Seven Millimetres of Brass and Everything Else Is Wood

Pen Turning
woodworkingcraftmakingmechanicaldesign
🎮 Play: The Turning Point

Restoring fountain pens eventually leads to a question you can’t ignore: where does the body come from? I’d spent weeks tuning nibs and replacing sacs, but the barrels themselves were always someone else’s work — vintage celluloid from a factory in Fort Madison, Iowa, or injection-moulded plastic from a plant I’d never see. When I opened up a 1940s Sheaffer Lifetime with a cracked barrel, the repair options were: find another dead pen to cannibalize, or learn to turn a replacement.

I ordered a mini-lathe. This is a technical deep-dive into how a pen blank becomes a pen.

The Geometry of a Pen Blank

A pen blank is a standardized unit: ¾” × ¾” × 5”, sold in pairs (upper and lower barrel). The standardization exists because the internal geometry is fixed by the kit hardware. A 7mm slimline kit — the universal beginner project — requires a 7mm hole drilled through the centre of the blank to accept a brass tube.

That tube is the structural reference for everything that follows. You’re not turning wood to a specific diameter; you’re turning wood down to the tube, using brass bushings as your gauge.

BLANK CROSS-SECTION (before turning)

         ¾" (19mm)
    ┌─────────────────┐
    │                 │
    │     ○ 7mm       │  ¾"
    │     hole        │
    │                 │
    └─────────────────┘

BLANK ON MANDREL (during turning)

    bushing    blank    bushing
      ║══════════════════║
      ├──┤              ├──┤
      target diameter = bushing OD

The bushings are precision-ground to the exact outer diameter specified by the kit. When the wood is flush with the bushing, you’ve hit the target. The pen hardware — clip, cap, nib cone — will slip over the barrel with the correct fit.

Drilling: The Operation Where Beginners Fail

The blank must be drilled dead-centre and parallel to the grain. This sounds straightforward. It is not.

Wood has density gradients. The bit follows the path of least resistance, which means it wanders toward softer early wood and away from dense late wood. In figured woods — burl, spalted maple, anything with character — the density variations are chaotic. The bit can drift 2-3mm over a 5cm hole, which doesn’t sound like much until you realize the wall thickness is only 6mm to begin with. Drill off-centre by 2mm and you’ll reveal brass on one side when you turn the blank round.

The protocol:

  1. Mark the centre with an awl (creates a pilot divot)
  2. Use a pen vise or V-block to hold the blank square
  3. Drill at low speed — 500 RPM maximum
  4. Retract frequently to clear chips (every 5-10mm of depth)
  5. Listen for pitch changes that indicate binding

That last point is the one nobody writes down. The drill bit sings at a consistent pitch when cutting cleanly. When chips pack in the flutes, the pitch drops and the vibration increases. If you force it, the bit seizes, the blank spins in the vise, and you’ve ruined both the workpiece and possibly the bit.

The CA Finish: Superglue as Lacquer

Cyanoacrylate (CA) glue — superglue — is the standard finish for turned pens. This initially seemed absurd. Adhesive as topcoat? But the chemistry is sound.

Thin CA is a low-viscosity monomer. Applied to spinning wood, it flows into the grain, then polymerizes almost instantly under the friction heat generated by a paper towel pressed against the surface. The result is a cross-linked acrylic shell, chemically bonded to the wood fibres, that can be sanded and polished to optical clarity.

The application sequence:

  1. Sand the turned blank through grits: 150 → 220 → 320 → 400 → 600
  2. Apply thin CA with the lathe spinning at ~1000 RPM
  3. Immediately press a folded paper towel against the surface (the friction cures the CA)
  4. Wait 30 seconds between coats
  5. Repeat for 6-10 coats
  6. Wet-sand with micro-mesh: 1500 → 1800 → 2400 → 3200 → 4000 → 6000 → 8000 → 12000

The micro-mesh progression is where the finish transforms from “decent” to “glass.” Same abrasives used for polishing acrylic headlight lenses. By 12000 grit, you’re not removing material so much as burnishing the surface molecular layer.

There’s a parallel to the pyrography discovery from last week — heat as medium rather than hazard. Here, friction isn’t a problem to manage; it’s the curing mechanism. The paper towel generates enough heat to polymerize the CA in seconds. Too slow and the glue pools. Too fast and you burn through the paper towel and glue your fingers to the workpiece.

First Blank: Walnut, 7mm Slimline

My first blank is walnut — stable, closed-grain, forgiving. The drilling went cleanly (I retracted every 8mm like a paranoid machinist). The brass tube is epoxied in place and curing overnight.

Tomorrow I mount it on the mandrel and find out whether I’ve learned anything from watching videos, or whether this is another hobby where the hands have to fail before they understand.

The kit cost $2.75. The blank cost $4. The lathe cost considerably more than I’m willing to write down. But somewhere in the math is the fact that I’m no longer dependent on finding vintage barrels in acceptable condition. If a pen needs a new body, I can make one.