What type of drill bits are required to enlarge a bore hole in wood? I have the standard lamp auger kit and at 5/16 it is either too small for whistles or too much work for the reamers that are used in conical instruments. I assume the work will have to be repositioned in a chuck but am unsure whether the enlarged bore will end up concentric with the outer turning. What are the best methods to achieve this?
Oh. I thought this was a thread about Bloomfield.
You could check with Paul Busman - he makes most wonderful wooden whistles. I made a bit for myself from a piece of 5/16 rod with a cutter brazed onto it about 2 inches from the end. The 2 inch bit tracks the thru-hole, keeping my cutter/reamer aligned with the original bore. All it takes is a piece of tool steel, or tungsten carbide (requres diamond to shape and sharpen). You can even braze on a crude augur to eject chips, if desired.
It’s easier to hold the spindle in a chuck, than to use the boring centers. but you have to have a sufficient lathe spindle bore to allow it to pass, or you’ll have stability problems. Right now, I’m considering making a boring machine with various sized hollow collets to handle different ODs of wood spindle. first turn the spindle, then drill the thing through on the lathe with the 5/16 bit, and remove it. Mount in an appropriately-sized collet, and spin it up in the boring machine. All it takes then is a mechanism to push the boring rod through. If you want to get fancy, you can use hollow tube with the cutters on the outside, and vents drilled just ahead of the cutter, then blow compressed air into the tube to clear chips. Easy to make if you have a lathe and a milling machine, and costs lots less than a gun drill that a lot of the wooden whistle makers use.
Have fun! 
serpent
There was a recent thread here: http://groups.yahoo.com/group/flutemakers/ on the topic. I believe it was also recently discussed on this forum, though I can’t remember how long ago.
As Serpent mentioned there are several ways to do it, and if I remember correctly, some of these threads went into detail on them. I think there’s even a post from Paul in there somewhere.
Best,
Erik
Many thanks for the replies.
Serpent - the reason given for turning on a pre-bored centre is that the outer turning stays concentric to the bore. Your idea of the drilling machine sounds more of a commercial type set up, I can understand the need for chip clearance when speed is more of a consideration. My humble ambition of making a very small number of instruments dictates simple but effective answers. I have heard of people using re-shaped spade bits to enlarge holes but I’ve no idea of the profile.
Browsing through Gary Cook’s recorder making page it appears as though he is using a ‘beam drill’ for the long hole boring - this would be an easier solution but from what I’ve read these type of bits suffer from too much wander.
Erik, I’ll try searching the flute forum.
FWIW-- I do my bores with a custom made gundrill. I first drill a 7/16 starter hole approx 1/2" deep. Then I use a boring bar to bore this out to exactly .500", which is my final bore size. This starter hole is used to keep the gundrill on center as it enters the wood. I can’t comment on lamp augurs, as I’ve never used them.
So, the first rough turning step is just the outside? One doesn’t both turn the piece to a slightly large OD and bore a too-small ID before letting the wood rest the first time?
Tanx, Charlie
I do a rough turn OD, but on size ID before the resting phase. About a month later, I redo the inside which will have shrunk a couple of thousandths by then. I keep doing this until it doesn’t shrink any more before proceeding to turn the OD to it’s final dimensions.
You don’t need to make a drilling machine to use the drilling rod I mentioned. In fact, you can even mount it in a hand drill if you wish. The drill cutter will in fact follow the original pilot hole perfectly, no matter how you turn either it, or the material.
Chip clearance is important. Excessive chips can cause your cutter to bind in the hole being enlarged. I offered both mechanical and pneumatic ideas. The pneumatic is easier to accomplish if the boring rod remains static and the material itself rotates, but it can be done either way, given your engineering expertise is up to the task.
Paul’s point about stabilizing the wood, and subsequent shrinkage, is well taken. You could easily make a slightly-undersized follower pin that fit over the original follower section, and tracked the hole once drilled, after it has shrunken a few thousandths.
Using the follower pin ahead of the cutter obviates the need to keep the stock on a lathe. I suggested the boring machine as something fairly simple that one might wish to build, if it were desired to make multiples. I was trying to keep all my suggestions within the purview of things you can make for yourself given a reasonable amount of mechanical skill. I’m not a master machinist, and I don’t play one on TV, but I do manage to fabricate a goodly number of my own tools. Sometimes they’re utter failures, but most of them work, if I give them sufficient thought beforehand, and enough care during fabrication.
I think being able to do what you want WRT making whistles, is almost as much a matter of attitude as it is skill. And in the end result, while it takes talent to squeeze really good music from a whistle, it requires only learnable skills to make one. No magic. 
Cheers,
serpent
(quote)And in the end result, while it takes talent to squeeze really good music from a whistle, it requires only learnable skills to make one. No magic. (quote)
Yeah-- when I expressed doubt that I could ever learn whistlemaking, Glenn Schultz told me " simple as pi. Even a Podiatrist could do it…" 
wow! you guy are great. keep up the magic. i can imagine you get great satisfaction from working with wood.
in 8th grade (30 years ago) i was challenged to make oak salad bowls for my mother. it was a set of six (the size of our family). each one got smaller on the lathe. i adjusted the sizes for consistency.
i think my mother (anno 1925) still owns a set of 6 bowls about 5" in diameter. occasionally she’ll put a few olives in them.
it pulled down my grade point average.
- tom