USB camera module mounting holes: match the board, not the cable

A USB camera module is a printed circuit board with four small holes near its corners. Those holes — their diameter and their centre-to-centre spacing — are the whole mechanical story. A mount cut for one module outline will not take another: the patterns differ by tens of millimetres, not fractions, and no adapter plate recovers the difference. This guide is for anyone fixing USB (UVC) board camera modules into a machine, a case or a bench stand. You will read the pattern off the mechanical drawing, check screw size against hole size with one subtraction, and choose between a bracket cut to the pattern, a slotted bracket that spans a range, or a housing built around the module. Do it before ordering hardware, and the camera lands on a mount that fits the first time.

The holes belong to the board, not the cable

The cable predicts nothing about the mount. Ribbon-cable camera modules share one dominant outline, so most ready-made brackets are cut for that footprint, with mounting holes about 2.0 mm across. A USB camera module is a different board: its outline, hole count and hole positions follow whichever sensor and interface layout the designer chose, and every module family lands in a different place. A bracket made for a ribbon camera misses a USB module's holes completely.

That is why the mismatch shows up as a total miss rather than a couple of millimetres off. Treat the ribbon-cable module as a separate mechanical species — its flat-flex connector, with its own latch and length limits, has nothing to do with how a USB module bolts down, as the ribbon cable replacement guide explains. The decision follows: read the USB module's own pattern first, then buy the bracket.

Read the mechanical drawing before you order anything

The drawing — a dimensioned PDF, DXF or STEP file from the module maker — is the only authority for four numbers:

• hole diameter, usually one value for all four holes;
• pitch in X and pitch in Y, measured hole-centre to hole-centre;
• board outline and corner radii, so a case grips edges rather than components;
• the offset from the hole datum to the sensor's optical centre.

Makers publish STEP files for exactly this purpose, and the housing design guide shows how to build from them; the same files give your bracket its hole positions. Pull the numbers once, keep them with the project, and re-check them at every hardware revision. Outlines and hole patterns do move between revisions, which is why a hardware revision compatibility check starts on the drawing, not the box label.

The optical-centre offset is not cosmetic. Object-space shift equals mounting offset divided by magnification. At the 0.05-0.2 magnifications typical of inspection optics, a 10 mm placement error swings your region of interest 50-200 mm across the scene. Only the drawing states that number.

Screw size against hole size

One rule decides the screw: it passes only when its thread diameter is no larger than the hole. These are the standard values:

Camera boards usually cut holes at or just under the thread diameter for a snug location fit — the 2.0 mm holes on the common ribbon-camera footprint are exactly that, sized for M2. A close-enough M2.5 screw cannot even start: the drill that would cut an M2.5 thread is already 2.05 mm across.

Worked example: will an M2.5 screw pass a 2.0 mm camera hole?

Inputs, each from its source:

• hole diameter 2.0 mm — the dimensioned drawing of the common ribbon-camera footprint;
• M2.5 tapping drill diameter 2.05 mm — standard metric coarse-thread table, pitch 0.45 mm;
• M2 thread diameter 2.0 mm — same table, pitch 0.4 mm.

The rule, in words: whatever goes through the hole must be no bigger than the hole, and the interference is how much the hole is short by.

The arithmetic, written out:

• M2.5 against the 2.0 mm hole: 2.05 mm − 2.00 mm = 0.05 mm oversize. The tapping drill will not enter, so no M2.5 thread can form, and the 2.5 mm screw itself is further off still. Forcing it cuts a thread into the laminate and lifts pads.
• M2 against the same hole: 2.00 mm − 2.00 mm = 0.00 mm. A line-to-line pass: the screw slides under finger pressure and clamps as a snug location fit, which is how the pattern was designed to be used.

Result: M2.5 is out, M2 is the screw for a 2.0 mm hole. Generalize the threshold like this: any oversize above zero means the screw does not pass, and more than about 0.1 mm of interference means you would be machining the board instead of clamping it. When you want a free-running fit rather than a snug one, spec the ISO 273 medium hole — 2.4 mm for M2, 2.8 mm for M2.5, 3.4 mm for M3.

Three ways to hold the module

A bracket cut to the pattern fits fastest and also sets the optical height. It works only when the bracket's pitch equals the drawing's pitch in both axes, so check X and Y separately — brackets exist that match on one axis and miss on the other.

A slotted bracket absorbs pitch differences between modules, which is the flexible answer when one station takes several module types. Slots give a few millimetres of adjustment per axis; the small brackets that carry an M12 lens on a board typically use a 20 mm hole spacing, which fits boards laid out for it and nothing wider.

A case built for the form factor grips the board on its own datum, carries the strain relief and turns the module into a bolt-in sensor block — the right answer wherever a machine will bump, wash or dust the camera.

If the hardware you have is one size off, adapt the bracket, never the board: installing threaded inserts in oversized holes is the standard repair on plates and castings, and a bushing solves the same problem in minutes.

Before any of the three, clear the overhangs: the USB socket, IO header and lens barrel all stick out past the outline, and the bracket must miss them. It is the same verify-first discipline as a camera IO board pin alignment before the board goes under screws.

Which module style you are mounting

Board cameras arrive in three mechanical styles, and the style decides how much weight the hole pattern carries on its own. If the module choice itself is still open, the camera finder filters board-level cameras by mount, interface and shutter.

Values as printed in each product's data sheet; open a part for its drawing and full specifications.

A C-mount module bolts through the lens mount as well as the board, because the barrel accepts standard C-mount clamping hardware; the bracket work shrinks to a plate that takes both. Lens mount thread sizes differ across modules — M12, C-mount and others — and each brings its own clamp family. The LS-BCM-0003 is a 3.1 MP USB3 board camera with a 1/1.8" global-shutter sensor and a C-mount, so it takes either route.

An S-mount (M12) module has no structural mount worth loading: the barrel is a focus mechanism and must stay free. Clamp the PCB edges instead, exactly as the drawing shows. The LS-BCM-0043 is a 1.3 MP USB3 binocular module with M12 lens mounts and a global shutter. Its data sheet lists 1280 × 1024 at 123 fps. A stereo pair like this earns its pattern extra respect, because both heads must hold a fixed relative pose.

A bare board arrives with no fixings beyond the PCB holes, so standoffs and a housing carry everything. The MV-CB060-10UM-B is a 6 MP 1/1.8" USB3 camera supplied as a bare board; plan its standoffs straight from the drawing, and the small-form-factor USB module guide covers how such modules integrate on the software side.

On the bench: stands and slide tables

With the module on its bracket or in its case, the assembly mounts like any machine-vision camera. A slide-table stand gives height and focus travel, and the camera stands range adds tilt stages, X/Y plates and rotary stages for fine posing. The LS-MNT-0040 is a professional slide-table stand with a 700 mm height and a 400 × 450 mm base — a stable home for a bracket-carried USB module while you set focus and field.

Pose the part, pose the camera, then lock the stand down: an X/Y stage under the bracket beats re-drilling anything will ever manage.

Set the optics once the board is fixed

The hole pattern fixes where the sensor sits; the lens decides what it sees. Keep the two errors apart — a mounting error moves the field, a lens error sizes it — and work them in that order: mount first, optics second.

When field of view and working distance are settled, the lens focal length calculator turns them into a focal length and filters the lens finder to match:

On M12 boards, lock the focus once it is set. Setting holder height and back focus is a one-time job you want done with the board finally bolted down, so the setting survives every later handling.

Checks before you order

Run this list with the drawing open; every line is a number that goes on the order:

• hole diameter in mm — sets the screw;
• pitch in X and in Y — sets the bracket;
• optical-centre offset — sets how the bracket orients the module;
• screw length — passes the board and engages the standoff without bottoming out;
• slot range on an adjustable bracket, checked in both axes;
• clearance for the USB socket, IO header and lens barrel overhang;
• a strain-relief anchor on the bracket or case, with a service loop of cable;
• drawing revision matched to the board revision you will receive.

When the usual answer is wrong

Clamping the lens barrel to carry the whole camera is the classic mistake. The S-mount thread is a focusing mechanism, and clamp load plus vibration walks the focus — the same physics that makes autofocus versus fixed focus on mobile robots a mounting question first and a lensing question second.

Cable ties and hot glue belong to bench experiments only. Glue creeps, ties stretch, and neither returns the camera to a repeatable pose after a bump, which quietly invalidates every calibration you took.

Assume no universal adapter exists. Pitch differences between module families run to tens of millimetres per axis; the 20 mm spacing common on M12 lens brackets is one layout, not a standard.

Separate the two failures as well. If the module streams cleanly over UVC but will not bolt down, the electronics are finished and the drawing is the next document to open. If the image itself is broken, start with the image format and wiring checks instead.

The decision in one line

Read the drawing, take the four numbers, run the subtraction, and order a bracket cut to the pitch or a slotted one that spans it. The board-level cameras category filters by mount and interface, and everything mechanical sits under camera stands and brackets in the accessories finder. The configurator's stand step walks the station in order, and the cameras topic page gathers the rest of the board-camera guides. If you want a drawing checked against a bracket before you buy, the contact page reaches the applications team.