Dividing head and rotary table

[Alberto-sp]

At the bottom line, an indexer is a rotary table with fixed (fraction) plates. Cutting gears on a rotary table is basicly an exercise in futility. Cutting bevel gears, or anything other than straight 90 degree spur gears takes much more work. A good understanding of gears and how they work would be a starting point there.

A rotary table usually has 72 rotations to a full circle. An indexer usually has 40 rotations to a full circle. 72 divisions will give better resolution when dividing a circle into degrees, minutes, and seconds. However, dividing a circle with an indexer can be done, albeit at lower resolution. All that is needed is a "fraction plate" with a circle of even numbered holes. Just decide how many sides are needed and mill away.

In my own case, I have both, plus a spin indexer and some specifically sided collet blocks. But mostly because I do model building where physical size of the fixture matters. For most work, I can use most any fixture to get 6, or 12, or even 30 sides. But for cutting gears, an indexer is a must. I cut worm wheels with 40 or 50 teeth and a diameter of less than an inch, 25mm. There is no room for an "almost" fit.

For general uses, a rotary table with an attachment of a fraction plate and associated parts would be the preference in my shop. The fraction plate can be broken down, removing the fraction plate and reinstalling the handwheel. The one thing it cannot do is tilt. In most cases, with spur gears, tilting is really not an issue. Only when one gets into bevel gears and the like does tilting become necessary. And that's where my sine vise comes into play. But my fixtures are small, doing full size work requires full size fixtures. That is a call only you can make. As you gain experience and more complicated work rears its' ugly head, purchasing another fixture comes into its' own. But it does spread the cost out. . .

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I really have to improve my english. Yesterday I bought the rotary table with the dividing head and start planning the construction of a sine table. Ant this morning the first mensage I see, yours, saying rotary table is not good. But in a second read, and in the last paragraph you says yes. So here we go. And I know I´ll enjoy making the sine table.

EDIT: making some research I have found this book that looks very good and interesting for hobby machinist

 

[JohnDB]

Some of the new rotary tables that come with indexing plates have a 90:1 ratio where a regular dividing head has a 40:1 ratio.

A dividing head weighs around 75 Kg....(150 lbs)
A rotary table 12Kg. (26 lbs)

A dividing head can also be set up to work with the x axis on your larger mills for making any angle of gear (worm gears etc) ...it requires some gearing....but it's very possible. (Lots of Yak shaving)


Considering the cost? A rotary table with indexing plates looks a lot more feasible. 150 lbs of dividing head alone on a small mill or a mill with a max table load of 300 lbs is beginning to push limits that aren't exactly a good idea.

My question is "Will it hold steady when clamped?" Can an arbor be mounted to the rotary table? (Especially since a tailstock comes with it?)

 

[Winegrower]

Some different uses I have actually needed to do and what I chose:

Hex 5C collet block: Mill a wrench hex or bolt head on a small shaft. Simple and quick.

Spin Indexer: As above, but with different divisions, like 3, 5, etc. I made a triangular rotary broach tool, and tipped the indexer up slightly for the side relief On the tool. Another time I used the tilt feature, but on the dividing head to cut the rotary broach tool relief, maybe 10 degree down tilt.

Dividing head: I made a tubing bender with rollers and needed to mill a circular groove on a shaft, so I set up a tailstock and used a ball end end mill, cut the groove while rotating the part smoothly with the crank handle.
Also made some lathe change gears of around 50 to 65 teeth.

Rotary table: when I added a 4” riser to my mill, it was just slightly too small in diameter to fit. It’s about 14” in diameter, too big for the lathe, so I set up the 12” rotary table (on a friend’s mill, as mine was not worth reassembling, cutting, disassembling, reassembling, etc), used a couple bars on the rotab to rest the riser on, and took 0.050” or so off the riser ID.

For the most part there was one easiest and most obvious tool for the job, though I suppose technically the rotary table, at least the Bridgeport 12” has the accuracy to move angles down in the seconds range. That wouldn’t be much fun. For example, try milling the riser on your spin indexer…or your 6” rotary table…

Edit: oops, I milled a bit off the OD of the riser to fit the ID of the mill column.

 

[Alberto-sp]

Thanks for your answers.

One question. It said you need to tilt the dividing head or the rotary table to cut bevel gears, but in this video simply put the rotary table in the correct angle and cut nornmaly

 

[Bi11Hudson]

I really have to improve my english. Yesterday I bought the rotary table with the dividing head and start planning the construction of a sine table. Ant this morning the first mensage I see, yours, saying rotary table is not good. But in a second read, and in the last paragraph you says yes. So here we go. And I know I´ll enjoy making the sine table.
EDIT: making some research I have found this book that looks very good and interesting for hobby machinist

Quite honestly, my English is not so good anymore either, after several(6+) strokes. I have several books of the "Workshop" series. There are times I need to relearn things I already know but forgot. A good source, especially when they can "joggle" my memory. My nature for explaining what is taking place is to cover both the good and bad points of a given solution. Then give my opinion of why I use a particular system. With machine work, especially on this board, there are many ways of doing things. What works for me may not work for the next guy. I try to leave that option open whenever possible.

Many rotary tables (certainly not all) have a through center that is reamed for morse taper. I got lucky, the one I bought did so. I took a broken off taper drill and seated it in the taper. That left what was left of the drill sticking up in the center of the table. To that stub I clamped a 3 inch chuck to get the chuck centered. The clamping I used was a simple device I finagled, not something bought or machined. I leave the exact process to the individual.

But with the chuck centered on the table, it was a mechanical process that went as planned. The chuck is not exactly on center, the TIR of the chuck throws it off some. My inexact work also is off center. Even after checking, it is pretty close, a few thou, 1 or 2 tenths of a millimeter.

The chuck came off a Horrible Fright 6 X 12. To remount the chuck on the lathe, a backing plate would be worth the effort, mine is "dedicated" to the table. Most of the time, I have the fraction plate attached so the rotary table becomes an indexer. But the option is open to convert to a rotary table if needed. (rarely)

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