Why Key Blank Selection Is a Hardware Decision, Not Just a Supply Run
This article covers the two most overlooked variables when ordering or cutting replacement keys for commercial door hardware: blank material composition and cutting depth specifications. It is written for facility managers ordering duplicates for a large campus, contractors closing out a hardware package, and maintenance personnel troubleshooting a key that works on Monday and sticks on Friday. Getting either variable wrong does not just create a nuisance -- it can accelerate cylinder wear, void manufacturer tolerances, and compromise an entire master key system.
What Is a Key Blank?
A key blank is an uncut key identified by a manufacturer code and keyway profile. It serves as the raw material for any cut key. The keyway must match the cylinder exactly -- but the blank material and the depth increments cut into it are equally important to long-term performance and system integrity. A blank that fits the keyway but is cut to wrong depths, or made from material that is too soft or too hard for the cylinder's pin stack, is a service problem waiting to happen.
Key Blank Materials: Brass vs. Nickel Silver vs. Steel
Commercial key blanks are manufactured in three primary alloys. The choice affects durability, machinability, and compatibility with high-security cylinders.
Nickel Silver
Nickel silver -- an alloy of copper, zinc, and nickel -- is the standard material for commercial and institutional key blanks in the United States. It machines cleanly, holds cut edges well, and is hard enough to resist deformation in heavy-use cylinders. Corbin Russwin's Pyramid system specifications, for example, call explicitly for nickel silver keys as the required blank material for factory-cut patented keys. The same expectation appears across Sargent, Corbin Russwin, and BEST cormax systems. When a facility manager orders blanks for a hospital or school master key system, nickel silver is not optional -- it is the spec.
Brass
Brass blanks are softer, less expensive, and widely available at hardware retail. They are acceptable for low-cycle residential or light commercial applications. In high-pin-count commercial cylinders -- especially 6-pin and 7-pin configurations used in institutional master key systems -- brass blanks wear faster at the bitting positions and can allow slight deformation under repeated use. Over time, a brass duplicate in a precision cylinder can alter the shear line just enough to cause intermittent failure, particularly in a master-keyed opening where tolerance windows are already tighter.
Steel and Specialty Alloys
Steel and proprietary alloy blanks are reserved for high-security cylinders with patented mechanisms. Medeco M4 cylinders, for example, require blanks with specific geometric features -- including a movable element -- that cannot be replicated in standard brass or nickel silver stock. Cutting a Medeco key requires a machine with a high-security angle cutter (the HPC Tiger SHARK, for instance, uses a dedicated CW-1012 tool steel cutter at an 86-degree angle specifically for Medeco work). The blank material and the cutter angle are inseparable when cutting high-security keys -- using the wrong cutter on a Medeco-spec blank damages both the blank and the cutter.
Cutting Depths: How Bitting Works and Where It Goes Wrong
Every key manufacturer specifies a depth-and-space table that governs how deep each cut can be and how far apart the cuts are spaced along the blade. These are not arbitrary -- they are engineered tolerances that determine whether the pin stack aligns correctly at the shear line.
Depth Increments
Most commercial cylinders use a system of numbered depth increments, typically 0 through 9, where each increment represents a precise change in cut depth (measured in thousandths of an inch). The key cutting machine's code database -- whether on a computerized unit like the HPC Tiger SHARK or a manual code machine -- stores these depth-and-space specifications by manufacturer and keyway. Cutting a key from a code without confirming the correct manufacturer bitting table is one of the most common sources of field failures on replacement keys.
MACS: Maximum Adjacent Cut Specification
The Maximum Adjacent Cut Specification (MACS) is the largest allowable difference in depth between any two adjacent cuts on a key. Manufacturers set MACS values to prevent the creation of keys that are mechanically unworkable -- extreme transitions between a shallow cut and a deep cut can stress the blank during insertion and cause the key to bind or snap. In a master key system, MACS also serves as a design constraint: the system designer cannot assign bittings that violate MACS even if those combinations would mathematically expand the key space. MACS varies by manufacturer, which is why depth tables are brand-specific and cannot be borrowed across product lines.
Why Duplicate Keys Cut from a Worn Original Fail
When a key has been used for years in a high-cycle opening -- a school corridor door, a retail stockroom, a hospital medication room -- the bitting edges wear and round off. A duplicate cut by tracing the worn original rather than cutting from the original code produces a key that reflects the worn profile, not the true bitting. The resulting duplicate may operate the lock initially but will cause premature pin wear and can fail entirely as the cylinder ages. The correct practice is to cut duplicates from the original code or from a fresh original key, not from a field-worn copy.
High-Security Cylinders and Restricted Blanks
For facilities running patented key systems -- Corbin Russwin Pyramid (7-pin), BEST CORMAX, Medeco M4 -- blank availability is intentionally restricted. Corbin Russwin Pyramid blanks, per factory specification, are shipped directly to the owner via secured carrier with a bitting list. Medeco M4 blanks require authorization through a registered dealer program, and the blanks themselves incorporate a patented movable element that cannot be reproduced on standard key machines. These restrictions are the point: an unauthorized duplicate cut from an off-the-shelf brass blank on a standard machine will not operate a properly functioning high-security cylinder.
This is a meaningful distinction for specifiers in healthcare and education environments where key control policies must address who can duplicate keys, through what channel, and what documentation is required. A key control policy that relies on restricted blanks is only as strong as the authorization controls around blank distribution.
Practical Guidance for Ordering Replacement Blanks
- Always confirm the keyway code, not just the physical profile. Two blanks that appear identical may have different bitting spaces for different manufacturers.
- Specify nickel silver for any 6-pin or 7-pin commercial cylinder in a master key system.
- Do not cut from a worn original -- request the code from the keying record and cut from it directly.
- Verify MACS compliance before assigning new bittings in a system expansion. This is the system designer's responsibility, not the technician's -- but the technician needs to flag when a code pulled from the field appears to violate the manufacturer's adjacency rules.
- For high-security or patented cylinders, source blanks only through the authorized channel. Corbin Russwin, Sargent, and Medeco all maintain registration or authorization programs. Blanks obtained outside these channels are a security gap regardless of how well they are cut.
- Match the cutter angle to the blank type. Standard commercial cylinders typically use 90-to-100-degree cutters; Sargent cylinders use a 76-degree cutter; Medeco requires an 86-degree high-security angle cutter. The wrong cutter angle produces a bitting profile that will not align the pin stack correctly even if the depth number is right.
Cylinders and Key Blanks at DoorwaysPlus
DoorwaysPlus carries cylinders and keying components from Corbin Russwin, Sargent, and other preferred commercial lines -- brands chosen for system stability and parts availability rather than lines that cycle through platform redesigns on short schedules. If you are building out a master key system, replacing cylinders on an existing keyway, or sourcing restricted blanks for a patented system, the team at DoorwaysPlus can help confirm the right blank material, bitting specifications, and cylinder compatibility before the order ships. Contact us or browse cylinders and keying supplies at DoorwaysPlus.com.