Steel Type and Holders for Industrial Part Identification

A university key shop can hold thousands of padlocks, lock cylinders, and keys that look nearly identical. Lose track of which key fits which cylinder and the entire system stops working. The fix most maintenance and manufacturing operations reach for is steel type: hardened steel characters that stamp a permanent serial number directly into the metal, so the mark survives handling, cleaning, and years of daily use that would rub off ink or peel a label.

DePaul University in Chicago has done exactly that for more than 20 years. This post explains how steel type works, how slotted and utility type differ, which industries rely on it, how long a good set lasts, and when a numbering head is the better tool for the job.

How do you permanently mark keys, locks, and small parts?

You stamp them with steel type. A hardened steel character is pressed or struck into the surface, leaving a serial number that won't fade, wash away, or rub off the way ink and adhesive labels do. For small, near-identical items handled every day, a stamped mark is the only one that reliably stays put.

The DePaul University key shop in Chicago lives with that problem at scale. Every padlock, lock cylinder, and key on campus needs a unique identifier so the shop can track and organize them across thousands of students, faculty, and rooms. For over 20 years the shop has marked each piece with its own serial number using a holder and type set from Durable Technologies.

When Key Shop Supervisor Tom Hojnacki needed a set with more characters, he came back to the same source he had relied on for two decades.

The Durable Mecco utility type and holder set we bought over 20 years is used multiple times every day with virtually no visible wear, mushrooming of the top, or chips. The set looks almost like new! We had another holder from another company that mushroomed which required us to cut it down and re-grind the top in order to use it. The Durable Mecco set is a nice kit and never wears out so when we needed a new larger character set, we knew who to call. — Tom Hojnacki, DePaul University Key Shop Supervisor

The Durable Mecco utility uype and holder set is flexible and rugged enough for most manual marking jobs, from facility key tracking to part identification on a shop floor.

What is steel type and how does it work?

Steel type is a set of individual hardened steel character stamps. Each blank carries one letter, number, or symbol on its face. You load the characters into a holder, line up the word or code you need, then strike or press the holder to drive the whole sequence into the part in a single impression.

Because the characters sit on a common standard blank size, one holder works across multiple character sizes. Swap the characters, keep the holder. The type itself is through hardened, so the working face holds its shape through repeated strikes instead of deforming.

What is the difference between slotted type and utility type?

Slotted type is the heavier-duty option for hard materials and high-impact marking. Utility type is the all-purpose choice for general identification on a wide range of parts. Slotted type also carries a slot on one side so the operator can feel and confirm character orientation before striking.

Slotted steel type is built for the toughest applications in steel mills, forging mills, and foundries. It is through hardened for durability and comes in standard character sizes from 3/32 inch up to 3/8 inch, with other sizes available on request.

Utility steel type covers everyday marking where interchangeable information is required. It uses a smaller standard blank, is through hardened and annealed at the hole, and runs in standard sizes from 1/16 inch up to 1/4 inch. DePaul's key shop uses utility type, which suits the small characters and tight surfaces of keys and cylinders.

Standard slotted and utility type from Durable Technologies will satisfy industrial marking jobs where the information changes from one part to the next.

Which industries use steel type for part marking?

Any operation that needs permanent identification on metal uses steel type. That includes steel mills, forging and casting shops, machine shops and tool rooms, manufacturers stamping serial and part numbers, and facility key shops like the one at DePaul.

The common thread is traceability. A stamped serial number, part number, date code, or lot code ties a physical part back to its record, whether that record is a maintenance log, a quality file, or a campus key database. Ink and labels can't survive heat, solvents, abrasion, or decades of handling. A struck impression in the metal can.

Durable Technologies also makes steel marking type for every O.E.M. impact press, including G.T. Schmidt, Pannier, Matthews, Hilti, Columbia, and Automator, plus can-marking embossing type and other styles, so a marking standard set up on one machine can carry across a plant.

How long does steel type last?

A properly made set lasts for years of daily use without losing its mark. DePaul's utility type and holder has stamped parts multiple times every day for more than 20 years with virtually no visible wear, no mushrooming of the top, and no chips.

Mushrooming is the failure mode to watch for. When a holder or stamp is too soft, repeated hammer blows spread and deform the struck end into a mushroom shape. Once that happens, the tool has to be cut down and the top re-ground before it can be used safely again. Tom Hojnacki saw that firsthand with a holder from another supplier, which is part of why he stayed with the same set for two decades. Through hardening is what keeps the working face and the struck end holding their shape.

That longevity is why Durable Technologies builds its type from special tool steel and through hardens it. The set is meant to outlast the marking job, not get replaced on a schedule.

Can steel type be used by hand or in a press?

Both. Hand-held holders are struck with a marking hammer for low-volume work, field marking, or small parts like keys. Press-style holders mount in an impact press for higher volume and consistent depth across every part.

Steel type holders are made from shock-resistant tool steel. The press-style version is supplied with a shank (sold separately) that is compatible with Durable line of impact presses. The M-E-Conomy hand-held version (for slotted type) is a 5-inch holder used with a marking hammer, sized for several pocket widths and heights so it fits the character set you run. Type retaining pins hold the characters in place during the strike.

If you already run an impact press, Durable Technologies can match a holder and shank to it. If you mark by hand, the hand-held holder and a marking hammer cover the same work at lower volume.

When should you use a numbering head instead of steel type?

Use a numbering head when you mark consecutive or repeating sequences at volume, such as serial numbers, part numbers, and date codes. The wheels advance automatically or by hand between parts, so you never reset individual characters one stamp at a time.

Numbering heads come in four configurations: press-style automatic, press-style manual change, hand-held manual change, and a hot-stamping version. Automatic heads advance the wheels on each impression for high-volume consecutive numbering. Manual heads hold the same sequence until an operator changes it with a spanner wrench, which suits lower-volume runs and fixed codes. For applications that transfer ink from a ribbon, the hot-stamping configuration adds a heated wheel shaft and temperature control.

The decision comes down to your specific marking requirements. Information that changes part to part and isn't sequential fits steel type in a holder. A running serial or date sequence fits a numbering head. Durable Technologies builds both to the same character sizes, so a plant can standardize across methods.