Best set-up for boring deep wide holes?

[M_Chavez]

Hello all,

I would be grateful for some advice on how to accurately bore deep wide holes.
I am looking for the best set-up for making hollow dowels, 14" long and, say 1" OD and and internal diameters varying from 13 to 19mm right down the centre of the dowel (i.e. 1 dowel with 13 mm ID, one with 16mm ID, one with 19mm OD, etc, so the ID needs to be consistent for each piece but vary between pieces).

I have got a pillar drill with 650mm chuck-to base and I now have a Record DML24x lathe (24" between chucks) at my disposal.

What would be the best and the most accurate way of boring square blanks to arrive at the hollow dowel?
I can think of 3 ways of doing it:
1) Make up a jig to hold the blank in the pillar drill, hollow out with a long wide drill bit (auger? flat?). Fix between cone centres on the lathe and turn.
2) Turn the dowel on the lathe, fix on the lathe with a scroll chuck, support with a home-made roller steady, first put a short, then a long wide drill bit into the tailstock and bore.
3) Bore a small pilot hole on the lathe using a hole boring tailstock kit and then enlarge the hole on the lathe or the press with a flat bit to the required size.

Any suggestions on what method to chose (or any alternatives) would be of help.

Thank you.

 

[MikeG.]

This sort of thing crops up intermittently. My approach, without knowing exactly what you are doing, would be to slice the piece of timber in half lengthways, run a groove through the long axis of each inner face, then glue it back together again. Then, once the glue is dry, drill in from each end along the hole created by the pair of face-to-face grooves. Only once I had established the hole would I suggest turning the outside.

 

[M_Chavez]

Thank you.

The intention is to try my hand at making woodwind instruments - at this moment I am not sure whether the glue joint will affect the sound, but it might have a negative impact on the looks...

 

[MikeG.]

I was wondering whether you might be making pipes for an organ.

I guess the other approach would be to use an auger of suitable length, but start with over-sized stock. You just bore through the length of the stock in the general direction of the other end, then use the "in" and the "out" hole as the centres on your lathe. A hundred years ago, lots of water pipes were made by boring out tree trunks by hand. Village pumps often featured such pipes vertically........so clearly it can be done.

 

[marcros]

I would start with a square block. Turn the ends round between centres but not to final dimensions. Like MikeG said, I would start with the hole, but I personally would hold it in a lathe chuck and drill on the lathe. decent drill bits, slow speed, slow feed and keep withdrawing to clear. With care, you should be able to drill from both ends and meet in the middle. even going to 7-8" in length you are going to need long drill bits.

Then turn the outside between centres. The 19mm may want a bit of thought with regards to work holding.

 

[Phil Pascoe]

I doubt your lathe has the power to handle holes that size, and if you bore from both ends the holes won't align perfectly in the centre, which I wouldn't think would be good sound wise. If you try a flat bit on a lathe in an existing hole you'll probably be lucky not to wreck something.

 

[M_Chavez]

Thanks - I never thought about the lathe power, but yes, it is only a 250w.

Looks like the pillar drill is the easiest (and cheapest) way to go, but what would be the best drill bit type for this work?

 

[Eric The Viking]

Don't forget that a tailstock drill should self-centre, whereas a pillar drill won't.

I'd think that would make quite a difference. Also I have successfully welded rod onto ordinary twist drills in the past to extend their length (but only for dolls' house construction - a bit easier and smaller, I think!). Personally I'd try the lathe first, and go quite slowly.

E.

 

[Phil Pascoe]

Don't forget that a tailstock drill should self-centre ...

You've obviously never had holes miss each other in the middle by over an inch.

 

[Jacob]

Google "how are flutes made" etc etc
Loads of interesting info out there, "gun drills"apparently (new to me, I'd often wondered - now I know!):
http://www.mcgee-flutes.com/making.html
And there's plenty of low tech method descriptions - hollowing out two halves, or starting with hollow bamboo being the main options.
You can make woodwind instruments square section as an elongated box, which is how larger organ pipes are made, but smaller sizes also possible.

 

[custard]

Thank you.

The intention is to try my hand at making woodwind instruments - at this moment I am not sure whether the glue joint will affect the sound, but it might have a negative impact on the looks...

I can't speak to the impact of a glue joint on the sound, but if you're working with the right wood, and if you have decent hand planing skills, then the glue joint can be invisible.

This is a table lamp I made, the stem is a solid piece, split in two with a channel cut down the centre, then the two halves glued back together. You can't see the glue line.

However a lot of that is down to the choice of timber. This is made from Swiss Pear, which is extremely fine grained. I only mention it because I understand Pear is the traditional timber choice for woodwind instruments.

 

[Eric The Viking]

Don't forget that a tailstock drill should self-centre ...

You've obviously never had holes miss each other in the middle by over an inch.

Nope you're right, I haven't. but part of the skill is breaking down an awkward task into processes that do work. If the objective is a hole concentric with a cylinder, then a lathe would, to an extent make that job easier. And once the drill starts guiding itself (if it's an auger or a conventional fluted twist drill), you really cannot correct it, no matter how you're doing it.

Actually, I'd probably do what Custard and others have suggested - make two semicircular channels and aim for an invisible glue line. And/or bore it by hand completely - slowly and carefully.

 

[Just4Fun]

When I was at school in the 1970s one thing we made in woodwork class was a standard lamp. Most of the height was a metal tube but half way up there was a wooden section which we drilled using a brace & bit so the cable could run up the middle. It was long enough that we had to drill in from both ends with the holes meeting in the middle. With the wood held vertically in the vice it took 3 people to drill the holes. One person used the brace & bit and the other two eyeballed the bit from front and side, guiding the brace operator to keep it vertical. We all managed to drill the hole without coming out of the side of the piece, but I can't remember how close we got to having the two holes meet spot on.
I have never attempted anything similar since then.

 

[Andrewf]

I have drilled a few deep holes into end grain. I do have a couple of very long anger bits, that I inherited from my father. Not sure of the correct name for the type, but they have only one flute and no centre point. This means that they can be guided easily, and don't pull themselves off course.
Though if you need accurate holes drilled on a lathe, I would be tempted to drill a small through hole, and then finish with a boring bar.

 

[xy mosian]

My school experience with a standard lamp used a shell auger through a hollow tailstock. A quick internet search for Lamp Standard Shell Auger, throws up a couple, by Robert Sorby or Record. Whether these are still available I cannot say.
A few years after leaving school, late sixties, I needed to make a long hole down the centre of some music stand pedestals. These were 1 1/4"(32mm) diameter and about 32" ( 800mm) long. I attempted forming the hole as two semi circular grooves and glueing up, I also cut a small section groove down one half of a blank then glued up to form pilot for a long auger. The auger was hard work and left a rough finish internally, this may not matter to you as you may well be using a reamer to finally shape the hole. The two semi circular grooves would have worked well had I had the use of a router.
Luckily I found some Dodds pattern shell augers, lamp standard shell augers before being re-named. The next problem involved making a hollow rotating centre. In the end I used an oversized tapered bearing, the inner part being attached to the work piece and the outer being attached to a jury rigged tailstock, made of 3/4" (19mm) ply. The guide hole was part of the piece which held the inner part of the bearing to the workpiece. This worked very well, driven by a half horse power motor at low speed and stopping within 1/2" (13mm) of the drive centre. Generally I was within 1/16" (1.6mm) of centre. I then drove the work with an expanding center to turn the outside. The process of forming the hole was not quick, but reliable.
I made some larger holes unsucessfully, mainly as either my elastic drive belt slipped, or the auger bit too well. This may be a job where a scraping cut could be better.