Fire by friction and the sets are always going to be something of a personal preference. For everyone that says use a bigger / fatter drill there will be someone who tells you something different in as much as using a thinner drill.
Some will tell you to use a bowed stick for bowing, others will tell you to use a straight stick. Some people prefer short bows, others prefer long ones.
For all methods there are equal arguments.
I use a longer bow for a few reasons, firstly I prefer it, secondly it has taught me greater control, thirdly I get more rotations per drive and fourthly I teach people and it's easier to help someone else with a longer bow (it's easier to use for team bow drill as well).
The bow I tend to use is quite straight with a kink towards the base and it has been carved to produce a flat area on the inside. This means that when I push and pull the bow it's in a straighter line, I find it reduces the amount of force required so I find it less tiring to use.
For one person I also use a drill that's rarely more than 1" - 1.25" diameter. The thermal mass is smaller and it reaches temperature quicker, this also is the same for the hearth. A bigger drill does increase the level of friction, it also requires more effort to drive, the thermal mass is larger and heat dissipation over a larger area is greater and more downward pressure is needed to achieve a coal.
The downside to this is that the coal is generally smaller than it would be with a larger drill. This is where use of other natural materials come in, like the humble cramp ball as an ember extender, thistle down and the down from the seed heads of reed mace mixed in with dried grasses as the center of my tinder bundle. The down from Rosebay willow herb will work as will clematis heads.
I very rarely burn in or pre cut / carve the holes or the ember notch. This is normally the last thing that I do as it reduces the chance of moisture getting into the hole or the notch itself.
Once you have burnt in when you bow start bowing slowly, get into a rythm. Keep the drill as upright as you possibly can locking it in against leg or ankle. Keep the bow level, this should help to stop the string from moving up, down the drill and potentially into the socket at either end.
You'll start to get a little smoke and at around this stage you'll notice a change in the feel of bowing, apply slightly more pressure and drill slightly quicker, the smoke will start to spiral around the drill, once this happens apply more pressure and bow harder (remember this is still controlled). If you lose sight of the hearth there is a good chance you'll have a coal to be proud of
Don't try to move the coal, move the hearth away from the coal holding it gently in place with a blade of grass or a small stick or twig. This should leave the coal in the ember pan. Don't breath or blow on the coal, there will be moisture in your breath, fan it gently with your hand. Leave the coal to coalesce and make the tinder bundle (if you haven't already). The rest is up to you.
