# Compound indexing for 127



## Smithdoor (Jan 18, 2015)

Has any one else  use compound indexing for making gear like the 127 tooth gear or 157 tooth gear using a BS-0. 
I just working some drawing and have not seen any one even taking about compound indexing, hard to find any data today.

Dave


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## joconnor (Jan 18, 2015)

Hi Dave 
No, but I needed to make a 44 tooth change gear for my mill and the the rotary table and plates I have could not handle that number. I made an arbor that would hold the gear blank and a 44 tooth gear from my South Bend change gear set. I set that up between centers on the rotary table and mounted a spring latch to the mill table to index the arbor. The project worked great. Maybe you could borrow the gears with those numbers and finish your job also. Good luck.


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## Terrywerm (Jan 18, 2015)

Are you referring to compound indexing or differential indexing? There is a big difference.

Compound indexing is an old method using two separate simple indexing movements to create an index movement of a specified amount. It is seldom used anymore because high number plates are easily found or made, allowing the necessary divisions to be created. 

Differential indexing requires an indexing head that also has the change gears with it, known as a Universal Indexing Head. It cannot be done with a rotary table or with a semi-universal indexing head. The gears are set up so that the number plate is also rotated a certain amount as the indexing is done. It is complicated, and is beyond what I can do with my rotary table, thus I have not learned how to do it.


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## Smithdoor (Jan 18, 2015)

Compound indexing Not differential indexing NO GEAR TRAIN

Dave



terrywerm said:


> Are you referring to compound indexing or differential indexing? There is a big difference.
> 
> Compound indexing is an old method using two separate simple indexing movements to create an index movement of a specified amount. It is seldom used anymore because high number plates are easily found or made, allowing the necessary divisions to be created.
> 
> Differential indexing requires an indexing head that also has the change gears with it, known as a Universal Indexing Head. It cannot be done with a rotary table or with a semi-universal indexing head. The gears are set up so that the number plate is also rotated a certain amount as the indexing is done. It is complicated, and is beyond what I can do with my rotary table, thus I have not learned how to do it.


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## Terrywerm (Jan 18, 2015)

Okay.  Compound indexing it is!  

It can be done, but it is a bit complex as well. I have never done it, but can see where it might be useful. Here is a link to where you can find the information you seek:  http://babel.hathitrust.org/cgi/pt?id=mdp.39015002958927;view=1up;seq=79


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## Smithdoor (Jan 18, 2015)

It is easer than trying to set up gears. I had a dividing head back the 70's that was very old that did the dividing not hard to do just have not seen since, I had the chart in a Machinist Hand I used 

Dave



terrywerm said:


> Okay.  Compound indexing it is!
> 
> It can be done, but it is a bit complex as well. I have never done it, but can see where it might be useful. Here is a link to where you can find the information you seek:  http://babel.hathitrust.org/cgi/pt?id=mdp.39015002958927;view=1up;seq=79


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## Reeltor (Jan 18, 2015)

terrywerm said:


> Okay.  Compound indexing it is!
> 
> It can be done, but it is a bit complex as well. I have never done it, but can see where it might be useful. Here is a link to where you can find the information you seek:  http://babel.hathitrust.org/cgi/pt?id=mdp.39015002958927;view=1up;seq=79



That link made me go cross eyed when I tried to read it   :nuts: It's definitely a "bit complex"

I think I'd find a buddy with a cnc to make a new 127 hole plate.  You could make a new plate with a rotary table, it would be tedious, but could be done.

Mike


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## Smithdoor (Jan 18, 2015)

FYI Most CNC indexers only have accuracy of ± 20 sec a dividing head is less than ±0.1 sec on a cheap one. 

Dave



Reeltor said:


> That link made me go cross eyed when I tried to read it   :nuts: It's definitely a "bit complex"
> 
> I think I'd find a buddy with a cnc to make a new 127 hole plate.  You could make a new plate with a rotary table, it would be tedious, but could be done.
> 
> Mike


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## Reeltor (Jan 18, 2015)

Smithdoor said:


> FYI Most CNC indexers only have accuracy of ± 20 sec a dividing head is less than ±0.1 sec on a cheap one.
> 
> Dave



I had no idea :thinking:
thanks


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## umahunter (Jan 18, 2015)

Look up oxtool on YouTube spindexer he does a video series on making indexing plates and mods  for a 127 hole plate on a spin indexer might be worth a look


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## Terrywerm (Jan 19, 2015)

After reviewing the math behind the process, it isn't actually that bad, but most indexing heads and rotary tables use a number of flat head screws to attach the plate to the head, not a stop pin like the book talks about. If you need to turn the plate and the crank together for a certain number of holes, what do you use as a reference for when to stop turning the plate?  I might have to experiment with this a little bit. I don't doubt that it works, I just don't completely understand a couple of the pieces of the puzzle.


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## Smithdoor (Jan 19, 2015)

Yes it use two index circles making the gear
here is part of a chart it when up to 
250
Had the dividing head sold it back in the 70's
The last one I cut was 53 teeth
On the chart it use 43 holes and 49 holes
The 43holes x 40 = 1720 parts
Then add in the 49 hole x 1720 parts = 68,800

Dave




terrywerm said:


> After reviewing the math behind the process, it isn't actually that bad, but most indexing heads and rotary tables use a number of flat head screws to attach the plate to the head, not a stop pin like the book talks about. If you need to turn the plate and the crank together for a certain number of holes, what do you use as a reference for when to stop turning the plate?  I might have to experiment with this a little bit. I don't doubt that it works, I just don't completely understand a couple of the pieces of the puzzle.


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## Reeltor (Jan 19, 2015)

terrywerm said:


> After reviewing the math behind the process, it isn't actually that bad, but most indexing heads and rotary tables use a number of flat head screws to attach the plate to the head, not a stop pin like the book talks about. If you need to turn the plate and the crank together for a certain number of holes, what do you use as a reference for when to stop turning the plate?  I might have to experiment with this a little bit. I don't doubt that it works, I just don't completely understand a couple of the pieces of the puzzle.



Terry,

My universal Van Norman dividing head has a lock for the location of the plate.  By releasing the lock and leaving the index pin in a hole you can turn the entire mechanism.  I don't know if semi-universal heads have this feature or only the universal ones.  I definitely don't understand most of pieces of this puzzle and would need to see a YouTube of someone demonstrating the process.

Mike


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## Ebel440 (Jan 19, 2015)

This won't really help but you don't need an indexer on a Cnc to make a new plate you could just do it as a bolt circle.


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## Terrywerm (Jan 19, 2015)

I did some more research on this and found that the older index heads came with the stop pin feature for compound indexing, but it has largely faded away since the advent of NC and CNC and the ability to layout a hole circle on a mill without an indexer. So, those of you that have some of the older index heads may have this ability. The newer ones do not, but I found a couple of YouTube videos showing what one fellow did to be able to do compound indexing with a modern indexing head.

[video=youtube;exruE7sHXso]https://www.youtube.com/watch?v=exruE7sHXso[/video]

[video=youtube;S1zovk1KODs]https://www.youtube.com/watch?v=S1zovk1KODs[/video]

I also did some digging and found the necessary numbers for 127 divisions in Machinery's Handbook:




Keep in mind that this chart assumes a 40:1 ratio as you would find with an indexing head, and they will not work with a rotary table, which usually uses a 90:1 ratio. Sadly, a chart does not exist for a 90:1 ratio, nor did they supply the math to figure it out, and I have not yet gotten through it myself with any real success, so I suspect I am missing something. 

Hope you all find this useful!


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## Smithdoor (Jan 19, 2015)

That is closer than a cnc is and lower cost
I will take time for 90 tooth worm good news have the work is done 
I have some where the math on this type. 
Just think of doing this without a computer or even a calculator 


Dave



terrywerm said:


> I did some more research on this and found that the older index heads came with the stop pin feature for compound indexing, but it has largely faded away since the advent of NC and CNC and the ability to layout a hole circle on a mill without an indexer. So, those of you that have some of the older index heads may have this ability. The newer ones do not, but I found a couple of YouTube videos showing what one fellow did to be able to do compound indexing with a modern indexing head.
> 
> [video=youtube;exruE7sHXso]https://www.youtube.com/watch?v=exruE7sHXso[/video]
> 
> ...


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## OldMachinist (Jan 19, 2015)

I bought a set of the high number index plates years ago just for doing gears with prime number amounts of teeth like 127. I don't know if you can still get them anywhere.


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## Smithdoor (Jan 28, 2015)

This for 90 tooth worm
Dave


*Divisions*Plate letter*Hole circle* Number of turnsHoles *Second Hole circle **holes* No of times a roundDegrees and minutes per cutMax error on last tooth cut in degreeds            *127*C*39* 613 *49**1 * 925 ° - 31/60 '0.0002037




terrywerm said:


> I did some more research on this and found that the older index heads came with the stop pin feature for compound indexing, but it has largely faded away since the advent of NC and CNC and the ability to layout a hole circle on a mill without an indexer. So, those of you that have some of the older index heads may have this ability. The newer ones do not, but I found a couple of YouTube videos showing what one fellow did to be able to do compound indexing with a modern indexing head.
> 
> [video=youtube;exruE7sHXso]https://www.youtube.com/watch?v=exruE7sHXso[/video]
> 
> ...


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