01
A grade that cannot hold the tolerance
A 4,000 mm aluminum frame drawing with a ±0.05 mm flatness callout will move after machining. Stress relief and temper state matter more than the alloy number here.
Material Guides
CNC Machining Material Guides
Grade selection decides machinability, achievable tolerance, and finish. These material guides explain how we pick stock for CNC parts, and when a grade should be ruled out.
Aluminum 6061 / 6082 / 7075Stainless 303 / 316L / 17-4PHTitanium TC4Steel 1045 / 4140 / 12L14Engineering plasticsFree DFM in 12 hours
15 yearsMachining since 2011
127High-precision CNC machines
±0.005 mmAchievable tolerance
3Wholly-owned plants
Where material choices go wrong
Four failures we see on incoming drawings
Most of these are caught at quoting. Some are caught at first article. Both cost time.
02
Machinability ignored until the quote
Nitronic 60 and 17-4PH in H900 run at very different cycle times. If the drawing says "stainless" with no grade, the price you get back will be wrong.
03
Finish planned after the alloy is fixed
Hardcoat anodizing on 7075 darkens differently than on 6061. Electroless nickel on 303 vs 316L reads differently under inspection light too.
04
Heat treatment left off the drawing
65Mn spring parts or 4140 shafts with no hardness callout come back soft, then fail in the field. Hardness range belongs on the print, not in a note.
How we work
Grade, temper, and process decided together
These material guides are the decision path our engineers use before a program is written.
Selection logic
Start from the function, not the datasheet
We read the part as a load path first. A bracket that only locates a sensor does not need 7075. A rotating shaft at 8,000 rpm does. Aluminum 6061-T6 covers most housings and fixtures; 6082 behaves close to 6061 with slightly better strength and is common on European drawings; 7075-T6 goes where stiffness per kilogram matters.
Temper state is part of the grade. 6061-T6 and T651 differ in how they were stretched after quenching, which changes residual stress and how a thin wall behaves after the vise is released. T6511 is extruded bar, so it suits long profiles. On a 300 mm plate, that difference shows up as a few hundredths of a millimeter of bow.
- 1Thin wallsChoose a stress-relieved temper or plan a rough and finish pass with a rest.
- 2Wear surfacesHardness callout decides between 4140 pre-hard and a case-hardened steel.
- 3Seawater or washdown316L for corrosion, 17-4PH where strength and corrosion both matter.
- 4Weight budgetTitanium TC4 or magnesium AZ31B before reaching for carbon fibre.
Stock and process
What we check before the first cut
Incoming stock gets a material certificate check and a hardness spot check on heat-treated lots. For titanium and stainless, we confirm the mill cert grade against the drawing before the bar goes to the lathe. Traceability is written to the traveler.
Machining strategy follows the material. Aluminum runs at high spindle speed and generous coolant. 316L and TC4 need lower surface speed, rigid setups and more attention to heat, because heat is what kills tool life and surface finish. Plastics such as PEEK and POM need sharp tooling, air blast, and a stress-relief anneal before finishing if the tolerance is tight.
- 1CertificatesMill cert and heat lot recorded against the part number.
- 2Stress reliefApplied to long or thin parts before final finishing.
- 3ToolingGrade-specific inserts and cutters held for repeat runs.
- 4InspectionFirst article plus in-process checks, 100% before shipment.
Quick reference
Common CNC materials at a glance
Use this as a first filter. Final grade still depends on load, environment and finish.
| Material | Typical use | Watch out for |
|---|---|---|
| 6061-T6 aluminum | Housings, fixtures, brackets | Warp on thin plate; specify T651 |
| 6082-T6 aluminum | Structural frames, Euro drawings | Slightly lower fatigue life than 6061 |
| 7075-T6 aluminum | Aerospace ribs, high-load links | Poor weldability; anodize color shifts |
| 303 stainless | Shafts, fittings, bushings | Free-machining sulfur reduces corrosion |
| 316L stainless | Marine, medical, food contact | Gummy; slower speeds, rigid setup |
| 17-4PH stainless | Valve parts, high-strength shafts | Hardness depends on H condition |
| Ti-6Al-4V (TC4) | Aerospace, motorsport, implants | Low thermal conductivity; tool wear |
| 4140 steel | Shafts, gears, tooling bodies | Pre-hard vs Q&T changes machinability |
| 12L14 steel | Connectors, small turned parts | Not for welding or high load |
| POM / PEEK | Insulators, seals, wear pads | Thermal growth; need anneal |
What we run
Machining and finishing for these materials
One shop handles the cut, the heat treatment coordination, and the finish.
01
5 Axis CNC Machining
16 simultaneous 5-axis centers for contoured surfaces, undercuts and parts that would need four setups on a 3-axis machine.
02
CNC Milling & Turning
27 three-axis machines and 16 mill-turn centers. Shafts, housings and turned parts from bar up to 4,000 mm.
03
Rapid Prototyping
One-off parts for fit checks before tooling. No minimum order quantity, from a single piece to 10,000+ runs.
04
Sheet Metal Fabrication
Enclosures and brackets in aluminum, stainless and cold rolled steel, matched to the machined parts.
05
Part Surface Finishing
Anodizing, electroless nickel, zinc, black oxide, powder coating, bead blasting and polishing to your Ra callout.
06
Vacuum Casting & Die Casting
Bridge volumes in ABS-like or PC-like resin, and ADC12 die castings when the part moves to production.
Scope
Material and process limits
| Item | Range | Notes |
|---|---|---|
| Achievable tolerance | ±0.005 mm | Dependent on feature size and material |
| Fine finish | Ra 0.2–0.8 μm | Polishing or fine turning |
| Standard finish | Ra 0.8–1.6 μm | Typical machined surface |
| As-machined finish | Ra 1.6–3.2 μm | Non-critical faces |
| Maximum part size | 4,000 mm | 4,000 × 400 × 150 mm travel |
| Aluminum grades | 6061, 2024, 5052, 5083, 6063, 6082, 7075 | Plus ADC12 for casting |
| Stainless grades | 303, 304, 316, 316L, 420, 430, 431, 440C, 17-4PH | Mill cert on request |
| Titanium and special | TA1, TA2, TC4, Inconel, AZ31B, AZ91D | Lower cutting speeds |
| Plastics | ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE | Air blast, no coolant |
| Laser marking | 1.5 mm minimum character height | On anodized and plated surfaces |
Why GreatLight
What the numbers say
15Y
Machining since 2011
Three wholly-owned plants, 7,600 m² of manufacturing space, and 150 technicians working from the same process sheets.
127
CNC machines on the floor
16 simultaneous 5-axis centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers.
±0.005
Millimeters, in production
Equivalent to ±0.0002 in. Verified with first article and in-process checks, not only at final inspection.
99.99%
Qualification rate
Raw material check, in-process monitoring and 100% inspection before shipment. Reports on request.
12 h
Quote and DFM analysis
A drawing review with material and process notes comes back within 12 hours. Production can start within 24 hours.
3–5 d
Typical shipping window
Parts ship in 3–5 days after release. Historical late-delivery probability is below 2%.
ISO 9001:2015Quality management
IATF 16949:2016Automotive
ISO 13485:2016Medical devices
ISO 27001:2022Information security
Industry requirements
What each sector demands from the material
Aerospace
7075-T6 and Ti-6Al-4V ribs, brackets and housings where weight and fatigue life drive the grade choice.
- ±0.005 mm
- 100% inspection
- Mill certs
Automotive & EV
6061 and 6082 housings, 4140 shafts and 12L14 turned parts. Consistent hardness lot to lot.
- IATF 16949
- 3–5 day ship
- No MOQ
Medical Devices
316L and TC4 instrument parts, with Ra 0.2–0.8 μm on contact faces and documented material traceability.
- ISO 13485
- Ra 0.2–0.8 μm
- Traceable lots
Industrial Machinery
65Mn spring parts, 1045 and 4140 wear components, Nitronic 60 for galling resistance at high temperature.
- Heat treatment
- Hardness reports
- 4,000 mm travel
FAQs
Questions engineers ask about material guides
Should I specify 6061-T6 or 6061-T651?
T6 is the base temper after solution heat treatment and artificial aging. T651 adds a controlled stretch before aging, which lowers residual stress.
If your part is a thin plate, a long frame, or has a flatness callout under about 0.1 mm, specify T651. For compact blocks and housings, T6 is usually fine and easier to source.
When is 6082 a better choice than 6061?
6082 has slightly higher yield strength and is widely stocked in Europe, so it often appears on drawings from EU customers. It machines in a similar way to 6061.
Its fatigue performance is a little lower. For cyclic-load brackets, 6061-T6 or 7075-T6 is the safer pick.
Can you machine titanium and stainless to the same tolerance as aluminum?
Yes, but the setup changes. TC4 and 316L cut at lower surface speeds and generate more heat, so we use rigid fixturing, sharp tooling and more frequent in-process checks.
For thin walls in titanium, we often leave stock, stress relieve, then finish. That adds a step but holds the ±0.005 mm callout on the finished part.
How do I choose between 303 and 316 stainless?
303 contains sulfur for machinability. It turns cleanly and holds tight tolerances, which suits shafts, bushings and fittings in dry or lightly humid conditions.
316 and 316L trade some machinability for corrosion resistance, including chlorides. For washdown, marine or medical contact, use 316L.
What hardness should I call out on a steel part?
Put a range on the print, not a single value. For 4140 shafts, something like 28–32 HRC gives the machinist room and still hits the wear requirement.
For 65Mn springs, the tempering temperature sets the final hardness. Tell us the load and cycle count and we can suggest a range.
Does the alloy affect which surface finish I can get?
Yes. Hardcoat anodizing builds a thicker oxide layer and shifts the color differently on 7075 than on 6061. Electroless nickel covers uniformly, which helps on complex 316L parts.
If color match across two parts matters, keep them in the same alloy and the same anodizing lot.
Can you supply material certificates with the parts?
Mill certificates and heat lot numbers are recorded against the part number and can be issued with the shipment. Hardness and dimensional reports are available on request.
For regulated programs, include the certificate requirement on the purchase order so it is written to the traveler.
What happens if my drawing names a grade you cannot source?
We come back with an equivalent or a near-equivalent and say what changes. Sometimes it is a temper state, sometimes a different alloy family with comparable strength and corrosion behavior.
You get that answer in the 12-hour quote window, before any material is ordered.
Send a drawing and get the material call reviewed
Upload your files and an engineer will check grade, temper, finish and tolerance together, then quote within 12 hours.
Quote and DFM in 12 hoursNo minimum order quantity100% inspection before shipmentNDA on request
