How many turns how many holes ?

[H. K. Barrows]

I have a 7.00 dia. that needs 222 teeth 32 d/p I"m lost I would like to learn how to do the calculations What hole plate and turns and holes Best Regards Red redcraftm

 

[Jasonb]

Would help to know what the worm ratio is on your dividing head or rotary table and what hole patterns you have available on the wheels.

15 holes on a 37 hole plate should would work if you have 90:1

 

[kvom]

Jason's math is (15/37)/90 = 1/222. This works exact since 37 is a factor of 222.

 

[SmithDoor]

What type of dividing head do you have or number of teeth on rotary table?.

Dave

I have a 7.00 dia. that needs 222 teeth 32 d/p I"m lost I would like to learn how to do the calculations What hole plate and turns and holes Best Regards Red redcraftm

 

[H. K. Barrows]

Hello I have B/O 40:1 index tool with all plates

 

[SmithDoor]

Hello I have B/O 40:1 index tool with all plates

It simple to calculate
37 hole plate X 40 tooth worm gear = 1,480
Next 1,480 ÷ 222 = 6.66666

It does not work.
Do have a rotary table?

Dave

 

[SmithDoor]

Here a chart for compound indexing it will do all the 250

 

[per_e]

Here is a simple excel sheet for a 40:1 dividing head. Put in the number of teeth in the yellow cell, and the dark green cells shows the result.

 

[methuselah1]

Your best plan, I think, would be to investigate the possibility of rigging up the detent and plates from your dividing head (40:1) onto your rotary table which is likely to be 90:1 (or 180:1) and get the job done that way. The spread sheet that someone has kindly provided is for compound dividing, which took a genius to come up with, but uses two detents, and two rows of holes simultaneously. The idea is that one plate and detent still control the worm and wheel, the other detent is used to reposition the plate itself for each division.

If you have a banjo and changewheels, your easiest option is to set up a geartrain, 4/9, and differentially index the job.

Or find someone local to hob or shape your gear. It may not cost as much as you think.

Or make a fresh dividing plate blank, and have a CNC put in the 111 circle of holes. 127 is another useful row, as well as any other high primes you can't get right now.

-Andrew

 

[awake]

The math is as follows (on edit: the forum software is messing up the formatting ...):

worm ratio
-----------------------
desired # of teeth

=

holes to move
----------------------------
holes in index circle

Let me re-write that as follows to make it easier to refer to:

W / N = H / C, where W = worm ratio, N = desired # of teeth, H = holes to move, and C = index circle used.

The key to being able to index without using compound gearing is that you can choose C such that (factors of C) * (factors of W) = N. To say this another way, you need to have all of the factors to get to N available to you either in the worm ratio (W) or in the index circle.

Let's factor 222: 222 = 2 * 3 * 37.

Thus, we need to have these factors available in either W or C. If we have an index circle with 37 holes, that takes care of that factor. A worm ratio of 40 has the factor of 2 that we need ... but not the factor of 3. By contrast, worm ratios of either 60 or 90 have both the 2 and the 3 available. The only way to achieve the indexing with a worm ratio of 40 is to put the factor of 3 into C - in other words, to have C = 37 * 3 = 111.

Thus, you could achieve this indexing using a 37-hole circle only if your worm ratio is either 60 or 90, OR if you have a 111-hole circle. (I am assuming the common worm ratios of 40, 60, or 90, and no compound indexing.)

 

[SmithDoor]

If you had rotary table you make a 111 indexing plate.
This why they used compound indexing. I seen used by Cincinnati milling machines into the 1960's
Cincinnati used a 100 tooth plate with the standard plate.
If used on a BS 0 a 49 hole plate with 100 plate would give you 196,000 spaces more than most cnc indexer.

Dave

The math is as follows (on edit: the forum software is messing up the formatting ...):

worm ratio
-----------------------
desired # of teeth

=

holes to move
----------------------------
holes in index circle

Let me re-write that as follows to make it easier to refer to:

W / N = H / C, where W = worm ratio, N = desired # of teeth, H = holes to move, and C = index circle used.

The key to being able to index without using compound gearing is that you can choose C such that (factors of C) * (factors of W) = N. To say this another way, you need to have all of the factors to get to N available to you either in the worm ratio (W) or in the index circle.

Let's factor 222: 222 = 2 * 3 * 37.

Thus, we need to have these factors available in either W or C. If we have an index circle with 37 holes, that takes care of that factor. A worm ratio of 40 has the factor of 2 that we need ... but not the factor of 3. By contrast, worm ratios of either 60 or 90 have both the 2 and the 3 available. The only way to achieve the indexing with a worm ratio of 40 is to put the factor of 3 into C - in other words, to have C = 37 * 3 = 111.

Thus, you could achieve this indexing using a 37-hole circle only if your worm ratio is either 60 or 90, OR if you have a 111-hole circle. (I am assuming the common worm ratios of 40, 60, or 90, and no compound indexing.)

 

[H. K. Barrows]

Thanks for so much help. With a I cheated on the computer I made 222 divided print out then mount it disk ali put direct index cut the segment of teeth needed for what I needed work thank for all you'r help. In the future I will set the mill and the dividing head up lock door and just go one seep at time do it as all of have taught me Best Regards Red