Retrofitting Knob Locks to Lever Locks Made Easy

April 2, 2012
Use A1 Security Manufacturing’s BUL-3 retrofit jig for bored lever locks

As locksmiths, we retrofit knob locks to lever locks for a number of reasons including replacing old and worn locks, upgrading to electrified and electronic access control, and satisfying code and act requirements. A common requirement is satisfying the Americans with Disabilities Act (ADA). The ADA requires lever handle equipped locks on specific door applications to enable physically challenged individuals to operate the locking mechanism in order to gain access or egress.

In order to meet ANSI/BHMA Grade 1 and Grade 2 requirements for bored locks equipped with levers, lock manufacturers have designed or redesigned their leversets with external or internal through bolting. Most lock manufacturers use external through bolting, which requires two additional cross bore holes drilled into the face of the door on opposite sides of the lock body.

When retrofitting a knob lock with a leverset, depending upon the application, drilling external through bolting can be part of the retrofit. The purpose of external through bolting is to prevent forcibly rotating the lever to retract the latch, permitting unauthorized entry. Each lock manufacturer determines the position of the through bolting. There is no standard for the location or diameter of the through (thru) bolts.

Important: The through bolting dimensions are determined and notated on the template by looking at the door, no matter which side you are on.

The through bolt holes can be in the 6 and 12 o’clock, 2 and 8 o’clock or 4 and 10 o’clock positions. Most leversets through bolting is in the 6 and 12 o’clock position with a distance of 2-3/4”. This positions the holes 1-3/8” above and below the centerline of the 2-1/8” cross bore. Two less common 6 and 12 o’clock positions are 2-5/8” or 2-21/32”.

Over the years, a few lock manufacturers have changed the positioning of the through bolting on specific leverset models. For adaptability, several lock manufacturers have cylindrical locks equipped with resettable positioning, enabling easier retrofitting to a pre-drilled door prep for the through bolt holes. Some lock manufacturers have positioned the through bolting very close to the outer edge of the crossbore, making it difficult to cleanly drill the holes without some type of jig.

The A1 Security Manufacturing BUL-3 Retrofit Jig is a two-part hardened steel through bolt tool having three drill locations and two holes for drilling the anchor plate tabs (lugs). The BUL-3 has a built in adjustable squaring slide to insure the positioning for retrofitting external through bolted leversets whose backsets are up to five inches. The tool can be used on doors up to two inches thick. The A1 Retrofit Jig mounts onto the exterior and interior faces of the door using the 2-1/8” cross bore hole to locate the jig. A 3/8” X 3” socket head clamp screw is used to secure the BUL-3 to the door. A 5/16” hex wrench is included. Note: the ¼” diameter dowel pin should always be above the hex head bolt.

Always read the lock’s installation instruction and look at the template before drilling the through bolts. If no template is available, one method of determining the proper positioning is to place the inside rose assembly against one of the BUL-3 guide plates in order to determine if and where the two rose assembly holes or tabs align with the openings in the jig.

This Retrofit Jig has three drill positions with three different sized holes for 5/16”, 3/8” or 7/16”. Each of the two same diameter holes align with a different position and spacing. Remember to always drill the two holes from both side of jig to insure against damage to the door face.

If the door is hollow metal, a polymer or a veneered door, anchor plate lug holes may be required for the exterior and interior face of the door. These holes accommodate the pointed tabs that lock manufacturers build into the mounting plates. These tabs are designed to prevent rotation of the roses assemblies. The lugholes are at the 3 and 9 o’clock positions of the BUL-3.

To help identify a lock, look at the latch faceplate to find the name of the lock company. Some lock companies private label a different lock manufacturer product. The name on the latch faceplate can be either company that manufactured the lock or the company that private labeled the lock.

Our chart, available online with this article, lists  the more common lock manufacturers whose lever equipped cylindrical and tubular locks are equipped with external through bolting. Not all through bolt holes in all locks can be drilled using the BUL-3 Retrofit Jig.

Manufacturers and models include:

  • Arrow: GI Series and RI Series
  • Cal-Royal: GN (Most); Calypso, Apollo, Commander, Explorer, Pioneer SL (Most)
  • Corbin Russwin: CL3300 Series, CL3500 Series, CL3800 Series manu. from 2007-present
  • DORMA: C800, C1800, C1700 Series
  • Falcon: T Series, W Series
  • Hager: 3400 Series, 3500 Series. Enlarge Through Bolt Holes To 3/8”
  • Marks USA: 195/295/395, 175/275/375/475
  • Medeco: Embassy 17
  • PDQ: XGT/GT, SA (Spirit), SD
  • Sargent: 10 Line (manu. before Feb 17, 2004), 10 Line (Enlarge Through Bolt Holes To 3/8”), 6500
  • Schlage: A1, D Series Rhodes, ND Series Rhodes
  • Stanley: K2 Cylindrical
  • Townsteel: CF Series, CS Series
  • Yale: Yale 4600LN (Enlarge Through Bolt Holes To 3/8”), 4700LN, 300LN, 5400LN

Some holes are in the 6 and 12 o’clock positions are a few thousands off from 2-3/4”. This can include 2-5/8”. To resolve this problem using the A1 BUL-3, some locksmiths will drill the 5/16” hole, remove the jig and redrill the opening using a larger diameter bit, usually a 3/8” diameter. For a lock equipped with a 2-5/8” distance, drilling two 3/8” diameter holes provide the extra 1/8” to accommodate the two through bolts.

The use of a retrofit jig simplifies the task by properly locating the through bolt holes.

Important: Always wear eye protection and follow all safety rules when operating electrical equipment.

For more information on any of the installation tools in this article, contact your local locksmith distributor or A1 Security Mfg. Telephone: 877-725-2121. Web Site: