Bow Drill – How many things could be ‘just not quite right?’ (The Drill)

Profile of the drill / spindle

The story so far, we have identified 10 things that might not be quite right about the ground before we even started looking at our bow drill set, 4 things to consider about the ember pan and the 18 things to perfect on the hearth board. If you have found this blog and not read the previous two that dealt with the ground & ember pan, and then the hearth board I suggest have a quick read of those.

This time lets focus on the drill. The set I am describing is the hazel drill in to a lime hearth board. The first few things to consider are to do with the quality of the wood itself, so are the same as for the hearth board, and some are to do with how the drill and hearth board connect, so a little poetic licence to repeat them here.

  1. Dry – a well-seasoned drill
  2. Not Punky – if sourced as dead standing, the wood should not be decaying or breaking up.
  3. Thumb nail hard – if your thumb nail can just leave an impression in the wood, then this is medium density.
  4. Not to thin – doesn’t create enough friction and in turn heat and fine powder (i.e. fuel)
  5. Not too thick – too much friction and the drill may be hard to rotate, actually needs more downward pressure. A thicker drill is better for a group bow drill set.
  6. Just right thickness – between forefinger and thumb thick, 20 to 30mm (ish)
  7. Straightness of the drill – the Woodland Ways instructors will cut green hazel, straighten them while they are still green by bending in the opposite direction of any kinks. These will then be bundled together, tied and left under cover outside to dry slowly. But, every 10 to 14 days of that drying process, they will be untied, checked, tweaked with a little bend here or there as required, and retied. When happy, they will be left to fully season for at least a year.
  8. Roundness of the drill – is the whole length of the drill a round circle in profile (as you look down from the ends). If that profile is oval, it will cause the drill to rattle in the hearth board notch. That rattling is the drill jumping slightly and causes the notch in the hearth board to become oval, and in turn the drill is likely to pop out of the notch. Carving can take out any ovalness.
  9. Length – with your foot on the hearth board, the drill should come to mid shin. Or, the span between spread out fingers from thumb to little finger times one and a half. Or, if you’re me, 300mm! Woodland Ways instructors will cut the drills slightly long, because they are used often and wear down.
  10. Length – too long and any wobble caused by the bowing will be exaggerated
  11. Length – too short and your foot will be in the way and you may drag the knuckles of your bowing hand on the ground and the tip of the bow on the ground (which could flick dirt on the ember).
  12. Top of drill – sharpened to a long (twice the width of the drill), tapered point (see diagram) to reduce friction with the bearing block. When burning in, you do want the very top point to be polished, as this will reduce friction.
  13. Top of drill – during the bowing process, friction will cause the tip to become rounded, more surface area will then come in contact with the bearing block, eventually making it more difficult to bow, sharpen to a point regularly, but try to leave the rounded polished tip.
  14. Base of drill – initially carved to help burning in with a shallow (width of drill), blunt point (see diagram) to maximise friction with the hearth board
  15. Base of drill – make sure the tip of the shallow point is central, if it is offset, the drill will rattle in the hearth board, makes the bowing uneven and may lead to the drill popping out.
  16. Burning in – gently, using less downward pressure and slower strokes than when going for the ember. Aim is to seat the drill by rounding off the three angled cut edges (see diagram), warm the drill and hearth board, drive off any moisture, not to create lots of dust and not polish the bottom of the drill.
  17. Base of Drill – after burning in or between embers, the base may become polished if not enough downward pressure is applied. Reduces friction and therefore the amount of fuel and heat produced. Roughen surface with tip of knife
  18. Foot to secure the hearth board – not touching the drill or else the drill will rub against the boot, reduces efficiency and more energy needed to bow.
  19. Foot to secure the hearth board – not too far from the drill or the drill won’t be at a 90 degree angle to the hearth board (assuming your wrist is locked into your shin to prevent wobbling). The drill will pop out.
Profile of the drill / spindle
Profile of the drill / spindle.

The diagram above shows the process of (a) creating a domed base of the drill, the three cuts becoming progressively steeper towards the base makes it more rounded, and (b) pointing the top of the drill. For both ends, the cuts are repeated all the way around the drill as if sharpening a pencil. When looking end on to the drill, the profile wants to remain round, i.e. lots of cuts. (You can point a stick with three cuts, but the profile viewed end-on would be a triangle).

I was on the ten-day survival course in August this year as a customer with my partner Katie, in one of the sessions the instructor took us through fire lighting techniques, including bow drill. Nothing unusual about that, and as expected they got an ember quickly. But it went out. A second time, the ember died. And after a third attempt, another ember just wouldn’t stay smoking and coalesce. (And this was using a matched set he knew worked). He was excited about this because it had never happened to him before. While we went off to source the materials for our bow drill set, he was on a mission to find out why. By first swapping the hearth board, the same thing happened. Using the original hearth board and a new drill, he got a good ember that stayed alight. Conclusion, something was wrong with the drill that had previously been OK. By gently carving the burnt end of the drill base, an orange stain to the wood appeared. By removing the bark from the side of the drill, several holes were discovered. Conclusion, it may have been a wood worm, and the excretion (orange stain), was somehow extinguishing the ember.

Interestingly mouse urine has a similar fire-retardant property. Found out when a mouse had eaten through his fire kit bag (doing what mice do!) and the hearth boards and drills that had soaked up and smelt of urine didn’t produce embers.

So, number 20 – make sure your drill has no woodworm!

And number 21 – make sure your drill hasn’t been urinated on by a mouse!

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