Rear Cover Flange in 6061-T6, Turned and Milled, Four Bearing Fits in One Part

About This Part

This rear cover shows how much capability hides in a familiar part shape. It is a circular flange-style cover for motors and gearboxes, machined from 6061-T6 disc stock, and almost everything on it is a mating interface: a bolt circle, a set of bearing fits around the center, a fine thread pattern, and a keyed orientation slot. The route is ordered so every later feature inherits one clean reference from the first operation.

Turning comes first. The blank is chucked as a disc, and the end faces and outside diameter are cut in one clamping, which establishes the axis every concentric feature will be measured from. Milling follows: the P.C.D. 58 hole rings, the obround lightening and routing slot, and the open notch that keys the cover to its housing are all cut with the turned rim as reference, so hole patterns and orientation features stay true to the bore axis rather than to the chuck jaws.

The center is where this part earns its tolerance. Four fits cluster around the axis: Ø53.50 H7 as the main precision bore with an effective precision depth over 3 mm, Ø62 e7 as the outer spigot, Ø17 g6 and Ø10 P7 as pilot and dowel locations. Fine boring all of them without re-clamping keeps the cluster concentric by construction. Coaxiality is held at 0.008, hole position at 0.012 to datum A, and a further form control at 0.004, all read on the CMM rather than inferred.

The small features are treated with the respect small features need. Four M2-6H holes are tapped on an even circle and two more run straight through, tapped by hand after chamfering so a 2 mm tap does not snap in a nearly finished part. Eight positions of paired Ø2.20 mm through holes are drilled on the same pattern. Edges are broken all around, with default chamfers at C0.2 and radii at R0.2, and general tolerances default to GB/T1804-m with geometric defaults at GB/T1184-K.

Finishing is clear anodize, which keeps the natural aluminum color while hardening the surface, followed by laser marking. Anodize grows a thin layer on every face including the bores, so film thickness is part of the fit conversation; masking the fits is available where the assembly needs bare metal. Inspection closes the route: CMM on position and form, bore gauge on the H7, g6 and P7 fits, thread go no-go gauges, micrometer checks on key dimensions, and a film and appearance check before packing.