Arrow BM-LB Lock Body...
IN STOCK (leaves warehouse same day if ordered before 3pm ET)
$435.44
$343.76
Arrow BM-LB Lock Body

Arrow BM-LB Lock Body

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Model: BM20-LB

In Stock (leaves warehouse same day if ordered before 3pm ET)

$435.44
$343.76
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BM Series Mortise Locks

The BM Series are engineered for strength and performance, and precisely manufactured to exact standards.

Arrow BM Series Lever Mortise Locks are intended for heavy duty use in schools, hospitals and commercial buildings where security, durability and low maintenance are required.

  • Handing: Handed; field reversible. The lockset can be re-handed without disassembling the lock case.
  • Door Thickness: 1-3/4" (4mm) standard. Optional door thickness available; consult factory.
  • Backset: 2-3/4" (70mm).
  • Lockcase: Heavy gauge steel, with zinc dichromate finish for corrosion resistance. 5-7/8" (149mm) x 4" (102mm) x 15/16" (24mm).
  • Armored Front: Heavy gauge steel, 8" (203 mm) x 1-1/4" (32mm) x 3/32" (2mm). Accommodates flat doors and doors beveled 1/8" (3mm) in 2" (51mm).
  • Faceplate: Wrought brass or bronze, attached by machine screws to lockcase front.
  • Latchbolt: Stainless steel, 2 piece mechanical with anti-friction insert. 5/8" (16mm) x 1" (25mm) x 3/4" (19mm) throw.
  • Auxiliary Latchbolt: 9/16" (14mm) effective throw and 3/8" (10mm) effective auxiliary latch deadlocking.
  • Deadbolt: One-piece stainless steel, 19/32" (15mm) x 1 1/4" (32mm) x 1" (25mm) throw.
  • Hub: Lever: nickel steel, 5/16" (8mm).
  • Spacing: Center to center, hub to cylinder: 3-5/8" (92mm).
  • Center to center, hub to turnpiece: 2-7/16" (62 mm).
  • Strike: Wrought brass or bronze, ANSI straight lip standard, 4-7/8" (124mm) x 1-1/4" (32mm) 1-1/8" (29mm) lip to center. Optional strikes, lip lengths and ANSI wrought strike box available.
  • Keys: Two nickel silver standard.

Keying Features Available:

    • Master keying
    • Construction master keying
    • Visual key control
    • Concealed key control
    • High security cylinder
    • Interchangeable core (IC) - Pointe, Pointe Flex
  • Warranty: Five-year Limited

Manufacturer Resources

Product Specs

Catergory:
Mechanical Locks
Product Group:
Security Locks
Product Subgroup:
Parts and Accessories
Series:
6730
Subcategory:
Safe Lock
Product Type:
Mechanical Safe Locks
Department:
Safety

Arrow BM20-LB – Frequently Asked Questions

1) What door thickness and backset does the Arrow BM Series mortise lock body fit?
Standard is a 1-3/4 inch door with a 2-3/4 inch backset. That is the normal commercial opening, so it drops into a standard ANSI mortise pocket. Other door thicknesses are available as a factory option rather than off the shelf.
2) Do I have to order the Arrow BM lock body handed, or can I flip it on site?
Order it either way. The BM Series is handed but field reversible, and the re-hand is done without opening up the lock case. That matters if you are stocking spares for a building with doors swinging both directions, one body covers both.
3) Will the Arrow BM mortise lock latch into my existing ANSI strike?
The latchbolt throws 3/4 inch and the bolt face is 5/8 by 1 inch stainless, two-piece with an anti-friction insert. The auxiliary latch gives 9/16 inch effective throw with 3/8 inch deadlocking. Standard strike supplied is an ANSI straight lip, 4-7/8 by 1-1/4 inch with 1-1/8 inch lip to center. If your frame is already prepped to that ANSI strike, it lines up; optional strikes, lip lengths and an ANSI wrought strike box are available if the frame or jamb condition needs them.
4) Which function should I pick for a classroom versus a storeroom door?
Three functions are offered: 12 Storeroom, 17 Classroom, and 20 Entrance/Dormitory. Storeroom keeps the outside lever locked at all times with key access only, classroom lets a key lock and unlock the outside lever so a teacher can secure the room, and entrance/dormitory is the function for apartment and dorm entries. Pick by how the door needs to behave, not by finish or trim, since the function is built into the lock body.
5) Will the Arrow BM lock case fit my mortise pocket, and does it handle a beveled door edge?
Lock case is heavy gauge steel with a zinc dichromate coating for corrosion resistance, measuring 5-7/8 x 4 x 15/16 inches. The armored front is 8 x 1-1/4 x 3/32 inches and works on flat doors or doors beveled 1/8 inch in 2 inches, which is the usual bevel on a commercial door edge. Check the pocket depth against the 15/16 inch case before you commit.
6) Where do the cylinder and thumbturn holes fall on the Arrow BM mortise lock?
Center to center from hub to cylinder is 3-5/8 inches, and hub to turnpiece is 2-7/16 inches. Those are the two numbers you need to check against an existing door prep or an escutcheon before ordering, since trim that does not match the spacing will not cover the holes.
7) Is the Sargent and Greenleaf lock body for the 6730 a drop-in replacement for the Arrow BM-LB lock body?
Treat them as separate parts and confirm what is actually in the door before ordering. The Arrow BM-LB is a mortise lock body built around the BM Series case dimensions - 5-7/8 inch by 4 inch by 15/16 inch lockcase, 2-3/4 inch backset, 3-5/8 inch hub-to-cylinder spacing - and it is offered in 12 storeroom, 17 classroom and 20 entrance/dormitory functions. The Sargent and Greenleaf part is a lock body for the 6730 and carries no BM case dimensions or mortise function codes with it. If you are replacing the guts of an Arrow BM mortise lockset in a school or hospital door, the BM-LB is the body that matches that prep; if the existing unit is a Sargent and Greenleaf 6730, order the S and G body.
8) Can I key the Arrow BM mortise locks into my building master key system?
Yes. The BM Series supports master keying, construction master keying, visual key control, concealed key control, and high security cylinders. Interchangeable core is available in Pointe and Pointe Flex, which is the route to take if you rotate cores rather than rekey pins. Two nickel silver keys come standard.
9) Is the Arrow BM heavy enough for a school or hospital corridor door?
That is exactly the application it is built for. Arrow states the BM Series lever mortise locks are intended for heavy duty use in schools, hospitals and commercial buildings. The wear parts back that up: stainless steel latchbolt and one-piece stainless deadbolt, nickel steel lever hub, and a zinc dichromate coated steel case.
10) How far does the deadbolt throw on the Arrow BM mortise lock?
One inch, from a one-piece stainless steel bolt measuring 19/32 by 1-1/4 inches. A full inch of throw is what most jurisdictions look for on a mortise deadbolt, and it means the frame strike prep has to be deep enough to take it rather than just a shallow latch pocket.
11) Both the Arrow BM-LB and the Sargent and Greenleaf body are listed under series 6730 - what actually differs between them?
The shared 6730 series designation is where the overlap ends. The Arrow BM-LB is the BM Series mortise lock body, with a stainless steel two-piece latchbolt with anti-friction insert and 3/4 inch throw, a one-piece stainless deadbolt with 1 inch throw, an 8 inch armored front, and a field-reversible handing that can be changed without disassembling the case. The Sargent and Greenleaf 6730 body is sold as a lock body for that maker's 6730 and does not carry those BM latch, deadbolt or armored front dimensions. Match the body to the housing it goes into rather than to the series number.
12) What material is the faceplate on the Arrow BM mortise lock, and how does it attach?
Wrought brass or bronze, fastened with machine screws to the front of the lock case. Because it is screwed on rather than integral, the faceplate is the piece you swap if a finish change is needed on a door without pulling the whole lock body.
How fast can I get the Arrow BM20-LB delivered?
Most orders ship the same day from our distribution partners, with quick delivery throughout the continental U.S. Need it urgently? Contact Us for expedited shipping options.
Can I return it if it doesn’t work for me?
Yes—ZenSupply offers a hassle-free return policy. If the product isn’t the right fit, reach out to our support team for a return authorization or setup a return by following our return instructions.
Does the Arrow BM20-LB come with a warranty?
Absolutely. The Arrow BM20-LB is backed by a manufacturer’s warranty. For full warranty terms, check the product documentation or Contact Us.
How do I get technical support or installation help for the Arrow BM20-LB?
You can call, text, or email our expert support team for fast answers. We’re here to help with product selection, installation tips, and troubleshooting. Contact Us
Why buy the Arrow BM20-LB from ZenSupply?
ZenSupply makes it easy to get the commercial door hardware you need—fast shipping, expert support, and rewards on every order. Our team is always ready to help you choose the right product for your project.
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