Screw Press

Part of Printing

How to design and build a wooden screw press for letterpress printing.

Why This Matters

The wooden screw press was the machine that made the printing revolution possible. From Gutenberg in the 1440s through the late 18th century, nearly every book in Europe was printed on some variation of the wooden screw press. It is a simple machine — a large threaded wooden screw driving a flat platen down against a flat bed — yet it is capable of producing thousands of good impressions per day in skilled hands.

The screw press is achievable with basic woodworking skills, some iron hardware, and timber of adequate quality. No foundry, no steam engine, no precision machining is required. A community with competent woodworkers can build one. Once built and correctly set up, a wooden screw press has a working life of decades.

How the Screw Press Works

The screw press applies force through mechanical advantage. A long threaded wooden post (the screw) passes through a threaded wooden block (the nut) fixed in the upper frame of the press. When the operator turns a horizontal bar (the bar or rounce) attached to the screw, the screw moves vertically, carrying a platen downward to press paper against the inked type.

The thread on the screw converts rotational motion into downward force. A coarser thread (fewer turns per unit length) moves the platen faster but provides less mechanical advantage; a finer thread moves it more slowly but multiplies force more. For printing, a relatively coarse thread (one complete turn advances the screw about 25–30mm) provides a good balance of speed and force.

Design Dimensions

A press for folio printing (sheets approximately 300mm × 420mm) requires:

Component	Dimension	Notes
Printing bed	400mm × 550mm	Must be wider and longer than sheet
Platen	300mm × 420mm	Slightly larger than printing area
Screw diameter	80–100mm	Larger = stronger, slower
Screw thread pitch	25–30mm per turn	Adjust for speed vs. force
Frame width	550–600mm	Clear of platen sides
Frame height	600–700mm	Press top to bed surface
Bar length	600–700mm total	Leverage for the operator

These dimensions are guidelines. Adjust to available materials, intended sheet size, and the operator’s physical size.

Materials

Wood

All structural elements are made from dense, straight-grained hardwood. The screw itself must be the best available wood — dense, straight, knot-free. Historically, applewood, pear, box, or very dense oak was used for screws. The wood must be thoroughly dry before turning — any subsequent moisture changes will distort the thread and make the press inoperable.

Required pieces:

• Screw: One piece, 100mm diameter, 500mm long, straight-grained, absolutely dry
• Nut: One piece, 150mm × 150mm × 100mm, same species as screw (same wood expands and contracts together)
• Frame uprights (cheeks): Two pieces, 80mm × 120mm × 700mm
• Frame top (head): One piece, 100mm × 200mm × 700mm
• Crosspiece (hose or till): One piece supporting the nut, 80mm × 200mm × 650mm
• Platen: Built-up laminated construction, see Platen Design
• Bed: 50mm hardwood planks, joined flat, 400mm × 600mm

Iron Hardware

A modest amount of iron hardware improves press durability and function:

• Iron bands around the nut (prevent splitting when the screw is tight)
• Hinge for the platen (allowing it to pivot slightly for self-leveling)
• Guide rods or channels to prevent the platen from rotating as the screw turns
• Bed-slide hardware if the press uses a sliding-bed design

Iron can be replaced with heavy hardwood for all but the most critical functions, but the press will require more frequent maintenance and adjustment.

Building the Screw

The screw is the most technically demanding component to produce.

Turning the Blank

The screw blank must be cylindrical — any taper or eccentricity causes the thread to engage unevenly. Turn the blank on a pole lathe or by hand with a drawknife and spokeshave, checking frequently against a cylindrical template.

Final diameter should be uniform to within 1mm along the full length.

Cutting the Thread

Method 1: Thread box A thread box is a wooden tool with a V-shaped cutter mounted inside a cylindrical hole. The blank is pushed through while turning, and the cutter traces a helical thread. The thread box itself must be made first — usually from hardwood, with a sharpened iron or steel cutter.

Building the thread box:

1. Bore a hole through the box body to fit the blank with 1–2mm clearance.
2. Cut a slot through the side wall of the hole at the thread angle (arctan of pitch/circumference).
3. Mount a sharpened cutter in the slot at the correct angle.
4. Test on scrap wood of the same species as the screw.

Method 2: Hand-cut thread Mark the thread helix on the blank with a thin cord wrapped at the correct pitch, then carefully trace with a saw and chisel. This is slower and less uniform than a thread box but requires no additional tooling beyond what most shops already have.

Cutting the Nut

The nut thread must match the screw thread exactly. Make the nut after the screw, using the screw itself as the master:

1. Bore a hole through the nut blank, slightly undersized relative to the screw diameter.
2. Coat the screw thread with lampblack or chalk.
3. Force the screw into the nut blank with firm rotation. The black/chalk marks the high spots.
4. Carefully pare away the marked spots with a sharp chisel.
5. Repeat until the screw turns through the nut with light friction — snug but not binding.

The fit should be close but not tight. A very tight fit makes the press difficult to operate; a loose fit allows the screw to wobble, causing imprecise impression.

Frame Assembly

The frame must be rigid and square. All joints should be mortise and tenon, pegged with hardwood pins after gluing and assembly.

Assembly sequence:

1. Join the two cheeks (uprights) to the head (top beam) with large mortise and tenon joints. Draw-bore-peg for maximum rigidity.
2. Install the crosspiece that carries the nut. This piece must be very firmly attached — it bears the full printing force.
3. Install the nut in the crosspiece hole (usually with iron bands to prevent splitting).
4. Insert the screw through the nut and check operation.
5. Attach the platen to the screw bottom — the connection must allow slight self-leveling motion (a loose pivot ball or simple hinge) so the platen can adjust to align with the form.
6. Mount the bed to the base of the frame. The bed surface must be parallel to the platen when it descends to printing position.

Verifying Alignment

With the press assembled, lower the platen to the bed and check alignment:

• The platen must descend without touching the cheeks.
• The platen face must be parallel to the bed (check with thin strips of paper at all four corners — they should all have equal resistance when the platen is lightly closed).
• The screw must turn smoothly without binding at any point through its range of travel.

Operation and Maintenance

Operating the press: Apply the bar with one or two hands, turning clockwise to descend and apply pressure, counterclockwise to release. The impression stroke should be a smooth, controlled motion, not a slam. Experienced pressmen developed a feel for the exact amount of turn needed — applying full pressure in one motion, then releasing.

Oiling: The screw and nut surfaces must be regularly lubricated with tallow (rendered animal fat), linseed oil, or beeswax to prevent wear and reduce operating effort. Apply at the start of each working session.

Checking the nut: Over time, the nut wears and develops looseness. Re-fit by removing the nut and tightening the thread with a sharp paring chisel, removing high spots as in the original fitting procedure. Replace the nut when it becomes too worn to tighten further.

Seasonal adjustment: Wood changes dimensions with humidity. In dry seasons, the screw may become loose in the nut; in wet seasons, it may bind. Store the press in a stable environment if possible, and adjust fit seasonally.

A well-built wooden screw press, properly maintained, will give reliable service for a generation. The techniques for building and maintaining it are fully within the capabilities of any community with skilled woodworkers.