How do you disassemble the L.C. Smith lock?

Courtesy of Jim DeMunck, as instructed by John Miller of the Marlin Firearms Repair Dept.

A mainspring vise is the best and proper way to disassemble the Smith lock, but simple modified pliers were often used in the Marlin Repair Dept. with smooth jaws so as to not mark the spring or sear edges; sometimes with a small piece of leather. Locks might require disassembly and reassembly many times in the course of a stubborn repair.

DISASSEMBLY

With the lock in the fired position (hammer forward):

Grasp the bottom of the sear and the top of the mainspring up as close to the bridle as you can and compress. It helps to loosen the bridle screws before you do this so you are not struggling with them while holding the spring in compression (which use of a mainspring vise avoids).

With the spring compressed just enough to take the upper arm pressure off of the hammer, remove the bridle entirely and lift the hammer off of the plate. Now with the spring still held in compression, take your other hand and simply hold the sear in its position by upward pressure on the tail (horizontal extension). It takes very little to hold it against the spring as you have so much leverage.

Now release, slowly, the pliers/vise on the mainspring to allow the spring to relax. The upper leg will extend up and stop against the rear bridal bolster on the lock plate. It's almost all the way relaxed but still has some compression.

You now have in your hand, held in place easily by one finger and your thumb, the partially compressed mainspring and the sear.

Lastly, grab the lockplate anywhere you can get a solid grip, and allow the sear to rotate under the partial spring pressure. The tail will rotate down and towards the front. As it does the spring is totally relaxed and the sear is simply lifted from the plate. The mainspring will then fall free of the plate.

REASSEMBLY

Place the mainspring onto the plate with the longer leg up against the rear bridal lug and the 'V' up under the headless screw at the rear of the plate.

Place the sear in its pivot hole with the tail well down and forward so it is not engaging the spring. Now rotate the sear backwards engaging the mainspring and taking it into partial compression.

At this point lay the plate on a flat surface, hold the bottom of the sear and the top of the spring leg and compress with your pliers/vise enough to drop the hammer into its pivot in the fired position. The bridle then drops into position and screws down. If you grab the spring too far forward, you won't be able to drop the bridle into place. Simply hold onto the sear and reposition your pliers or vise and try again.

Of the two screws in the bridle, the round head one goes in the rear position. The flat headed one is fitted in the front position to lie against the frame edge inside and level the plate surface on the exterior. You usually see file marks across it; the head filed flat but at an angle, and sometimes a witness mark.

Doing any of this should not leave any marks, gouges or scars on the parts, especially the spring. That can weaken it. Some of the springs are nicely finished; others rather crude looking in comparison. But adding nicks and dents to them can only damage or weaken it.

DON'T use a side cutter to grab, hold and compress mainsprings!