Thread: Guessing Game Mk III : What Engineering Marvel is this.?

That dividing head is set up with a gear drive from the table of a small milling machine.
that would be to enable the milling of something like a rifle barrel , or a course multi start thread on a tube or similar.

Originally Posted by cuppabillytea

What does it divide?

Also called an indexing head as it indexes the work to the number of splines ,gear teeth , and if geared to the table feed can be used to do things wich involves calculations I am not capable of

Neither am I apparently. They never let me play with one.

Ok I'm awake again and the coffee is starting to take effect...
I knew that anyone who has been near a milling machine would have identified it as a dividing head without any difficulty, but there is a name for this type of dividing head that no-one has come up with. To keep things moving along I'll give it to Ron as he gave the most correct detail earliest.
This is a 'Universal' dividing head which is a cunningly contrived piece of kit from the pre-electronic era, this one was made in Italy in the 1960s but patented sometime in the 20s I think.


An explanation for the curious (skip this unless you are as curious as I am about how stuff works)

A workpiece (piece of metal being machined, for example a gear blank) is held either in the lathe-type chuck or, with the chuck removed, some other form of workholding, and turned by one of 4 different methods to rotate the workpiece by a specific fraction of a turn, for example if you were cutting a 36-tooth gear you would want to cut one tooth and then turn the piece 1/36th of a turn to cut the next tooth.
You can see just behind the chuck in the first photo there is a plate with a number of slots in it, this is the mechanism for 'Direct Indexing'; the chuck freewheels and the little yellow knob is used to engage a little pawl in one of the slots. The plate has 12 slots on one side or can be flipped over and has 16 slots on the other side. The plate can be swapped out for another with different numbers of slots in it, but obviously there are limitations to how many slots can be made in the plate deep enough to hold the thing still. I think 16 slots is the most on this one. This method is useful for simple things like making 6 flat sides on a bolt head etc but not much more than that.

For a wider range of numbers, the second photo shows the mechanism for 'Indirect indexing', the round plate has several circles of holes and a crank handle that has a pin that engages with the holes; the crank handle turns the chuck via a 40:1 worm gear. The operator makes the crank longer or shorter to select which hole circle is used. For example, a particular number of gear teeth when divided by the 40:1 gear ratio might work out to 17/27ths of a turn of the crank. The operator would move the pin to the 27-hole circle and rotate the crank by 17 holes for each tooth. The yellow fingers that look like clock hands can be set to mark the gap between the 17 holes on the plate, so the crank is rotated from one hand to the next.

The next bit is where it gets really clever; prime numbers cannot be broken down to an exact fraction so even the indirect dividing business won't get the division accurately. A 127-tooth gear for example. The method that is used for this is called 'Compound indexing' and this is where the gear train on the back of the dividing head comes in. The third photo shows the gear arrangement on the back of the gadget. As the crank is rotated, the spindle turns and the shaft coming out the back end of the chuck rotates with it; this then drives a set of gears that rotate the hole plate itself. So, you might use the 27-hole circle and rotate the handle by 17 holes, but the 17th hole will have moved by a certain amount and will be in a different place from where it started. By changing the gears and changing the hole circle that is used, this can rotate the workpiece by any required number of divisions including prime numbers.

I would have showed a video link rather than the above explanation but I have never yet found a video that shows compound indexing; it seems to be a lost art. If I ever finish restoring this thing (lots of bits were missing when i acquired it) I might make a video myself.

The other thing that this device can be used for, as Ron said, is the gear train can be driven off the table of a universal milling machine and can make the workpiece rotate as it goes past the cutter. This is how helical gears are cut (or any other helical feature). This is called 'spiral milling' and requires a universal milling machine, where the table of the machine can be set to a specific angle. The calculations involved are mind-boggling and even reading the tables that have the calculations already made gets my head swimming.

An 'Indexing head' or 'Spin Indexer' is a relatively simple device that can do 'Direct Indexing' only.
A 'Semi-Universal Dividing Head' has the hole plate and crank but not the gear train, so can do Indirect Indexing only.
The device in the photo is a Universal Dividing Head and I reckon it's design is just as clever as the Falkirk Wheel, if less impressive to look at.

In these photos, the universal dividing head is mounted on a metal shaper (another obsolete bit of kit) for cutting internal splines etc.

Ok I am still at work and ratted around a bit and found this.

What is it.

[url=https://

Ron

Spoiler alert!! Clicking on that photo opens up a gallery which includes photos of the box and instructions for it.

I just tried to fix that....I hope
Computers and on site hosting is not my thing.
please don't cheat.

aahhh POD , interesting that you talk about the indexing head being used on a milling machine , then you show it on a shaper.