View Full Version : Division chart for 90:1 gear ratio

Bob Quale

03-04-2005, 11:20 PM

I have a dividing table with a 90:1 gear ratio, I seem to have miss placed my indexing chart.

Might anyone have access to a chart? or link or the like?

Thanks Bob

CharlesM

03-04-2005, 11:51 PM

Bob,

Try this link:

http://www.atmsite.org/contrib/JSAPP/divide/divhead.html

Just substitute 90 for 40 and everything works the same.

------------------

Charles McGough

Sterlington, LA

mklotz

03-05-2005, 11:59 AM

Bob,

The free program, DIVHEAD, on my page can be easily customized for any

dividing head, regardless of gear ratio or available hole plates.

As an example, when run, it produces an output that looks like:

--------------------

DIVIDING HEAD CALCULATIONS

Number of workpiece divisions [14] ? (you enter desired divisions here)

DH Worm Gear Ratio = 90:1

No rapid indexing plate available

Divisions of Workpiece = 14

Ratio/Divisions = 90/14 = 6.428571429

Turns required = 45/7 = 6 & 3/7

6 full turns of crank

and 9 holes on 21 hole plate

or 21 holes on 49 hole plate

--------------------

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things

http://www.geocities.com/mklotz.geo

John Stevenson

03-05-2005, 12:16 PM

Bob, Here's a text I posted back in 1998 on the same subject.

The spreadsheet is here:-

http://www.metalworking.com/dropbox/_1998_retired_files/division.xls

**********************************************

Just lately there has been a number of enquiries on the Ng about division

tables for Rotary tables / dividing heads with other than the standard

40 : 1 ratio.

The standard series of 3 dividing plates are as follows:-

Plate 1 15,16,16,18,19,20.

Plate 2 21,23,27,29,31,33.

Plate 3 37,39,41,43,47,49.

These three plate are suitable for any ratio as all the division breaks down

into prime numbers or numbers that are divisible by the holes on the plate.

NOTE 1:-

For the readers who are going to make their own plates I would miss out the

first hole [ 15 ] and move the 21 to the first plate to make room on the

second for a 28 hole circle. This is because any numbers need to be divisible

by 15 can be handled by 20,21 or 27 and a 28 is handy for 28 and 56 divisions

which is not obtainable with some of the non standard rotary tables [ see chart ].

I am posting this information in the metalworking drop box at

http://www.metalworking.com

This file will be under division.txt and an Excel spreadsheet called division.xls

will be with it. The table covers 40, 60, 80 and 90:1 ratios.

The first number is complete turns and the fraction is the number of holes on

that circle. So 3 21/33 is 3 complete turns and then 21 holes on a 33 hole circle.

These are now posted in the Public domain and are free to anyone to use as required.

There are NO restrictions on reuse or copying

Feel free to use and enjoy.

John Stevenson

mklotz

03-05-2005, 01:24 PM

John,

The standard hole plates you list are, I believe, the ones normally supplied

with 40:1 dividing heads. They will not provide all the divisions up to fifty

(the nominal standard) with a 90:1 DH, e.g.,

90/28 = 3 & 3/14 = 3 & 6/28

and the 40:1 set you listed doesn't provide a 14 or 28 hole plate.

If the OP is going to make his own plates, the 'minimum hole drilling' set for

all divisions up to fifty and a 90:1 ratio is:

3,5,13,14,16,17,

19,22,23,29,31,37,

41,43,47,49,

For a 40:1 ratio, the 'minimum hole drilling' set is:

4,5,6,17,19,21,

23,27,29,31,33,37,

39,41,43,47,49,

While the set of typical 40:1 plates you list may be the easiest to obtain in

the marketplace, my point is that the right set to self-make is a function of

the DH gear ratio.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things

http://www.geocities.com/mklotz.geo

John Stevenson

03-05-2005, 07:12 PM

Marv.

Bob didn't say he was going to make any plates, only that he had lost his chart.

Whist i accept what you say about choice of numbers I posted that list for the standard Brown and Sharp set because it is the standard.

John S.

Bob Quale

03-05-2005, 09:23 PM

Thanks guys!

I'm going away for a few days, when I get back I can settle in and do some work. I also want to try the software program!

Thanks again Bob

mklotz

03-06-2005, 02:52 PM

I wrote a short program to generate a 'turns and holes' table for:

any gear ratio

any collection of hole plates

any maximum number of divisions

It's called DIVHEADT and it's now part of the DIVHEAD.ZIP archive on my page.

Running it for a 90:1 gear ratio, the standard (i.e., 40:1) hole plates and a

(arbitrarily selected) maximum of fifty divisions produces:

-------------------------

Turns & holes/plate for dividing head with worm gear ratio = 90:1

Available hole plates =

15, 16, 17, 18, 19, 20, 21, 23, 27, 29, 31, 33, 37, 39, 41, 43, 47, 49,

2 => 45 & 0

3 => 30 & 0

4 => 22 & 8/16 or 9/18 or 10/20

5 => 18 & 0

6 => 15 & 0

7 => 12 & 18/21 or 42/49

8 => 11 & 4/16 or 5/20

9 => 10 & 0

10 => 9 & 0

11 => 8 & 6/33

12 => 7 & 8/16 or 9/18 or 10/20

13 => 6 & 36/39

14 => 6 & 9/21 or 21/49

15 => 6 & 0

16 => 5 & 10/16

17 => 5 & 5/17

18 => 5 & 0

19 => 4 & 14/19

20 => 4 & 8/16 or 9/18 or 10/20

21 => 4 & 6/21 or 14/49

22 => 4 & 3/33

23 => 3 & 21/23

24 => 3 & 12/16 or 15/20

25 => 3 & 9/15 or 12/20

26 => 3 & 18/39

27 => 3 & 5/15 or 6/18 or 7/21 or 9/27 or 11/33 or 13/39

28 => a plate with an integer multiple of 14 holes is required

29 => 3 & 3/29

30 => 3 & 0

31 => 2 & 28/31

32 => 2 & 13/16

33 => 2 & 24/33

34 => 2 & 11/17

35 => 2 & 12/21 or 28/49

36 => 2 & 8/16 or 9/18 or 10/20

37 => 2 & 16/37

38 => 2 & 7/19

39 => 2 & 12/39

40 => 2 & 4/16 or 5/20

41 => 2 & 8/41

42 => 2 & 3/21 or 7/49

43 => 2 & 4/43

44 => a plate with an integer multiple of 22 holes is required

45 => 2 & 0

46 => 1 & 22/23

47 => 1 & 43/47

48 => 1 & 14/16

49 => 1 & 41/49

50 => 1 & 12/15 or 16/20

-------------------------

If you have different hole plates, you can either download the program and use

it to generate the appropriate table or supply me with the hole plate data and

I'll run the case for you.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things

http://www.geocities.com/mklotz.geo