How to Use a Starrett Automatic Center Punch
By Products for bench top machinists | LittleMachineShop.com | Published: 2026-10-29
Category: How-to Guides
Learn how to use a Starrett automatic center punch for accurate marking on metal. Step-by-step technique, force adjustment, and common mistakes to avoid.
Quick Answer
To use a Starrett automatic center punch, press the tip against your workpiece, adjust the knurled cap for the desired mark depth, and push down until it fires—no hammer needed.
Why an Automatic Center Punch Beats a Hammer
A manual center punch requires a hammer and two hands, which can be awkward on small or curved parts. An automatic center punch stores energy in its spring and releases it when you press down, so one hand is always free to hold the work steady.
The Starrett automatic center punch has all-steel handles and parts, making it durable for repeated shop use. Its adjustable cap lets you vary the force from a light dimple to a deep, prominent mark without changing tools.
Choosing the Right Mark Depth
The depth of your center punch mark matters. A deep mark gives drill bits a positive starting point and prevents walking, but on thin sheet metal it can deform the surface. A lighter mark is better for layout lines or when you need to remove the mark later.
With the Starrett 18A, you screw the knurled cap down for a heavy blow and loosen it for progressively lighter marks. Start with a light setting on a scrap piece to feel the trigger point before marking your actual workpiece.
How to Use an Automatic Center Punch
- Set the striking force: Turn the knurled cap at the top of the punch. Screw it down for a heavier mark, or loosen it for a lighter one. Start with a medium setting and test on scrap material. Adjust before you mark the final part—changing it mid-job is fine, but it's easier to set it once.
- Position the punch tip: Place the tip exactly where you want the mark. On curved or slippery surfaces, hold the punch perpendicular to the work and use your free hand to steady both the punch and the workpiece. Check alignment twice—once the punch fires, you can't easily move the mark.
- Apply downward pressure: Push down smoothly and steadily on the punch. The internal mechanism will release with a sharp click, leaving a clean dimple. Do not jerk or twist the punch while pressing. Let the spring do the work—extra force from your arm doesn't make a better mark and can cause the tip to slip.
- Inspect the mark: After firing, check that the mark is centered and deep enough for your purpose. For drilling, the dimple should be large enough to guide the drill bit. If it's too light, increase the force and mark again, but avoid re-punching the exact same spot if possible. A clean, single mark is more accurate than a double-punched one, so verify before you re-punch.
Product Highlight
- Automatic Center Punch, Starrett: The Starrett automatic center punch has an all-steel handle and parts, and its mechanism fires automatically when downward pressure is applied. This means you can keep one hand on the workpiece for better accuracy and control compared to a manual punch and hammer.
Automatic Center Punch, Starrett
