# Need a manual for a 72:1 rotary table.



## Boot (Feb 3, 2012)

I bought a Grizzly 4" rotary table with index plates yesterday. I doesn't come with a manual or instructions on how to set up the index plates or use the table. My mistake for not asking. But I need a chart or something as such to set up the index plates for cutting different divisions on it. Does anyone out there have something I could use for this 72:1 ratio table? My MHB has for a 40:1 not a 72:1 as far as I can see. I would like to be able to download and print something to take out to my shop . I don't know how to set the 2 bars on the face of the plates or how to unlock and lock the gearing with the little lever behind the dial. Little Machine shop shows most of these settings ,but nothing that I can see on the indexing plates. I fully realize that one rotation of the handle moves the table 5°. The vernier also moves behind the dial ,why is this? One confused Boot thanks you.


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## mklotz (Feb 3, 2012)

Go to my page and download the DIVHEAD archive. In it you will find a program named DIVHEADT which was explicitly designed to make turns and holes tables for rotary tables with unusual gear ratios or hole plates.

Put the data for your table into the associated data file and run the program. It's output will be a file which you can then print and carry to the shop for reference.

If you encounter problems, feel free to contact me via PM or email.


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## prof65 (Feb 3, 2012)

Hi Boot

Some good info in this manual:

www.littlemachineshop.com/instructions/UsingARotaryTable.pdf

Roberto


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## Boot (Feb 3, 2012)

Thanks Roberto . I did download this . Thanks for your help. It will definately help in understanding it's operation. 
and Thanks to Marv. also even though I can't download Divhead.


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## rhankey (Feb 3, 2012)

Hi Boot,

Try this attached spreadsheet, as I coincidentally was trying to figure out division options for a dividing head I am considering.

Do the following one time setup:

In cell D4, tell it how many handle crank revolutions to produce 360 deg (in your case 72, but for most it will be 40, or 4 for Hardinge)
In rows 7 through 29, list out all the plate hole counts you have (Circles). If you have more plate circles than I have provided room for, simply copy an existing row so that you get the formatting and formulas.

In cells G5 to NA29, the table lists how many hole stops it takes for each of your circles to achieve any number of divisions from 2 through 360. Those cells highlighted in GREEN are valid intersections. those not in green are invalid, as they require you to step 1.23 holes (as an example). This table is handy should you want to print it out and tape it to the wall.

Alternatively, you can type the number of divisions you desire in cell D2, and it will list the results in column E.

Enjoy.
Robin


View attachment Dividing Head - Circle Hole Calculator.xls


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## mklotz (Feb 3, 2012)

Boot was overwhelmed by the prospect of running a DOS program so I offered to run the case for him.

As you can see from the output, the hole plates are chosen to provide all the divisions through fifty; beyond that some are possible but many require higher number hole plates which the program specifies.

Alternatively, those higher number divisions can be done by using my ROTARY program.


Turns & holes/plate for dividing head with worm gear ratio = 72:1

Available hole plates =
16, 17, 19, 20, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 

2 => 36 & 0 
3 => 24 & 0 
4 => 18 & 0 
5 => 14 & 8/20 or 10/25 or 14/35 or 18/45
6 => 12 & 0 
7 => 10 & 10/35 or 14/49
8 => 9 & 0 
9 => 8 & 0 
10 => 7 & 4/20 or 5/25 or 7/35 or 9/45
11 => 6 & 18/33
12 => 6 & 0 
13 => 5 & 21/39
14 => 5 & 5/35 or 7/49
15 => 4 & 16/20 or 20/25 or 28/35 or 36/45
16 => 4 & 8/16 or 10/20
17 => 4 & 4/17
18 => 4 & 0 
19 => 3 & 15/19
20 => 3 & 12/20 or 15/25 or 21/35 or 27/45
21 => 3 & 15/35 or 21/49
22 => 3 & 9/33
23 => 3 & 3/23
24 => 3 & 0 
25 => 2 & 22/25
26 => 2 & 30/39
27 => 2 & 18/27 or 22/33 or 26/39 or 30/45
28 => 2 & 20/35 or 28/49
29 => 2 & 14/29
30 => 2 & 8/20 or 10/25 or 14/35 or 18/45
31 => 2 & 10/31
32 => 2 & 4/16 or 5/20
33 => 2 & 6/33
34 => 2 & 2/17
35 => 2 & 2/35
36 => 2 & 0 
37 => 1 & 35/37
38 => 1 & 17/19
39 => 1 & 33/39
40 => 1 & 16/20 or 20/25 or 28/35 or 36/45
41 => 1 & 31/41
42 => 1 & 25/35 or 35/49
43 => 1 & 29/43
44 => 1 & 21/33
45 => 1 & 12/20 or 15/25 or 21/35 or 27/45
46 => 1 & 13/23
47 => 1 & 25/47
48 => 1 & 8/16 or 10/20
49 => 1 & 23/49
50 => 1 & 11/25
51 => 1 & 7/17
52 => 1 & 15/39
53 => a plate with an integer multiple of 53 holes is required
54 => 1 & 9/27 or 11/33 or 13/39 or 15/45
55 => a plate with an integer multiple of 55 holes is required
56 => 1 & 10/35 or 14/49
57 => 1 & 5/19
58 => 1 & 7/29
59 => a plate with an integer multiple of 59 holes is required
60 => 1 & 4/20 or 5/25 or 7/35 or 9/45
61 => a plate with an integer multiple of 61 holes is required
62 => 1 & 5/31
63 => 1 & 5/35 or 7/49
64 => 1 & 2/16
65 => a plate with an integer multiple of 65 holes is required
66 => 1 & 3/33
67 => a plate with an integer multiple of 67 holes is required
68 => 1 & 1/17
69 => 1 & 1/23
70 => 1 & 1/35
71 => a plate with an integer multiple of 71 holes is required
72 => 1 & 0 
73 => a plate with an integer multiple of 73 holes is required
74 => 0 & 36/37
75 => 0 & 24/25
76 => 0 & 18/19
77 => a plate with an integer multiple of 77 holes is required
78 => 0 & 36/39
79 => a plate with an integer multiple of 79 holes is required
80 => 0 & 18/20
81 => 0 & 24/27 or 40/45
82 => 0 & 36/41
83 => a plate with an integer multiple of 83 holes is required
84 => 0 & 30/35 or 42/49
85 => a plate with an integer multiple of 85 holes is required
86 => 0 & 36/43
87 => 0 & 24/29
88 => 0 & 27/33
89 => a plate with an integer multiple of 89 holes is required
90 => 0 & 16/20 or 20/25 or 28/35 or 36/45
91 => a plate with an integer multiple of 91 holes is required
92 => 0 & 18/23
93 => 0 & 24/31
94 => 0 & 36/47
95 => a plate with an integer multiple of 95 holes is required
96 => 0 & 12/16 or 15/20
97 => a plate with an integer multiple of 97 holes is required
98 => 0 & 36/49
99 => 0 & 24/33
100 => 0 & 18/25


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## lensman57 (Feb 3, 2012)

Hi,
I bought exactly the same rotary table from Arc Euro Trade here in the UK last week, the manual that came with the table is written in an English language that is totally incomprehensible to me, more like a Google translation from the Chinese language. I also found out that the dedicated tailstock only matches the centre height of the table in one orientation because the rotary face is not located centerally on the table, very disappointed to be truthfull.

regards,

A.G


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## Boot (Feb 4, 2012)

Thanks AG.  The table you bought is exactly the same as The Little Machine Shop has for sale. I downloaded their instructions and they are written in very good English. It isn't exactly like mine. Mine has 3 plates they have only 2. The instructions on how the table works was worth downloading. I think you will enjoy it. Check it out.  Marv sent me a program printout that answers all my questions. I'm finally seeing the light.  Thanks again for your input . Boot


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## Boot (Feb 4, 2012)

Thanks for the spread sheet answer to my problems Robin.  I don't understand it all together. I will try to comprehend it more as I get into using the table. Check Marv's answer it totally helps me choose the plate and the number of handle turns needed. 
Thanks again , Boot


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## mklotz (Feb 4, 2012)

Recently I've supplied turns and holes tables for several people who had rotary tables but lacked the turns and holes tables for them. While I'm willing to continue doing that, it is, for the benefit of future readers, worth reviewing how to determine turns and holes via simple mathematics that can be done by hand.

Let's say the table has a gear ratio of G:1. This means that it requires G full turns of the table crank to rotate the table through one complete revolution.

We'll also say that we want to divide our workpiece into N divisions. What we're really saying is that we need to move the table 1/N revolution between each division.

This means that to move the table 1/N revolution, we have to turn the crank G/N turns. When we perform this division, we need to do it, not with a calculator, but as we learned in grade school, to yield a mixed fraction.

An example will make this clearer. Suppose we have a 72:1 table. Thus G=72. We want to drill seven holes equally spaced around the workpiece. Thus N=7.

G/N = 72/7

Seven will divide into 72 ten times with a remainder of 2 so:

G/N = 72/7 = 10 & 2/7

This gives us the answer we seek. We need to turn the table crank 10 full revolutions plus 2/7 of a revolution. 2/7 of a revolution can be done by stepping off two holes on a seven hole plate.

But, but, the manufacturer did not include a seven hole plate! What do I do now?

If you multiply BOTH the numerator and denominator of a fraction by the SAME number, the value of the fraction will not be changed. Using this fact, we have:

2/7 = 4/14 = 6/21 = 8/28 = 10/35 = 12/42 = 14/49 = ...

so stepping two holes on a seven hole plate is the same thing as stepping ten holes on a 35 hole plate or 14 holes on a 49 hole plate. Keep multiplying numerator and denominator until the denominator corresponds to a hole circle on a plate you have. 

If you learn this simple procedure you'll be able to use any rotary table you encounter, even if the turns and hole table is unavailable.


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## lensman57 (Feb 4, 2012)

Boot  said:
			
		

> Thanks AG.  The table you bought is exactly the same as The Little Machine Shop has for sale. I downloaded their instructions and they are written in very good English. It isn't exactly like mine. Mine has 3 plates they have only 2. The instructions on how the table works was worth downloading. I think you will enjoy it. Check it out. Marv sent me a program printout that answers all my questions. I'm finally seeing the light. Thanks again for your input . Boot



Hi Boot,
Thanks for the pointer, I will have a look at their website.

regards,

A.G


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## John S (Feb 4, 2012)

lensman57  said:
			
		

> Hi,
> I bought exactly the same rotary table from Arc Euro Trade here in the UK last week, the manual that came with the table is written in an English language that is totally incomprehensible to me, more like a Google translation from the Chinese language. I also found out that the dedicated tailstock only matches the centre height of the table in one orientation because the rotary face is not located centerally on the table, very disappointed to be truthfull.
> 
> regards,
> ...




?????????????
It matches the orientation of the table when located by the locating tenons and the holding slots are in the correct position.
Any other mounting face has no tenons or holding slots.

John S.


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