Uses for Interchangeable Core Padlocks

May 2, 2019
These tough, quick change artist padlocks provide key control and weather resistance

Blam!  The four-wheel drive pickup was now a two-wheel pickup.  The rear axle (and the beer) were in the street.   The padlock and gate at the beachfront park were intact.  This actual event on the Jersey Shore illustrates real-world padlock applications where physical attack, weather and corrosion resistance are primary concerns.

Interchangeable Cores allow the professional locksmith or end user to keep up with lost keys, as well as constant facility and personnel changes.  These cost-effective solutions provide a balance between operational maintenance and attack resistance.

Of course, when protecting high value or hazardous assets, defense against professional surreptitious entry and extended forced entry attacks may indeed require more complex solutions.  Those would include military weapons storage and high value assets in remote locations.  The vast majority of your applications, however, will use a robust, weather or corrosion-resistant padlock.

Interchangeable Cores do need a brief clarification.  The Best style Small Format Interchangeable Core (SFIC) is standardized throughout the industry and available from virtually all domestic manufacturers. 

Large Format Interchangeable cores allow clients with key-in-knob or lever (KIK) cores to transition to I-Core systems.  However, locking lug configuration and size of all LFIC cores (ABUS, ASSA, Corbin Russwin, Medeco®, Sargent, Schlage® and Yale) are specific to each brand, and are not interchangeable between brands.  Schlage uses the term “Full Size Interchangeable Core” rather than the more common LFIC.  Extremely high levels of pick and tamper resistance have been difficult to build into the smaller Small Format I-Core. 

Medeco has been proactive in providing a number of housings and cores to fit other brand LFIC systems, as well as a full line of the more popular Small Format Interchangeable cores and padlocks. 

Aluminum, brass, and steel bodies provide a wide variety of cost and performance options, with stainless steel alloys often used in corrosive atmospheres.  Brass bodies with heat treated steel or plated shackles are the most popular as they provide a good balance of strength, corrosion resistance, and manufacturing cost.  

Chromium plated bodies and shackles allow a higher level of corrosion resistance and ductility to be built-in at lower cost than with stainless.  Aluminum bodies have become popular where strength is less of an issue.  Bright anodized colors and resistance to some corrosive atmospheres often make aluminum a popular lower-cost option.  Dissimilar metals can be an issue, however.

ASTM Standards

ASTM F883-13 is an industry specification guideline produced by the American Standard for Testing and Materials (ASTM International) guiding padlock standards in the North American market.  Tests for Forcing, Surreptitious Entry, Cycle, as well as Corrosion and Environmental are included in the standard.

It is important to understand which tests and test levels (Grades 1 through 6) of each test that a given padlock meets.  A statement that a product meets ASTM F883 standards only implies that it meets the lowest levels. Test results are seldom offered; however here are some clues. 

Shackle thickness counts, and high quality interchangeable cores are much more difficult to bump.  Some resist 10 minutes or more of professional bumping attacks. Deadlocking or key retainer padlocks cannot be shimmed open.  Meeting Grade 4 of all the ASTM F883 categories provides a very secure padlock.

A free copy of the earlier ASTM F883-4 is available at:   The current F883-13 version adds bumping tests to the surreptitious entry section.  The values in minutes for bumping tests in the current standard are: Grade One, 2 ½; Grade Two, 5; Grade Three, 7 ½; Grade Four, 10; Grade Five, 12 ½; and Grade Six, 15-minutes.  Multiple Mil-Specs also exist for various threat levels and environmental conditions.  These often refer back to the ASTM standards.

Manufacturers typically strive for a balance between ductility and surface hardness. Boron Alloys have been a popular way to provide necessary ductility to resist hammer blows and freezing attacks.  After heat treating and annealing, a carburization process is often used to add surface hardness.  Some shackles are hardened to a level which (with a 3/8” shackle) will often defeat a 42” bolt cutter.  These will sometimes rate the Grade Six 10,000 lbf shackle cutting standard.

In recent years, various devices have been employed to add additional shackle protection.  These have included shielded hasp housings (like on job boxes), hockey-puck style housings, and shrouds. 

Tensile Force is a shackle pulling test.  ASTM standards go from a low of 225 lbf for grade one, up to 9,000 lbf for grade six.  Additional forcing tests for shock, plug pulling, and torque are also considered in the ASTM tests. 

Brass bodies, springs, and parts have been forever popular due to their environmental tolerance and alloy compatibility.  Using dissimilar metals is generally discouraged for outdoor applications, although additional corrosion resistance is sometimes engineered into the product.  Shackles however, are a different matter, as strength, ductility and cutting resistance are  important factors.

Weatherized coverings are available from most padlock suppliers.  These rubberized covers tightly seal shackle and key entry points against harsh elements.

Surreptitious Entry tests for picking, manipulation, impressioning, shimming, drilling and rapping are also included in the ASTM tests.  Bumping was added to the list as this method was popularized.  The ASTM standards test these attacks from one to fifteen minutes for the various levels.  Levers, pins or bars can extend bumping times to the point that it becomes an ineffective attack method.  We have seen cases where the most practical attack was a K-12 saw through a rebar-reinforced concrete block wall.

Since the vast majority of padlock protected assets are of moderate value, sophisticated professional attacks are seldom a concern.

The following is a current list of the manufacturers that produce Interchangeable Core padlocks.  Virtually all offer Small Format Interchangeable Core padlocks, and major hardware companies will also offer their own style of Large Format I-Cores.

ABUS: The well-known German lock manufacturer provides a full range of 83 Series® aluminum, brass, chrome plated brass, and hardened steel padlock bodies that accept 5, 6, and 7-pin Small Format Interchangeable Cores.  The company also offers an LFIC version that accepts the high security Vitess™ 83 LFIC cylinder.  Search: ABUS USA 2019 Security Catalog.

American Lock® is a 100 year-old Milwaukee based company, affiliated with Master Lock.  The manufacturer provides a comprehensive line of anodized aluminum, brass, and solid steel Best style Small Format I-Core padlocks with a wide range of shackle options and weather covers.  The company also provides aluminum and brass padlocks fitting Schlage Full Size and Yale LFIC cores.

Best created the I-Core market to serve larger organizations that have a lot of doors and people.  They focus strictly on SFIC systems.  Since most of these large educational, military, commercial and industrial facilities had in-house lock shops, the market was not readily available to the locksmithing trade.  In recent years, Best products have become available through major hardware distribution channels. 

Many historic Best padlocks like the legendary 6B have been replaced with a slimmed down but upgraded line.  Current padlocks are machined from solid brass with 626 satin chrome plating or 606 satin brass available.  Metallurgy in the XSPL shackle option allows an ASTM grade six (10,000 lbf) shackle cutting test on the 41B model.  Available options meet grade four for all ASTM tests for the 21B and 41B.  Weather covers, shackle shroud attachments, and other options are also available.

Corbin Russwin, a component of the ASSA ABLOY group, produces brand-specific LFIC padlocks with basic, Security, and Pyramid High Security cores in the solid brass bodies.  A sleeve insert allows standard KIK cores or their own LFIC cores to be used in the LFIC housing.  This is the only OEM not currently offering SFIC padlocks. CorbinRusswin/pdf/45012.pdf

GMS is a Bellevue, WA, company producing standard six and seven-pin Small Format Interchangeable Cores and padlocks as well as Schlage compatible LFIC cores and padlocks.  Solid brass bodies with double ball bearing locking lugs and hardened steel shackles of 5/16 and 3/8” diameter provide a number of options.

Medeco is ASSA ABLOY’s high-security lock resource from Salem, VA.  They have thrived on producing heavy duty attack-resistant locking devices.  In recent years they have moved into I-Core markets with a variety of padlock products, and cores.  The System Series padlocks provide substantial security with both Small and Large Format I-Cores.  Medeco’s LFIC padlocks are available with the Medeco3 high-security core, as well as the Medeco X4, and with the electronic Medeco M3, X4 CLIQ® and Medeco XT.

The company currently provides the X4 mechanical cores to fit Corbin Russwin and Sargent LFIC padlocks, and will soon introduce the XT electronic LFIC core for Corbin Russwin and Sargent I-Core padlocks as well.  They also produce Small Format padlocks for use with all SFIC systems, and provide the Medeco “B”, the patented Medeco X4, and electronic Medeco XT SFIC cores as well.  Search:

Olympus is a niche cabinet lock and padlock manufacturer in Lynnwood, WA.  They currently offer standard padlocks and a Large Format brass body Interchangeable Core padlock that accepts Corbin Russwin LFIC format.

Pacific Lock Company (PACLOCK) is a Valencia, CA, company that builds an extensive line of aluminum, brass, and steel padlocks for virtually all Large or Small Format Interchangeable Cores.  These come with standard shackle configurations, hockey puck, and a shutter style.  A unique cone-shaped hockey puck padlock is available that deflects drilling attacks. The company also offers some interesting Bluetooth operated padlocks.

Sargent has been around in North America for a long time and is now one of the ASSA ABLOY companies as well.  The solid brass LFIC padlocks accept Sargent’s Degree®, Signature, and Medeco’s X4 and XT LFIC cores.  The company’s Small Format I-Core padlocks accept all standard SFIC cores. 

Schlage division of Allegion has been at this business for more than 90-years.  Three basic lines of I-Core padlocks are offered.  The 20 and 40 series are available in brass or chrome plated forms, and the heavy duty 70 series in steel body with 7/16” shackle.  Each is available for use with KIK cylinders, the standard SFIC core, and Schlage’s LFIC core (which they call the Full Size Interchangeable Core).  Schlage also offers a cylinder housing which allows the Full Size I-Core padlock to accept the KIK cylinder.   Shrouded padlocks are shown in the Portable Security brochure, but don’t appear to be listed in the July 2018 price list.  

Wilson Bohannan was founded in 1860 at Brooklyn, NY.  Mr. Bohannan’s company thrived during the early years by focusing on the railway industry’s needs.  In 1927, the company moved to larger facilities at Marion, OH.  The all-weather brass body 86 series is designed to serve the larger industrial, military and institutional markets that use the standardized Small Format Interchangeable Core. The larger 3/8” shackle exceeds ASTM 883-13 Grade Six for cutting. 

Yale was founded in 1868 by pin tumbler inventor Linus Yale and Henry Towne at Stamford Ct.  The company was acquired by ASSA ABLOY about year 2,000, and was subsequently moved to the present location at Berlin, CT.   Padlocks are offered with Conventional, Security, and Keymark® Six and seven-pin Yale style Large Format Interchangeable Cores.  A sleeve is available to accommodate standard KIK cylinders in the LFIC padlock.  The solid brass cases are also available for the popular Small Format I-Core.

Large Format Interchangeable Core padlocks provide an opportunity to serve your clients who want to stay with their brand-specific standard commercial keying systems.  Cylinder housings (or sleeves) available from Corbin Russwin, Schlage and Yale allow the customer to transition from standard cores to the Interchangeable core format.

Small Format Interchangeable Cores and padlocks are standardized throughout North America (and many places where US Military forces have served). This is an “Open Architecture” format allowing you and the customer to shop for the best product fit.  Your primary concerns will be quality, availability, and cost – and focusing on the customer’s needs.

Cameron Sharpe, CPP wrote for Caterpillar and Honeywell before working 25-years in hardware and electronic access distribution. [email protected]  

About the Author

Cameron Sharpe

Cameron Sharpe, CPP, worked 30 years in the commercial lock and electronic access industry. Contact him at [email protected].