Measure STEP files on Android — and actually trust the numbers

Updated 7 July 2026 By the tool room at Saptasati Industries 6 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 certified exactness, 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 section 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.

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.

   One part stays lit, the rest of the assembly dims to context — no more measuring the wrong bracket.

3. Snap center-to-center for pitches; edge-to-edge for gaps.

   Watch the tag: exact ✓ means the number came from true 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