There are many alloy steels to consider for your project, but to help you make the right choice, we have compiled the top 12 steels available for CNC machining. These common steels listed in the table below all show moderate machinability, as well as various other desirable characteristics though this list is not all-encompassing.
| Grade | Type | Description | Advantages | Disadvantages | Applications |
|---|---|---|---|---|---|
| 1215 | Low Carbon Steel | This grade, also known as a "screw stock", is used extensively in automatic screw machine operations. | As a lead-free alternative to 12L14, 1215 carbon steel contains the same amount of sulfur and phosphorus and has good machinability. | It is difficult to weld and is not suitable for case hardening. It is generally utilized where mechanical properties can be sacrificed for machinability. | Couplings, bushings, inserts, studs, pins, hydraulic hose fittings |
| 1018 | Mild Carbon Steel | Best steel for carburized components with good weldability. | Good machinability and weldability. | Provides moderate mechanical properties such as ductility and strength. | Spindles, mechanical parts, tie rods, anchor pins. |
| 4140 | Low Alloy Steel | Alloy steel low in manganese, chromium, and molybdenum. | High resistance to impact fatigue, and abrasion. Good machinability in the annealed condition. | Post-heat treatment may be required. | Spindles, couplings, nuts, bolts, machinery and automotive parts. |
| 8620 | Low Alloy Steel | High ductility and strength. Responds well to nitride hardening and offers good wear resistance. | Great wear resistance and high strength. | Poor response to induction or flame hardening. | Camshafts, gears, piston pins, chains, and fasteners. |
| 8630 | Low Alloy Steel | A high-strength alloy with high hardenability. | Responds well to heat treatment. | Heat treatment may be required before or after machining or welding. | Block valves, gears, forged connectors, crankshafts. |
| 1045 | Medium Carbon Steel | A versatile medium carbon steel alloy with relatively high strength and hardness, allowing for wear-resistant applications. | Great weldability and machinability. High strength and hardness. | Post-heat treatment may be required to relieve stress. | Light gears, axles, forged connecting rods, bolts. |
| 1144 | Free Machining Medium Carbon Steel | A free machining resulfurized carbon steel with excellent wear resistance. | Excellent resistance to wear and deformation. High hardness and strength. | Overall weldability is poor. | Screws, nuts, rods, gears, pistons. |
| SS 303 | Free Machining Stainless Steel | One of the most readily available and highly machinable of all austenitic stainless steel grades. | High corrosion resistance, moderate cost, and good machinability. | Cannot be hardened by heat treatment. Not recommened for marine applications. | Aircraft fittings, electronic hardware, bushings, nuts and bolts, screws. |
| SS 416 | Free Machining Stainless Steel | High machinability superior to any other stainless steel. | Excellent machinability, outstanding strength, moderate corrosion tolerance. | Not suitable for marine or chlorine environments. Weldability is poor and availability are limited. | Bolts, valves, pump shafts, gears, nuts. |
| SS 304 | Stainless Steel | One of the most common stainless steel alloys with great weldability. | Excellent weldability and machinability, low cost, good corrosion resistance. | Susceptible to stress corrosion cracking in some situations above 60°C. Some other stainless steel alloys have better resistance to pitting and crevice corrosion. | Heat exchangers, screws, food handling, utensils, auto parts, construction applications. |
| SS Grade 17-4 | PH Stainless Steel | It is a grade of martensitic precipitation hardening stainless steel with chromium up to 30%. | Extremely high toughness, corrosion resistance, and strength. | Efficient and careful heat treatment is required. | Oil and gas applications, nuclear reactors, aircraft turbines. |
| 4130 | Chromium-molybdenum Alloy Steel | 4130 alloy steel is designated by AISI and SAE, a chromium-molybdenum steel with low carbon content. | It is a special welding steel that can be welded by all commercial methods and is easily machined in the normalized/tempered condition. | Machining may become difficult when the hardness of the steel is increased. | Bearings, vehicle parts, and gears, rock crushing machinery, drill bits and taps, mills and cutters. |