Anybody ever do Compound indexing for an oddball division with an indexer?

[OldMachinist]

Here's a look at my high number index plates.


The plate on top has 143, 133, 123, 113, 110, 103, 93, 83, 73, 69, 64, 57 and 51 holes
Next one has 147, 137, 127, 117, 107, 97, 87, 77, 71, 70, 66, 59 and 52
Next 149, 139,129,119, 109, 99, 89, 79, 67, 61, 53 and 24
Bottom one 141, 131, 121, 111, 101, 91, 81, 73, 68, 63, 54 and 28

 

[xalky]

I don't think I can fit that many holes on my smaller plates unless I go with smaller holes and a smaller pin. Something to think about

 

[OldMachinist]

When I need to use a high number plate I have to mount the dividing head so the plate overhangs the front of the milling machine table.

 

[springer]

I would suggest that you make a index plate with 71, 113 and 127 holes.

i think this sounds like the easiest and most accurate way to do it. if you have to use a smaller plate than what a 113 hole circle diameter would have to be, just make several diameter hole patterns skipping the appropriate number of spaces when drilling. for example, if you made a single plate to do 113 divisions and had 3 different diameters, drill the first circle, say 4" diameter, skipping every 2nd and 3rd hole starting with your first; then drill another circle of holes with a 3.5" diameter skipping every 2nd and 3rd hole, but this time start with the original 2nd hole position...

makes sense in my head, maybe not in these words though...

 

[Smudgemo]

i think this sounds like the easiest and most accurate way to do it. if you have to use a smaller plate than what a 113 hole circle diameter would have to be, just make several diameter hole patterns skipping the appropriate number of spaces when drilling. for example, if you made a single plate to do 113 divisions and had 3 different diameters, drill the first circle, say 4" diameter, skipping every 2nd and 3rd hole starting with your first; then drill another circle of holes with a 3.5" diameter skipping every 2nd and 3rd hole, but this time start with the original 2nd hole position...

makes sense in my head, maybe not in these words though...

I mentally did the palm-forehead thing because this idea actually unfolded in my mind as I read this. Of course - measuring radial degrees is not dependent on distance from the center. It's the same thing as how a bike computer operates. The calculations are dependent on how many times the wheel goes around, not where you place the magnet on the spokes.

This is super-helpful, and so is the link martik777 provided (which I've bookmarked.) I think the only trick using calculations or a DRO would be programming the second and third pitch circle diameters and making sure your first hole is the appropriate number of degrees from the first hole of the outer PCD. Yes?

Best,
Ryan

 

[Bob Korves]

Find somebody with a CNC milling machine to make you the dividing plate(s), or to just drill the holes on blanks that you supply. You may find it cheaper than you might imagine. I have also had some parts laser cut to unbelievable accuracy, including small holes. You might need to make a new pin to index the holes...

 

[benmychree]

I wanted to make a set of gears for my lathe for metric threading as well, so I did as Brown & Sharpe suggests, and did it by differential indexing, a method that has not been discussed in this forum; the drawback to it is that you need a dividing head that is equipped for the hob, it has a gear train in which the dividing head's spindle drives a train of gears that connect to the dividing plate, so that as you crank the indexing crank for indexing, the dividing plate also moves, it rotates to, in effect make the move either longer or shorter than it would normally be. This is shown in their book, "Practical Treatise on Milling and Milling Machines" which is pretty easily found on E Bay and other used book lists, and is a real asset for beginners and should be a part of one's library; it contains tables on indexing by several methods, so that no calculations are necessary.
I made the change gears for the prime numbered gears (the only ones that make this process a necessity), and with these change gears that fit my gear cutting machine, I was able to make the lathe gears, which were larger diameter than the dividing head would accomodate.

 

[xalky]

Here's what I ended up doing. I already had a 113 tooth gear, so I used it to index off of. It's working out great!





Now that I'm making this one, I have a better idea on how to proceed with the next gears that I have to make. Thanks for all the replys guys. This is my first gear that I ever made from scratch. I'm pretty confident that I'll be able to do the next ones without much fretting. )

Marcel

 

[Smithdoor]

Yes I have and it simple to set up on a BS-O dividing head
Need drawing and chart just email me

Dave