How to Copy a Part Without CAD

Most people who need a part printed do not have a file. They have a broken bracket, a missing clip, or one surviving example of something the manufacturer stopped making. That is the normal case, not the awkward one.

The route is: measure it, photograph it, describe it, and we draw it. No CAD skills required at your end.

First, be clear about what we are not doing

We do not have a 3D scanner. No structured light, no photogrammetry rig, no point cloud. We should say that plainly, because scanning gets talked about a great deal and it would be easy to imply otherwise.

That is less of a limitation than it sounds. Scanning is genuinely brilliant for organic, sculpted shapes — a carving, a body panel, a face. For the parts people actually need copied — brackets, clips, housings, spacers, gears, mounts — a scan is often the slower route. Those parts are made of flats, cylinders, ribs and holes, and a set of good caliper measurements defines them exactly, whereas a scan gives you a slightly noisy mesh of approximately the right shape that then needs cleaning up and re-drawing anyway.

The output of measuring is a clean parametric model. That is better than a scan-derived mesh: it is dimensionally exact, we can thicken the bit that broke, and we can change it later.

What to measure

Get a pair of digital calipers. They are inexpensive, they are the single most useful tool for this, and a ruler will not do — a ruler is fine for envelope sizes and hopeless for a fit.

Then work through:

1. The overall envelope. Length, width, height.
2. Every hole. Diameter, and the distance from hole centre to hole centre — not to the edge if you can help it. Centre-to-centre is what has to be right; an edge can move.
3. Thicknesses. Wall thickness, plate thickness, rib thickness. Measure in several places; moulded parts taper.
4. The mating features. Whatever the part clips into, sits on or bolts to. These are the dimensions that must be right.
5. Anything round. Diameters at each end of a taper, and how deep it goes.

Measure everything more than once, in more than one place. Moulded and extruded parts are rarely as round or as square as they look, and finding a 0.3 mm discrepancy now is cheaper than finding it in a printed part.

What to photograph

Photos carry the shape; measurements carry the size. Together they are enough.

• Every face. Six shots, straight on, not at an angle.
• Put a ruler in frame alongside the part in a couple of them. It lets us sanity-check everything else.
• Plain background, good light. A sheet of paper on a windowsill beats any amount of fiddling.
• Close-ups of the fiddly bits — the clip, the boss, the thread, the broken face.
• A photo of where it fits, still installed if possible. This is the one people forget and it is often the most useful of the lot.

The most useful thing you can do

Post us the part. If you have it, even in pieces, send it. Measuring it ourselves removes every ambiguity, and the broken pieces tell us why it failed — which is the information that stops the replacement failing the same way. A part that snapped at a thin section wants a fillet and a different print orientation, not a faithful copy of the flaw.

If posting is not an option, measurements and photos work. Say which dimensions are critical and which have room to move — that one sentence is worth more than any extra measurement, because it tells us where to put the unavoidable error. Our guides on measuring a bracket and tolerances and fit go further on both.

Then what

We draw the model from what you send, and you get to look at it before anything is printed. If a fit is critical, a small test coupon — just the hole or the clip, minutes and a few grams — settles the clearance before we commit to the full part. That is covered under 3D design help and replacement plastic parts.

Where this is the wrong process

Straight about the limits:

• Complex organic or sculpted shapes. A statuette, a body panel, a curved handle with no flat reference. Calipers cannot describe those and we cannot scan them. Find a scanning service.
• Precision parts. If the original was machined to a bearing fit, a copy measured with calipers and printed in plastic will not reproduce it. See 3D printing vs CNC machining.
• Metal parts under real load. We can copy the shape; plastic will not do the job. Vehicle structure, brakes, steering, lifting gear — no.
• Parts still available to buy. If the manufacturer sells it for a few pounds, buy it. Custom work is for the parts nobody sells any more.
• Anything still in copyright or patent. Copying for your own repair is one thing; reproducing someone's product is another.

Get an estimate — describe the part, no file needed · upload photos · see how pricing works