by adding a thin layer of nickel about 0.1mm in thickness.


Carburizing hardens the metal surface by heating the metal in the presence of carbon monoxide and charcoal. It also enhances the resistance to wear and tear of CNC metal parts.

Powder coating:

This method is done by adding dry thermoplastic or thermoset powder to the surface of the steel. The surface finish range is between 0.15 and 0.3 mm thick. The benefit of powder coating is to prevent metal parts from corrosion.


Grinding helps to remove the burs from the surface of the metal and also removes the irregularities from the surface. All this is done by using a grinding wheel.

Consideration 4: Tool Selection in Production

Tool selection in production has a significant impact when choosing CNC metal service. Every material has different characteristics that are linked to alloying elements and hardness. This influences the selection of cutting tool geometry, grades and cutting data.

Tool selection does not mean material characteristics only. While planning a successful metal-cutting operation, the following are important aspects to consider:

  • Workpiece material
  • Type of Cutting Oil
  • Shape of the workpiece
  • Machining conditions
  • Required level of surface quality

Material of tool:

Solid carbide is a material that creates a reliable cutting tool.

A less expensive option compared to solid carbide is using a steel tool body with brazed carbide pockets which can drop the cost by 75%.

On the other hand, high-speed steel tools and carbide-tipped tools have higher costs so are used in the machining of smaller workpieces for the best surface finish.

Selection of high-speed cutting oils:

Metal working fluid provides cooling and lubricating effect for various processing operations. It ensures the accuracy and quality of the workpiece surface and also prolongs tool life.

Cutting oil classifications for respective materials are described below:

  1. Silicon steel cutting oil
  2. Carbon steel cutting oil
  3. Stainless steel cutting oil

Silicon steel cutting oil:

Silicon steel is relatively easy to cut. So, cutting oil with low viscosity is preferred for such types of materials.

Carbon steel cutting oil:

When selecting cutting oil for carbon steel, the viscosity depends on the difficulty of the process. The use of Sulphur cutting oil prevents the rusting problem of chlorine-type cutting oil.

Stainless steel cutting oil:

As this material is susceptible to hardening, so cutting oil with high viscosity and strength is used.

Discussing the technical aspects covers 4 of the top 5 tips. Hang around as the last tip is the most important i.e., cost estimation.

Considerations 5 :Cost Control and Estimation for Custom CNC Machining Services

As a prospective customer, before you choose your service provider for CNC parts, costing is an aspect you must comprehensively understand.

Normally, customers go for instant quotes from various machining service providers. If you understand the dimension of costing yourself, you will have an upper hand to negotiate positively. Let us dive into it.

Broadly speaking, two types of costs are involved in machining:

  • Variable costs
  • Fixed costs

For this article, let us focus on variable costs i.e., that depend on the number of parts and operations. We can divide machining features into four classes:

  1. 1)Parts requiring rotary machining only
  2. 2)Parts involving prismatic features
  3. 3)Parts requiring slab features
  4. 4)Parts requiring pockets and holes

Your part can be a combination of multiple classes. Without going into too much detail, you should know how many combinations of these 4 classes your part requires.

For instance, Type i parts will require only turning operations on a CNC lathe. Type ii parts will require face milling operations while end milling operations for Type iii. Last but not the least, Type iv requires reaming and drilling operations.

If a part requires milling and turning operations simultaneously, the cost will be higher.

So, the next time you are choosing your custom CNC machining service provider, be sure to negotiate costs based on the classes of machining operations involved. We believe that customer knowledge is a win-win situation for both ends.


With these 5 tips, we aim to educate our prospective customers with comprehensive knowledge of manufacturing processes. You just need to pick the right metal CNC service by:

  • Visiting their website
  • Inspecting their portfolio
  • DFM feedback for achievable level of intricacy and surface finish for the type of material
  • Upload a CAD file for custom parts
  • Receiving an instant quote
  • Actively negotiating costing and lead time by evaluating your CAD (Computer Aided Design) file
  • Understand the usage of tooling operations on your custom CNC parts

And remember to always demand a proper video or voice conference from your online CNC machining service provider. This will help to clarify several aspects beforehand for seamless provision of services with available machining capabilities.

Worthy Hardware is a CNC manufacturing and sheet metal fabrication company,including CNC machining services,CNC milling services, CNC turning services, laser cutting services and stamping services.Call us +86-76989919645 or email us [email protected] for more discounts for your projects.