Thursday, November 7, 2019

Bow Drill - Horse Chestnut

It's always irritating to have a failure, but then there's typically more to learn from getting things wrong.

Today I went out and sourced some Horse Chestnut from a group of trees I had seen before and thought would have plenty of dead, dry and standing to collect.  As it happened there was not a huge amount - just about everything was green, but there was enough to collect for a set.

Poor image of some fat sticky buds
In my selected wood I could see that pith might be an issue so I collected a larger piece with the idea of carving my spindle with the pith off centre.  Good idea I reckon but ultimately poorly executed as the pith needed to be even more off centre or indeed carved out entirely (which would have meant getting a larger piece of wood).

Pith off centre but not enough


The bottom end view


The top end view
I started to burn in the set, and immediately I could tell that my base board was probably too hard.  I got a nice little shiny circle.  I roughed it up, hoping to salvage the set and tried again with a bit more pressure.  The top of the spindle collapsed and it shot out of the bow.

I reshaped the top and tried a few more times with basically the same results, and also managed to cut my finger on one of the times the top of the spindle collapsed.

Pith causing the top of the spindle to collapse
In the final image below, you can see the problem with the hard hearth - my spindle end is very flat, and to make matters worse the bowl is very close to the right hand edge in this photo.  If my spindle was not collapsing then I may have been able to get it working, but it would have been touch and go.


Lessons:

  1. If there is a pith problem carve it well away from centre, or out completely
  2. Check the hardness of the hearth
  3. Be very careful not to have the bowl too close to an edge - a wider area of hearth may help with this