Press Construction

Part of Printing

A printing press applies even, controlled pressure to transfer ink from raised type onto paper. Building one from scratch requires woodworking, metalworking, and an understanding of mechanical advantage — but the result is a machine that can produce hundreds of identical pages per day, making mass literacy achievable.

Why Press Construction Matters

Without a press, you can print by hand-rubbing the back of the paper against inked type — this is slow, uneven, and tiring. A press multiplies productivity 10-50x while improving quality. The Gutenberg-style screw press remained the dominant printing technology for 350 years because it is effective, reliable, and buildable with pre-industrial materials. It is the right technology for a rebuilding scenario.

Press Design Overview

A printing press has five main components:

Component	Function
Frame (hose)	Structural support — holds everything in alignment
Platen	Flat plate that presses paper against type
Screw mechanism	Converts rotational force into downward pressure
Bed (coffin)	Sliding platform that holds the type form
Tympan and frisket	Paper holding and ink masking system

The Frame

The frame must be rigid enough to withstand several tons of downward force without flexing. Any flex wastes pressure and produces uneven prints.

Materials

• Hardwood — Oak is ideal. Beech, maple, and ash work well. Avoid softwoods (pine, fir) — they compress under load.
• Dimensions — For a typical book-printing press with a 30x45 cm print area:
  • Uprights (cheeks): two posts, 15x15 cm cross-section, 180 cm tall
  • Cross-beams (cap and sill): 15x15 cm, 60 cm long
  • Base: heavy timber sill, 15x20 cm, 120 cm long

Construction

1. Cut the uprights — Two identical posts. Mortise holes at top, bottom, and at the platen height for cross-members.
2. Cut the cap beam — The top cross-beam that holds the screw nut. Bore a centered hole for the screw to pass through. This hole must be reinforced — the entire pressing force passes through it.
3. Cut the sill beam — The bottom cross-beam. It anchors the uprights and supports the bed.
4. Assemble with mortise-and-tenon joints — Pegged, not nailed. The joints must be tight — any looseness translates to uneven pressure.
5. Brace diagonally — Add diagonal braces between uprights and base to prevent racking.

Alignment is Critical

The frame must hold the platen perfectly parallel to the bed. If the frame is twisted or the screw is off-center, one side of the sheet prints heavier than the other. Check alignment with a straightedge and level during assembly, and correct before final pinning.

The Screw Mechanism

The screw is the heart of the press. It converts the rotational force of a lever into massive downward pressure.

The Screw

Specifications for a book press:

• Diameter: 6-10 cm
• Thread pitch: 8-12 mm per revolution
• Material: hardwood (box, lignum vitae, or dense oak) or iron
• Length: 50-70 cm

Making a wooden screw:

1. Turn a cylinder on a lathe (or shape with draw knife and rasp)
2. Mark the spiral thread line using a template wrapped around the cylinder
3. Cut the thread groove with a gouge, following the marked line
4. Smooth the thread with a file
5. The thread must be consistent in pitch and depth — variations cause the screw to bind

Making an iron screw (superior but harder):

1. Forge a round bar to the desired diameter
2. Heat and chase the thread using a die (or file by hand — very slow)
3. An iron screw is stronger and smoother than wood

The Nut (Female Thread)

1. Bore a hole through the cap beam matching the screw’s outer diameter
2. Cut matching internal threads using a tap (a hardened threaded rod)
3. For a wooden screw in a wooden nut, rub both with tallow for lubrication
4. Alternatively, cast a bronze or iron nut with internal threads for greater durability

The Lever (Bar)

A long horizontal bar inserted through the top of the screw provides mechanical advantage:

• Length: 80-120 cm
• Material: hardwood or iron
• Inserted through a hole or slot near the top of the screw
• The printer pulls the bar to rotate the screw, pressing the platen down
• Longer bar = more mechanical advantage = less effort needed

Mechanical Advantage Calculation

With a 100 cm lever arm and a 1 cm pitch screw, the mechanical advantage is approximately 628:1 (2 x pi x lever length / pitch). A 20 kg pull on the lever produces over 12,000 kg of force on the platen. This is more than sufficient for printing.

The Platen

The platen is the flat surface that presses paper against inked type. It must be perfectly flat and rigid.

Construction

1. Material — A thick slab of close-grained hardwood (30-40 mm thick), a stone slab, or a thick iron plate
2. Size — Must cover the entire print area plus a 3-5 cm margin
3. Flatness — Check with a straightedge across multiple directions. Any curvature causes uneven printing — heavy in the center, light at the edges, or vice versa.
4. Attachment — The platen hangs from the screw via a ball joint or simple hook. It must be free to self-level against the type form.

The Hinge (Pivot)

The platen should be able to tilt slightly to accommodate minor irregularities in the type form:

1. Attach the platen to the screw with a rounded pin or ball that allows pivot
2. This self-leveling action ensures even pressure across the entire print area
3. Without a pivot, any slight tilt in the screw produces heavy printing on one side and light on the other

The Bed and Carriage

The bed holds the locked-up type form and slides under the platen for printing.

Construction

1. Bed surface — A perfectly flat slab of stone (marble or slate is ideal) or thick hardwood plank
2. Rails — Two parallel wooden or metal rails on which the bed slides
3. Runners — The bed rides on greased runners along the rails
4. Handle or crank — Allows the printer to slide the bed in (under the platen) and out (for inking)
5. Dimensions — The bed surface should match or exceed the type area; the rails extend far enough for the bed to slide completely out from under the platen

Why the Bed Slides

The bed must slide out from under the platen so the printer can:

1. Ink the type (with the bed extended toward the printer)
2. Place the paper (using the tympan)
3. Slide the bed under the platen
4. Pull the press
5. Slide the bed out
6. Remove the printed sheet

Tympan and Frisket

The Tympan

The tympan is a hinged frame covered with parchment or cloth that holds the paper flat against the type form during printing.

1. Build a frame matching the bed dimensions
2. Cover with stretched parchment, vellum, or smooth cloth
3. Hinge to the far edge of the bed
4. The paper is placed on the tympan, which folds down onto the inked type
5. Packing (sheets of felt or paper) between the tympan covering and the paper provides a slight cushion for even impression

The Frisket

The frisket is a thin frame with a cutout that masks the non-printing areas of the paper, preventing ink smudges from type furniture and the chase edges.

1. Build a light frame matching the tympan
2. Cover with thin paper or parchment
3. Cut windows where the printed text should appear
4. Hinge to the tympan
5. The frisket folds down onto the paper, exposing only the areas that should receive ink

Assembly and Alignment

Final Assembly Checklist

Check	How to Verify
Frame is plumb (vertical)	Hang a plumb line from the cap beam
Screw is centered	Drop a plumb bob from the screw center — it should hit the bed center
Platen is parallel to bed	Place paper between platen and bed, press lightly — impression should be even
Bed slides smoothly	Push the bed in and out — should move freely without binding
Screw turns freely	Rotate with the lever — should require moderate, consistent effort
Press applies even pressure	Print a test sheet of solid type — ink density should be uniform

Test Printing

Before printing text, test with a solid block of type or a flat woodblock:

1. Ink the surface
2. Place paper
3. Apply pressure
4. Examine the print — it should be uniformly dark across the entire area
5. If one area is heavier, adjust: shim the bed, adjust platen pivot, or correct frame alignment

Start Gentle

For your first test prints, apply moderate pressure and increase gradually. Too much initial pressure can damage type, tear paper, or reveal structural weaknesses in the frame that are better discovered gently.

Maintenance

• Lubricate the screw with tallow monthly
• Check frame joints for looseness — tighten pegs as needed
• Keep the bed surface flat — replace if it warps
• Clean the platen after each session — dried ink builds up and causes uneven pressure
• Inspect the screw threads for wear — replace before they strip

Common Mistakes

1. Soft wood frame — Pine and fir frames flex under pressure, wasting force and producing uneven prints. Use hardwood exclusively for structural components.
2. Screw not centered — An off-center screw applies asymmetric pressure. The platen presses harder on one side, producing one heavy side and one light side on every sheet.
3. No platen pivot — A rigidly attached platen cannot accommodate minor irregularities. Even a 0.5 mm tilt across the platen width causes visible print quality variation.
4. Bed not flat — A warped bed causes the type form to sit unevenly. Check bed flatness with a straightedge before every printing run.
5. Over-tightening — Excessive pressure does not improve print quality — it damages type, tears paper, and strains the frame. Apply only enough pressure for clean, full ink transfer.

Summary

Press Construction — At a Glance

• Five components: hardwood frame, screw mechanism, flat platen, sliding bed, and tympan/frisket
• The frame must be rigid hardwood (oak preferred) — any flex wastes pressure
• The screw provides ~600:1 mechanical advantage with a 1m lever arm
• The platen must be flat and pivot-mounted for self-leveling against the type form
• The bed slides in and out: ink type (out), place paper (out), press (in), remove (out)
• Alignment is critical — platen parallel to bed, screw centered, frame plumb
• Test with solid blocks before printing text — impression must be uniformly dark
• Lubricate the screw with tallow; check frame joints regularly for looseness