Crossbow Building Wiki


This article describes a traditional Finnish type crossbow and is a summary of an article written by Olavi Paateri and Martti Arkko. For bibliographical details, refer to the bibliography page.


The bow is made of spring steel, with nocks forged in the typical medieval style. The bow's dimensions are the following:

  • Length: 860mm (before forging the nocks)
  • Width: 45mm in the middle, 27mm at the nocks
  • Thickness: 10mm in the middle, 7mm at the nocks
  • Deflex: 50-60mm

Once the bow is reduced to correct dimensions and deflexed and nocks are forged, it's sent for heat treatment. It should left soft enough to give in (bend) before breaking to avoid accidents.

The bow is attached to the stock by binding it with leather straps in the through the characterictic hole in the stock.


The bowstring is made from linen in the typical endless loop fashion. Sailmaking twine (in Finnish: purjelanka) is used for serving the bowstring. The distance between the posts in the jig should be 15-20mm shorter than the distance of the nocks.

The bowstring can optionally be protected against moisture by rubbing it with beeswax and/or linen oil.


Lockplates are made from a piece of steel with following dimensions:

  • Length: 320mm
  • Width: 45mm
  • Thickness: 2,5mm

After cutting the lockplates to their finished shape (whatever that is), holes are drilled for screws that attach the lockplates to the stock. Then the lockplates are forged so that they follow the curvature of the stock.

Trigger and nut[]

Trigger and nut are the typical medieval two-piece type. The trigger is forged from steel and the nut is made from moose horn with a steel reinforcement where it contacts the trigger. A 6mm steel axle goes through a hole in the middle of the nut, and through the lockplates.


Stock is made from a piece of birch and is of the following dimensions:

  • Length: 900mm
  • Width: 50mm
  • Thickness: 40mm

It's made in the typical medieval fashion.

The top and bottom of the stock at the front end are covered with ~4mm thick ivory plates made from moose horn. The plates should extend beyond the end of the stock (to prevent the bow from moving up- or downwards. A shallow groove is ground to the upper ivory plate; this acts as a groove for the bolt. The upper plate does not have to extend all the way back to the nut.

The cocking device[]

A forged iron hoop (for the user's foot) is attached to the bow using the aforementioned leather bindings. A simple strap with pulleys is used for cocking.


A number of nice but unnecessary accessories described in the article.


A brief description of bolt making is also included. The process is not the original Finnish one, so it's only described briefly:

  • Shafts are from birch, are 16-18mm thick and 450-55mm long. They are turned on a lathe. Although not explicitly mentioned, they are apparently of even thickness their whole length. The ends of the bolts are ground flat, to 3-4mm thickness, so that they fit snugly between the fingers of the but.
  • Boltheads are made from 15mm steel rod. A 25mm deep socket hole is drilled to one end with 13mm drill. The socket is forged into conical shape while hot, apparently with piece of steel with the proper conical shape. The tip of the bolthead is also forged.
  • Vanes are made from turkey or goose feathers and they're 170mm long. They are attached with glue and with thin linen thread bindings.

Draw length[]

The draw length is not given in the article, but measuring from the images it's around 200mm. This gives the bow fairly conservative power stroke of ~140-150mm.