[BobWarfield]

A couple of wild ideas since making those worm gearsets can be painful.

Somewhere I have seen a fellow that built a CNC rotary table using a right angle planetary drive instead of the worm setup. I think it may have been a Bayside drive. These come up on eBay with fair frequency. The ones well suite to your application have a 30 to 50:1 ratio, and people usually won't bid much for one anyway.

If it is going to be used purely as a 4th axis for CNC, another thought comes to mind. Such a table only needs to stand vertically, and need not sit horizontally, right? So you can mount the motor's axis to be parallel to the table's axis of rotation and use a gear or even a belt drive in that case. It's pretty easy to make timing belt pulleys on your mill (sorry, it's easy if you have a rotary table, doh!), or they could be bought cheaply. Timing belts will have less backlash than a worm you make as well, I would think. You might still need some further reduction to up your resolution, however. A typical stepper's 200 steps/revolution multiplied by the total reduction will give you your resolution. Think about what kind of accuracy will be required to get the equivalent of the worm gear's reduction you are contemplating.

To completely bootstrap such a beast without owning a rotary table, I would consider a couple of approaches. First, you can rig up a way to use the change gears from your lathe to index the table and thereby make the first set of timing pulleys. Or, you could rig up a gear on the lathe spindle as a way to index that and then rig a way to mill the grooves in the aluminum on the lathe. I've seen both done very readily.

Keep going, it's an interesting project. I'm lazy, so I'll be making that motor mount to go on my Phase II table. (chair)

Best,

BW

[Dfennell]

Looks cool and I think you are right about the holes, since they go away at the end of the process. Do you know of a supplier where one can just buy a set? And what would you think the tooth ratio should be?

I can think of quite a few places to buy worm gears, but they are EXPENSIVE. If you bought the gears, might as well just buy the table setup.

As far as the number of teeth on the gear goes, I think that it would be dictated by the TPI of the worm you use and the diamater of the table you intend to make. Bottom line is if it's to be used as a CNC'd axis and your microstepping, the number of teeth won't be much of an issue for accuracy. You could also just mimic another design.

Here's another thought on drilling the holes for the worm - consider that a 10tpi acme thread has a 4deg pitch; you could just tilt the head of your mill column 4deg and drill away, then the gashes would be perfectly set up to use. You also wouldn't think twice to form a cutter from a piece of 10tpi acme thread either :-)

[JBV]

From the link i posted previously (in swedish) a 60 teeth module 1 wormgear + a matching worm cost about $30 including tax... Not bad at all!

[lwill]

Here is a company that sells gears to use with standard screw threads. They also work well as simple rack and pinions.
http://dynamicgear.com/sg/web/index.htm
I have made a few using the dimentions they list and a tap, saved alot of math. They worked fine, but were not for precision / heavy use.

[handlewanker]

Hi JBV, if the worm wheel is held in the four jaw chuck in a lathe and the bore clocked up true then, provided the blank does not move in the chuck, it will be as accurate as when it was made. If you're going to bore the wheel in the mill with a boring head, just make sure you rotate the spindle to clock the bore true, and lock the X Y axis slides.
Have you thought about using a castiron gear and an acme thread worm offset at the helix angle? Ever so simple.
Ian.
Ian.

[DarkDesigns]

Hello all, justa little background, new to the site, R&D Designer for a company that produces Pharm. Packaging Equipment.

I have a small shop which is humbly stocked with 2 9" lathes and a small mill.

I'm looking for small project plans, ie: notably a small 4" roatary table. Just basic designs, I can use to design my own, looking for ideas.

thanks.

[handlewanker]

Hi all, you can also find a source of cheap worm drive gearboxes attached to windscreen wiper motors, but I'm not sure if the ratio is suitable for dividing uses.
Ian.

[vegerj]

JBV,

Funny, I'm JAV! I am a precision machining instructor in Indiana. I love this machinist vise. Could I have a couple of the plans to add to my student project collection. I'm always looking for projects that they can make to learn machining skills as well as adding tools to their war chest/tool box.

Thanks
JAV