Pen Blank Calculator

Blank dimensions for pen kit mandrel and tube.

Tube outer diameter (mm)

Tube length (in)

Finished pen diameter (in)

Number of barrels

Board thickness (in)

Tab to move between fields

Min blank cross-section (in)

0.63

Blank length per barrel (in)

2.23

Total blank length (in)4.45

Drill bit size (mm)7

Drill bit size (in)0.28

Min wall thickness (in)0.11

Blanks per 5" stick2

Blanks From Thickness1

Waste Vol0.4

How to Use This Calculator

Enter Tube outer diameter (mm), Tube length (in), and Finished pen diameter (in).
Set Number of barrels and Board thickness (in).
Review Min blank cross-section (in) and Blank length per barrel (in).
Use Total blank length (in) and Drill bit size (mm) to inform your decision.

How the result changes with Finished pen diameter (in)

Tube outer diameter (mm): Outer diameter of the brass pen tube. 7mm for slimline, 10mm for cigar/sierra kits.
Tube length (in): Length of one brass tube barrel.
Finished pen diameter (in): Desired maximum outer diameter of the finished pen barrel.
Number of barrels: Number of tube barrels in the kit (most pens have 2).
Board thickness (in): Thickness of the lumber you plan to cut blanks from.

Min blank cross-section (in): Minimum square blank side dimension.
Blank length per barrel (in): Required blank length for each barrel (tube + trim allowance).
Total blank length (in): Total linear inches of blank material for all barrels.
Drill bit size (mm): Drill bit diameter to match the tube OD.
Drill bit size (in): Drill bit diameter in inches.
Min wall thickness (in): Thinnest the wall will be at finished diameter. Below 1/8" risks breakage.
Blanks per 5" stick: How many barrels you can cut from a standard 5" pen blank.

Identify Input Parameters
4 parameters
Tube outer diameter (mm) = 7, Tube length (in) = 2.1, Finished pen diameter (in) = 0.5, Number of barrels = 2 = 5 input(s) provided
Calculate Min blank cross-section
Min blank cross-section = max(finishedPenDiameter + 0.125, tubeODInches + 0.25)
0.625 = 0.625
Calculate Blank length per barrel
Blank length per barrel = tubeLengthIn + 0.125
2.225 = 2.225
Calculate Total blank length
Total blank length = blankLengthPerBarrel * numberOfBarrels
4.45 = 4.45
Calculate Drill bit size
7 = 7