Precision CNC Machining Aluminum Bearing Housing with Coaxial Bores and 0.01mm Concentricity

Dongguan Changxinda Precision Technology Co., Ltd. was established in 2008 as a drawing-to-part machining supplier. The plant operates 4-axis and 5-axis machining centers, turn-mill combined lathes and precision CNC lathes, employs over 90 people, and exports 50 to 60 percent of its output to buyers in robotics, automation, medical equipment, automotive, aerospace, laser, LED and lithium battery equipment. We are a job shop in the true sense: no standard product line, no catalogue part numbers — everything is built against the customer drawing.

This page covers aluminum bearing housings and flanged bore housings machined from 6061-T6, 7075-T6 or 5083 stock, in which a bearing seat, a seal seat and one or more coaxial bores must align with each other and with the mounting face. The part is simple to describe and unforgiving to make. A bearing that sits 0.01 mm off centre runs hot, a seal seat that is not square to the bore leaks, and a housing that is out of round will not accept an interference fit at the specified press force.

The bore is the part. Everything about the process is arranged to protect it until the last cut.

• One set-up for coaxial features. Where two bores share an axis, they are machined from a single setting on a horizontal or 4-axis machine, so the axis is generated once instead of being re-established after a re-chuck. This is the only reliable way to hold concentricity across two separated bores.
• Drill, semi-finish bore, finish bore. The bore is never brought to size in one pass. A 0.3 to 0.5 mm semi-finish allowance is left, the part is allowed to settle, and the final cut is taken with a boring head or a twin boring bar at low radial engagement.
• Clamping force control. Thin-wall housings distort when the chuck or vice closes on them. Final boring is done with reduced clamping pressure on finished datum surfaces, and roundness is measured with the part free standing, not clamped in the fixture.
• Face and bore in the same operation. The mounting flange face is faced after the bore is finished whenever geometry allows, so squareness of the face to the bore axis is a machine accuracy function rather than a handling function.
• Seal and snap ring features. Grooves, O-ring seats and snap ring grooves are cut with form tools or thread milled, with groove width and position checked against the drawing before the part leaves the machine.

The declared capability for this part family is 0.01 mm concentricity between coaxial bores, bore size to H7 with a cylindricity of 0.008 mm, and squareness of the mounting face to the bore axis within 0.01 mm.

• Bore sizes are sized with a boring head and verified with an inside micrometer and a bore gauge, then confirmed on the CMM.
• Roundness and cylindricity are measured at three heights in the bore, not at a single section.
• Concentricity is reported as a single value between the two bore axes, referenced to the drawing datum.
• Surface roughness of the bearing seat is held at Ra 0.8 or better, since a rough bore reduces the effective interference of the fit.
• Press fit validation on request: we machine a gauge pin to the mating tolerance and record the press force.
• First article report supplied with a ballooned drawing.

Housings in this family differ in bore count, bore spacing, flange pattern, material and sealing arrangement. None of that requires new tooling — only a new program and a new inspection plan.

• Drawing input: STEP, IGES, X_T, DWG, DXF or PDF, or a sample part for reverse engineering.
• Bore configurations: single bore, stepped bore, twin coaxial bore, or bore plus cross hole.
• Materials: 6061-T6, 7075-T6, 5083, 2024 aluminum, plus 304 and 316L stainless steel where corrosion resistance is required.
• Surface treatment: clear anodizing, black anodizing, hard anodizing, chromate-free conversion coating, bead blasting.
• Features added in house: helicoils, pressed bushings, dowel pins, O-rings, grease nipples, name plate engraving.
• Prototype quantity: from one piece with no tooling charge and no minimum order quantity.
• Drawing review: within 24 hours, with tolerance and cost comments returned in writing.

Housings for prototype builds and housings for production releases are scheduled differently, because the risk is different.

• Recurring orders are given a reserved machine slot, which keeps the quoted lead time stable across releases.
• A named project engineer owns each order and sends a weekly status update with photographs of work in progress.
• If a date becomes at risk, we say so in writing at least 5 working days before the ship date — not on the ship date.
• Shipping by express, air or sea, door to door; export documents prepared by our own team; bores protected with plugs and VCI paper.