How to make a combination latch: yours will open, someone else’s won’t

How to make a combination latch with your own hands

This simply designed lock is very convenient and reliable in operation. It cannot be opened from the outside without knowing the access code, which can be easily and quickly changed if desired. To make such a lock, all you need is the ability to use a grinder, a drill and welding.

Will need

Materials:

remains of a metal sheet;
bolts, nuts, washers and screws;
a piece of reinforcement;
iron nail, etc.

Tools: ruler and marker, triangular file, open-end wrench, welding, grinder and drill.

Manufacturing process of automatic door latch lock with access code

We cut out a strip of 130×30 mm. On a rectangular plate, set off the diameter of the washer from the long side, draw a line and at one end make a protrusion 5 mm wide. Cut out a strip with a protrusion. We apply the strip with the protrusion to the strip 130x30 mm in length, joining the sides, mark the contour of the protrusion on the latter and make a corresponding cutout.

We draw a vertical line from the inner edge of the protrusion. Between it and the far end of the strip we draw a median line. We step back 5 mm to the right and draw a second line.We measure 25 mm from each line and drill two matching holes with a diameter of 10 mm.

On the strip with a cutout at the far edge, mark and drill two holes with a diameter of 8 mm. The center of the outer hole is 10 mm from the sides of the strip. The distance between the centers of the holes is also 10 mm.

We insert the protrusion into the cutout of the strip and place it on a rectangular plate so that the ends of the strips are 20 mm from the edge of the plate.

We transfer the centers of the right holes in the strips to the plate and drill two lower holes with a diameter of 10 mm and the upper one with a diameter of 8 mm. We remove the jumpers between the three pairs of holes in the strips and get three elongated holes.

We find the middle between two holes with a diameter of 10 mm on the plate, put 5 mm to the sides and drill two of the same holes, and we get one elongated one.

Insert an L-shaped piece of reinforcement into the hole of the strip with a cutout with a diameter of 10 mm with the short side and weld it, and a piece of reinforcement to the strip with the protrusion.

We draw radii on wide washers and make grooves 10 mm deep.

On the ends of the washers welded under the bolt heads, we apply 12 marks evenly in a circle and make grooves with a file, marking every second one with numbers from “I” to “VI”.

Using bolts, we assemble a plate, a strip with a protrusion and large washers with the grooves oriented to the left. We mark on the strip the points of intersection of the circle line of the washers and the axis of the grooves.

Drill two holes with a diameter of 4 mm. We insert pins into them from the side opposite to the piece of reinforcement and weld them.

We connect the strip with the L-shaped handle with a washer and a bolt, which we weld to the plate so that they can move relative to each other. We combine the protrusion of the strip with the cutout of the other and insert bolts with marked washers on top.

We make two shaped parts with a cutout and a hole with a diameter of 12 mm from sheet metal and a corner. We weld the sheet part vertically along the edge of the plate so that the strip with the handle moves freely within the cutout.

We install the strip with the protrusion in place, insert bolts into the holes from below the plate, put washers on top, tighten the nuts, then large washers with slots and secure with nuts. We cut off the protruding ends of the bolts.

We fasten the assembled structure with screws from the inside to the door leaf, and opposite to the jamb - a part from the corner. When the door is closed, the latch slides along the inclined edge of the part on the jamb and eventually falls into the gap.

When the slots on the large washers do not coincide with the position of the pins, the closed door cannot be opened from the outside. If there is no need for a latch, then lift the plate with the handle and move it to the right. To engage the lock, move the top plate to the left.

To open the door from the outside, you must enter the code correctly. To install a different code, unscrew the nuts and change the position of the slotted washers, then tighten the nuts again.