Anyone know how to bore a spiral hole?

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As part of an installation an artist friend has asked me if I could bore a spiral hole of about 1" dia endways through a seasoned hardwood log. Log would be about 14" dia (ish) and about 3ft long. Dia of the spiral not too important but minimum about 3" OD. It is important to the artist that the spiral be contained entirely within the log. She will not encounter through drilling and plugging. I've done some oddball stuff for this lady over the last thirty years but this one has me stumped. She only asked me a couple of hours back and no doubt I'll be pondering for days. Hence this post. The final product would be only a minor component of the whole which is intended to have a practical and useful purpose. On this I am sworn to secrecy. I can say that there will also be a ballista type machine involved in the apparutus and the intention is saving, rather than taking, of life. The project is somewhat W. Heath Robinson, but it is food for thought. I'm in England and have always had a great love for WHR's designs.
I know the above is daft but (1) the only daft question is the one that you don't ask and (2) anything is possible.
Many thanks, Nick.
Avid reader of this group, infrequent poster. Thanks to all for keeping it alive.
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A large trained woodworm?
Sounds just the sort of idea an arty-farty type with no sense of reality or practicality would come up with.
--
Stuart Winsor

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Sorry about my previous rather snide remarks.
Find a blacksmith who can make you a suitable spiral, get the end hot and see if you can use it to burn your way through.
Use a piece of round bar the same diameter as the inner of the spiral, around which a couple of turns will fit, and fix it co-axially in the end of the log to act as a guide.
--
Stuart Winsor

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wrote:

perhaps but the end product is intended to have a practical purpose. There will be no monetary gain to either the artist or any collaborators. This lady regards her work/hobby as therapeutic and gives all her efforts to charities for children. Trust me, she has a great sense and many years experience of the real world. No apology required as I know this is a very oddball enquiry. Also I have thick skin. I would say that I've been insulted by professionals but that is not necessary.
I have a couple of spirals such as you describe, but too small for this task. I might give them both a try in shorter logs. However, as this is end grain hardwood, I fear the metal will fail before the timber yields. Also, am I likely to live long enough to burn a 1" spiral over a length of 3ft? If of any success I will contact the local blacksmith. Excellent chap, known him for forty years. Never failed to produce. Once made me a very large pair of door hinges (6ft long x 9" high each) and very ornate. All he had to work from was the shadow remaining on an old door. These are still in everyday use.
Thanks, Nick.
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Does it have to be a smooth spiral? If not, split it on center, lay out the holes on this cross section then drill intersecting holes. Maybe this would work? phil k.
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On 10/5/2012 5:40 PM, Nick wrote:

Don't groak the 'She will not encounter through drilling and plugging.' part but drilling and boring the spiral (helix?) on a lathe should do the job. And if she really wants a plug to fit, again a lathe is your first choice.
FYI: *If you happen to have an NC machine (lathe would be easiest) lying about that is unused I could easily generate NC code to do the above job (as I understand it ??) with no problem -- but-- I too am sworn to secrecy as to how I can do that!
HTH, John
* no BS on that part, its what I do for a living.
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If you don't have some special tools for such spiral drilling, I would suggest getting a practice log, to do whatever test cuts may need doing, before committing to the usable/project log.
Not having special tools, I would attempt the following on a test log, first: Cut the log such that, looking on end, the cut lines look like a tic-tac-toe board. Cut (hand cut?) the helix around the center section, with some partial cutting on the corresponding mating sections, then glue the log back together.
A saw mill could best slice the log, but most saw mills need the log to be at least 4' long, so the mill can grasp the log securely for the cutting. Slicing a 7' log will give you a practice log and a project log.
Sonny
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Progressively larger cork screws. **************************************** On Friday, October 5, 2012 2:40:37 PM UTC-7, Nick wrote:

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Nick wrote:

You are not a pioneer. Rifling gun barrels has been going on since the mid-1800's. Check that subject.
You may have, however, an easier way out; ballistas did not have rifled barrels. In fact most did not have barrels at all.
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On 10/6/2012 8:39 AM, HeyBub wrote:

hole that spirals through the wood. But when I read the post about drilling a gun barrel, I could see your question could be interpreted differently.
Did you mean cut spirals as in a gun barrel or did you mean a hole that spirals through the piece of wood. ie you could not see through it as the loops would block your view. ie DNA molecule
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On 10/7/2012 2:40 PM, Nick wrote:

I used DNA to convey the concept of a spiral, with out think of the fact that it was a double spiral.
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I was in one of the famous chateaus in France a couple of years ago. It had a double helix staircase made of stone. Kerry
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Nick wrote:

drill hole in 2nd slice at an angle (matching it to the 1st slice hole), etc. glue slices back together after trimming the holes to provide a smooth transition from 1 slice to the next. you won't even need a practice log, just some boards.
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On Sat, 06 Oct 2012 08:56:09 -0700, Gary Kunstmann wrote:

Maybe I'm missing something here, but I thought the OP asked for a spiral. The answers I'm seeing seem to create a cone. The answer above could possibly be read either way, so it might actually refer to a spiral.
--
When fascism comes to America, it will be wrapped in the flag and
carrying a cross.
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On Saturday, October 6, 2012 10:56:23 AM UTC-5, Gary Kunstmann wrote:

I like this solution, also, rather than my (total) suggestion.
When done assembling a sucessfully "drilled" log, if finishing the hole is needed, prefinish before assembly, then run a "pig" through the hole with finish soaked onto it, for a final finish coat.
Sonny
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On Friday, October 5, 2012 2:40:37 PM UTC-7, Nick wrote:

Well, training termites will take too long. One can imagine making a spiral tool holder by bending steel pipe, and mounting a small air-tool with a cutting tip (a burr that would act as a big rotary file). You'd advance the tool in corkscrew fashion into the work.
Easier, though, would be to make the log into a pipe and a plug, and cut the spiral onto the outer diameter of the plug, then cement it into the pipe. I'd start with two logs, actually, and put some slight taper onto the plug (so it is easier to put in).
This sounds like an Archimedean screw mechanism; it's one of the classics, Archimedes and Rube Goldberg would both appreciate the artwork.
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You have seen a mortising chisel, I assume? If not, it is a square chisel with a drill bit riding inside of it to remove most of the wood.
Perhaps the idea could be modified to suite your need. Make a spiral of a steel tube, slightly smaller in diameter than your desired hole. Wind in an a mandrill in the desired spiral, probably with it filled with sand after it has been tempered to soft. (to keep it from crushing) After that, put a spring inside it, perhaps like a garage door spring, and fit a bit to ride in the tip of the tube like a mortising bit, driven by the spring inside the spiral steel tube. Enough of a picture?
--
Jim in NC


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Sit the spiral hole down and read "War and Peace" to it.
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Having trouble visualizing what kind of 'spiral' you mean and how uniform it must (or mustn't) be. For an inside threaded straight hole, you could drill out the majority, then use something like the auger at http://www.homedepot.com/h_d1/N-5yc1v/R-202935069/h_d2/ProductDisplay?catalogId053&langId=-1&keyword=anchor&storeId051 to create the spiral thread.
For a large worm-hole spiral maybe http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId051&langId=-1&catalogId053&productId 2703690 , then a flex-shaft drill, then back to the spiral. For a 3" OD wormhole (that you could stick your arm into) I have no idea. Might wetting it slightly as you proceed help? Let us know what you end up doing.
On 10/5/2012 5:40 PM, Nick wrote:

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On 10/5/2012 5:40 PM, Nick wrote:

I think we have a terminology issue here...
A spiral is a circular form of ever increasing radius... Think a pencil tied to a string that was wrapped around a center point unwrapping the string as the circle is drawn. If a drill expanded in radius as it drilled, the result would be a cone, but the chip production would clog the exit hole very quickly.
A helix is the DNA style circular form that could be made by twisting two rods around each other. This is similar to a screw thread. Rifling can have 6 or more parts, but is the same process. In most cases the inner diameter can be bored first, then the threads added as a second operation. You might call this an open-centered helix.
I think what you want is a closed center helix... Based on your 1" diameter, 3" O.D. minimum, part of your post... Here is the way I might attempt it... Make a steel tube About 1/2" diameter with the form of the helix you want, Snake a flexible shaft tool like a Foredom drive cable through the tube, attach a 1" ball end mill to the end of the shaft, rig a way to blow compressed air down the tube, and fit a shop vac hose around the outside of the hole to try to keep the cuttings from binding. You will want to make a starting block that establishes the form of the hole, which you will clamp onto the end of the log, then turn on the vac, the air, and start the tool spinning, and slowly feed it into the log. The helix ought to be self guiding after it gets started.
Stuart
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