The overhead drive is one of the most common methods used to drive the cutters used in ornamental turning. (Cutters would be held in either a cutting frame or a drilling frame.)
The benefits of using an overhead drive over a direct drive are :
The motor to use for the overhead drive is the next thing to consider. It should be powerful enough to drive the cutter when cutting very hard woods, and turn it fast enough to make the cuts. But it can't be too fast or the belting will jump off the idler pulleys.
Generally, the guidelines recommended are :
One motor which is commonly used is from Penn State Industries - the Variable Speed Midi Lathe Conversion Kit. Another is the Sherline Variable speed motor.
If you chose to repurpose a router for this use, be sure to put a speed controller on the power feed. Rockler sells one, item number 25278.
These work by changing the frequency of the power. Be aware of these things if you incorporate this into your design :
Using a router is not recommended.
A belt is needed for the overhead drive motor to drive the cutter.
I used round belting from McMaster-Carr, part number 59725K729. It is made from polyurethane rubber, is 1/8 inch diameter, and is orange (because I liked the colour). It is sold by the foot.
Other types of belting are available, and they all have plusses and minuses, and varying costs. One common alternative is to use one which has a more rough texture. The argument made for this is that it doesn't slip as easily (though I've not had that problem, but others may have).
It will need to be replaced over time, but 20 or 30 feet will last quite a while.
A forum user (who goes by "Sherweld") posted directions on the Ornamental Turners International forum for a jig that makes it much easier to weld the cable into a continuous loop. The picture to the right shows the ends just before they were melted and joined. Melting the ends to join them is done using a soldering iron.
I made one of these jigs from a scrap piece of walnut and parts I bought at the local hardware store. The metal parts cost less than $10.
I've used this a number of times, and it has never failed me.
This YouTube video is a quick overview of my overhead drive: