Starrett 18A Automatic Center Punch: One-Handed Drill Starts with Adjustable Strike

# Starrett 18A Automatic Center Punch: One-Handed Drill Starts with Adjustable Strike

A drill bit can skate away from a pencil mark on flat metal before it begins cutting. A conventional center punch can make the guiding dimple, but using one also means positioning the point, holding the work securely and swinging a hammer. The Starrett 18A replaces that hammer blow with an internal spring mechanism: place the point, press downward and the tool trips to make the mark.

That one-handed action is the strongest reason to buy it. The other is control. Starrett gives the 18A an adjustable knurled cap and specifies a 15–20 pound striking range, placing it between the lighter 18AA and heavier 18C in the same family. It is a compact marking tool for repeatable drill starts, not a general-purpose chisel or a substitute for proper workholding.

One-handed actuation keeps the other hand available

Starrett says the 18A's internal mechanism strikes when downward pressure is applied, so no hammer is required. In practical terms, you can place the point on a layout mark and press from directly above while your other hand manages alignment, a clamp or another part of the setup. After firing, the mechanism resets for the next mark.

The benefit is not simply speed. Removing the hammer from the sequence reduces the number of things you must coordinate at the instant the punch is placed. The resulting dimple gives a drill tip a defined starting point and helps reduce wandering. It does not guarantee a perfectly located hole: accurate layout, a securely supported workpiece, the right drill and eye protection still matter. Do not hold a small or sharp workpiece by hand merely because the punch itself operates one-handed.

A 15–20 pound strike sits in the middle of Series 18

Starrett's Series 18 comparison lists the 18A at 15–20 pounds of striking force. The smaller 18AA is listed at 4–6 pounds, while the larger 18C is listed at 40–65 pounds. Those model-specific ranges make the 18A the middle choice, useful when the lightest model is not enough but the heavy 18C would be unnecessary.

The knurled cap regulates the stroke. Starrett instructs users to turn it counterclockwise to decrease striking pressure, and says spring tension remains constant enough to produce uniform marks in depth and size at each setting. The published endpoints do not establish equal increments or calibrated force settings, so the cap should be treated as an adjustable control rather than a numbered torque-like scale. Test the mark on scrap of the same material before working on a finished part.

Five inches and a 9/16-inch body make fit measurable

The 18A measures 5 inches (125 mm) overall, and Starrett lists the punch body at 9/16 inch (14 mm) in diameter. These are dimensions of the complete tool and its body—not the size of the point or the dimple. They help answer whether the punch will fit a pocket, tool roll or a tight setup and whether the knurled steel body will feel substantial enough for a controlled palm press.

Those measurements also separate the 18A from nearby Series 18 models. The 18AA is 4 inches long with a 7/16-inch body; the 18C is 5-1/4 inches long with an 11/16-inch body. If a buyer needs a smaller body or much heavier strike, changing models is more honest than expecting the 18A's adjustment to cover the entire family.

The removable point makes wear serviceable

Starrett specifies an all-steel handle and parts, a knurled handle and a removable point that can be reground or replaced. That matters for a tool whose working tip repeatedly meets metal: routine wear does not automatically retire the complete punch. Follow the manufacturer's service guidance and preserve the point geometry rather than grinding it casually.

The steel construction is not described as stainless or corrosion-proof. Keep the punch dry and clean, and store it so the point is protected. Buy the Starrett 18A when you regularly need centered drill-start marks, value hammer-free one-handed actuation and want a midrange adjustable strike in a 5-inch body. Choose the 18AA for a smaller, lighter strike or the 18C for substantially heavier marking, and use a different tool for chiseling, driving pins or other impact jobs.