Boring a large hole

[Eric Mckenna]

I am trying to bore a 12" x 18" hole in a pine log. I have come up with several ideas on how to do this. I need to produce at least 2 a day. If there is anyone with ideas please help.

 

[john lucas]

Are you talking about a 12" hole 18" deep or a an oval hole that is 12x18. If it's a round hole it can be done with a captured bar hollowing system.

 

[rjones]

need a little more information. How big is the log, how long, were you want the hole, how deep you need it.

 

[Eric Mckenna]

Are you talking about a 12" hole 18" deep or a an oval hole that is 12x18. If it's a round hole it can be done with a captured bar hollowing system.

I am cutting a round hole 12" wide and 18" deep. Cutting time is more the issue than the hole. This is for production

 

[Steve Worcester]

I am cutting a round hole 12" wide and 18" deep. Cutting time is more the issue than the hole. This is for production

Depending on the level of precision required and whether the log has been cleaned up on the outside, so you could put a steady rest on it.

Assuming you are boring down the endgrain, you are going to have to use real long screws (lag bolts) because they don't like to stay in any end grain , let alone Pine. I can tell you you should start with the largest longest drill bit you can find to start the hole. And I don't see this as a real fast (or safe) venture.

 

[WODAD]

Can't say for sure about the pine, have done some (several) vessels that were approx. 12 plus inches deep but only 7-8 in. wide & tappered. didn't mark the time but were completed in one day. Turned a large black walnut vessel that was 19 inches deep and 17 wide on the inside that one averaged 19 hours and was brutal! did take several beaks that are included in the time.

If you do not have a steady rest hollow with the tailstock in place get in there at least half way, farther if possible, before you take away the tailstock to finish. loosen the belt on your lathe so if you get a catch you can live through it. take you time a pay attention.

maybe I'm just lucky but it has worked for me. 2 a day seems like a push.

Good Luck!
Frank D.

 

[Dale Miner]

Still don't know the specifics of your project, but this idea comes to mind.

Figure on laminating wood in layers to get to the 18" depth, perhaps 1.5 inches per layer. Use a router to cut the holes prior to laminating, depending on final accuracy, to size or slightly undersize. If the OD will need turned, attach a temporary end cap to support the piece while turning the OD. If inside accuracy requires final turning, use a steady on the od and a long stout box rest in the ID using a bevel angle sufficiently acute to allow reaching the bottom. The round carbide tools may also work in this application.

Later,
Dale M

 

[MichaelMouse]

Djembe? Isn't the work normally done by burning out the center?

I suppose I'd go with augers, gouges, and then maybe clean up on the lathe if it were necessary.

Sure would be nice if it could go through-and through, though.

 

[john lucas]

If you build a captured boring bar similar to Lyle Jamieson's but make it 1 1/2" in diameter you should be able to bore it out fairly quickly to that depth. I took a class from Frank Sudol many years ago and we hollowed using a bar that big. It was almost effortless to 14 or 16" (I don't remember for sure how deep because it was quite a few years ago). I hollow to 12" with a 3/4" bar. Beyond that it starts to chatter and makes cutting slow.
With a laser attachment to guide you it will go very quickly because you always know where the cutter is and you won't have to stop and measure.
You can also do the outside with this system.

 

[Eric Mckenna]

Solution

I am cutting a round hole 12" wide and 18" deep. Cutting time is more the issue than the hole. This is for production

The solution for the large bore is a custom HSS bit 12" wide and 18" long powered by a 5 hp motor and a reduction gearbox. Of course everything will be homemade. It will be a pleasure to see how well it is gonna work.

 

[Joe Greiner]

Oh. Well then, you need one of these: http://www.malcolmdrilling.com/equipment.php

The largest I've ever drilled was about 12 feet diameter x about 75 feet deep.

 

[Rick M]

Well, I guess that'll pretty much eliminate the need for calipers, but it might get "interesting" if the bit starts to wander. . .