In ref to pen making: I'm probably giving you more info than you want, Marc. Hope I don't put you off. Penmaking is wonderful...demanding and fun.
Yes, there are different sizes of drills and bushings. The drill size is for the outside diameter of the brass tube (that goes inside your wood and pen). The bushing is generally, usually close to the outside diameter of your fittings (pen parts).
Find a company that has the styles and prices that you want to start with. Choose the pen style, buy the recommended bushings, drill bit, mandrel and pen kit for that style pen. Often the drill bit and the mandrel can be used for several styles of pen parts; but you will definitely need different bushings for each style. You will also need a pen press which gives you a way to hole the tiny parts in alignment and gently/firmly press the metal bits into the pen barrels.
It's best to buy and use all one company's items together and not mix diferent company parts because there are small differences (maybe .5 mm etc.) that can make differences in how the set up works.
It's also best to avoid relying totally on your bushings when matching your wood and metal edges. Sometimes bushings are not accurate. If you have calipers (I use digital ones from Harbor Freight), you can measure the metal part and your wood so the wood is about 3/1000" larger than the metal when finished. But that's for when you get more experience and if you get fussy.
The main pen supply importers are: PSI
http://www.penstateind.com and Burea
http://www.bureahardwoods.com and Craft Supplies
http://www.woodturnerscatalog.com (PSI and Burea are resold through smaller companies and sometimes you can get a slightly better price...although sometimes, smaller companies create their own styles also.) CraftSupplies only sells through their own store/website.
Shop tools you may already have or will need:
--an accurrate Bandsaw or TableSaw with fence or sliding jig to cut the pen blanks to length. If you do not have a bandsaw or table saw with jig, try to find pen blanks already cut for the style you want to do.
--Drill Press and drilling jig (can be set up with wood and clamps or bought) OR a Jacob's chuck that fits the tailstock of your lathe...you'd need a regular chuck for the headstock to hold the pen blank. (This method is considered very accurate). Again you can find pen blanks that have been predrilled for certain diameters and avoid drilling at first go.
---sand paper (I use up to 2000 grit in white), later you may find you want to work with MicroMesh or Abralon, but paper is cheaper to start with and handy.
---a finish material... I use Deft Gloss Lacquer hand applied, some use a friction polish, others use CA glue (I'm highly sensitive to the CA and can't have it in the shop.)
--Glue to keep the brass inside the wood and do repairs if needed. I use 2-part epoxy, others use Gorilla or CA --you may want something to keep the glue out of the end of the brass tube...I use dental wax, others use potato slices or Play Dough and some are so experienced at this very little goes beyond the edge of the brass. You cannot have glue in the tube and have your pen work well, there just isn't enough room in there for the glue and the parts too. I tried... oh, how I tried.
