McIver Engineering mills and turns 6061, 6060, 5083, 5052 and 5005 aluminium at our Smithfield workshop, for aerospace, electronics enclosures, transport and prototype work, from single parts to repeat batches.
Aluminium is chosen for the ratio it offers rather than for outright strength. At around a third of the density of steel it takes weight out of moving assemblies, portable equipment and anything that has to be lifted or flown, while its high thermal conductivity makes it the obvious choice for heatsinks, electronics enclosures and cooling plates. Its natural oxide layer gives useful corrosion resistance without any coating, and anodising builds on that when service conditions are harder.
It also machines fast. Aluminium cuts at high spindle speeds and heavy feed rates with modest cutting forces, so a machined part is often cheaper in aluminium than in steel even before the material cost is compared. That speed is why aluminium dominates prototype and low volume work, where the cost of getting a part in your hands next week matters more than the last few percent of strength.
The trade offs are real and worth designing around. Aluminium is soft, so it marks, galls and picks up easily, and threads in aluminium do not tolerate repeated assembly the way threads in steel do, which is why highly cycled fastener locations are often specified with steel inserts. It is around three times more thermally expansive than steel, so a close fit between an aluminium housing and a steel shaft behaves differently hot than cold.
The machining risks are chip welding and stress. Aluminium is gummy and will weld itself to the cutting edge if the tool is dull, the chip is not evacuated or the coolant is inadequate, and once a built up edge forms the finish tears. We use sharp, polished, high helix cutters with wide flutes, deliberate chip evacuation and full engagement rather than rubbing passes. On thin walled parts machined from plate, residual stress released during cutting is managed by roughing, then finishing after the part has relaxed, rather than cutting to size in one hit and watching it bow.
Aluminium is rarely left exactly as machined. Anodising is the usual finish because it grows out of the metal rather than sitting on top of it, giving a hard, non conductive, corrosion resistant surface that will not chip off like paint. Anodising is arranged as a finishing step with an outside treater and managed as part of the job, with Type II and Type III both available, so parts come back to you finished rather than needing another handler.
It has to be planned, not added at the end. The anodic layer adds thickness, so a close tolerance bore or a spigot fit machined to nominal will be undersize once treated, and any surface that must stay electrically conductive or dimensionally exact needs masking. Anodising also reveals the surface underneath rather than hiding it, so tool marks, scratches and inconsistent finishes show up more clearly after treatment than before.
Tell us at enquiry stage if parts are to be anodised, which surfaces are critical and which must remain untreated, and we will allow for it in both the machining and the sequence. Alloy choice matters here as well, since different alloys take colour differently.
Linishing is done in our own workshop, so a consistent grain or a dressed surface can be put on a part before it leaves us. Bead blasting and tumbling are arranged externally alongside anodising, so a single order still covers the part from bar or plate through to finished.
On the mills the everyday aluminium work is electronics and instrument enclosures, mounting plates, machine brackets, guide and clamp blocks, manifold bodies, jigs and fixtures, and lightweight structural parts machined from plate. On the lathes it is spacers, standoffs, bushes, adaptors, rollers, knobs and threaded fittings.
Jigs, fixtures and test rigs are a large slice of it. Aluminium is the natural choice for tooling that has to be handled, moved and modified, and its speed of machining means a fixture can be cut, tried and revised inside the same programme of work.
We also combine machining with fabrication, laser cutting and folding aluminium sheet for enclosures and covers, then machining the faces, bores and mounting features that have to locate accurately.
We hold tolerances as tight as 0.01 mm on critical features in aluminium. Because aluminium cuts so freely, the practical limit on a given part is usually not the machine but the part itself, how it can be clamped without distortion, how much residual stress the plate releases as material is removed, and how thin the walls become.
Where a part is thin walled or long and unsupported, we sequence the work to suit, roughing first, allowing the material to move, then finishing to size, and using soft jaws or purpose made fixtures rather than clamping harder. It is a slower route but it is the one that delivers parts that still measure correctly after they come out of the vice.
Mark up your drawing so the features that actually matter carry the tight tolerance and the rest is open. If parts are to be anodised, note it on the drawing so the allowance for coating thickness is built into the machined size rather than discovered at inspection.
We work in 6061 and 6060, and in 5005, 5052 and 5083 on the plate and sheet side. 6061 covers most general machined work, 6060 extrusion suits framing and profiles, and the 5000 series grades are used where weldable, corrosion resistant plate is needed. If your drawing calls up a different alloy or temper, send it with your enquiry and we will confirm availability before quoting.
6061-T6 machines cleanly, welds acceptably, anodises predictably and is readily available in plate, bar and extrusion. That combination makes it the practical default for brackets, housings, plates and enclosures where the part needs to be strong enough, light and stable rather than pushed to a strength limit.
Yes, through an outside treater rather than in our own workshop, and we manage it as part of the job so parts come back to you finished. Type II and Type III anodising are both available that way. Tell us at enquiry stage if parts are to be anodised, because it affects how tight-tolerance features are machined and which surfaces need masking.
Linishing is done in our own workshop, so machined and fabricated aluminium can be dressed to a consistent grain before it leaves us. Bead blasting and tumbling are arranged externally, along with anodising, and we handle that coordination rather than passing you between suppliers.
We hold tolerances as tight as 0.01 mm on critical features. Aluminium cuts freely and finishes well, so the practical limits on thin walled or long unsupported parts usually come from clamping and residual stress in the material rather than from the machine.
Part size is limited by our machining envelopes rather than by the alloy, so turned diameter and length and the largest milled part are the same in aluminium as in any other material we cut. Send the overall size with your enquiry and we will confirm it against our machines before you commit engineering time.
We machine to a standard machined finish unless your drawing nominates something specific. If a surface roughness figure or a particular appearance matters, call it up on the drawing at enquiry stage and we will confirm what we can hold on that feature and whether a finishing step is needed.
Yes. There is no minimum order quantity, so a single prototype bracket or housing is quoted the same way as a production batch. Send a STEP or IGES model, a 2D drawing or a sample part and we will work from that.
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