Here is what I recommend for constructing your pieces. First and foremost, make your fireboard and your drill out of the same material. If your drill is too hard, it will drill through your board. Too soft and it will be less effective.
Remember the rule of thumb. Make your fireboard as thick as your thumb and wide enough for your drill and to be stable when you apply pressure downwards with your foot. Your drill should also be about as thick as your thumb and the length of your hand when you make the "hang ten" hand sign. I like to maximize friction at the bottom by making the drill blunt and minimize it at the top by pointing it slightly. You can always cheat a little by adding a couple grains of sand in the notch before you drill. By the way, you don't need a perfectly cylindrical drill. Bevels will help hold your cord.
As for the the hand socket, any hard material will work well if it is smooth. I have used pieces of split logs, bone (my favorite) and even a sea shell (no joke!). The coolest socket I've used is that on the side of my Fehrman Peacekeeper. Micarta wears like iron!
For your bow, make it as long as possible but not unwieldy. Make sure to twist your drill around the string so it lies on the outside of the bow, not inside it. I don't know how many books I've seen with this illustration done wrong. Use full-length strokes going the full length of the bow. The longer the drill spins, the hotter it will get.
These are just a couple tips for the construction of the bow drill. I have a lot more for the actual use of it, tinder bundle prep and technique. If you ever get a chance to come on one of the trips I post here on the forums, I'll gladly show you in person. For now, here are some pics of me teaching it to show you the right form.
One last thing, remember, when you get a coal and transfer it to you tinder bundle, hold that bundle high and blow up into it. That is the way to do it to keep the smoke out of your face. You see a lot of guys blowing down onto it and then cough in the process. Why cough and breathe smoke when lifting it requires no effort?
