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Sargent LB-7857 Institutional Privacy Function Mortise Lock Body
The Sargent LB-7857 is the bare 7800 Series heavy-duty mortise lock body (case only) configured for the Institutional Privacy function. This is the single cyl lock case that drives the latchbolt; it is ordered separately from trim, cylinders and knobs so you can rebuild or reconfigure an existing Sargent mortise opening without buying a complete lockset.
Institutional Privacy Function Operation
The 7857 (Institutional Privacy) function works as follows, per the Sargent catalog:
- Key outside retracts latchbolt, overriding thumbturn when held in locked position
- Thumbturn inside locks & unlocks outside trim
- Trim outside unlocks when the door closes or operating trim inside
- Trim inside always retracts latchbolt
- Auxiliary deadlatch
- Note: Key locks & unlocks trim outside
Lock Body (Case Only) -- Field-Configurable
This listing is the mortise lock case only. It accepts the standard Sargent 7800 Series knob trim, escutcheons/roses and cylinders sold separately, so it drops into an existing prepped door. Select your finish and handing below; the case carries an auxiliary deadlatch where the function specifies one (see operation above). All 24 finish x handing variants ship at one price.
Key Product Features
- Series: Sargent 7800 Series heavy-duty mortise (Knob line).
- Function: 7857 Institutional Privacy (Sargent function; catalog lists no ANSI number).
- Operation: Key outside retracts latchbolt, overriding thumbturn when held in locked position.
- Cylinder configuration: Single cylinder.
- Deadbolt: No (per the 7857 function).
- Finishes: Six BHMA finishes -- 626, 630, 613, 613E, 612, 625.
- Handing: LH / RH / LHR / RHR (specify at order; mortise cases are field-reversible).
- Grade: ANSI/BHMA A156.13 Series 1000, Operational Grade 1 and Security Grade 1 (with standard trims).
- Cycle test: independently verified UL test of 16,000,000 cycles (Sargent Verification ID V584148) -- 16x the ANSI Grade 1 minimum.
- Fire rating: UL/cUL listed for A-label openings (3 hours) and lesser ratings, up to 4'x10' single / 8'x10' pair; UL 10C positive-pressure.
- Construction: 12-gauge heavy-duty wrought steel case (0.109" min), zinc dichromate plated; 0.125" cold-rolled steel inside front.
- Front: 8" x 1-1/4" armored front plate (ANSI/BHMA A156.115), field-adjustable flat to 1/8" bevel in 2".
- Backset: 2-3/4"; latchbolt 3/4" one-piece anti-friction stainless steel, reversible.
- Field-reversible handing: mortise case is rehanded without opening the lockbody.
- Cylinder: accepts the standard Sargent #41 (1-1/8") cylinder; standard LA keyway; masterkeyable with other Sargent product.
Technical Specifications
| Feature | Details |
| Function | 57 Institutional Privacy |
| Series | 7800 Heavy-Duty Mortise (Knob line) |
| Type | Mortise lock body (case only) -- trim & cylinder ordered separately |
| Cylinder | Single cylinder |
| Deadbolt | No |
| BHMA Finishes | 626, 630, 613, 613E, 612, 625 |
| Handing | LH / RH / LHR / RHR |
| Grade | ANSI/BHMA A156.13 Series 1000, Operational Grade 1 & Security Grade 1 (standard trims) |
| Cycle Test | 16,000,000-cycle UL test (Verification ID V584148) -- 16x ANSI Grade 1 minimum |
| Fire Rating | UL/cUL listed, A-label (3 hr) up to 4'x10' single / 8'x10' pair; UL 10C positive-pressure |
| Backset | 2-3/4" |
| Armored Front | 8" x 1-1/4", ANSI/BHMA A156.115, flat-to-1/8" bevel field-adjustable |
| Case | 12-ga heavy-duty wrought steel (0.109"), zinc dichromate; 0.125" cold-rolled inside front |
| Latchbolt | 3/4" one-piece anti-friction stainless steel, reversible |
| Field Reversibility | Rehanded without opening the lockbody |
| Cylinder (Keyed) | Standard Sargent #41 (1-1/8"), LA keyway; masterkeyable |
Ordering & Installation Information
Order the 7857 lock body by finish and handing using the options above. Because this is a case-only part, pair it with the correct Sargent 7800 Series trim, cylinder(s) and knob for a complete opening. Typical lead time is 2-4 weeks. Confirm the existing door prep and handing before installation.
| Finish with BHMA code | 626 - US26D Satin Chrome or 630 - US32D Satin Stainless or 613 - US10B Oil Rubbed Bronze or 613E - US10BE Oil Rubbed Bronze Equal or 605 - US3 Polish Brass or 606 - US4 Satin Brass or 612 - US10 Satin Bronze or 619 - US15 Satin Nickel or 625 - US26 Polish Chrome |
| Door Handing | LH or RH or RHR or LHR |
| Brand | Sargent |
| Series | Sargent - 7800 Series |
| Part Type | Lock Body |
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