# Hole Layout Using a Single Datum (Plates + Center Punching)

Accurate hole placement in FRC depends on using a **consistent datum** and properly marking drill locations before cutting.

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</div>## Using a Datum for Hole Layout

A datum is a fixed reference edge used to measure all features from.

For plates, the best datum is usually:

- A straight factory edge of the material

All hole locations should be measured from this same edge:

- Measure X distance from the datum
- Measure Y distance from the datum
- Do not switch reference edges between holes

Using one datum ensures:

- Holes stay aligned in a grid
- Parts match CAD layouts
- Errors do not accumulate across measurements

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</div>## Marking Hole Locations

Once measurements are made:

- Mark each hole location clearly with a pencil or scribe
- Use a combination square or speed square to ensure straight layout lines when needed
- Double-check critical dimensions before punching or drilling

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</div>## Center Punching

A **center punch** is used to lock in the exact drill location before drilling.

### Why it is used:

- Prevents the drill bit from “walking” (sliding off the mark)
- Improves accuracy on metal surfaces
- Creates a small indentation that guides the drill bit

### How to use it:

- Place the punch directly on the marked point
- Hold it steady and perpendicular to the surface
- Strike firmly with a hammer to create a visible dent

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</div>## Best Practice Workflow

1. Choose a single datum edge
2. Measure all hole positions from that datum
3. Mark each point clearly
4. Use a center punch on every hole location
5. Drill carefully, keeping the bit centered in the punch mark

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</div>## Key Idea

Good hole accuracy comes from consistent measurement from the same datum and center punching every mark before drilling.