⌖ Position
Position · Ubicación · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
The position of the hole or pin (diameter) must lie within a cylindrical tolerance zone 0.1 mm in diameter, centred on its true position and measured from datums A, B and C in that order. The Ⓜ modifier (maximum material condition) grants extra geometric tolerance when the hole comes out larger (or the pin smaller) than its MMC limit.
What controls
Controls the actual location of a feature of size (hole, shaft, slot, median plane) relative to a datum reference frame, comparing its actual location with its true (theoretically exact) position defined by basic dimensions. The tolerance zone is normally a cylinder (with ⌀, for holes or shafts) or two parallel planes (for slots or median planes) centered exactly on the basic position. It is a clear improvement over the classic ± coordinate tolerancing method: it defines a real (circular) acceptance zone rather than a square one, giving more usable area for the same functional control.
How to verify
On a CMM, the datum reference frame is established first (A, B, C in order of precedence), then the actual location of the feature is measured relative to that frame and compared with the basic position; the result is expressed as the diameter of the tolerance zone actually used (true position). In a shop without a CMM, a functional (go/no-go) gauge built to the feature's virtual condition is the fastest method for series production. Position in the GD&T sense CANNOT be verified correctly with calipers or a conventional micrometer: they only measure distance along one axis, not the combined radial deviation in the plane.
tolerance zone
Cylinder (with ⌀) centered on the exact basic position relative to the datum reference frame.
Datums and notes
Usually uses three datums A|B|C in order of precedence.
Workshop guideline values
- General
- 0.1–0.3 mm on through holes or fastener holes in general machining.
- Accuracy
- 0.03–0.08 mm on dowel pins, threads or close fits.
- High precision
- 0.005–0.02 mm on precision fits or reference hole patterns.
Guidance only: the drawing's value always wins.
Common mistakes when interpreting it
- Reading the value as a radius instead of a diameter: the tolerance zone with ⌀ is a circle with that full diameter, not that value as the maximum distance from the center.
- Forgetting that without Ⓜ there is no bonus tolerance: the feature must meet the stated position at its actual size, with no extra margin even if the hole comes out larger.
How to get it in the workshop / if it comes out of tolerance
The most widely used symbol in the shop for holes and shafts. With Ⓜ it allows bonus tolerance when the feature departs from MMC — the hole gets larger or the shaft gets smaller.
If a drilled hole wanders, always start with a spot drill before the drill: without it, the drill "walks" on entry. Check axis backlash and the work offset (G54) before blaming the program. When Ⓜ is present, remember that you gain extra tolerance if the hole comes out larger than its MMC (or the shaft smaller): a part that looks "out" on position may still be good if the size gives you bonus — calculate the virtual condition before rejecting it.
Other symbols in Location
Related tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.