VC Virtual condition
Virtual condition · Modificadores de zona · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “Hole ⌀10 H7 + ⌖ ⌀0.05 Ⓜ → VC ⌀9.95” states a virtual condition requirement. The functional gauge also embodies the datums in the frame: its locators reproduce A, B and C in the order cited. That is why a part can fail the gauge by not seating properly on the datum even though the hole is in the right place.. The Ⓜ modifier (maximum material condition) can allow bonus tolerance depending on the actual size of the feature.
What controls
A size boundary that results from combining the size at the material condition with the accompanying geometric tolerance, and that represents the worst case for assembly: for a hole, the MMC size minus the geometric tolerance; for a shaft, the MMC size plus the tolerance. It is the size the functional gauge is made to and the value to compare against the mating feature. It is not a dimension of the part and is not dimensioned on the drawing: it is calculated from the feature control frame and the size tolerance.
How to verify
It is not measured directly: it is calculated and then checked. The quickest way in production is a functional gauge machined to the virtual condition — a pin of that diameter for a hole, a ring of that diameter for a shaft —: if it goes in without forcing, the part meets both size and geometry at once, with bonus included. On a CMM the same result is reached by measuring actual size and geometric deviation and checking that their combination does not violate the virtual boundary.
Datums and notes
The functional gauge also embodies the datums in the frame: its locators reproduce A, B and C in the order cited. That is why a part can fail the gauge by not seating properly on the datum even though the hole is in the right place.
Workshop guideline values
- General
- Hole ⌀10 minimum with position 0.2 Ⓜ → virtual condition ⌀9.8; ordinary mounting fasteners.
- Accuracy
- Hole ⌀10 H7 with position 0.05 Ⓜ → virtual condition ⌀9.95; close fits.
- High precision
- Hole ⌀10 with position 0.01 Ⓜ → virtual condition ⌀9.99; precision dowel pin bores.
Guidance only: the drawing's value always wins.
Common mistakes when interpreting it
- Reversing the calculation: for a hole the geometric tolerance is subtracted from the MMC size and for a shaft it is added; the hole loses usable diameter and the shaft gains it.
- Calculating it with the nominal size instead of the material condition size set by the size tolerance.
- Treating it as a dimension to be measured on the part: it is a calculated boundary embodied by the gauge, not a drawing dimension.
How to get it in the workshop / if it comes out of tolerance
Calculate: hole MMC − geo; shaft MMC + geo. If the pin fits within the virtual condition, the assembly works with bonus included.
If the functional gauge does not go in, separate the two causes before touching the program: measure actual size and geometric deviation separately. If the size is close to MMC, opening the hole up by a few hundredths frees up geometric zone; if the size is fine, the problem is location or tilt, and you need to look at spot drilling, the work offset or tool rigidity. A gauge that always rubs on the same side points to a systematic offset of the origin, not to process scatter.
Related symbols
Other symbols in Zone modifiers
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.