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How to Transfer Hole Locations
Guide · Updated October 28, 2026
When a part has to bolt to an existing one, you can copy its holes. Use transfer punches, spot through the holes, or measure each hole and drill by coordinates.
Measure accurately
Check calipers on gage blocks. The free Gage Block Calculator builds the stack.
Step by step
- Clamp the parts: Clamp them in their final position.
- Transfer punch: Use a punch matching the hole and tap it.
- Or spot through: Spot drill through the holes on the drill press.
- Or measure: Measure coordinates from datum edges.
- Center punch: Deepen the marks.
- Drill: Drill and check.
- Test fit: Assemble.
Worked example: edge to center
Measure from the edge to the near side of a 0.250 in hole: 1.375 in. The center is 1.375 + 0.125 = 1.500 in. Measuring to the far side gives 1.625 in, so center = 1.625 − 0.125 = 1.500 in. Averaging both readings cancels hole size error: (1.375 + 1.625) ÷ 2 = 1.500 in.
Transfer punch accuracy
Transfer punches are only as good as the fit in the hole.
Coordinates
Measure every hole from the same two datum edges.
Common problems
Holes don't line up: parts shifted. Wrong mark: punch too small.
Tips
- Punch: transfer punch set.
- Height: height gage layout.
- DRO: DRO basics.
Worked example: transferring a four-hole pattern
A 4 in × 3 in cover plate has four 1/4-20 clearance holes that must line up with tapped holes in a housing. Clamp the cover in position with two toolmakers clamps, run a 0.266 in (letter H) drill through one cover hole just deep enough to spot the housing, and pin it with a 1/4 in dowel or a transfer screw. Spot the opposite corner, pin it, then spot the last two. Remove the cover, drill the housing with a #7 (0.201 in) tap drill and tap 1/4-20.
If you are working from a drawing instead of a mating part, convert hole positions to X/Y from one datum corner and check them with a height gage or by stacking gage blocks against a parallel: a hole at X = 0.750 in is checked by a 0.750 in stack plus half the pin diameter. A 0.002 in transfer error at each hole can stack to 0.004 in across the pattern, which is enough to bind 1/4-20 screws in a close-fit 0.257 in hole, so use transfer punches or screws that match the hole closely.
After drilling, test fit the cover with all four screws before tapping the rest of the job. If a hole is off, open the cover hole rather than enlarging the tapped hole.
FAQ
How do I transfer holes?
Transfer punches, spotting or measuring.
Which is most accurate?
Spotting through or measuring.
Why average?
It cancels hole size error.
Why clamp first?
So parts do not shift.
Do I need layout dye?
It helps.
Related guides and calculators
- How to Use a Transfer Punch Set
- How to Use a Height Gage for Layout
- Digital Readout (DRO) Basics for Machinists
- Layout Dye and Scribing Basics
- How to Center Drill and Spot Drill
- How to Use a Pipe Tap (NPT)
- How to Use a Tap Wrench
- How to Use Transfer Screws to Locate Holes
- All free machinist calculators
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