Pilot Holes

[upiper71]

A question for pipemakers..whenever you drill into some hardwood, eg cocobolo,ABW, fruitwood, or whatever you drill, how long is your pilot hole to aerate the wood and where do you typically drill it?

Do you have to drill the entire length of the bore?

I've been quite curious, what effect this will have in the long run to the wood? Any suggestions would be most welcome and forever appreciated..

Daryl Mc.

[Doogie]

It is done with a gun drill, Or d-bit if you don't want to buy a gun drill.. Yes, the pilot hole is made with just one drill... I'll try to post some pics if I get a chance... I'm sure others have a bunch to share/add as well...

[upiper71]

It is done with a gun drill, Or d-bit if you don't want to buy a gun drill.. Yes, the pilot hole is made with just one drill... I'll try to post some pics if I get a chance... I'm sure others have a bunch to share/add as well...

Are gun drill bits relatively expensive or D bit's? I've heard people makin their own, if so what would you use a piece of cold steel and sharpen it down?

What are the dimensions of it? Could I by the plans from NPU for such a thing?

Daryl

[billh]

Get the DMQuinn CDROM, it discusses D bits as well as many other useful topics.

Gun drills are about $80 to $100 each, but you need a good compressor to use them.

Actually I am of two minds about the pilot hole, at least where chanters are concerned. Here's why...

DMQuinn recommends step boring from the large diameter down to the smallest. I started out going the other way, but as usual David' advice was sound, and I get considerably better results taking his advice (with little pilot D bits used to center each downwards step relative to the last). The trouble is, if you've already got a pilot bore down the center which is your smallest diameter, there's no way to guarantee that it will end up being concentric with your other step bores.

My solution at the moment is to step-drill first, rather than pilot boring. In actual fact I don't see a lot of advantage in putting a single small diameter pilot bore in a chanter blank, since the exposed surface will end up getting bored away later. Also, for a reasonable thickness blank (say 35 mm or so in the round), adding a 4 or 5mm pilot hole probably doesn't hasten the stabilization all that much - the surface area of the pilot bore is much smaller than that of the outside, so the majority of moisture exchange still takes place at the outer diameter of the blank; I don't think the wood 'breathes' much better with that small bore than without. The two rationales for pilot boring are either that
a) the pilot bore is 'close' to the final bore size, thus the newly-exposed wood surface aids in the stabilization of what will end up being the final inner bore, a fraction beneath;
b) the pilot bore reduces the effective thickness of the blank and thus allows moisture to travel into/out of the wall faster.
I don't think either really applies to a small pilot bore in a chanter blank, except perhaps that 'a' may apply at the throat itself.

Drones are a different matter, but then the entire pilor bore gets drilled away and thus maintaining concentricity with the pilor bore, when doing the final boring, doesn't seem important at all.

Of course for instruments with bigger central bores, such as flutes, there's a clear advantage to pilot boring and settling afterwards, since the area of the pilor bore is quite significant.

Bill

[upiper71]

Thanks Bill. I think you've pretty much summed up what I've asked about "boring the hole" procedure. As I stated in an earlier post, I intended this not for commercial use, but to satisfy my own curiosity of wood dynamics pertaining specifically to chanter's and reg's.

I've found a good supplier of honduras rosewood, although I don't know how that will fair in this up-and-down weather we get here in Canada, especially in Montreal.

As far as the CD ROM goes, I will get it. I'm sure it'll be put to good use..

Thanks again for the reply,

Daryl Mc.

[Doogie]

Wow, I never thought about step boring the pilot hole starting with the largest bit first down to the smallest bit last when I think about it it makes sense to do it that way.. Thanks Bill ... I'll give it a try and see what becomes of it.. I've always drilled my pilot hole through the blank, turned round centering on the pilot bores and then step bored the blank with the smallest dia.. and ending with the largest and then reaming...

[daveboling]

DMQuinn recommends step boring from the large diameter down to the smallest. I started out going the other way, but as usual David' advice was sound, and I get considerably better results taking his advice (with little pilot D bits used to center each downwards step relative to the last). The trouble is, if you've already got a pilot bore down the center which is your smallest diameter, there's no way to guarantee that it will end up being concentric with your other step bores.

Bill, I am using the pilot hole to center the larger cutters, i.e. I have a dowel pin in the center of the cutter to make sure that the step bores are concentric. I'll try to get a picture/drawing of the cutter assembly posted so that it makes a bit more sense.

dave boling

[mirabai]

Seth Hamon asked me to "chime in" on this so here goes:

Starting with well seasoned wood is a given. This means at least a few years old. Incidently, how you store your wood at this point can make a big difference in if and how much it warps. I then rough turn the chanter first, with the oversizing increasing toward the reed end. This, of course, hastens drying and wood unstressing while accomodating any bit wander. After a year or so I step bore from large to small using spur bits that center on the previous spur's center hole. I do this only to the 1/4" size. The depth of each step is left plenty short of the final bore dimension; perhaps an inch. I then use a D bit that I made that has steps turned into the end stepping down to 7/32" and then 3/16" which is the final throat dimension. I then follow that with the 3/16 " all the way through. I also have a one piece D type step drill that matches the bore with steps every 32nd that I can use to clean up the whole (hole) affair assuring concentricity. It binds a bit so I don't use it for the entire process. (If this drill/reamer were made better I would still use a 1/4 inch pilot and follow it with the big step drill.) I then ream it undersize, rough turn to closer tolerance and set it aside for a year or so before finishing.

Just an aside, I did without gun drills for 27 years and have been kicking myself ever since converting to the true faith a few years ago. They are absolutely worth the extra expense both in terms of efficiency and quality of the bore. They're fast, they keep the wood from burning and the bore comes out straight and like a mirror. I've been very disappointed in some of the bores of seen on some very highly regarded makers' drones that are obviously not using gun drills. Although this last point is not relevent to the bulk of the bore in the chanter, it is relevent in the very sensitive throat area. The other points are all very relevent to chanters and regs.

Tim Britton

[Doogie]

Thanks for the info Tim...

[billh]

DMQuinn recommends step boring from the large diameter down to the smallest. I started out going the other way, but as usual David' advice was sound, and I get considerably better results taking his advice (with little pilot D bits used to center each downwards step relative to the last). The trouble is, if you've already got a pilot bore down the center which is your smallest diameter, there's no way to guarantee that it will end up being concentric with your other step bores.

Bill, I am using the pilot hole to center the larger cutters, i.e. I have a dowel pin in the center of the cutter to make sure that the step bores are concentric. I'll try to get a picture/drawing of the cutter assembly posted so that it makes a bit more sense.

dave boling

There's usually more than one way to skin a cat. The dowel pin makes sense for the larger cutters. What about the smaller ones - those are the ones where it counts most, they need to be truly concentric with the pilot.

With gun drills especially, there is a strong tendancy for a larger bore to follow "tangentially" to a previously drilled pilot, that is, so that the larger bore touches the smaller one at one point.

Seems to me that small-to-large should work for D bits, but only if each bit has the necessary pilot pin. I am not sure small-to-large will work well for gun drills, since I think it would be all too easy for the gun drill, even if initially perfectly centered on the pilot via a D bit, to drift to its 'preferred' tangential position with respect to the previously bored small hole. That was my experience anyway. It means that your step drilling has to stop much farther from the "ideal" final location, to allow for this possible (likely?) mis-centering.

Bill

[ausdag]

Why not just one pilot hole and straight onto the reamer(s)?

DavidG

[billh]

Why not just one pilot hole and straight onto the reamer(s)?

DavidG

Well, two things - it's faster, and it saves wear on the reamers.

If you're using hardened steel multi-flute reamers, instead of homemade reamers, these may be minor considerations, but chances are pretty good that such reamers (which are almost certainly ''sent out" to a big machine shop or toolmaking firm) are going to be straight tapers. See previous threads for discussions about straight vs wiggly tapers. If you do manage to find a machine shop that will make a complex taper on a reamer, how sure are you that they will meet your spec?

Even if you have achieved that perfect bore design and are ready to spend the bucks for a 'professional' multiflute reamer, those things can be hard to sharpen. Even the hardest tool steel will dull fairly quickly when used on ebony, so there's still something to be said for roughing out the bore with something else (like step drilling).

I suppose an alternative is to get an undersized "straight" reamer and rough out the bore with that, then finish up with the specialty reamers.

Bill

[PaisleyBuddy]

I have a dowel pin in the center of the cutter to make sure that the step bores are concentric. I'll try to get a picture/drawing of the cutter assembly posted so that it makes a bit more sense.

dave boling

What's a dowel pin? Isn't dowel made of wood?

[billh]

I have a dowel pin in the center of the cutter to make sure that the step bores are concentric. I'll try to get a picture/drawing of the cutter assembly posted so that it makes a bit more sense.

dave boling

What's a dowel pin? Isn't dowel made of wood?

Err, "wooden dowels" are made of wood, yes

In this case dowel pin just means "cylindrical pin-like thingy".

[daveboling]

I have a dowel pin in the center of the cutter to make sure that the step bores are concentric. I'll try to get a picture/drawing of the cutter assembly posted so that it makes a bit more sense.

dave boling

What's a dowel pin? Isn't dowel made of wood?

Dowel pins are a hardened steel pins that have been ground to a precise size (usually within 0.0001" (0.00254mm) of a particular size) with a toolpost grinder (a grinder that fits where the tool on a lathe usually resides). They are chamfered on each end. They can be press-fitted to the center of a tool for use as a pilot to assure that the cutting tool is (almost) perfectly centered with respect to the pilot bore.

If you make a piloted D-bit, and bring the cutting edge all the way to where the pilot pin is, you can get down to within about 1.5mm (0.060") of the pilot bore size. At that point I leave the reamer to clean up the last bit of bore sizing. However, with the pilot pin taking up part of the volume where the wood cuttings lay, you have to be more careful that the shavings don't "pack in" the flute of the D-bit.

dave boling