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How to Use a Transfer Punch Set
Guide · Updated October 27, 2026
Transfer punches have a precise body diameter and a center point. Fit one in an existing hole, tap it, and it marks the hole center on the part underneath. It's the fastest way to match a bolt pattern.
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Step by step
- Clamp the template: Clamp the template or mating part to the workpiece in its final position.
- Pick the punch: Choose the punch that is a close slip fit in the hole, not loose.
- Mark: Insert the punch and give it one firm tap with a light hammer.
- Deepen the mark: Remove the template and deepen each mark with a center punch.
- Drill: Spot-drill, then drill to size. Use a pilot drill for larger holes.
Accuracy tips
- A loose punch puts the mark off-center, so go up a size if one fits.
- For a tapped hole, use a punch that fits the thread's minor diameter, or a thread-transfer screw.
- Hit each punch only once.
Related: drilling speeds and feeds, pin gage sets.
Worked example: picking the punch for a 1/4-20 clearance hole
Transfer punches are sized to fit closely in the hole. For a 1/4-20 screw in a close-fit 0.257 in (letter F) clearance hole, use a 1/4 in or 17/64 in (0.2656 in) punch that just slips in; a punch 0.010 in undersize can wander about 0.005 in off center. For a #10 screw in a 0.201 in hole, a 13/64 in (0.2031 in) punch is the closest common size.
Tap the punch once with a light hammer; a second blow often makes a double mark. Follow the mark with a center drill before drilling the tap drill, for example #7 (0.201 in) for 1/4-20 or #21 (0.159 in) for 10-32.
Quick shop check
Common problems: punches that are much smaller than the hole wander. If the transferred mark is more than about 0.010 in off, re-locate it by layout and a wiggler before drilling. Clamp the parts together before punching so they cannot shift.
FAQ
What is a transfer punch?
A ground pin with a center point that fits an existing hole and marks its center on the part beneath.
How accurate are transfer punches?
Good enough for clearance holes, typically within a few thousandths. Use a mill and DRO for tighter positions.
Can I use one for threaded holes?
Use a punch sized to the minor diameter, or a threaded transfer screw.
How do I check punch diameters?
Mic them on a micrometer that has been checked with gage blocks. A free calculator at gageblockcalc.com builds the check stacks.
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General shop information only — follow your gage manufacturer's instructions and your quality system.