The old order or the box says 7KC37AB15DS3626, 8K37D4AS3626 or just 7K Series. Which BEST lock is it, and will a new one go into the holes already in the door? The 9K is covered in our BEST 9K and 45H guide.
7KC, 8K or 6K: lever or knob, medium or heavy duty
BEST lists four cylindrical series among its mechanical locks, two with levers and two with knobs. Its documents give these BHMA grades:
| Series | Trim and duty | Grade per BEST |
|---|---|---|
| 7KC | Lever, medium duty | Grade 2 |
| 6K | Knob, medium duty | Grade 2 |
| 9K | Lever, heavy duty | Grade 1 |
| 8K | Knob, heavy duty | Grade 1 |
The FAQs link them in pairs: the 6K shares its latch with the 7KC, and the 8K shares the latch and retractor assembly with the 9K. Neither knob series has a lever option. For a heavier lock, the 7KC catalog points to the 9K and the 6K catalog to the 8K.
Some of our product titles call the 7KC the 7K Series. According to the 7KC FAQ, the original 7K was a tubular lock with different components and door prep guidelines, it is no longer available, and the C was added to set the cylindrical 7KC, launched in 2001, apart from it. Our door lock types guide explains cylindrical and tubular locks.
How to read a BEST 7KC number
The How To Order table in the 7KC catalog runs: series, backset, core housing, function, lever, rose, strike, finish and options. Applied to 7KC37AB15DS3626:
| Code | Meaning |
|---|---|
| 7KC | 7KC Series cylindrical lever lock |
| 3 | 2-3/4 inch backset (2 is 2-3/8, 4 is 3-3/4, 5 is 5 inch) |
| 7 | 7-pin housing for BEST cores (0 is keyless) |
| AB | Entrance function, ANSI F109 |
| 15 | Contour angle return lever |
| D | 3-1/2 inch rose, the only one listed |
| S3 | 4-7/8 inch ANSI strike (STK is the standard 2-3/4 inch strike) |
| 626 | Satin chromium plated finish |
The other functions are D storeroom, R classroom, L privacy, N passage, Y exit and 1DT, a single dummy lever. Lever 14 is curved with a return, 16 curved with no return. Finishes are 605, 606, 612, 613, 625 and 626. The How To Order table lists two options: L8, a drive-in latch for the 2-3/8 and 2-3/4 inch backsets, and SCH, a 15 lever for a Schlage non-IC cylinder, which is not included. So 7KC30N16DS3626 is a keyless passage set with the 16 lever.
Our lock functions guide, SFIC and LFIC guide (cores for the 7 housing) and finish codes chart explain the rest.
How to read a BEST 8K number
The 8K number reads the same way, with a knob for the lever. Take 8K37D4AS3626: 2-3/4 inch backset, 7-pin housing, D storeroom (ANSI F86), the 4 round knob, A rose, S3 strike and 626 finish. The 8K table has no 2-3/8 inch backset. Knob 6 is the tulip. The 8K FAQ gives the roses as A, 3-3/8 inch concave; C, 2-9/16 inch concave; D, 3-3/8 inch convex; and E, the rose for thick doors.
The 8K offers far more functions: its FAQ counts 7 single keyed, 5 double keyed and 6 keyless functions, and the catalog adds special and electrified ones. For locks that secure both sides of the door, the catalog notes that building codes and the Life Safety Code control their use. Among the options, BRK lets a keyed 4 or 6 knob break away and spin freely under about 300 inch-pounds of force, which leaves entrance by key only.
You do not order a left or right hand 8K: the FAQ explains that you pull the core and turn the knob face. An 8KW is the electrified 8K, with DEL fail safe and DEU fail secure functions, also covered in the 8K service manual; our fail safe and fail secure guide explains the two.
How to read a BEST 6K number
The 6K is the simplest. Its catalog and FAQ list one knob (4, round), one rose (K, 3 inch) and three finishes: 630, 606 and 605. BEST's PL78 ordering list prints the sample 6K37AB4KSTK630: 2-3/4 inch backset, 7-pin housing, AB entry function, round knob, K rose, standard strike, 630 finish. Backsets are 2-3/8, 2-3/4, 3-3/4 and 5 inch. Keyed functions are AB, D storeroom and R classroom; keyless ones are N passage, Y exit, L privacy, P patio and dummy trim.
The sample printed in the 6K catalog, 6K37AB4CSTK626, carries a C rose and 626 finish that the same table does not list; if your 6K number shows codes like these, check the replacement with us. The FAQ says the knob turns to suit either hand once the core is out.
Will it fit your door prep?
All three catalogs call for a 2-1/8 inch hole for the lock body. The 6K and 8K FAQs say both fit the common cylindrical (161) door prep; the 7KC FAQ says the 7KC fits the standard 161 prep and, with the ATB option, the Schlage ND80 prep.
One BEST door and frame template serves several series. The 7KC service manual lists K08 (STK strike) and K09 (S3 strike) for 63K, 73KC, 83K and 93K locks, where the second digit is the backset code: 73KC is a 7KC with a 2-3/4 inch backset. K10 to K13 do the same for the 3-3/4 and 5 inch backsets.
| Series | Door thickness | Source |
|---|---|---|
| 7KC | 1-3/8 to 2 inch | Catalog, FAQ |
| 6K | 1-3/8 to 1-3/4 inch | Catalog, FAQ |
| 8K | 1-3/8 to 2 inch, up to 3 inch with E rose | FAQ |
The 8K documents differ at the edges: the installation instructions in the 8K manual give 1-3/8 to 2-1/8 inch for standard trim, and one catalog paragraph gives 1-3/4 to 2-1/4 inch with spacers for 1-3/8 inch doors. For a door near either end, ask us before you order. The installation instructions start on page A-1 of both service manuals.
BEST documents for the 7KC, 8K and 6K
- 7KC: catalog, FAQ, service manual
- 8K: catalog, FAQ, service manual (also function conversion and wiring instructions)
- 6K: catalog, FAQ
All of them are on the BEST literature page. Latches, strikes and trim parts have part numbers of their own in the service manuals. Browse BEST products and our cylindrical locks.
Not sure which of the three you have, or which one suits your door? Our customer support team is available Monday - Friday, 8 AM - 4 PM Central Time, at 1-888-800-7789 or [email protected].
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