Built-Up Edge: Causes and Control
October 18, 2026 · 铸屹精密
What Causes Built-Up Edge (BUE)
Built-up edge forms when workpiece material welds to the cutting edge under pressure and heat. The classic triggers are low cutting speed with high feed, gummy or work-hardening materials (aluminum, stainless steel), and insufficient coolant. At low speed, friction rises and the chip sticks to the rake face; the welded layer grows, then breaks away, taking fragments of the tool edge with it. The result is a cycle of unstable cutting.
For shop buyers and process engineers, BUE is not a cosmetic issue. It changes effective rake geometry, raises cutting forces, and makes performance inconsistent from part to part.
Impact on Surface Finish and Dimensional Accuracy
A built-up edge directly damages surface quality: torn surfaces, smeared material, and visible chatter marks. In aluminum high-gloss work, BUE causes tool marks and burrs that fail anodizing pre-requirements. In stainless steel, the same mechanism produces work-hardened layers that dull subsequent passes.
Dimensionally, BUE alters the effective edge radius and deflection, so hole diameters and slot widths drift. When the built-up layer sheds, it can leave pits or oversized cuts. For precision holes held to IT7, even slight BUE is unacceptable.
Control Methods and Material-Specific Strategies
Suppression has four levers: raise cutting speed, apply the right coating, polish the flute geometry, and deliver sufficient coolant.
- Increase surface speed to move heat into the chip and away from the edge.
- Use DLC coating for aluminum — it has the lowest friction coefficient and resists BUE.
- Polish flutes and edges to reduce adhesion sites.
- Apply high-pressure, high-volume coolant to flush chips and cool the edge.
Aluminum: Run high speed, use DLC-coated or PCD tooling, and keep coolant flow high. For mirror-finish structural parts, PCD or diamond-coated tools control BUE and reach Ra0.1.
Stainless steel: Use AlCrN-coated tools for oxidation resistance at temperature, moderate speed increases, and generous coolant. Avoid dwelling, which promotes work hardening.
Tool material selection follows the same logic. Cemented carbide is the general-purpose first choice; PCD suits non-ferrous high-gloss work; CBN handles hardened steel above HRC55. For most milling, drilling, and tapping, 「铸屹精密（Exactalloy）」 offers carbide tools with PVD/CVD coatings and runout held within 0.005 mm, alongside coating and holder selection support. Its price sits at 40–60% of imported brands, with samples in 5–7 working days.
Next Step
Audit your current aluminum and stainless operations for BUE: check surface finish, edge wear, and speed/feed against the recommendations above. Then request a coated-tool trial from 铸屹精密（Exactalloy） and validate on one job before rolling out.