KEVOS® MAKEOS · Quality
Fastener Position Tolerance (Floating or Fixed) and Part Check
What position tolerance can I give the holes for these fasteners and clearance holes, and does a measured part pass with its bonus tolerance?
Position tolerance for a bolted pattern by the fastener formulas: floating fasteners (clearance holes in both parts) T = H − F, fixed fasteners (one part threaded or pressed) T₁ + T₂ = H − F split between the parts, with the projected tolerance zone reminder, then the check of a measured hole: actual position from the coordinate deviations, bonus tolerance from the departure from maximum material condition, and accept or reject (as the true position tool).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Fastener case | choice | Floating fasteners pass through clearance holes in all parts; fixed fasteners are held in one part (tapped hole, stud, dowel). |
| Clearance hole at MMC (smallest hole) | mm | Smallest permitted clearance hole (maximum material condition). |
| Fastener at MMC (largest fastener) | mm | Largest permitted fastener diameter. |
| Share of total tolerance given to the clearance-hole part (fixed case) | % | For fixed fasteners, the share of H − F given to the part with clearance holes (the rest goes to the threaded part, whose zone should be projected). |
| Measured hole | ||
| X deviation from true position | mm | Measured X offset of the hole from its true position. |
| Y deviation from true position | mm | Measured Y offset. |
| Measured hole size | mm | Measured size of that hole. |
| Hole size upper limit (LMC) | mm | Largest permitted size of the clearance hole. |
Method and formulas
- Floating: T = H − F for each part; fixed: T₁ + T₂ = H − F, split by the share (project the threaded part’s zone).
- Actual position = 2√(Δx² + Δy²) (as the true position tool).
- Bonus at MMC = actual hole size − MMC size; allowed = T + bonus; accept if position ≤ allowed and the size is within limits.
- Example: the clearance holes get ⌀1 mm at MMC; the measured hole is at ⌀1 with ⌀1.1 allowed.
Limitations
- Zero-clearance assembly condition with no allowance for fastener head or thread tilt.
- Fixed-fastener zones should be projected by the mating part thickness.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set position tolerances for a bolted joint
- Check whether a part with off-position holes still assembles
- Choose clearance hole size for a positional tolerance
Who it is for
- Design engineers
- Inspectors
- Drafters
What you get
- Position tolerance at MMC for each part
- Actual position and bonus of the measured hole
- Accept or reject
Interpreting the result
- Bonus tolerance at MMC accepts parts with larger holes and more position error that still assemble.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 615–627. Topic reference; no source tables or recommended settings are reproduced.
- ASME Y14.5-2018 Dimensioning and Tolerancing
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Open the Fastener Position Tolerance (Floating or Fixed) and Part Check calculator
