Dividing a circle into equal parts

[Maets]

Have you ever had to divide up a circle into equal parts?  Every once and a while a project presents itself that I need to equally and accurately divide a circle up into a number of equal parts.  While making the banjo I hit on a simple method that works!

I have a number of circular saw blades laying around.  I use them for various projects.  Turns out they are perfect for marking of divisions on something else.


Say I want to divide up this disk.


Lay a saw blade on top and start marking at what ever interval fits your needs.


A different blade and a different interval with each blade offering a lot of possibilities.


Remove the blade and you are ready to weld, paint, whatever.

Simple but effective.

[jcbanner]

Thats such a simple method that it must be cheating. No trig, no getting out protractors, no wrapping string around and diving that into equal parts trying to re-wrap the object.

I will have to remember this one

[Wilhelm Smydle]

I have been cheating for years,
 my local craft shop sells plastic canvas disks with evenly spaced holes.
The saw blade technique is another layout tool I will rember.

[Maets]

Cheating is good, when it saves time and gives a good result.  Over the years I have tried a number of ways. This is clearly the easiest I have ever used.

[Herbert West]

Who cares how you do it, as long as the finished product looks good.

[Mr. Boltneck]

I've seen machinists use a similar technique of indexing the head of a lathe by counting gear teeth.

[Maets]

Anyone else with time saving techniques?

[RJBowman]

There is a device for making saw blades on display at the Henry Ford Museum, and has a big metal disk full of holes for aligning the cutter that cuts the teeth in the saw blade. So your method of using saw blades to subdivide circles is more or less the same method that machinists use to make saw blades.

Of course, if the saw blade maker's angles are off, your project will be off too.

[Ponyboy]

A few years back, I worked as a fabricator for a motorcycle shop. One technique that I used quite often to match up holes (for motor mounts, fender struts, seat pan brackets, etc.), was to take a sheet of A4 and rub my index finger across the floor to get it really dirty and then run said finger over the holes I was trying to match. It leaves the exact size of the hole as well as the spacing. beats pulling out the calipers and tape measures...

[IGetPwnedOften]

I've used that method myself many times - it's surprising accurate; basic like brass rubbing but with engines and oily fingers.

The sawblade idea is genius, although of course it does rather depend on the item being bigger than the blade, although for smaller pieces I suppose you could lay it on top of the blade and use a straight edge from one side to the other...

[Maets]

The sawblade idea is genius, although of course it does rather depend on the item being bigger than the blade, although for smaller pieces I suppose you could lay it on top of the blade and use a straight edge from one side to the other...

That works and I have also used some small gears for laying out some smaller pieces.