Four key principles for milled parts.
Maximize internal corner radius
All internal vertical corners get a radius from the round cutting tool. Larger radius = larger, more rigid tool = faster material removal = lower cost. Avoid sharp internal corners.
Limit pocket depth to 4-6× tool diameter
Deeper than 6× tool diameter requires long slender tools that vibrate and cut slowly. For 10mm wide pocket, depth ≤ 50mm ideal.
Use standard end mill diameters
Design internal radii and hole sizes to match standard end mill and drill diameters (3, 4, 5, 6, 8, 10, 12, 16, 20mm). Avoid custom tooling.
Avoid tall thin walls
Tall thin walls vibrate during machining (chatter), causing poor surface finish and dimensional drift. Aspect ratio limit: height ≤ 4× thickness for aluminum, 3× for steel.
Pocket floor corners matter too.
Standard square end mill: leaves sharp corner where floor meets wall. Stress concentration here for loaded features.
Designed-in floor radius: requires bull-nose or ball end mill. Reduces stress concentration. Slightly higher cost but better fatigue performance for cyclic-loaded parts.
Recommended floor radius: 0.5mm minimum, 1-2mm for fatigue-critical features. Specify ≥ 0.5mm for any pocket where stress matters.
Drilling and reaming rules.
Standard depth
Depth up to 4× diameter standard. Beyond requires peck drill or gun drill (specialty cost).
Practical minimum
Below 2mm diameter, drills deflect and break. Use EDM or laser drilling instead.
Reamed bore
For H7 fits, drill undersize then ream. Plan for reaming step in DFM.
Chamfer entry
Specify chamfer at hole entry for fastener alignment and burr prevention.
Thread depth
Thread depth 1.5-2× diameter for full strength. Longer adds cost without strength.
Min standard thread
Specify M3 or larger for production. M2 and smaller are fragile and slow.
When to specify 5-axis milling.
5-axis wins when
3-axis adequate when
FAQ
Specify internal radius equal to or greater than 1/3 of pocket depth. For 15mm deep pocket: R5 minimum. This allows 10mm tool to reach bottom — much faster than smaller tool. Smaller radius forces specialty tooling and slower cutting.
Yes. Aluminum forgives more — thinner walls, deeper pockets, faster cutting. Stainless and titanium need stiffer tooling and slower speeds — keep walls thicker, pockets shallower. Plastics machinability varies by material.
Default ISO 2768-m or ±0.1mm works for most features. Reserve tighter tolerances (±0.025) for bearing fits, mating surfaces, dowel pin holes. Never specify ±0.01 unless truly required — costs 5-10× more.
Generally 5-axis is faster and more accurate when geometry justifies it. For simple prismatic parts, 3-axis 1-2 setups is cheaper. Break-even: when part needs 4+ setups in 3-axis, 5-axis usually wins.
Standard milled finish: Ra 1.6-3.2 µm. Fine milling (CBN/diamond): Ra 0.4-0.8 µm. Below Ra 0.4 needs grinding or polishing. Specify per function — over-specified surface finish drives cost.
Yes. Every quote includes DFM review at no extra cost. We identify cost-driving features and suggest design changes that maintain function while improving manufacturability. Often saves 20-40% on machining cost.
Get an instant quote
Send your CAD — we reply with detailed pricing, lead time, and DFM feedback within 4 working hours.
Talk to an engineer
WhatsApp our team directly. Most messages answered within 12 minutes during work hours.
Explore all services
CNC, 3D printing, injection molding, sheet metal, casting, finishing — one quality system, one partner.
Working on a live project? Send the STEP file and the two or three features you are unsure about — an engineer replies with DFM notes and a price, usually within four working hours.