The latch in a BEST cylindrical lock has worn out, or the key turns in the core and the latch does not move. To order the right part you need the lock series, 7KC, 8K, 9K or 6K, and the backset.
Find the series and backset in the lock number
In BEST's How to Order tables the series comes first and a single digit for the backset follows. On the 7KC and 6K, the BEST parts and ordering list PL78 uses 2 for 2-3/8 inch, 3 for 2-3/4, 4 for 3-3/4 and 5 for 5 inch. For the 8K and 9K it lists only 3, 4 and 5. In the example 7KC 3 7 AB 15 D STK 626, the 3 after 7KC stands for a 2-3/4 inch backset.
The 6K catalog also writes the backset into the series name: 63K for 2-3/4 inch, 65K for 5 inch. PL78 names the special backset options 64K and 65K, 74KC and 75KC, 84K and 85K, 94K and 95K. Our BEST 9K and 45H guide reads a full 9K number field by field.
If your paperwork says 7K without the C, check the lock first. BEST's 7KC FAQ says its older 7K was a tubular lock with different components, and that the C was added to tell the two apart. Our door lock types guide explains cylindrical and tubular locks.
BEST 7KC latches by backset
PL78 and the 7KC service manual both list deadlocking latches for the 7KC, under different names:
| Backset | PL78 | 7KC manual |
|---|---|---|
| 2-3/8 in. | 7KCL2 | 6KL2-NF, 6KL2-WF |
| 2-3/4 in. | 7KCL3 | 6KL3-NF, 6KL3-WF |
| 3-3/4 in. | 6KL4 | 6KL4-NF, 6KL4-WF |
| 5 in. | 6KL5 | 6KL5-NF, 6KL5-WF |
In the 7KC service manual NF is a narrow face, 1 inch, and WF a wide face, 1-1/8 inch. Each of these packages includes the latch and two A25359 latch screws. The manual also lists two drive-in latches, 6KL2-L8 for 2-3/8 inch and 6KL3-L8 for 2-3/4 inch, and PL78 offers the L8 drive-in latch option on those two backsets only.
The 7KC catalog uses a third set of names for a latch ordered without the lock: 72KCL2, 73KCL3, 64KL4 and 65KL5, each with a 1/2 inch bolt throw. If your paperwork shows a name that is not in the table, call us with it, the backset and the face width.
BEST 6K latches
PL78 lists four deadlocking latches for the 6K: 6KL2 for 2-3/8 inch, 6KL3 for 2-3/4, 6KL4 for 3-3/4 and 6KL5 for 5 inch. It adds two drive-in latches, 6KL2-8 and 6KL3-8.
The 6K catalog describes a 1/2 inch throw deadlocking latch. Its front is 1 inch wide as standard on the 62K and 1-1/8 inch on the 63K, with the other width as an option. The options are NF for a narrow face latch, WF for a wide face latch and L8 for the drive-in latch, which the How to Order limits to the 62K and 63K.
BEST 8K and 9K latches
The 8K catalog shows three deadlocking latches with a 9/16 inch bolt throw, a 2-1/4 by 1-1/8 inch beveled front and a tube that fits a 1 inch hole in the door edge: 8KL3 for a 2-3/4 inch backset, 8KL4 for 3-3/4 and 8KL5 for 5 inch. To order one without the lock, the catalog asks for the latch number with SL for a spring latch or DL for a deadlocking latch, plus the finish, as in 8KL3-SL. The 8K service manual lists seven latches:
| Backset | Deadlocking | Spring |
|---|---|---|
| 2-3/4 in. | 8KL3 | 8KSL3 |
| 2-3/4 in., 3/4 in. throw | 8KL3-3/4 | - |
| 3-3/4 in. | 8KL4 | 8KSL4 |
| 5 in. | 8KL5 | 8KSL5 |
The manual says to order the latch package by these names; each package includes the latch and two A25359 screws.
For the 9K, PL78 prints the same three latch numbers, 8KL3, 8KL4 and 8KL5, and BEST's 8K FAQ says the 8K knob lock and the 9K lever lock share the same latch and retractor assembly. Both How to Order tables offer a 3/4 inch throw latch as option 3/4.
What the throw member does
In BEST's 8K manual the throw member goes into the back of the core, and in both the 7KC and 8K manuals the core and throw member go into the lever or knob together with the control key. The 7KC troubleshooting table lists a key that spins freely but won't retract the latch or unlock the door, and names one possible cause: the throw member is not installed.
The 8K manual adds two causes tied to the pin count: a 6-pin core with a 7-pin throw member for the same spinning key, and a 7-pin core with a 6-pin throw member for a core that does not fit into the knob core hole.
Which throw member for which BEST lock
| Lock | Throw member | As listed |
|---|---|---|
| 7KC | B56165 | 6-pin and 7-pin cores, no spacer |
| 8K | B92506 | 7-pin |
| 9K | B92505 | 7-pin |
| 8KW | B92506 | 6-pin / 7-pin |
| 9KW | B92505 | 6-pin / 7-pin |
| 6K | 3125559 | standard throw member |
The 7KC manual calls B56165 the 7KC throw member and lists its support ring, A56170, as a separate item. The rest of the table follows PL78.
The 8K service manual shows a different number. Its knob parts list has B91912, an 8K throw member with blocking plate, one for a single-keyed lock and two for a double-keyed lock, plus H and HJ throw members, A55697 and A55696, for the two functions it marks as needing special ones. Its installation instructions put a spacer over the 7-pin throw member for 6-pin cores, with spacers supplied with the cores and not with locks, and say the blocking plate must be used when installing an 8K lockset. PL78, the newer document, lists B92506.
A 9K ordered with a non-IC option for another maker's cylinder is a different case: PL78 notes that it comes without a cylinder, prepped for that maker's cylinder and with a throw member for it. Our SFIC and LFIC guide explains BEST's 6-pin and 7-pin cores and the housings they go into.
BEST documents for these parts
These are on BEST's literature page under Mechanical Locks:
BEST locks and parts at The Builders Supply
Browse BEST products and our cylindrical and tubular locks. The 7KC and 8K manuals ask you to specify the finish with each latch; our finish codes chart explains numbers such as 626.
Not sure which latch or throw member your lock takes? 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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