Cutting Spirals (NOT Spiral Cutters)

[John Messinger]

Recently my wife and some aquaintences started a candy store as a new business venture. She wanted me to make some "sucker blocks" to display candy on a stick. I quickly made some square stadium seating types that look nice enough, but I wanted to make something a bit different such as a rotating stepped design that would spiral up rather than just a round wedding cake type of arrangement. I could not find anything on the internet that could help me do this so I came up with the following layout for a spiral and the jig to make the cutting faster and more reproducable. I don't expect this technique to have a lot of applicability, but perhaps model railroaders and the like could find it useful.

http://inlinethumb10.webshots.com/27209/2846595380092041178S500x500Q85.jpg (http://home-and-garden.webshots.com/photo/2846595380092041178izFdvx)


I'll describe a spiral of about 14 1/4" diameter with a layer of about 1 1/2" wide that spirals in. Depicted above: using compass, trammel points and straight edge, I have drawn a 7 1/2" radius circle and divided it into 8 equal sections. Then I drew a 5/8" radius center circle. Resetting the compass to 6 7/8" I drew an arc from one radial section line to the next. Resetting the compass again from the center 5/8" circle to each newly drawn arc I proceeded around the circle to give me a width of 1 1/2" to this initial layer. I determined the radius for the 5/8" center circle by trial and error. I cut this initial layer on the scroll saw by following the graphite line. A 1/4 x 20 stove bolt was placed in the center as an axle.


http://inlinethumb27.webshots.com/10522/2855586470092041178S500x500Q85.jpg (http://home-and-garden.webshots.com/photo/2855586470092041178voRHVR)

The above depicts the jig. Its main features are 1) a fence that extends to the right that the center axel slides along. 2) an additional "adjustable fence" on the left side of the band saw blade made from a 2" long piece of bandsaw blade. The piece of blade is clamped in a movable piece that can adjust to give a layer from about 1/4" to 2" wide. The ice pick is pointing to the "adjustable fence".

http://inlinethumb14.webshots.com/12045/2242686710092041178S500x500Q85.jpg (http://home-and-garden.webshots.com/photo/2242686710092041178ctChOA)


Side view. Incidentally, my band saw is a home built Gillium kit band saw that is very easy to clamp things to. I set the adjustable "fence" to 1.5 inches from the bandsaw blade and rotated the workpiece in.

http://inlinethumb12.webshots.com/18507/2676707750092041178S500x500Q85.jpg (http://home-and-garden.webshots.com/photo/2676707750092041178DLIawT)

Ta da!

[Chris Padilla]

Very interesting, John! Thanks for sharing.

[Cliff Rohrabacher]

And it's a real Spiral too~!!!
As opposed to the Involute which often gets called a spiral.

I was part of a team that once made a machine to cut involute using a bridgeport with a gear driven power feed, a south bend lathe head stock and a huge rotary table.

The involutes we made were prototypes for various kinds of pumps. One of which was in the running for the job of supercharger for the M1-A1.

[John Messinger]

Here is one of the simple ones.

http://inlinethumb61.webshots.com/42236/2079428160092041178S425x425Q85.jpg (http://home-and-garden.webshots.com/photo/2079428160092041178NGAsgp)