Would anyone here know what the actual increments/hole numbers are correct
for a 90:1 ratio Rotary Table?

I've read that there are a specific number of holes in plates, depending
upon the RT's turns ratio, but I don't have a good understanding of the
relationships of those numbers.

I know that there are folks posting here that know more about numbers than I
probably ever will, and maybe they could shed some light for someone in the
dark, about how the numbers on plates correspond to RT positions.
Is this sort of information in Machinerys Handbook?

I bought a set of 3 plates and associated hardware, that were said to be for
a 6" RT, but the actual correct make/model of RT was unknown.
PYH is the brand on the label, and the plates' center holes are too small
for the Phase II RT.

So, since the plates may, or may not be the correct number of holes for a
90:1 RT, I thought I'd take a chance on them.

If this plate set isn't the correct one for a 90:1 RT, they may work on a
dividing head or other indexing accessory.
Since the plate center holes and bolt circle don't match the 6" Phase II RT,
they might be adaptable to something else I may get in the future.


PYH TDM1F/6 6" Rotary Table Dividing Plate Set
Made in Taiwan

TDM1F/6
Cat # 51-225-1
Model # 05082466

Stock/SKU label number 87405082466 070 (looks like an Enco or maybe MSC
label)

These plates look about the same as the Enco/MSC import brand SPI 6" RT
plate set.

I don't know who wrote this, probably someone here.
If you recognize your work, please claim it.

I found this to be more help than anything else I ran across in trying
to decipher my indexer.
-------------------------------

Using the indexer

48:1
It's just a simple division using 48 as the main figure and then work in
fractions.

Taking your example of 30 you divide 48 by 30 to get 1 and 18/30th
remaining.

This means that for each 1/30 of a tun you need to take the handle round
one full turn and 18 holes on a 30 hole circle.
As there isn't a 30 hole circle you need to reduce to the lowest
denominator so 18/30 = 9/15 = 3/5.
You have 15, 16, 17, 18 and 19 so out of these you need to move 9 holes
on the 15 circle.
---------------------
40:1
It's just a simple division using 40 as the main figure and then work in
fractions.

Taking your example of 30 you divide 40 by 30 to get 1 and 10/30th
remaining.

This means that for each 1/30 of a tun you need to take the handle round
one full turn and 10 holes on a 30 hole circle.
As there isn't a 30 hole circle you need to reduce to the lowest
denominator so 10/30 = 5/15 = 1/3.
You have 15, 16, 17, 18 and 19 so out of these you need to move 5 holes
on the 15 circle.

That plate you have is only part of a set of plates as with just these 5
numbers you won't be able to do all numbers.
It's also an odd one as there are usually six rows per plate and three
plates per set.
-----------------------------------

Each full turn of the handle will rotate the head 1/40 of a full rev. If
you want it to rotate 1/30 of a rev instead you need to turn the handle
1 and 1/3 turn each time (40 divided by 30 = 1 1/3). Since your plate
has a 15 hole circle one third of 15 equals 5. You would turn the handle
one full turn plus five holes. That location becomes the starting point
for the next turn of the handle which would be another full turn plus
five holes and so on.
---------------------------------
Suppose you wanted to do 72 divisions. You'd need to turn the crank
40/72 of a turn (and do that 72 times). So to get 40/72, or 20/36, or
10/18, or 5/9 of a turn, you'd need some plate with a row of circles
divisible by 9 in it. Using J Tier's plates, you could do it with the
27-hole circle on his #2 plate, for example.


-------------------------
You set up the distance to turn with the two arms that should be in
front of the plate. If you need to move 10 holes, you set to show 11
holes, and lock them together (they now turn as a unit).

That is the hole its in, plus the 10 to move.

When you have moved it, you push the arms along to mark the next move.

Whenyou work with it, always do the same order of operations, such as:
turn crank, lock spindle, set arms ahead.

Otherwise you will get discombobulated as to where you are....

Once you have the hang of the system it will only take you a minute or
so to figure the number of holes to move.

normal set per B&S, L-W etc :
Plate #1 is 15, 16, 17, 18, 19, 20.
plate #2 is 21, 23, 27, 29, 31, 33.
Plate #3 is 37, 39, 41, 43, 47, 49.















Wild_Bill wrote:
Would anyone here know what the actual increments/hole numbers are
correct for a 90:1 ratio Rotary Table?

I've read that there are a specific number of holes in plates, depending
upon the RT's turns ratio, but I don't have a good understanding of the
relationships of those numbers.

I know that there are folks posting here that know more about numbers
than I probably ever will, and maybe they could shed some light for
someone in the dark, about how the numbers on plates correspond to RT
positions.
Is this sort of information in Machinerys Handbook?

I bought a set of 3 plates and associated hardware, that were said to be
for a 6" RT, but the actual correct make/model of RT was unknown.
PYH is the brand on the label, and the plates' center holes are too
small for the Phase II RT.

So, since the plates may, or may not be the correct number of holes for
a 90:1 RT, I thought I'd take a chance on them.

If this plate set isn't the correct one for a 90:1 RT, they may work on
a dividing head or other indexing accessory.
Since the plate center holes and bolt circle don't match the 6" Phase II
RT, they might be adaptable to something else I may get in the future.


PYH TDM1F/6 6" Rotary Table Dividing Plate Set
Made in Taiwan

TDM1F/6
Cat # 51-225-1
Model # 05082466

Stock/SKU label number 87405082466 070 (looks like an Enco or maybe
MSC label)

These plates look about the same as the Enco/MSC import brand SPI 6" RT
plate set.

Thanks for posting this info, RB. Some of the authors used to frequent this
newsgroup, but not anymore.

My experience with RCM leads me to believe it's because of all the
non-metalworking bull**** and worthless gossip getting posted here day after
day.

Here is the origin:

http://bbs.homeshopmachinist.net/arc...hp/t-7790.html

I know that at least a couple of these guys are a wealth of practical
information.

John Stevenson and Marv Klotz, just to mention a couple of them. Looking up
articles or websites of these guys will reveal lots of great info.
I believe John could write volumes about any number of ways to fabricate
almost any part, and Marv has a site with free software for solving lots of
metalworking problems/puzzles.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"RB" wrote in message
...
I don't know who wrote this, probably someone here.
If you recognize your work, please claim it.

I found this to be more help than anything else I ran across in trying to
decipher my indexer.
-------------------------------

Using the indexer

48:1
It's just a simple division using 48 as the main figure and then work in
fractions.

Taking your example of 30 you divide 48 by 30 to get 1 and 18/30th
remaining.

This means that for each 1/30 of a tun you need to take the handle round
one full turn and 18 holes on a 30 hole circle.
As there isn't a 30 hole circle you need to reduce to the lowest
denominator so 18/30 = 9/15 = 3/5.
You have 15, 16, 17, 18 and 19 so out of these you need to move 9 holes on
the 15 circle.
---------------------
40:1
It's just a simple division using 40 as the main figure and then work in
fractions.

Taking your example of 30 you divide 40 by 30 to get 1 and 10/30th
remaining.

This means that for each 1/30 of a tun you need to take the handle round
one full turn and 10 holes on a 30 hole circle.
As there isn't a 30 hole circle you need to reduce to the lowest
denominator so 10/30 = 5/15 = 1/3.
You have 15, 16, 17, 18 and 19 so out of these you need to move 5 holes on
the 15 circle.

That plate you have is only part of a set of plates as with just these 5
numbers you won't be able to do all numbers.
It's also an odd one as there are usually six rows per plate and three
plates per set.
-----------------------------------

Each full turn of the handle will rotate the head 1/40 of a full rev. If
you want it to rotate 1/30 of a rev instead you need to turn the handle 1
and 1/3 turn each time (40 divided by 30 = 1 1/3). Since your plate has a
15 hole circle one third of 15 equals 5. You would turn the handle one
full turn plus five holes. That location becomes the starting point for
the next turn of the handle which would be another full turn plus five
holes and so on.
---------------------------------
Suppose you wanted to do 72 divisions. You'd need to turn the crank 40/72
of a turn (and do that 72 times). So to get 40/72, or 20/36, or 10/18, or
5/9 of a turn, you'd need some plate with a row of circles divisible by 9
in it. Using J Tier's plates, you could do it with the 27-hole circle on
his #2 plate, for example.


-------------------------
You set up the distance to turn with the two arms that should be in front
of the plate. If you need to move 10 holes, you set to show 11 holes, and
lock them together (they now turn as a unit).

That is the hole its in, plus the 10 to move.

When you have moved it, you push the arms along to mark the next move.

Whenyou work with it, always do the same order of operations, such as:
turn crank, lock spindle, set arms ahead.

Otherwise you will get discombobulated as to where you are....

Once you have the hang of the system it will only take you a minute or so
to figure the number of holes to move.

normal set per B&S, L-W etc :
Plate #1 is 15, 16, 17, 18, 19, 20.
plate #2 is 21, 23, 27, 29, 31, 33.
Plate #3 is 37, 39, 41, 43, 47, 49.















Wild_Bill wrote:
Would anyone here know what the actual increments/hole numbers are
correct for a 90:1 ratio Rotary Table?

I've read that there are a specific number of holes in plates, depending
upon the RT's turns ratio, but I don't have a good understanding of the
relationships of those numbers.

I know that there are folks posting here that know more about numbers
than I probably ever will, and maybe they could shed some light for
someone in the dark, about how the numbers on plates correspond to RT
positions.
Is this sort of information in Machinerys Handbook?

I bought a set of 3 plates and associated hardware, that were said to be
for a 6" RT, but the actual correct make/model of RT was unknown.
PYH is the brand on the label, and the plates' center holes are too small
for the Phase II RT.

So, since the plates may, or may not be the correct number of holes for a
90:1 RT, I thought I'd take a chance on them.

If this plate set isn't the correct one for a 90:1 RT, they may work on a
dividing head or other indexing accessory.
Since the plate center holes and bolt circle don't match the 6" Phase II
RT, they might be adaptable to something else I may get in the future.


PYH TDM1F/6 6" Rotary Table Dividing Plate Set
Made in Taiwan

TDM1F/6
Cat # 51-225-1
Model # 05082466

Stock/SKU label number 87405082466 070 (looks like an Enco or maybe
MSC label)

These plates look about the same as the Enco/MSC import brand SPI 6" RT
plate set.

On 2009-01-06, Wild_Bill wrote:
Would anyone here know what the actual increments/hole numbers are correct
for a 90:1 ratio Rotary Table?

I've read that there are a specific number of holes in plates, depending
upon the RT's turns ratio, but I don't have a good understanding of the
relationships of those numbers.

Do you have a copy of _Machinery's Handbook_? There are tables
in there describing the circles needed to get each number of divisions
and such.

Most are for the 40:1 B&S dividing/indexing heads, which have
three plates of six circles each.

However there is also a table for the Hardinge dividing heads
which have a 20:1 ratio (IIRC), and need a lot more plates.

Also, there are formulas to allow you to calculate what number
of holes is needed for each number of index points, which might be where
you need to start, since you are using a rotary table instead of a
dividing/index head.

I know that there are folks posting here that know more about numbers than I
probably ever will, and maybe they could shed some light for someone in the
dark, about how the numbers on plates correspond to RT positions.
Is this sort of information in Machinerys Handbook?

Multi-page tables, including differential indexing (which
requires stacks of gears rotating the index plate as the crank is turned
to get some of the figures which don't work out well for a normal 40:1
ratio.

The 90:1 ratio is not chosen for good division ratios, but
rather to get an even number of degrees on one turn of the crank (4 for
a 90:1 ratio). The 40:1 comes out at 9 degrees on the dial which is
more awkward.

I bought a set of 3 plates and associated hardware, that were said to be for
a 6" RT, but the actual correct make/model of RT was unknown.
PYH is the brand on the label, and the plates' center holes are too small
for the Phase II RT.

So, since the plates may, or may not be the correct number of holes for a
90:1 RT, I thought I'd take a chance on them.

Well ... they *will* work on 90:1 for some numbers of holes.
Let's see -- 4 degrees per turn of a 90:1 crank, and divide that by 37
holes (one of the choices on the 40:1 plates) and you get 0.2432
degrees, or 0 degrees 14' 36"

If this plate set isn't the correct one for a 90:1 RT, they may work on a
dividing head or other indexing accessory.
Since the plate center holes and bolt circle don't match the 6" Phase II RT,
they might be adaptable to something else I may get in the future.

Right -- or adaptable to the RT, with a collar to ensure
centering and various other bits. The main thing is to get the formulas
out of _Machinery's Handbook_ so you can calculate how many holes will
be needed -- and remember that any integer multiple of the number of
holes needed can be used -- for example if you only need four holes, you
can skip over 9 holes per on a 36 hole circle, or 10 holes on a 40 hole
circle and so on.


PYH TDM1F/6 6" Rotary Table Dividing Plate Set
Made in Taiwan

TDM1F/6
Cat # 51-225-1
Model # 05082466

Stock/SKU label number 87405082466 070 (looks like an Enco or maybe MSC
label)

These plates look about the same as the Enco/MSC import brand SPI 6" RT
plate set.

How different do you expect a plate set to look (other than
overall size)?

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Wild_Bill wrote:
Thanks for posting this info, RB. Some of the authors used to frequent
this newsgroup, but not anymore.

My experience with RCM leads me to believe it's because of all the
non-metalworking bull**** and worthless gossip getting posted here day
after day.

Here is the origin:

http://bbs.homeshopmachinist.net/arc...hp/t-7790.html

I know that at least a couple of these guys are a wealth of practical
information.

John Stevenson and Marv Klotz, just to mention a couple of them. Looking
up articles or websites of these guys will reveal lots of great info.
I believe John could write volumes about any number of ways to fabricate
almost any part, and Marv has a site with free software for solving lots
of metalworking problems/puzzles.

Bill, thanks for adding that attribution. I know of Marv and his site,
need to revisit since my interests have changed since the last visit.
I don't know that I've seen John's site, but I'll look for it.

"Wild_Bill" wrote:

Thanks for posting this info, RB. Some of the authors used to frequent this
newsgroup, but not anymore.

My experience with RCM leads me to believe it's because of all the
non-metalworking bull**** and worthless gossip getting posted here day after
day.

Here is the origin:

http://bbs.homeshopmachinist.net/arc...hp/t-7790.html

I know that at least a couple of these guys are a wealth of practical
information.

John Stevenson and Marv Klotz, just to mention a couple of them. Looking up
articles or websites of these guys will reveal lots of great info.
I believe John could write volumes about any number of ways to fabricate
almost any part, and Marv has a site with free software for solving lots of
metalworking problems/puzzles.

Marv is still monitoring from time to time. He has piped up when I question or made a
comment refering to him.

Not only does Marv have a nice site, he shares his source code.

I always pay attention to John Stevenson except when locked in verbal combat with Evan.

Wes

Thanks for the additional info DoN. I thought that I'd remembered from
earlier rotary table and dividing head discussions, that there were details
in Machinerys Handbook. I've known that I should get one (one of the great
procrastinators, ya know).

I haven't used indexing plate sets, and the only differences that I've seen
is that generally, there may be 2 or 3 plates in a set. I wasn't aware that
there were a specific number of sets of holes (six per plate), or other
standards, but it stands to reason since these aspects have been figured out
before the manufacturing of plate sets began.
I'd read that some plates have different divisions on two sides of each
plate.
Other differences would be center hole diameter and number of hole for
attaching the plates (3 or 4).

For simple indexing, I have a 5C spin index, and that's about the extent of
my indexing experience.

What I think would be best for me is a digital readout that displays x
number of degrees with a resolution of .001, to be sure about the settings
before cutting.

The minutes and seconds method is beyond my comprehension (or desire to),
and it seems to be an unneccesarily more complex way of thinking about
locations in a single rotation. It may work well for others that have
experience with it, but it just seems to be way more complex than other
positioning methods.

The feeble grey matter doesn't function at the levels of a CNC computer. I
would see fitting a DRO to a indexing device to be an easier solution.
Encoders have become smaller, and digital counters aren't too complex to set
up, so having a display with 0-360.001 or 0-3600.00 seems to be a good way
to achieve positioning locations.

For any method of indexing, I wouldn't have a clue as to how much error
might be introduced by accumulation, at say, the last tooth on a 100T (or
113T) gear blank, for example. Hopefully, one could make other adjustments
in a design so a 113T gear wouldn't be required.
For cutting 6 splines on a shaft, I would assume this would be a fairly
simple task with indexing plates.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"DoN. Nichols" wrote in message
...
On 2009-01-06, Wild_Bill wrote:
Would anyone here know what the actual increments/hole numbers are
correct
for a 90:1 ratio Rotary Table?


Do you have a copy of _Machinery's Handbook_? There are tables
in there describing the circles needed to get each number of divisions
and such.

Most are for the 40:1 B&S dividing/indexing heads, which have
three plates of six circles each.

However there is also a table for the Hardinge dividing heads
which have a 20:1 ratio (IIRC), and need a lot more plates.

Also, there are formulas to allow you to calculate what number
of holes is needed for each number of index points, which might be where
you need to start, since you are using a rotary table instead of a
dividing/index head.


Multi-page tables, including differential indexing (which
requires stacks of gears rotating the index plate as the crank is turned
to get some of the figures which don't work out well for a normal 40:1
ratio.

The 90:1 ratio is not chosen for good division ratios, but
rather to get an even number of degrees on one turn of the crank (4 for
a 90:1 ratio). The 40:1 comes out at 9 degrees on the dial which is
more awkward.


Well ... they *will* work on 90:1 for some numbers of holes.
Let's see -- 4 degrees per turn of a 90:1 crank, and divide that by 37
holes (one of the choices on the 40:1 plates) and you get 0.2432
degrees, or 0 degrees 14' 36"


Right -- or adaptable to the RT, with a collar to ensure
centering and various other bits. The main thing is to get the formulas
out of _Machinery's Handbook_ so you can calculate how many holes will
be needed -- and remember that any integer multiple of the number of
holes needed can be used -- for example if you only need four holes, you
can skip over 9 holes per on a 36 hole circle, or 10 holes on a 40 hole
circle and so on.

How different do you expect a plate set to look (other than
overall size)?

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Wed, 7 Jan 2009 17:53:19 -0500, "Wild_Bill"
wrote:

there were details
in Machinerys Handbook. I've known that I should get one (one of the great
procrastinators, ya know).
------------
For hobby use the older editions may prove more helpful.
http://www.alibris.com/

For just the information on indexing see
http://lindsaybks.com/bks/mmindx/index.html
There are some other reprints available that are shown in their
catalog but not on their web page.
Indexing 869 $4.00

If you are exceptional ambitious you can even build your own
dividing head/indexer and/or custom plates from the Gingery
plans.
see bottom of http://lindsaybks.com/dgjp/djgbk/series/index.html

Several of the other Lindsay books also have information on
dividing/indexing and gear manufacture.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

On 2009-01-07, Wild_Bill wrote:
Thanks for the additional info DoN. I thought that I'd remembered from
earlier rotary table and dividing head discussions, that there were details
in Machinerys Handbook. I've known that I should get one (one of the great
procrastinators, ya know).

Grab one at a used bookstore -- or an eBay auction. I would say
that for a non-CNC hobby metalworker, anything from about the 15th
edition on would be quite useful -- though if you want specs of standard
collets, you need the 25th edition or later.

I haven't used indexing plate sets, and the only differences that I've seen
is that generally, there may be 2 or 3 plates in a set. I wasn't aware that
there were a specific number of sets of holes (six per plate),

The specific number of circles per plate is six for the B&S
ones, which come with a set of three plates.

You could have more circles (thus fewer plates) with larger
diameter plates and longer indexing arms.

or other
standards, but it stands to reason since these aspects have been figured out
before the manufacturing of plate sets began.
I'd read that some plates have different divisions on two sides of each
plate.

Thicker plates (to keep the holes from going through and
interfering with each other) and fewer plates needed for the a given
division ratio of the gears.

Other differences would be center hole diameter and number of hole for
attaching the plates (3 or 4).

And whether the holes are countersunk or counterbored. IIRC,
the B&S ones are counterbored, and fairly thick plates which can be
mounted from either side, though you have the same number of holes on
each side.

For simple indexing, I have a 5C spin index, and that's about the extent of
my indexing experience.

A resolution of one degree on those.

What I think would be best for me is a digital readout that displays x
number of degrees with a resolution of .001, to be sure about the settings
before cutting.

Hmm ... 0.001 degrees is 0 degrees 0' 4" which is probably fine
enough for most things.

The minutes and seconds method is beyond my comprehension (or desire to),
and it seems to be an unneccesarily more complex way of thinking about
locations in a single rotation.

It comes from an earlier culture -- the Egyptian, IIRC -- who
liked to base things on 60s -- and it is what our timekeeping comes from
as well.

But it is not that much more difficult than miles, feet, and
inches, or feet, inches, and fractions -- you are just accustomed to
those.

It may work well for others that have
experience with it, but it just seems to be way more complex than other
positioning methods.

However -- if you get a plan which specifies angles in degrees
minutes and seconds, you'll have to deal with it -- at least long enough
to convert it to decimal degrees. (This is where having an old HP 15C
scientific calculator is nice. It includes keys which will convert
either way -- useful for both time and angles.

The feeble grey matter doesn't function at the levels of a CNC computer.

Actually -- a CNC computer is running at a rather dumb level, so
you are probably better than it. It is just more patient at following
precise directions -- which *you* need to give it -- or a program (or
set of programs) on another computer needs to give it.

I
would see fitting a DRO to a indexing device to be an easier solution.
Encoders have become smaller, and digital counters aren't too complex to set
up, so having a display with 0-360.001 or 0-3600.00 seems to be a good way
to achieve positioning locations.

Hmm ... if it is reading the absolute angle in binary, it would
need at least 19 circles of encoding bars, which would make it fairly
large. For reading it incrementally, you would need a single circle
with 360000 bars, plus a single index indicator hole.

You *could* read the angle the crank turns, and count full
turns, but then you would not get a true reading to 0.001 degree out of
360 degrees. The backlash in the worm, and perhaps eccentricity of the
wheel could introduce a lot more error than that. You really want to
measure the angle at the rim of the table, which means that you would
need a scale wrapped around the rim of the table, and given the
resolution of the typical digital calipers (ignoring the 0.0005" step),
you would need a scale 360" long, or a table with a diameter of 114.59
inches, or 9.5493 feet.

For any method of indexing, I wouldn't have a clue as to how much error
might be introduced by accumulation, at say, the last tooth on a 100T (or
113T) gear blank, for example. Hopefully, one could make other adjustments
in a design so a 113T gear wouldn't be required.

That's what the worm gear and the plates are used for. You look
up in the table the number of teeth (divisions), it will suggest one or
more circles (so you may not have to change discs), how many full turns
plus how many holes to move from one to the next, and the angle to set
the arms to so they will guide you to the right hole. Then you shift
the pair of arms so the starting arm comes to rest against the pin were
the finish arm was at the end of your previous cranking.

When you complete your circle, you are *right* on by the nature
of the worm gear.

Note that you did not have to know either degrees and decimal
fraction, or the degrees, minutes and seconds. All you needed to know
was the number of teeth or divisions you needed to make, and where to
find the lookup table (either in Machinery's handbook, or on a metal
plate which came with your dividing head when new.

However -- cranking in degrees and decimal fraction or degrees
and minutes (I don't think that seconds are marked on the dial on a
rotary table) does lead to accumulated error by the time you finish your
circle.

Be warned that some numbers of divisions are very difficult on a
dividing head (unless you go to a differential head perhaps). 127 teeth
is an example of that which is important to lathe users.

For cutting 6 splines on a shaft, I would assume this would be a fairly
simple task with indexing plates.

Very much so. With a 90:1 ratio, you use a single hole on any
circle of the plate, and crank the table through 15 turns of the crank
and end up back at the same hole.

With my 40:1 B&S index head, it is 6-2/3 turns, so you would
need a circle with a integer multiple of three holes -- such as 18, or
36 to mention a couple of common ones. You would also need to set the
arms to stop you at the proper number of holes past the starting point.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

For a 90:1 ratio, you index 90 increments of the number of divisions you
want. For example, if you need 12 divisions, you index 90/12 that can be
halved to 45/6 and further reduced to 15/2. So, you need 7-1/2 turns of the
handle to make 12 equal divisions on a 90:1 rotary table. So, in this case
you can use any even number of holes in the dividing plate, 7 turns plus
1/2, 2/4, 3/6, ...

Another example, if you need 25 divisions, you'll need 90 increments of 25
90/25 reduces to (2*3*3*5)/(5*5) 18/5, that's 3-3/5 so you could use 3/5,
6/10, 9/15... So if you have a plate with 15 holes, you could use 3 turns
plus 9 holes.

Another example, if you need 100 divisions, you would have to turn 90/100
that reduces to 9/10, you could increment 9/10 or 18/20 ... depending on the
plates you have.

The bottom line is that if the plates you have fit your table then you can
reduce the ratio to minimum and raise it in minimum increments to see which
plate you need to use. If you need a number of holes that is a prime
number, you'll need that number of holes in the plate if it's a 40:1 or 90:1
ratio.

RogerN



"Wild_Bill" wrote in message
...
Would anyone here know what the actual increments/hole numbers are correct
for a 90:1 ratio Rotary Table?
snip

Thanks for including those examples Roger.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"RogerN" wrote in message
m...
For a 90:1 ratio, you index 90 increments of the number of divisions you
want. For example, if you need 12 divisions, you index 90/12 that can be
halved to 45/6 and further reduced to 15/2. So, you need 7-1/2 turns of
the handle to make 12 equal divisions on a 90:1 rotary table. So, in this
case you can use any even number of holes in the dividing plate, 7 turns
plus 1/2, 2/4, 3/6, ...

Another example, if you need 25 divisions, you'll need 90 increments of 25
90/25 reduces to (2*3*3*5)/(5*5) 18/5, that's 3-3/5 so you could use 3/5,
6/10, 9/15... So if you have a plate with 15 holes, you could use 3 turns
plus 9 holes.

Another example, if you need 100 divisions, you would have to turn 90/100
that reduces to 9/10, you could increment 9/10 or 18/20 ... depending on
the plates you have.

The bottom line is that if the plates you have fit your table then you can
reduce the ratio to minimum and raise it in minimum increments to see
which plate you need to use. If you need a number of holes that is a
prime number, you'll need that number of holes in the plate if it's a 40:1
or 90:1 ratio.

RogerN



"Wild_Bill" wrote in message
...
Would anyone here know what the actual increments/hole numbers are
correct for a 90:1 ratio Rotary Table?
snip

On Jan 9, 8:50*am, "RogerN" wrote:
For a 90:1 ratio, you index 90 increments of the number of divisions you
want. For example, if you need 12 divisions, you index 90/12 ...

I just made up the index tables for 40 and 90 using OpenOffice Calc.
Rather than posting it I'll describe how so you can make your own for
whatever number of divisions you need, or a different type of indexer.
I leave space at the top for headers, comments and the file name.
Don't type the quotes, only what's between them.

Enter headers "N" in cell A3, "40/N" in B3, "90/N" in C3.
Enter "1" in cell A4, "=1+A4" in A5. It should show 2.
Select and copy A5, then select a block from A6 downward. Paste.
The pasted cells should read
2
3
4
5
6 etc
Continue until you have all the sequential numbers you want in column
A. I went to 100.

Now type in the indexing formulas.
Enter "=40/A4" in B4, "=90/A4" in C4.
Select and copy B4 & C4, paste them in below as far as the end of the
numbers in A.
Select columns B and C and format their cells as Fraction. Change the
format code to # ??/??

You should see:
N 40/N 90/N
1 40 90
2 20 45
3 13 1/3 30
4 10 22 1/2

Columns B and C give the full and partial handle turns to divide by N
in column A. For instance, 3 on a 40:1 indexer requites 13 full turns
plus 1/3rd more, like 5 spaces on the 15 circle. The denominator of
the fractions is always the number of divisions N or a factor of it.
It may help to figure out and type in the factors of N in column D,
such as 63 = 3 X 3 X 7. Then you can see that 3, 7, 9 and 21 are all
factors of 63, and match them to the available hole circles. The
sector gear I recently made used 20/34 for 68 teeth.

You could create a short one-page table and then enter whatever value
of N you need as text to see which index circle(s) will work for it.

Jim Wilkins