Custom Machined Mounting Brackets

Brackets that line up first time

A mounting bracket has one job, to hold two parts rigidly in the right place, so the dimension that decides it is the bolt-hole pattern rather than the outline: hole positions, spacing and the flatness of the mating face. Machined from solid plate or billet, the bracket is one rigid piece with no weld distortion, and its holes are drilled from one datum, so an M8 pattern on Ø9 mm clearance holes bolts straight on instead of being drilled to fit on site.

Custom bracket specifications

Attribute	Capability
Materials	6061 & 7075 aluminium, mild & alloy steel, stainless
Process	3-axis & 5-axis milling from plate or billet
Bolt-hole position	True position from a common datum; interchangeable across a batch
General tolerance	ISO 2768-m / -f; ±0.025 mm on critical features
Finishes	Anodize (clear/black/colour), powder coat, zinc plate, bead blast
Quantity	One-off to production batch

Machined, formed or cast: choosing the process

A custom bracket is machined from solid, laser-cut and folded, or cast, and the cheapest route depends on the shape and the quantity: below about 100 pieces a bracket milled from solid usually wins, above that a folded or cast one often does. As a custom parts maker we pick the route rather than forcing every bracket into a mill:

Process	Best for	Notes
CNC machined from solid	Rigid, precise, complex, low–mid volume	One piece, no weld distortion, tight tolerance — our default
Formed sheet metal (laser + bend)	Simple flat / folded brackets, higher volume	Cheaper per part for plain brackets — ask us and we'll quote it
Cast	Complex shapes in large quantities	Tooling cost amortised over volume

For most one-off, replacement and precision brackets, machined-from-solid wins — no tooling, fast, and stronger than a folded part. For simple high-volume brackets, ask about formed sheet metal.

Bracket types we machine

Five shapes cover most machined brackets, from the 90° angle to the flat base plate, each milled from solid or formed to suit:

• L-brackets (angle) — the 90° structural connector
• Z-brackets & offset brackets — span two planes at a step
• U-brackets / channel mounts — straddle and clamp a part
• Gusseted brackets — with a rib for high load
• Flat-mount / base plates — single-face bolt-down

Motorsport and chassis brackets, billet and anodised, are on automotive CNC parts; brackets named by what they carry are in the names table below.

Instrument brackets and mounting plates

Instrument brackets are milled from solid in one clamping, so the bore that carries the instrument and the fixing holes keep their relative position to ±0.025 mm when the drawing asks for it; multi-hole plates and rails carry several devices on one bolt pattern.

Bracket and plate names, and what each one holds

The 12 names below are given by what the part carries, not by how it is made: a base plate carries a machine, a locating plate puts one part on two pins, a cylinder bracket holds a pneumatic cylinder by its end cover, and each difference changes what has to be measured or drawn.

Cylinder and actuator brackets: the hole square comes from the cylinder

A bracket that bolts to the end cover of an ISO 15552 pneumatic cylinder needs four holes on the cylinder's TG square and a centre bore that clears the cover's boss: for a 50 mm bore that is a 46.5 mm square for four M8 screws around a 40 mm boss.

The piston rod end is a separate thread, M10×1.25 on a 32 mm bore, M16×1.5 on 50 and 63 mm and M27×2 on 125 mm, and it carries a rod eye or a clevis rather than the bracket. The table follows the data sheets of ISO 15552 cylinders; a compact, round or short-stroke cylinder has its own pattern, so a bracket for one starts from its type number, or a photo of the cover with a ruler across the holes.

Valve actuators bolt on through an ISO 5211 flange, F03 to F16, and stepper and servo motors through a NEMA or IEC flange; both sets of patterns are on the adapter and mounting plates page. An electric linear actuator follows no common standard, so its bracket is drawn from the maker's mounting drawing or measured from the actuator itself.

An aluminium mounting plate with threads in two faces

An aluminium mounting plate machined by EKINSUN has 8 holes in its top face and 2 tapped holes in one long side face: on top, 4 tapped holes, 2 plain through holes and 2 larger holes in opposite corners. Two corners are cut at an angle, a third has a rectangular notch, and a raised lip runs along each short end; each of these is one more dimension to hold, written on a drawing or measured from the old part when there is no drawing. The plate is sand-blasted after machining, which gives the even matte surface in the photos; how blasting, anodising and other finishes treat tapped holes is under plate finishes.

Holes in two faces cannot all be machined from one direction: the side holes are made either in a second clamping with the plate stood on its edge, or on a machine that turns the part to the side. Unless the drawing says otherwise, the distance from the side holes to the top holes is then held to the general tolerance, ±0.3 mm over 30 to 120 mm under ISO 2768-m, so when a part screwed to the side has to line up with one screwed to the top, that dimension and its tolerance belong on the drawing.

The second clamping is set up once per order, which is why one plate tapped on two faces costs more than the same plate tapped on one face, and why the gap narrows over 10 or 20 pieces.

Tapped holes in the side of a plate: how big a thread the edge takes

A tapped hole in the side face of a plate leaves (thickness − thread diameter) ÷ 2 of metal on each side of the thread, so a 10 mm aluminium plate takes an M6 with 2 mm each side, while an M8 leaves 1 mm and tends to bulge or split the edge when the screw is tightened.

Depth matters as much as diameter in a side hole: an M6 needs 12 mm of full thread in aluminium, so the drill goes 15 to 17 mm into the edge, and that hole must not break into a hole drilled from the top face. Where the edge is too thin for the screw the part needs, a smaller thread with more depth or a thicker edge (a boss or a lip left standing) solves it; a wire thread insert makes the thread stronger but needs a larger hole than the screw, so it leaves even less metal in a thin edge (when an insert is the better choice).

Material and finish choice

6061-T6 is the default — light, strong, anodizes well. Step up to 7075-T6 for loaded brackets, or steel/stainless where strength or environment demands. Anodizing or powder coat adds corrosion protection and a finished look. Flatness and hole position are verified on inspection.

Design tips for a strong bracket

Four choices at the design stage decide whether a bracket cracks or lasts, and the first, an inside radius of 3 mm or more, costs nothing on a milled part:

• Fillet the inside corners. Sharp internal corners concentrate stress and are where brackets crack. A milled inside corner already carries the cutter’s radius, 3 mm from a Ø6 end mill, so a radius of that size costs nothing; a sharper corner needs a smaller cutter and more time, a larger radius is only a line on the drawing.
• Add a rib or gusset, not just thickness. A rib stiffens a bracket far more than extra wall, for less weight.
• Keep walls consistent to avoid distortion and chatter marks.
• Reference bolt holes off one datum so they stay true to position.

Send a sketch and we'll suggest tweaks for strength and cost before we cut.

Where a catalogue bracket stops

A zinc-plated 40 × 40 mm angle bracket or a stepper bracket for one NEMA size costs less from stock than made one-off; a bracket becomes a job for us when its hole pattern, its threads in a second face, its thickness, its material or its quantity is yours.

Where a catalogue bracket stops, and what is made instead

You need	From stock?	How it is made
A plain angle bracket, 40 × 40 mm, zinc plated, a box of 20	Yes — stock item	Buy it from stock at a local hardware or industrial supply store — or ask us, we may have it in stock.
The hole pattern of your own device, positions from one datum	No	Drawn from your device or the old bracket, milled from plate or billet
Tapped holes in the top face and in a side face	No	Second clamping or a rotary axis; thread size checked against the edge, as in the table above
A plate for a cylinder bore or motor flange that the catalogue lists in another thickness or offset	No	Hole square and boss bore from the cylinder table, thickness and offset to suit the machine
6061 or 7075 aluminium, 304 or 316L stainless, S235 or 1045 steel, in the thickness the load needs	Rarely	Milled from plate or bar, up to 1,200 × 600 × 500 mm
The bracket from a machine whose maker has gone	No	Measured from the old bracket or from the mating holes, drawn, approved, machined

One bracket, five or a batch: prototype, one-off and low-volume orders

A single prototype bracket, a one-off replacement and a small batch of 20 are machined the same way: the program, the clamping and the first-piece check are paid once per order, so one piece carries all of that cost and each further piece adds only its own machining and finishing time.

Bracket quantities: what an order of that size usually is, and what changes with it

Quantity	Usually	What changes
1 piece	A prototype to check the fit, or one replacement	Set-up sits on one part; the fit is confirmed before any batch
2 to 10	Spares, or brackets for a few machines	Same program; the unit price falls with each piece
10 to 100	A small batch for a production run	A holding fixture for the second face pays off; one finishing batch; parts interchangeable
100 and up	Series parts	A folded, stamped or extruded bracket may cost less: compare before ordering

Most bracket orders fall in the first three rows, and a batch of flange plates held to one bolt pattern shows how position is kept across a run; see low-volume machining, one-off parts and orders from 1 piece, and for folded sheet brackets in larger runs, laser-cut and folded brackets or stamped parts.

No drawing: a bracket made from the old part, a photo or a sketch

A replacement bracket, 1 piece or a batch, can be made without a drawing from the old part, from photos with a ruler in the frame, or from a sketch with the hole spacing; the hole positions and the thread sizes are the two things a photo never shows exactly, so they are measured on the part or written on the sketch.

A copy reproduces the old bracket’s geometry: the alloy and the section stay as they were or change where the old one cracked, and the copy is machined even when the original was cast or folded (copy the geometry, not the process; what changes when a discontinued part is copied). A bracket of flat faces and round holes needs no 3D scan to be redrawn; a scan earns its cost on curved or cast shapes.

Frequently Asked Questions