KNIFE BLOCK

At the present time there are two styles of knife blocks in common use, namely: The wedge adjustment block, which allows for a range from 5 to 12 points, inclusive; and the universal knife block which allows for a range from 5 to 36 points, inclusive. These blocks are fastened to the vise frame by two hexagon head machine screws and held rigid by four dowel pins. To remove the block it is only necessary to take out the two machine screws and work the block out of the dowel pin holes. A certain amount of care is necessary not to drop the block or bend the pins.

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.

Wedge Style Knife Block

The wedge style knife block is the old style quick-change block and is held to the vise in the same manner as the universal block. The left-hand knife is mounted and adjusted the same as with the universal block. The right-hand knife is held to the block by two shoulder screws which pass through the two friction springs and washers from the front of the block. This assembly holds the knife tight against the block, but permits the two strong springs to force the knife against the wedge.

The wedge is operated by a small hand lever and is graduated from 5 to 12 points, inclusive. By pulling the lever up or down the wedge moves and the knife follows the wedge.

Knife, Right Hand, Spring Plate

There is a steel plate assembled in the right side of the knife block which keeps the slugs upright as they travel through the knife block into the chase. This plate is called the knife spring plate and is held in place by two lugs at the back of the plate extending into the base of the right-hand knife. It is forced toward the left by a flat bronze spring, called the spring plate spring. There should be just enough tension on this spring to force the plate up against the outgoing slug with an even pressure so the slug will be held upright as it is being pushed into the chase by the ejector blade. The flat spring is so shaped that the ends fit behind rivet heads, to hold the plate in place. If the spring becomes bent so it will not stay behind the rivets, the lugs will work out of their seat and the gate will obstruct the passageway of the slug. This will oftentimes smash the face of the slugs.

Facts and Suggestions About Trimming Knives

The right-hand knife must be adjusted so that its edge is exactly parallel with the left-hand knife in order to make the slug of equal thickness throughout its entire length. The faces of the two knives separate slightly toward the front of the machine, which allows the slug to pass freely forward from the cutting edges. The right-hand knife must be shaped so there is a cutting edge of about ¹/₆₄ of an inch on the side that stands next to the slug. By having this edge the “gouging” of the knife into the slug is prevented, and slugs are trimmed to equal thickness at the top and bottom. This cutting edge must never be more than ¹/₆₄ of an inch.

Always remember that the knives can be set to trim the slugs perfectly from one point-size to another with accuracy, but it requires patience, as the knives must be adjusted to a thousandth part of an inch.

Keep the knife block and the knives clean. The seat of the knives should also be clean. It will be impossible to get an accurate adjustment if dirt or gum interferes with the movement of the knives.

The trimming knives should have exceedingly sharp or thin edges to work satisfactorily. If the knives become very dull or the cutting edge rounded or nicked, they should be taken off the machine and reground. Send them to the nearest agency as they are equipped with grinders and other fixtures to do this regrinding and maintain the correct angles and shape of the knives. Always send both the right-hand and left-hand knives, as they should be reground in pairs, and the cutting edges should exactly match each other in order to obtain good results.

Use a full measure slug when adjusting the trimming knives. Cast a full line of capital letters on the slug and hold the matrices for recast. Measure the slug on the ribs at the top and near the bottom. The slug should measure the same at the top edge and near the bottom if the knife which trims the smooth side is correctly set. The slug should measure the same at the top edge of both ends if the knife which trims the rib side of the slug is correctly set.

Before setting the trimming knives, make sure that the mold is properly seated in the mold disk and that there is no metal between the liners and the mold.

When the trimming knives become dull it is practically impossible to set them to trim accurately. Even when they are set nearly accurate, they will hold the adjustment only a short time.

Dull knives also cause trouble by making it difficult to eject the slug. This will often cause the clutch to slip.

When a long slug measures thicker or thinner at the ends than in the center, it is usually due to dull knives, but may be caused by the knives being forced in a twist or strain by the adjusting screws or some foreign substance behind the knives.