Granite Moulding Profile Match: Width and Height Are Not a Cross-Section
For a granite moulding profile match, width and height only describe a bounding box. What the workshop needs is the cross-section outline plus a mounting-face datum, copied 1:1 from a profile template — so run a trial length before the batch.
Why won't a factory quote a copy job from width and height alone?
Short answer: the workshop cannot work from width × height. It needs one cross-section outline plus one datum line. The same 100 mm wide × 30 mm high can be a full bullnose, a two-step profile, a 45° chamfer or a concave front — four different cross-sections with nothing in common once cut. Given only width and height, the workshop defaults to a square edge, and what comes back will not match the piece in your hand. A cross-section is what you see cutting across the length; width and height are only its bounding box. Every rise and fall inside that box, every rounded arris, every groove is lost if it is not handed over. So the first job is not measuring the two numbers more precisely — it is handing over the outline: a section drawing with an R on every arc and an angle on every slope, or a sawn-off piece of the old profile.
| What you have | What the workshop gets | What is still missing |
|---|---|---|
| Width × height only | A bounding box, enough to size the block | Every rise, arris and groove inside it |
| A section drawing | The turning points and curves, enough to build a template | Arris radii are guessed, not measured |
| A physical sample | The stylus can follow the whole profile, worn arrises included | Must be long enough to cross one full section |
Which line do I measure from?
From the mounting face — the flat back that sits against the wall or the floor. Every height is taken from it, not from the tip of the visible face and not from some arris in the middle. Once the old moulding is off the wall, that face usually carries mortar, chipped edges and chisel marks; measuring it as found stacks numbers on an uneven datum. Grind the mortar off, or bed the piece on a flat plate, then measure. An uneven datum does not spoil one dimension — it shifts the whole profile: the shape stays right but the entire piece reads taller or shorter than it is. It is also easy to miss later: no outline changes, and you only find out on the wall, when the moulding will not cover the joint or fouls something else. How the two ends turn a corner is a separate question; this is about the section itself.
What does the factory copy from?
A template plus copying. The factory builds one profile template from the section you send; the stylus of the copying machine runs along the template and the cutter head follows it, reproducing the shape 1:1 into the stone. Accuracy therefore depends on the template, not on how many dimensions you list. For a template, a physical piece does more than a list of dimensions — for example 100 to 150 mm long is enough for the stylus to cross one full section; that is an example, not a limit of our machines. Rounded arrises and knocked corners that you cannot measure are all carried on the sample. The template is a one-off cost shared by the whole batch: a short order and a long order pay for the same template work. We usually run this profile in Pink Hemp G564 (GB code G4564), keep 30 mm slabs, minimum order 100 ㎡.
Which shapes can't be made, or need an extra operation?
The cutter is round, so ask about three shapes before you commit. A sharp internal corner cannot be cut: the edge of a rotating cutter sweeps an arc, so the smallest internal radius equals the cutter head radius. For example, with a 100 mm cutter head the tightest internal radius is R50; anything tighter needs a smaller cutter, and a thinner shaft is less rigid and may not reach the bottom of a deep groove. An undercut — narrow outside, wider inside, hooked or dovetail — cannot be produced in one clamping: the cutter enters radially from outside the section, and the hooked part is masked by the stone in front of it. Not impossible, but not in one set-up: fill the hook and change the shape, losing one shadow line, or turn the piece over for a second clamping, adding an operation and a line where the passes meet. Deep narrow grooves are the same: the deeper and narrower, the more the shaft rubs the wall. Ask the workshop what ratio it can hold; do not set it yourself.
| Shape | Why | What to do |
|---|---|---|
| Sharp internal corner | The cutter edge sweeps an arc, so the minimum internal radius equals the cutter head radius | Accept that radius, or use a smaller cutter — ask what it can hold |
| Undercut (hooked, dovetail) | The cutter enters radially from outside; the hooked part is masked by stone in front | Not in one set-up: fill and reshape, or turn over for a second clamping |
| Deep narrow groove | The deeper and narrower, the more the shaft rubs the wall | Ask the workshop what ratio it can hold, then adjust the groove |
What if the profile is taller than the slab is thick?
Profile height is how far the moulding stands out, and it is capped by block thickness: a single-layer section cannot be taller than the slab. We keep 30 mm slabs, so a single layer tops out at 30 mm. Going higher leaves two routes: stack two layers, which means dealing with the joint between them, or order thicker blocks, with lead time quoted separately — do not apply the stock slab shipping days to that. Above the slab thickness you must build up, and it is a build-up through the thickness, not a corner joint: one section split into an upper and a lower part. The order must be build first, shape second — glue up the blank, then run the profile on the machine, so the moulded surface stays continuous. Shape first and build later, and the two moulded faces will hardly line up; the joint will show a step. Put the joint line on the shaded side or the lower edge, never on the visible face.
Should I run a short trial length before the batch?
Yes — more so on a copy job than on a new design. One wrong template takes the whole batch with it; everything goes back to the machine, which costs far more than a trial length. Run one piece first, for example one metre, and compare it side by side with the old profile on three points: does the cross-section match, arris for arris and curve for curve; does the mounting face sit flat, can both backs rest on one plane; is the colour and finish difference against the old piece acceptable, remembering that a polished old piece changes with time. Pass all three, then release the batch. What the trial really buys is moving the template risk forward, not a metre of stone. One more note: if you are designing a new profile rather than copying an old one, read our piece on window surround profiles — it covers the three numbers: face width, projection and termination.