I am looking to convert my sherline mill to cnc for the purpose of building some wooden clocks (among other things). The wooden gears can get quite large... so I'm thinking I need 4-axis so I can position the center of the gear flat on a rotary table and index the the rotation the distance of 1 tooth on the gear and then have a fine bit cut the shape of 1 tooth and then repeat for each tooth.

Here is a link to the provider of the clock plans I will attempt to reproduce. These plans are intended to be manually cut with hand tools and scroll saws and such.

http://lisaboyer.com/Claytonsite/videoplayer.htm

What do think?

Your machine will be perfectly capable of that level of work in wood without difficulty. Those are some truly brilliant clock designs on that site, and while there are minor flaws in the execution of a few, they are from construction limitations that would be eliminated entirely by the ability to use the capabilities of CNC and a rotary table. I would love to see that work when you are done!

The method you propose would work very well for you to make excellent and quite accurate gears, in fact it is the preferred method over cutting them flat without a rotary even if you have the space to.
There are also some aftermarket X and Y axis extensions available for the Sherline that give a significantly larger work area should you want it. The extensions would reduce what already little rigidity that type of machine has for cutting tougher materials, but for things like wooden clock parts it shouldn't pose an issue at all. It would work well for you if you ever find the need to cut larger pieces that aren't radially symmetrical, like the frames, plates, and dials for larger clocks.

If they were meant to be cut by hand, I would imagine the drawings aren't available in a machine readable format. Converting the drawings over to vectors you can use directly or building them up fresh in CAD looks to be possibly the only real sticking point to your idea, and that is certainly not insurmountable. How are you planning to do it, and what software are you using?

Actually converting the blueprints back into digital vector format will be the easiest part for me. I have lots of experience converting image data into vector. I can use an old copy of adobe streamline or I can use:

http://vectormagic.com/

There service was free until recently, but it really is impressive for vectorizing image data.

I am also very familiar with 3dsmax, photoshop, rhino (partially) and other 3d programs as I have used them for my job for years.

But... first things first... I need to convert my sherline mill.
Here is my current purchase list to begin my project:

sherline cnc rotary table = $320
sherline cnc mill upgrade = $250
xylotex 4 axis kit = $460
sherline z axis backlash kit = $35
pcmcia parallel port for laptop = $20 (newegg)
quality drill bits and tap for conversion of mill = $30
mach3 controller software = $180

I didn't know Sherline even had a Z axis backlash kit. Is it a problem with those machines?
I haven't used them heavily, so don't take it as gospel, but I didn't personally ever have any issues there when using them. Usually it is the only axis you don't have to worry about in that regard on most any mill as the motor/headstock assembly is heavy enough it keeps the nut bearing on only the lower thread surfaces no matter which direction you travel, unlike the horizontal axes.

Got to love the clock part. :D

YouTube - vericut clock part

I didn't know Sherline even had a Z axis backlash kit. Is it a problem with those machines?


That makes sense... but I've seen others recommending getting it when converting to cnc. Fortunately... it's relatively cheap compared to the other components needed for cnc.