making a corkscrew cut into a log? ideas on how to do it?

[mrbrb]

Hello Forestry Forum,

Heres another project i'm trying to figure out. How to make a kind of corkscrew form out of a large log- 36" diam x 8' length ewp.

I made a small version,  (see below) using a table saw: Resting a cylindrical piece of wood against the fence, raising the running saw exactly 8 turns into the wood, lowering blade, turning the piece 1/8" and moving it ahead 1/8", repeat, repeat, repeat, about 300 times.

I would like to do this on a much larger scale, out of a big log. Problem is, of course, you cant put a 1/2 ton log on a table saw, and the blade would be way too small. Im looking for a way to make a 12 to 16" diameter cut, (thus necessitating a huge blade, if I were to go w. a circular blade.)

My idea is to use a chainsaw w. a 24" bar, with a pivot point built into the bar at the engine end of the bar. (the chainsaw would make an 'arc cut')  The pivoting  chainsaw would be mounted to a carriage that advances after each cut. Corresponding with the advance of the saw, the log would be turned X degrees, to allow the spiral to occur as the cuts aggregate.

Heres a little model of what this could look like.  I have made jigs for chainsaws before, to make really specific miter cuts, but always with the pivot at the bar tip (a kind of chainsaw-chopsaw). The difference here is that the pivot would be at the inner end of the bar-  I'm worried about the chainsaw blade deflecting out of its cut. Know what I mean?

I dont know much about using big circular saw blades, and feel that I wouldn't be able to hack together something adequately, so thinking chainsaw would be the way to go.

Any ideas or warnings?

Thanks and all my best!
MrBRB

  

 

[moosehunter]

Some of the chain saw carvers I have seen could do that free hand. It will be interesting to see some ideas for doing it with a jig!

[kevin19343]

You must have some big wine bottles to open.

[DaleK]

I think your best bet is to decide how far you want to go on the log for every full rotation (say 24") and how deep you want to cut. Mark every 24" in a straight line and make a plunge cut to the depth you want. Rotate it 180 degrees and mark the halfway points and do the same. Then 90 degrees and split the difference, etc until you feel comfortable with cutting the spiral.

[thecfarm]

I sure don't know,but I am drying to find out why and what it will be used for???  ;D  I like that small one.

[Dave Shepard]

I would look for youtube videos of cutting drill bits, then try to copy that on a larger, wood cutting, scale. You have to control two motions simultaneously, the twist, and the feed past the cutter.

[GAmillworker]

Find someone that has a lathe on there cnc Router

Small version is Awesome

[mrbrb]

Thanks for the suggestions: Yes CNC milling is an option, but probably not possible at a large scale/ small budget, and I'd like to retain that Kerf look that many incremental cuts will give me.

I'm going to attempt the chainsaw jig. Still concerned about A:the deflection of the chainsaw bar out of its cut,  B: the amount abuse the chainsaw bar tip is going to get- im thinking that typical bars are not designed to do so much plunge cutting (maybe I can come up with a really wide bar?)

[pineywoods]

Here's how to lay out the corkscrew on the log. Assume you want a turn every 6 inches. You will need a piece of thin sheet metal or heavy construction paper 6 inches wide and several feet long. Attach the strip to the side of the log near one end, across the log at about a 45 degree angle. Wrap it around the log in a spiral with no overlap between layers. Leave a 1/8 inch gap between the edges of the wraps. Use magic marker, ink pen, paint, etc to mark the log in the 1/8 inch gap between the wraps. Gives a perfect spiral with one turn every 6 inches. For a different spacing, use a strip of appropriate width. FWIW, I didn't think this up. Old time backwoods gunsmiths used this method to make a wooden jig used to cut the rifles in gun barrels.

[m wood]

unless your trying to repeat the results multiple times, I would have to agree with moosehunter...freehand.  lay it out first of course.  My initial thought was also chainsaw, like a full scribe log home builder would do.  there are utube vids on the technique of "brushing" with the bar tip to create perfect fits when making saddle joints or swedish cope joints etc.  Some version of that method sticks in my mind for your project.  Good luck!
mark

[beenthere]

Seems doing this to a log is very similar to making threads on a machine lathe.
Just that the rotation of the log and the longitudinal travel of the chainsaw needs to be sync'd and the depth of the cut controlled. Figure out the "pitch" of the "thread" desired and then plan out the mechanics.
Admit I could be barking up the wrong tree here...  ;D

[Hilltop366]

Would a woodcarvers disc for a angle grinder work, some have chainsaw chain loops, others have replaceable cutters on them, I see by doing a web search that they can be had for less than the cost of a bar + chain.

I can see the value of making a jig for this if you want to repeat the process several times.

[SwampDonkey]

Can some sort of super sized wooden thread box be concocted? And would a custom V groove bit for a drill or drill press turn fast enough and be deep enough?

Just another thing to scratch the noggin over. ;)

[Farmerjw]

Router on a lathe bed?  Sears had a copy crafter thing in the 70's. 

[SPIKER]

I agree with others that if this is a one or two off thing then I would use the paper spiral wrap idea.   one thing is I would use two papers start 180deg apart on log end, then wrap so each paper is next to other one all way down log.   Peeled logs or try some big phone poles for first try.   Hooking up the log on a rotary device would be easy part, gearing that to a thread would be a 2nd story.

Mark

[Hilltop366]

Instead of doing the cut all at once have a angle grinder with carvers disc mounted on a plate on the shuttle where your chainsaw is on the diagram, make the plate adjustable in and out as well as side to side.

Once you make a pass adjust the cutter in and to the left make another pass until the ½ way point of the arc then start working your way out and to the left again.

[lowpolyjoe]

However you end up doing it, i'd love to see some pics of the final result.  A video would be even better

[mrbrb]

 

  

  

  

  

  

 

so the chainsaw jig actually worked...

[Ken]

There are some very creative people on this forum.  Great job

[SwampDonkey]

It probably took some doing, but you got'r done.  8)

[thecfarm]

I like the big ones even better. Good job. How long did it take to saw?

[Peter Drouin]

 smiley_clapping smiley_clapping I like that , Good job

[justallan1]

Great job. I'm not sure what they are, but they are nice. :D

Allan

[mrbrb]

I like the big ones even better. Good job. How long did it take to saw?

It took about 2 days to cut the longer spiral. The tall one has about 1000 cuts, and that was all done on a single chain, sometimes backcutting, with no noticeable difference in chain sharpness over two days. Deflection out of the cut was minor, and really only became a problem when hitting knots.  The entire log is on a platform that rolls on a band mill track, and the chainsaw is fixed to the track. The log is then moved incrementally by turning a long threaded rod, while it is rotated via an indexing sprocket...
The project gave me a lot of ideas about the potential for simply bolting jigs onto my band mill... since it is basically made of scrap metal, it is no big deal to punch a few holes in it and try out something new.
Thanks for the initial input on how to do this..
All the best

[Farmerjw]

Please tell me you have some video of that thing working/cutting please!

[Hilltop366]

Cool... you did it!

[lowpolyjoe]

Wow, that's amazing

[justallan1]

I think the biggest problem I have with this thread, or subject, is that I have absolutely no use for a giant corkscrew other than maybe for a set of stairs, but now I want to make a couple. :D
Thanks for sharing and the pictures.

Allan

[Busy Beaver Lumber]

That is one of the neatest things i have ever seen. Hats off to you for your ingenuity. I have great respect for all chainsaw carvers and would rather have a chainsaw carving in my house than any fancy hoity toidy piece of artwork. Well done Mrbrb