VESA: the 75, 100 and 200 patterns

Behind almost any monitor or television sit four threaded holes arranged in a perfect square. That square is a standard — it's called VESA — and it's what lets a wall bracket, an articulated arm or a desk stand from completely different makers fit your screen without anyone having to check with you. The trouble starts when the thing between the screen and the mount is a plate you printed: that piece of plastic makes the monitor's entire weight hang from four screws, and if you model it like any ordinary plate, it sags, creeps or cracks. This article is about exactly what the pattern measures and how to turn those figures into an FDM plate that carries the real weight of a screen, with one warning up front: not every weight belongs on printed plastic.

What VESA is and why it's a square

VESA (short for Video Electronics Standards Association) defines, among other things, the flat display mounting interface: a square pattern of four threaded holes on the back of the equipment. The standard is named after the side of that square in millimetres, and that is all there is to the name. A "VESA 100" monitor has its four holes at the corners of a 100 × 100 mm square; a "VESA 75" one, 75 × 75 mm.

The point of the square is that it's symmetric in both directions: you can rotate the mount 90° and it still fits. That geometric centre of the four screws is your dimensioning datum, not a promise about where the weight sits. On many monitors and televisions the pattern is offset from the centre of mass — often below it — so there's almost always a tipping moment pulling the screen forwards. More on that shortly. To dimension, measure half a side along each axis from the centre; don't chain your dimensions hole to hole, because the errors add up and the fourth screw won't line up.

The holes on the screen are threaded (they carry a factory nut or metal insert), not clearance holes. That matters for your design: on the monitor side you supply the screw, and your plate only needs a clearance hole for that screw to pass through on its way to the screen's thread. The thread that actually holds is in the equipment, not in your plastic.

The patterns and their thread

Four sizes cover the vast majority of equipment, and each one is paired with a different screw size. The thread isn't a detail: it grows with the weight the pattern has to carry.

The jump from M4 to M6/M8 is the part most often overlooked. A 100 × 100 monitor is held by four M4s because it weighs little. A 200 × 200 television can weigh several times more, and its wider pattern acts as a lever: as the screen tends to fall forwards, the top screws take far more than a quarter of the weight. That's why it steps up to M6 or M8, with more load-bearing cross-section. If you're designing an adapter for a large pattern, copy its thread size too: don't put M4 where the maker specified M8.

Creep and material: why PLA won't hang a monitor

A VESA plate lives under permanent static load, and that's the condition that punishes a thermoplastic most. Under constant stress plastics creep: they deform slowly and steadily, with no need for the load to increase. A plate that holds perfectly on day one can sag, loosen its screws or break weeks or months later, without warning. That's the trap with this kind of part: failure doesn't happen during assembly, it happens on its own, over time.

PLA is the worst possible candidate. It starts to creep appreciably even at room temperature, and its glass transition temperature is around 55–60 °C; the back of a switched-on screen warms up, and it only takes a heat spike — a hot summer, a nearby radiator, the electronics themselves — for a loaded PLA plate to start slipping. ABS isn't a good choice here either. To hang weight, reach for PETG, ASA, polycarbonate or nylon, materials with better creep resistance and higher softening temperatures; PC and nylon, in particular, come into their own when the load is serious.

Orientation, tipping and stiffness

Layer adhesion is the weak point of any FDM part. A bead is well fused along its run, but the bond between one layer and the next is more fragile: it's a glued joint, not continuous material. If the load tends to separate layers — to open the part like the pages of a book — you're working against the weakest seam you have. The full account of why the material is anisotropic is in Layer adhesion and anisotropy.

For a VESA plate you want to print it flat, wide face on the bed, for three reasons: the load runs along the beads rather than across them; the flat face seats cleanly against the monitor; and, above all, a wide part resists buckling outwards. But laying it flat doesn't remove the dangerous failure mode: the tipping moment. Because the centre of mass sits ahead of the plane of the screws, the screen pulls the top screws in a direction perpendicular to the plate, and on a flat-printed plate that pull — plus the pull-through under the screw head — acts right between layers, the weak direction. In other words, printing flat doesn't erase delamination; it moves it to the pull-out of the top screws.

That's why the top screws govern the design. Reinforce the section around them substantially, use wide washers that spread the head over more layers and, where you can, raise the perimeter count and solid layers there. The force they see isn't "weight over four": depending on the lever arm — the depth of the centre of mass against the height of the pattern — it can be considerably higher.

Thickness alone won't save a plate; geometry will. A thin, flat plate flexes; the same amount of plastic redistributed into ribs — ridges standing proud of the back face — multiplies bending stiffness while barely adding mass, because what matters against bending is the depth of the section, not its area (the second moment of area grows with the cube of the depth). Add ribs tying the four holes to each other and to the anchor point on the mount, and round the internal corners of the ribs: a sharp corner is a stress raiser where the crack starts. Ribs, gussets and fillets walks through sizing them.

The holes and adapting from one pattern to another

The screw on the screen side crosses your plate through a clearance hole, and that hole is subject to the same bias as any other in FDM: holes come out narrower than you model them. The bead encroaches on the diameter, the squish of the first layers narrows the mouth, and shrinkage pulls the whole hole in, all in the same direction. If you model the clearance hole for an M4 at exactly 4.0 mm, the screw probably won't pass. Give it clearance: for an M4 you want a generous hole, on the order of 4.3–4.5 mm modelled diameter, so the screw passes without binding even after the process closes the hole up; the clamping comes from the head against the plate's face, not the thread against plastic. The physical reason for that bias is in Real printed clearances, and the clearance diameters per thread size in Captive nuts and screw clearances.

The side where your plate joins the mount or arm is a different matter. There, if you need to thread into the plastic itself, don't trust a printed thread to hang weight: it tears out between layers as you tighten. Embed a heat-set insert or house a captive nut, which spreads the load over a metal face and gives a joint that takes a real tightening torque. How to size the boss that receives the insert is covered in Designing for heat-set inserts.

The most common case for a printed plate is precisely the one the market doesn't always cover: translating one pattern to another. A monitor with VESA 75 that you want to hang off an arm made for 100; a screen with its 100 × 100 going onto a mount with a different bolt pattern of its own. The plate acts as the go-between: one face replicates the screen's pattern, the other the mount's. The rule tolerates no approximations: respect both patterns at their exact figures. The 75 square measures 75.0 mm between centres and the 100, 100.0 mm; don't round or "almost" square it. Place each group of four holes with its own clearance according to its thread (M4 on the small side, whatever applies on the large one) and share the centre between the two patterns, so the load falls along the same axis and doesn't create an extra moment trying to tip the plate.

When you overlay two concentric patterns, the holes of the inner square fall near the ribs of the outer one. Use that: run the ribs through all four anchors of both patterns, so a single lattice of ribs stiffens both interfaces at once. It's easier to stiffen a plate that spreads the load across a grid than one that concentrates it at four isolated points.

Before you print: measure your monitor

No article can tell you the exact pattern of your equipment, and here precision isn't negotiable, because a screen hangs from those four screws. The sizes in the table are the standard ones, but the specific thread and sometimes the usable depth of the hole depend on the model; some makers use patterns or screws that stray from the norm, and some ship their own spacers.

Before you model an adapter that's going to carry weight, open your monitor's manual or its datasheet and confirm three things: the pattern (measure the two axes separately, don't assume it's square), the thread size and the screw length it accepts without fouling the internal electronics. If the manual doesn't say, measure it: the centre-to-centre distance with callipers for the 75 and 100 patterns, and with a rule or tape for the 200s (or measure edge to edge and subtract the hole diameter); the thread, by trying a known screw. An adapter with the wrong pattern, at best, doesn't fit; at worst, it goes in crooked, loads badly and ends up on the floor with the screen on top.

With the pattern confirmed, the right material, the clearances that Real printed clearances gives you and the joint to the mount solved with inserts, you have a plate that holds a light monitor with confidence. Don't treat it as if it were metal: plastic creeps and steel doesn't, so check now and then that it hasn't sagged, and for large, heavy screens leave the job to a metal plate. The natural next step is fixing that insert-based joint firmly to the mount: carry on with Designing for heat-set inserts.