Adjustable Scribing Tool (Offset Scriber) with Bearing Follower

Offset scribe for fitting boards, panels, worktops and trim to walls that aren't straight. Run the follower along the wall and the pencil draws a parallel line on the board. Cut to the line and the board fits the wall.

The offset adjusts continuously and locks with a single knob. It is read off scales engraved on both sides of the beam. Any ordinary pencil, mechanical pencil or pen of 5.5–8.5 mm fits.

Features

• Two followers on one tool:

  • Front point: offsets from ~29 to 100 mm. Gets into tight inside corners.

  • Rear 624 bearing: offsets from ~50 to 123 mm. Rolls smoothly along brick, stone, plaster or finished surfaces.

• The pencil stays in line with the follower. It runs through a slot in the middle of the beam, so the line is drawn exactly opposite the point of contact.

• Engraved scales, read at the pencil point. The scale on each side of the beam reads the offset for its follower directly, in mm, so you don't need a ruler.

• Solid lock. The carriage sits on a V-and-flat rail and is clamped from below by a single knob. Locking doesn't shift the setting.

• Quick pencil swaps. A V-block holder with a print-in-place jaw takes pencils of different diameters without changing the offset.

• No supports and only standard metric hardware.

No bearing? No problem. A no-bearing version is included. It has the front point and the front scale only, and needs nothing but two M5 screws and nuts.

What you need

Check your M5 nuts: they must be the thin DIN 934 type (4 mm). Thicker ISO 4032 nuts (up to 4.7 mm) won't fit the holder.

Printing

• Material: PETG. PLA works too, but PETG is tougher and better for a tool that lives in a toolbox.

• Supports: none.

• Orientation: print the STLs as they are oriented in the files, which is also how they're laid out on the plate (see the plate image).

• Settings: 0.2 mm layers, 3–4 perimeters and 20–30% infill work well. The parts are small and stiff.

Assembly

1. Pencil holder: snap the jaw free inside the carriage (a gentle push with a screwdriver). Drop an M5 nut into the slot in the top of the holder. Press an M5 screw head into the holder knob and thread it into the nut. If the head is too tight to press in, warm it with a soldering iron and push.

2. Lock knob: press the second M5 screw head into the end of the lock knob's neck.

3. Rail lock: drop the second M5 nut into the clamp bar's pocket. Set the carriage on the beam. From below, push the clamp bar up into the slot under the lock hole, with the nut side facing down, and thread the lock screw in from above.

4. Bearing (bearing version): drop the M4 nut into the hex pocket under the beam's rear tongue. Stack the bearing and then the spacer (small boss down) on the tongue and screw the M4 down into the nut. Tighten it firmly: the outer ring of the bearing must still spin freely.

How to use it

1. Loosen the lock knob about half a turn and slide the carriage.

2. Lower the pencil until its point touches the board (flush with the bottom of the beam) and clamp it with the holder knob.

3. Read the offset at the pencil point:

   • Front scale (with the front point on your left): distance from the front point.

   • Rear scale (other side, with the bearing on your left): distance from the bearing rim.

4. Lock, hold the tool square to the wall with the follower touching it, and draw along the wall.

Tips

• Use the front point for short offsets, tight corners and fine detail. Use the bearing for long runs and rough surfaces.

• Keep the beam square to the wall. A round follower reads slightly long where the wall surface is steeply angled (about 1 mm at 30°).

Customizing

The OpenSCAD source (scribe-tool-v5-master.scad) is included and fully parametric. Open it in OpenSCAD and use the Customizer:

• rear_follower: bearing or none

• offset_max: longest front offset, which sets the beam length (default 100 mm)

• scale_zero_adj / rear_zero_adj: calibrate a scale if it reads off when checked against a ruler

• nut_t, pip_gap and the knob fit values, for your hardware and printer