precision boring jig and some flute/whistle making info

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CarvedTones

Board of Directors, Vice President
Andy
Make sure and read this post as it calls into question the whole idea of using the bushing. The bushing did and will work, but I am liking the other way...

EDIT - barring an unforeseen problem with the jig, I think I completed it. I added a couple of posts for fixes for the compressed air and vacuum and added notes about it to this post.

Yes, another one of my boring posts...

I have had some success with flute/whistle making but my percentage is not nearly as high as I hoped it would be by now, so I finally broke down and bought a gun drill bit. A gun drill bit is a very precise machining bit for drilling long, very straight holes. They don't fit in standard chucks and they are partially hollowed inside so they can deliver coolant or air to clear sawdust through the tip while drilling. Lots of upsides.

The downside is cost, especially for hobbyists. These bits can cost over $100 each in the larger sizes, and then you need to hold it, feed it, put air to it, collect the chips/dust, etc. Russ Wolf, who makes a lot of large Native American inspired flutes, shows his methods in this video. When I visited David O'Neal of Rising Moon Flutes (a local here in Raleigh) he showed me a very similar setup. These guys are not hobbyists. They can justify sinking some $$$ into their setups because they are producing lots of flutes and selling them.

EDIT - If you can afford the gear, the way Russ demonstrates in the video is the way to go. His setup is better than mine, hands down. Even if you can't justify the cost you should watch it to see how a pro does it.

The reason I bought a gun drill is that I know a lot of the problems I have had stem from inaccurate and/or rough boring. My holes were nearly always at least slightly off center or had rough walls that sometimes had "strings" disturbing the airway. So I bid and lost, unwilling to chase and pay full price, several times. Finally a bit the right size for high D whistles and C fifes (which will be the bulk of your business if you do UK/US Colonial style instruments) showed up with a BIN a little over $20 delivered. I jumped on it. So after it gets here, what can I do with it if I am unwilling to spend much more? Well...

When I watched the Russ Wolf video, the thing that really stuck out was the bushing. It aims the bit exactly where i needs to go. Everything else he does just makes that easier, but the bushing is the key. Start the bit on center and keep aiming it on center and you have to drill a straight hole, right? That was my theory. So I cut a big chunk of hard maple and put a strip of plywood on the bottom to fit in the bed of my lathe. I Then held it down and poked it with my live center and then started a 1/2" brad point bit in the small dent that made so that I could chuck the bit (in my small parts chuck - it will not fit in a standard Jacobs):
gundrill1.jpg

Then I held the block down and pushed it in to drill a hole. I won't downplay that - it was nerve wracking and strenuous. I had to push down hard enough to be sure I wasn't getting the hole wallowed out, but also had to keep the block moving and drilling hard maple, even sideways, is not easy. But I got through it:
gundrill2.jpg

Next I took the bit out, ran it back through the other way and made sure it went right to the center of my chuck:
gundrill3.jpg

Rock on! So I chucked a blank I had rounded before:
gundrill4.jpg

I haven't talked about blowing the chips out yet. I bought some air nipples so I can turn/drill an adapter. But it turns out there is an easy way for now:
gundrill5.jpg

I will still make the adapter. EDIT - adapter made. Doing it like that requires an extra hand that I don't have and I ended up doing a lot of pushing the bit with my left hand and going slow. Anyway, now I am making progress.
gundrill6.jpg

But dust and chips are coming out, so I rig this up( EDIT - major improvement made) :
gundrill7.jpg

And I keep drilling.

So, does it work? Well...

In:
gundrill8.jpg


Out:
gundrill9.jpg


That is amazing! The bore is not only straight, it is as clean as a whistle; which is quite convenient, since that is what it may well become... :gar-Bi
 
Last edited:

Gotcha6

Dennis
Staff member
Corporate Member
Re: precision boring

Neat setup. Will you now finish the O D with the piece between centers or on a mandrel?
 

CarvedTones

Board of Directors, Vice President
Andy
Re: precision boring

Neat setup. Will you now finish the O D with the piece between centers or on a mandrel?

Actually a combination of chuck and shop made mandrel. I need to make a new mandrel for this bit as it is metric and very slightly over a half inch. My mandrel is just a short scrap of hard maple with a few inches matching the I.D. and about 3/4" matching the intended O.D. with the live center dimple on the end.

If you are interested in making whistles and flutes, this page calculates the hole placements given the diameter and desired key (there are a bunch of other settings you can tweak there but you will generally accept the defaults). The "embouchure" is the blown edge and you need a little more length (about 2" or less depending on the specific instrument). At .55" I.D., it gives me a number slightly under 12" for a high c fife, so that almost 14" blank has to be handled with care if it is to become a fife. More likely it will become a high d whistle as those are far more popular (most common key for Irish whistles) and need about 1.5" less length. For the whistles I do a second slightly larger bore by hand (literally - bit in one hand, blank in the other) so that a channel in the plug can aim the air right at the edge. If you want to look into Native American style flutes (NAF is a common abbreviation if you go googling), go here. You will find some calculators under the Crafting menu. Those are generally much larger.
 

CarvedTones

Board of Directors, Vice President
Andy
Re: precision boring

I got a PM with a little confusion about how I made the hole through the block. BTW, the block is 2" x 4", drilled in the 4" direction and about 1.5" or so taller than center height. Anyway, I wanted to add my reply to the PM to the thread in case I lost anyone else with the short description of making the initial hole...

I used the bit itself. In one of the first pictures, I have the bit mounted in my small parts chuck in the headstock. It would not hold it well enough to stay level unaided, so I used a 1/2" brad point bit just to make a dimple in my block so I could put the end of the bit in it to keep it level when I fired it up. Then I had to hold the block tightly against the bed and slowly slide it forward. That was not an easy thing to do.

Unless you use the actual bit turning in the center of your headstock to make the bushing, you will be very dependent on extreme accuracy, as in machinist type accuracy. I can't come close to that. My strip on the bottom actually even has a little play in it, but as long as I slide the bit through and make sure it is centered in my chuck on the headstock when I clamp the block in place that doesn't matter. When I push it through again, with a spinning blank in the way, it will go right back to the same spot, dead in the middle of the headstock chuck.
 

Mike Davis

Mike
Corporate Member
Re: precision boring (flute/whistle making)

First rule of machining, "No drill is precision".

For precise holes you must use a reamer. Drill bits always drift, even if you can't see it or measure it the hole is not straight nor round. By using a reamer you make the hole precisely to size and as straight as possible. The reamer will also smooth out any chatter marks and cutting lines inside the bore.

For your work something as simple as a turned dowel with fine sandpaper glued to the shaft may do the job. or better yet a series of sandpaper reamers very slightly increasing in size and at the same time reducing in grit fineness. The first and roughest of which may be slightly tapered.
 

CarvedTones

Board of Directors, Vice President
Andy
Re: precision boring (flute/whistle making)

First rule of machining, "No drill is precision".

For precise holes you must use a reamer. Drill bits always drift, even if you can't see it or measure it the hole is not straight nor round. By using a reamer you make the hole precisely to size and as straight as possible. The reamer will also smooth out any chatter marks and cutting lines inside the bore.

For your work something as simple as a turned dowel with fine sandpaper glued to the shaft may do the job. or better yet a series of sandpaper reamers very slightly increasing in size and at the same time reducing in grit fineness. The first and roughest of which may be slightly tapered.

These gun drills seem to come pretty darn close. Some of the pros are making burl flutes by boring a slightly oversized hole, gluing in a dowel and then drilling out the sound chamber in it.

I looked into making recorders and those have tapered bores. Professionally made reamers for them make gun drills look like a bargain by comparison.

Without going off on too much of a tangent (there are huge threads on this in various wind instrument forums), the advantage of a perfect bore with a prefect O.D. seems to be that you can crank out instruments on a production line faster because you can use the formula exactly and drill the holes where they are calculated at the size specified and cut the instrument to length and it will be perfectly tuned.

In a less perfect world like mine, I start with the hole slightly smaller and ever so slightly further from the blown edge than specified. Then starting with the one nearest the blown edge, I enlarge them to tune it. I use a freeware tuning program called mTuner, not just because I am cheap, but also because the way it works is to take several samples and graph them out so you can see how much of the time you were on the right note and how much you varied. Wind instruments are hard to tune because you can make them change pitch by breath control as well as opening/closing the holes.

Anyway, using my gift for over simplification, what determines the note is the volume of the air chamber between the blown edge and the first opening (end of the flute if all holes are closed). Other things come into play as far as quality of sound. For instance, with whistles the "gold standard" is a bore to length (length being distance from blown edge to the end) ratio in the low 20s. Anything outside 18-25 is likely to have issues. My choice of a 0.55" bore was literally a calculated decision. The reason the calculator I linked to has wall thickness is because even the air in the covered holes counts. If you have a really thick wall, by the time you get to the 6th hole there is a fair amount of air volume between the pads of your fingers and the bore.

For those of you still awake, my point is that there are two choices - machinist/factory precision or hand tuning. I am hand tuning. Whether or not there is sonic superiority in perfect bores has been argued for centuries because it is completely subjective. There are experts convinced that it matters and others convinced that it does not. There are some strong feelings about those opinions. I have seen nasty flame wars erupt over someone innocently asking whether or not they should oil the bore and if so with what.
 

CarvedTones

Board of Directors, Vice President
Andy
Re: precision boring (flute/whistle making)

Join us on today's episode of Redneck Engineering as Cleetus shows us how to make a new matic fittin' from a seasoned hikree branch... :gar-La;
gundrill10.jpg


1" hole about halfway in, 5/8" hole from the other side. The air nipple can then be forced a few turns with a grunt and a crescent wrench. I dropped a garden hose washer into the bottom of my 1" hole which my dull cheap Fostner had burnished to a very smooth finish. The adapter doubles as a handle for pushing and the washer, besides providing a decent seal, actually provides enough resistance to keep the bit from spinning with just slight help from a thumb on the base of the bit.

Adjust the PSI of the air fairly low (though larger diameters will need more). Just use trial and error.
 

CarvedTones

Board of Directors, Vice President
Andy
Re: precision boring (flute/whistle making)

A bonus episode! This last fix was just too easy. I mentioned earlier that my vacuum "solution" was working but not getting all the chips. Part of that was simple logistics. I need to feed the bit in with the channels oriented so one channel (I know they are called flutes, but that gets too confusing in the context of making woodwinds, so I am calling them channels) is up and one is down; neither is on the back side relative to the vacuum nozzle. But chips still will shoot down the channels and right through the bushing block. So I cut the bristle end off a couple of HF acid brushes and screwed them on the block like so:

gundrill11.jpg


Sorry about the blurry pics, but I think it is still pretty obvious how this works:

gundrill12.jpg


Now I just have to bore and round some blanks!
 

CarvedTones

Board of Directors, Vice President
Andy
The steady center was really taking a beating from this because I would usually have it barely off center; not on purpose, of course, it is just very difficult to adjust dead center. Being off center was a problem because the bushing aimed dead center.

I found out that a lot of flute/whistle makers don't use a bushing at all; they bore a pilot using a bit in the tailstock an then feed in the gun drill and count on it self centering because of the geometry. Also, many turn a collar and use a large bearing in the steady instead of trying to keep it between three wheels.

So I got a bearing:

gundrill13.jpg


Drilled a pilot hole and started the gun drill in. Pretty tight clearance drilling a .55" hole inside of a .75" ID bearing:

gundrill14.jpg


I got a 1" ID bearing also and may try that if I have trouble with the thin walls. Lots of work went into that bushing and it does work, but I think this is working better. I will post again when I work out chip collection details...
 

CarvedTones

Board of Directors, Vice President
Andy
A couple of additional pics to share. First is a head slap - DUH! - moment...

gundrill15.jpg


My bowl chuck takes spindles in the center, holds them much more securely and the drill can come out of the blank and inside the headstock spindle without touching anything. Much more secure and sensible.

That is a soft, but completely dry, piece of sweetgum. It's 14" long. It took about a minute of actual drilling time to bore clean through.

I used my cheap little HF air compressor with no pressure built up and it kept up with pushing chips out and there was an odd bonus to doing it that way. They did not fly all over the place:

gundrill16.jpg


They pretty much tail off by about 18" or so. I have an attachment for the vac I will position to get as much of the fines as I can, but if I don't use too much air pressure, I think I can let the chips fall where they may. :)
 
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