Mortise locks don't require a manual to disassemble. They require an understanding of the basic parts and what mechanical principles each fulfills. New or old ones function pretty much the same at the parts level.

Six parts or 128 parts, they really are all the same.

The outside trim has changed, and there are now lever return springs in many of them, but otherwise new and old operate very similarly.

You generally have a hub through which the lock spindle is inserted.
It may be one, two, three or four parts, but if it is more than one, the outside "locks", and there will usually be a button assembly involved in that locking.

The button assembly will consist of a button or two buttons, two activator arms, one of which is longer than the other and actually engages the hub, a timing lever to keep them operating together and a spring of some sort to bind them in one position or the other. The timing lever will pivot in its center over a post in the case.

You have a shoe assembly. If the trim is thumbpiece, the shoe will usually rest over a slot in the bottom of the case and have a long actuator leg to push back the latch assembly. It will pivot toward the case corner on a post from the case. It there are a hubs and a spindle, the shoe will usually connect between the latch heel and the hub and sit at about a 90 degree angle with the lower shoe leg when it is at rest gently binding on the ears of the hub. Either it will be spring activated or, more commonly, will respond to the latch return spring to keep it in position. It will pivot at the center V between the shoe leg and the actuator arm.

The latch may be a simple latch , a deadlatch or an anti-friction latch. The simple latch typically consists of the latch, a spring, and two case guides to keep it straight as it moves in and out. It will have a latch heel (or a double-sided one- one upper and one lower) which will be against the shoe arm. The deadlatch will require an extra latchpin to detect the open or closed position of the door, its spring, and a pivot assembly to block the latch when it is in the closed position. There will usually also be an intermediate cam which pivots when the hub is turned or shoe is pivoted, that will push the deadlatch pivot assembly to the "open" position. The anti-friction latch consists of a two part latchbolt with a pin connecting them together when the smaller latch can pivot. As it pivots, it begins the latch retraction process, reducing the wear on the actual latch. It may be two curved surfaces (usually indicating that the lock case can be re-handed in the field) or one angle and one flat, positioned in the opposite orientation to the actual latch. This permits a longer latch than would be feasible without the anti-friction component, as well as reducing latch wear.

If there is a cylinder operation, there will be a high hat cam which will be activated by the cylinder cam. It will pivot at its V in the middle and activate the intermediate cam in most units.

Some functions will also have a deadbolt. Deadbolts are simple devices which glide in a set of guides, and have a spring loaded trap lever to bind them in either the open or closed position. The cylinder cam pushes the trap lever down to its neutral position, permitting the bolt to travel, and the sloped notches in the deadbolt surrounding the trap lever provide a pushing or pulling operation as the cylinder cam rotates. In a few rare models, there will be a gear assembly which permits the bolt to travel beyond the distance the mortise cylinder cam could throw it. There are usually a simple rack and pinion device. Keil (and a few copycats later on) used a worm gear instead, so that instead of doubling the bolt throw it almost tripled it and permitted bolt rotation to engage T wings on the bolt behind the frame, effectively limiting frame spreading such as with a crowbar.

The Amarlite door company got a company to manufacture a telescoping bolt for narrow stile aluminum/glass doors for them that combined both the rack and pinion and the worm gear principle, but it is not the type of mortise lock that we are primarily discussing here, although they all really operate the same.

I should mention that I did not research the LIST council terminology for this post, so some terminology may be considered "obsolete". Also, it is NOTHING like the terminology used in Europe and Australia.

But through all of this are springs, springs, springs, of all shapes and types - coiled compression, coiled expansion, coiled hook and eye, and virtually every configuration of flat or wire spring imaginable. You CANNOT have too many resources for springs if you work with mortise locksets. Some of the new ones use spring packs that are really OEM material for their lever return springs. Buy them while it only takes eight weeks to get. Someday you won't be able to get them at all.

The rest is mostly brass. Bend it, straighten it, file it or make new parts from it.

Then all you need to understand is lock functions. But that is fodder for another post.

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