Linotype mechanism

by Alvin Garfield Swank; Raymond Means

Trimming Knives

The purpose of the trimming knives is to trim the slugs to the proper size and the sides parallel.

The measurement of a type-founders point is .0138-⅓ of an inch. The measurement of a linotype point is .014 of an inch.

The point unit now used on the matrices is the one used by the type-founders. The linotype point is still being used when adjusting the trimming knives. A 10-point slug, when trimmed correctly, should measure .140 of an inch, or 10 times .014 of an inch.

The left-hand knife trims the overhang from the smooth side of the slug and is held to the vise by two square head screws that pass through the front, and is adjusted by two screws, at the top and bottom of the knife block and bearing against the knife. This knife should be adjusted to be in line with the left side of the mold; it is only intended to remove the fins which form at the top of the slug. It is not intended to remove metal from the smooth side of the slug.

If the left-hand knife does not trim the overhang off the slug, it will cause the slugs to be thicker at the top than at the bottom, and be off their feet. This will cause trouble in the lockup of the form, the columns having a tendency to raise up in the center.

Always loosen the two screws which hold the knife to the vise when making any adjustment of the left-hand knife. Turning in on the adjusting screws without loosening the two lock screws may cause the knife to spring and trim the slugs more in the center than on the ends.

The right-hand knife trims the slug to thickness and is held to the slide bracket on the universal knife block, by two round head screws. It is forced to the right against the adjusting screws by two springs. The screws that hold the knife to the bracket should be loose when moving the adjusting screws outward, as the spring should force the knife against the adjusting screws in this movement. It is not necessary to release the screws that hold the knife to the bracket when turning the screws inward as the screws are forced against the knife in this adjustment.

The screws in the sector are set to step from one point size to another and should not be changed except when necessary to trim any body size to a special thickness.

Beneath the bracket to which the knife is fastened are two spiral springs that force the bracket and knob button against the sector screws. Moving the lever operates the sector, and the screw coming in contact with the button on the slide causes the knife to move in or out one point or as many as the lever is moved. When casting a 10-point slug, have the pointer on figure 10.

After having the knives adjusted to trim one size slug, the knife block is constructed so as to trim all others, by merely moving the handle on the knife block. When changing the universal knife block, be sure that one of the lever detent pins has entered the hole in the sector.

To adjust the trimming knives, first set the right-hand knife by turning the two adjusting screws that are in the knife block slide bracket and touching the side of the knife, so it will trim the ribs of a slug; then adjust the knife that trims the overhang from the smooth side of the slug; then re-adjust the right-hand knife to thickness and parallel. Do not attempt to adjust the knife that trims the overhang from the smooth side of the slug unless the right-hand knife is trimming the ribs.