Puukko Bolster Fitting Tutorial
On a basic level, making a Puukko style knife has a few more steps than a full tang knife equivalent. The most dreaded steps are usually getting the bolster to fit the blade and leatherwork for the sheath. Other Nordic style blades with both shoulders square are easier. However, on Lauri and similar blades where the grind goes all the way onto the tang, the task may seem daunting. Fear not, puukkos have been made like this for hundreds of years and it is deceivingly easy given the right technique.
This tutorial is not meant to get a perfect result. I actively chose -not- to file the shoulders of the blade. This is simulating a situation without diamond files, file guides or similar speciality tools. This guide is meant to show how easy it is to get acceptable results with very basic tools. Maybe this guide will inspire someone to try their first Nordic style knife.
For this tutorial I used an angle grinder, Dremel tool, hammer and an 15x30mm furniture pipe along with some abrasives for finishing. It took me approximately 20 minutes effective work-time.
For this project we will be using the Lauri Whittler 80 blade and a fabricated 19x30V brass bolster. Checking a blades suitability is done by comparing the size of the hole in the bolster vs the size of the tang. Make sure that the hole is not much longer than the tang is wide, and that it is no wider the blade. If the hole is wider than the blade it is impossible to get good results. Blade specific bolsters are linked on their respective product pages.
The tang is wider than the hole, so it needs to be ground down a little. I used an angle grinder with a flap disc for this. It can be done with whatever abrasive disc as long as you mind the heat. Most carbonsteels temper at 150-250 degrees C, keep this in mind and cool if need be. Gently grind the tang until the bolster slides on almost fully. This is approximately 1cm from fully seated.
Using a Dremel tool, widen the hole on the backside of the bolster. Do not go all the way through, but leave the material approximately 0,5mm thick at the front of the bolster. The ditch does not need to be wider then the tang is. It is partly to reduce friction between the bolster and blade, and partly to allow the brass to move when seating the blade into it. Wear eye protection, the flying brass particles tend to be hot and sticky.
Protect the blade and clamp it into a vice. Slide on the bolster and the tube, and then simply tap the tube with a hammer until the bolster is seated. It does not require a great deal of force. Check that the bolster is seated on the blade straight and true, adjust with more taps if necessary.
If there are no major gaps seen from the front it is a success. Give the bolster a few taps with the hammer to release it. You will notice that the indent on the top of bolster is anything but even. This is because Lauri blades are stamped from sheet metal, and that process tends to rip and bend the edges a bit. It is according to plan as I did not file the blade shoulders at all. Hardened steel will sink nicely into brass given the right circumstances.
Time to clean up the bolster. Using P120 sandpaper and a flat surface, rub the back of the bolster until you can see even grind lines on the whole surface. Try to get it as straight as possible as there may appear a gap between the bolster and handle material otherwise. It is ok to start with rougher grit if there are deep marks on the back. However, finish it up with finer grit so the sanding scratches don’t show from the sides of the bolster.
We do not want to remove a lot of material from the front after seating the bolster in place. I went straight to a P800 Abranet strip followed by a few seconds on a P1000 and P2000 soft sanding pads. The fronts of the bolsters are slightly rounded due to the same stamping process the blades goes through. Because of this I recommend using a soft backing under the abrasive if you want a quick result, and that is what we are going for here. If you want an absolute straight front, I recommend sanding it before grinding the ditch and tapping the bolster in place. The more material you remove after first seating in place, the more you will have to hammer it back to compensate.
After finishing the front to your design, tap it back in place using the same method. This is the final fitting so keep the bolster straight relative to the blade.
The end-result is not perfect by any means, but given the time and tools allocated I was positively surprised. The fit around the edge is good by almost any standard and the back has a small gap of a few tenths of a millimeter. By filing the top shoulder of the blade, or tapping a bit more, you can seat the blade fully into the brass.
There are a thousand ways to seat a bolster. This is one way that is quick and gets decent results. If you add another 20 minutes work time to the blade the fit will be so much better. Give it a try, you will be amazed how easy it actually is.
Kaj-Mikael / Bladepoint