I made a dividing head last year.
It can do both direct indexing and simple indexing with a 40:1 ratio. The gears came from Amazon. Dividing plates are a set that was purchased with my 8" rotary table. The shaft that the worm is on is a two-piece affair that allows the worm to be disengaged from the worm wheel to allow the spindle to spin freely, which allows for the direct indexing. The spindle holds 5c collets. I've got a small 4-jaw chuck that fits also.
Here's a pic showing the worm disengaged to allow direct indexing. The flathead screws on the top are there to provide for lubrication ports for the front and rear bearing surfaces, which are just steel on cast-iron plain bearings. The larger, center flathead screw allows for lubricating the worm and worm wheel.
This pic shows the cast-iron main body. The holes for the direct-indexing pin aren't in place yet here. You can see holes for dowel pins to attach to the trunnions, 3 threaded holes to attach trunnions, worm shaft, , set screws for front spindle bearing (2 @ 90 degrees), and spindle lock.
This pic also shows the split cotter for the spindle lock, the purchased worm wheel that has been bored out to the size of the spindle and keyed, the worm shaft (bearings not present), and the spindle nut.
Here we have the worm wheel mounted on the spindle with the front spindle bushing in place ready for assembly.
This project ended up costing probably more than a dividing head off of ebay would have, but it did give me a reason to go to the shop! OTOH, some random dividing head off of ebay probably wouldn't take 5c collets, either. . . . Those are usually pretty good money.
Jim