Measure STEP files on Android — and actually trust the numbers

Updated 28 July 2026 By the tool room at Saptasati Industries 8 min read

"Can you check the hole pitch?" is the most common reason anyone in manufacturing opens a CAD file. On the shop floor that question arrives on a phone. The good news: a STEP file carries the exact geometry, so a phone can answer as authoritatively as a workstation — if the viewer does measurement honestly. Here's what honest looks like.

1. Snapping: measure geometry, not pixels

Tapping "roughly where the corner looks like it is" produces garbage on a 6-inch screen. A usable mobile viewer snaps your finger magnetically to real geometric targets and tells you what it caught. PartLens colour-codes them the same way on screen and in its readouts: vertices (true corner points), centers (hole and arc centers — the workhorse for pitch checks), edges with their midpoints, and faces. Center-to-center on two dowel holes gives you the pitch in one gesture; on our own demo die that's a 2071.444 mm span resolved to the micron from the file's geometry.

2. Exact vs approximate — the honesty question

Every 3D viewer shows you a triangulated mesh, because GPUs draw triangles. The trap: some viewers also measure that mesh. A hole rim approximated by 24 chords measures smaller than the true circle; a curved flange measured across facets reads short. The error is invisible and unbounded — you can't tell how wrong a number is by looking at it.

The honest approach is to evaluate measurements against the STEP file's actual B-rep — the analytic planes, cylinders and NURBS the file defines — and to say so. PartLens tags every value exact ✓ when it was computed from that true geometry and approximate ≈ when only the mesh was available, and it never silently swaps one for the other. When a job demands an authoritative exact query, an embedded OCCT industry kernel double-checks results in a sandboxed process. If you quote numbers to customers, insist on a viewer that makes this distinction — whatever viewer that is.

3. Sections: measuring what you can't see

Wall thickness, internal clearances, seat depths — half the dimensions that matter are inside the part. A section view cuts the model with a plane; a good one keeps the cut live while you drag, and draws the resulting 2D profile separately so you can read it like a drawing. PartLens clips per-fragment on the GPU (smooth even mid-assembly) and computes the profile curve in a dedicated window — the same interaction we show in the inspection act of our homepage, running on a real 1.25M-triangle production die.

4. Datum-style checks: coordinates the way inspection reads them

A raw XYZ position is meaningless until it's relative to the datum your drawing uses. PartLens lets you pick a zero point and directions, then reads positions the way an inspection sheet would — X this, Y that, from your datum. It also detects holes and slots analytically (diameter, count, through/blind), which turns "check all six clearance holes" from twelve taps into one glance.

5. One-tap features, weight and assembly clearance

Android v2.26 adds four focused measurement modes: Smart, Feature, Edge Length and Angle. A single pick can read a bore or boss diameter, fillet radius, taper or included angle, chamfer width, true arc length or face area from retained STEP identity where available. The selected face is outlined before the result is committed, so you can verify what the app actually measured.

The Weight and clearance panel adds envelope, surface area, volume, material-based mass, centre of gravity, stock utilisation and projected area along X/Y/Z. PartLens withholds volume, mass, utilisation and projected area when the geometry is not a closed solid rather than presenting a plausible-looking bad number. For assemblies, select two parts to distinguish a clear gap, touching contact and a material clash.

A real shop-floor measuring workflow

1. Open the customer's STEP straight from WhatsApp.

   No upload, no login — see how to open STEP files on Android.

2. Isolate the component in question.

   PartLens hides every other occurrence and auto-fits the selected branch — no more measuring the wrong bracket.

3. Use Smart or Feature for a bore, radius, taper, chamfer or face.

   Confirm the outlined face, then watch the tag: exact ✓ means the number came from retained geometry.

4. Cut a section for anything internal.

   Drag the plane, read the live 2D profile, measure on it.

5. Screenshot the evidence.

   A measured, annotated screenshot in the group chat settles arguments faster than any phone call.

Frequently asked questions