Pen Blank Size Calculator
Calculate pen blank dimensions for any kit.
Get length, width, and grain direction for perfect pen turning blanks.
Pen blanks must be cut slightly larger than the finished tube dimensions to allow for turning, squaring, and finishing. The critical measurements are length, width (cross-section), and the drill bit size that matches the brass tube’s outer diameter.
Standard Pen Kit Tube Dimensions
| Kit Style | Tube OD (mm) | Tube Length (mm) | Drill Bit (mm) | Min Blank Cross-Section |
|---|---|---|---|---|
| Slimline / 7mm | 7.0 | 52.0 | 7.0 | 19 x 19 mm (3/4" x 3/4") |
| Fancy / Euro | 8.0 | 53.0 | 8.0 | 20 x 20 mm |
| Cigar | 10.5 | 58.5 | 10.5 | 22 x 22 mm |
| Sierra | 10.0 | 57.0 | 10.0 | 22 x 22 mm |
| Bolt Action | 10.0 | 63.0 | 10.0 | 22 x 22 mm |
| Wall Street | 12.5 | 65.0 | 12.5 | 25 x 25 mm |
| Majestic | 12.0 | 70.0 | 12.0 | 25 x 25 mm |
| Rollerball | 10.0 | 55.0 | 10.0 | 22 x 22 mm |
Blank Length Formula
Blank length = Tube length + 3 mm trim allowance (per end) Total blank length = Tube length + 6 mm
For a Slimline pen with a 52 mm tube: blank length = 52 + 6 = 58 mm (round to 60 mm for safety).
Blank Cross-Section Formula
Minimum cross-section = Tube OD + (2 x minimum wall thickness) Recommended wall thickness after turning: at least 2–3 mm per side. So: Minimum blank width = Tube OD + 6 mm (for 3 mm walls on each side). Recommended blank width = Tube OD + 10 mm to 12 mm (gives comfortable turning margin).
Worked Example — Cigar Pen Kit
Tube OD = 10.5 mm, tube length = 58.5 mm. Blank length = 58.5 + 6 = 64.5 mm, round up to 65 mm. Minimum blank = 10.5 + 6 = 16.5 mm square (too thin for comfort). Recommended blank = 10.5 + 12 = 22.5 mm, so use a 22 x 22 mm or 3/4" x 3/4" blank. Drill the blank with a 10.5 mm bit on the lathe or drill press.
Grain Direction
For best appearance, orient the grain lengthwise along the pen barrel. If making a two-barrel pen (upper and lower), cut both blanks from the same piece and mark them so the grain flows continuously when assembled.
Material Waste Estimate
Typical waste from a pen blank is 60–75% of the starting material volume (most is turned into shavings). A 22 x 22 x 65 mm blank (31.5 cm³) yields a barrel with roughly 8–12 cm³ of finished wood.