DRAWING DETAILS / CNC MACHINING INSIGHTS
A flange pattern is more than a group of equally spaced holes. Its function depends on the center reference, bolt-circle definition, hole type and the mating component. A complete drawing callout makes that relationship reviewable before production is released.
Define the pattern from its functional center
Start by showing the center feature that governs the pattern: a bore, shaft axis, locating diameter or other interface. Then identify the bolt circle, the quantity of holes and the angular arrangement. The pattern should not depend on a reviewer inferring the center from a CAD image.
When the flange mates to another part, provide relevant mating geometry. Our assembly-fit guide explains the information that helps an RFQ review understand an interface.
Give each hole a complete callout
| Pattern detail | Useful drawing information |
|---|---|
| Hole quantity and arrangement | Quantity, equal spacing where intended, and clocking or angular reference if needed. |
| Bolt-circle reference | Circle definition and the center feature or drawing reference. |
| Hole type | Diameter plus through, blind, threaded, counterbore or countersink requirement. |
| Clocking feature | Visible angular reference and the related feature or view. |
For hole details that include recesses, see our counterbore, countersink and spotface guide. The flange pattern and the individual hole geometry should both be complete.
Make clocking intent explicit
If all holes are equally spaced and rotational orientation does not matter, state the pattern clearly. If one hole, notch, port or connector feature establishes orientation, show the angular relationship from a named reference. This is especially important when a flange has a repeated pattern plus one non-symmetrical feature.
Connect inspection to the assembly
Identify the dimensions that control mating, sealing or alignment. A pattern used only for fastener clearance may need different attention than one that also establishes location. Our CNC inspection requirements guide explains how to mark functional features for a clearer review.
RFQ questions to answer
- What center feature establishes the bolt-circle reference?
- How many holes are present, and how are they arranged?
- What complete hole callout applies?
- Does any feature control the rotational clocking of the flange?
- Which dimensions affect mating or alignment?
Keep the flange pattern unambiguous
ExactMach coordinates drawing-defined CNC milling, CNC turning, prototypes and custom parts around Shenzhen and Dongguan for international orders. A clear bolt-circle callout helps the manufacturing review understand the released flange requirement before production begins.