Rotary table math lesson needed

[torker]

I give up! I've used my r/t to drill simple bolt patterns (even spaces). Now I need to make the gear for my threading dial. 32 teeth...no problem, I'd use an indexing plate. I bought them some time ago but hadn't even taken them out of the bag. No plate with 32 holes in it! Read chinese instruction "book"...all 4 paragraphs. It makes absolutely NO sense the way they've written it, it's absolute gibberish. It doesn't even show how the plates/handle etc. are supposed to be mounted. I did a Google search and read a lot of stuff. Read a blurb by John Stevenson in Metalworking.com...he talks a bit about the three plates that I have. I read some stuff in Little Machineshop but I still am not grasping how these things work. Did a search here and found a thread about using the vernier dials but it still looks foggy. I need to have --360 divided by 32= 11.25 degrees. Now I'm lost. Does anyone have a link to somewhere were I can learn to deal with degrees, minutes, etc. and how it all relates to vernier dials and dividing plates? I remember learning this stuff years ago(just the math part) but for the life of me I can't remember any of it. My wife laughed at me(she's pretty good with math)..til I took her down in the shop and asked her to please just go ahead and set
up the r/t for me....hahaha..not so easy is it. I HAVE to get this figured out. I want to make some new gears for my quill drive also. Sure would appreciate any help! Thanks!
Russ

[John Stevenson]

First off what is the ratio of your rotary table 40:1 , 60:1 or 90:1

Secondly what number of holes do you have in the plates?
Should be a 16 hole for 60 and 90:1 or a 20 hole for 40:1

John S.

[sch]

Marvin Klotz always useful web site has the
following link which may be of use:
http://www.geocities.com/mklotz.geo/rotary.zip

Tony Jeffree wrote up the following which may or may not be of use:
http://www.jeffree.co.uk/Pages/divheadmk1.html

Any plate with a multiple of 16 holes should
be usable to get your 32t gear.
Steve

[mklotz]

Using the ROTARY program freely available on my site:

Number of divisions = 32

DIVISION degdec deg min sec
0 0.0000 0 0 0
1 11.2500 11 15 0
2 22.5000 22 30 0
3 33.7500 33 45 0
4 45.0000 45 0 0
5 56.2500 56 15 0
6 67.5000 67 30 0
7 78.7500 78 45 0
8 90.0000 90 0 0
9 101.2500 101 15 0
10 112.5000 112 30 0
11 123.7500 123 45 0
12 135.0000 135 0 0
13 146.2500 146 15 0
14 157.5000 157 30 0
15 168.7500 168 45 0
16 180.0000 180 0 0
17 191.2500 191 15 0
18 202.5000 202 30 0
19 213.7500 213 45 0
20 225.0000 225 0 0
21 236.2500 236 15 0
22 247.5000 247 30 0
23 258.7500 258 45 0
24 270.0000 270 0 0
25 281.2500 281 15 0
26 292.5000 292 30 0
27 303.7500 303 45 0
28 315.0000 315 0 0
29 326.2500 326 15 0
30 337.5000 337 30 0
31 348.7500 348 45 0
32 360.0000 0 0 0


Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

[torker]

John...Sorry...I should have added...it's a 90:1 table. It has three plates...#15 through 20...another 21,23,27,29,31,33...another 37,39,41,43,47,49. So it does have a #16. I'm assuming you'd machine 16 teeth then move it over 11.25 degrees and do the next 16? I had a bunch of this kind of info on my old computer but it crashed and I lost it all.
Marv...I had your site bookmarked before I lost it all....great place!
Steve...thanks for the links!
Russ

[torker]

I am just trying to make sense (again) of the flung dung directions again. they have a table that says for 32 teeth it requires 2 26/32 turns. So would you adjust the arms on the dividing plate so there where 13 holes betwwen them? Then turn it twice and turn it the rest of the 13 holes?
Russ

[John Stevenson]

OK here's how it works and this applies to any ratio.
First off forget degrees, you are working in divisions and fractions- always fractions.

The formulae for any ratio is the ratio of the R/T or dividing head over the number of teeth to be cut.
In this case it's 90/32 which is 2 turns and 26/32 left over.
Now break this down as we don't have a 32 circle and you get 13/16
Now we have a 16 circle so you set the two quadrant arms so there are 13 holes between the two arms.

To use you start off with the pin in the index hole on the 16 circle, thats the numbered one.
Place the left hand quadrant arm against the pin, lock the head and cut the first tooth.
then wind round two full turns so you come back to the index pin then go an extra 13 holes so you are in the hole at the side of the right quadrant. Lock the head.
Then swing the quadrant round the same way you went so that the left hand arm is against the pin.
This puts it in position for the next move.

Get into a habit of doing this before you make the cut and you won't get confused.
Now cut the second tooth.
Move another two full turns plus 13 holes and reset the arms, third tooth etc.

It pays to do a dummy run before you start cutting to make sure on the 33rd move you end up where you started.
It is easy to setup one hole out and it's an accumlative error.

Don't ask me how I know, [ learn some new words that day http://bbs.homeshopmachinist.net//biggrin.gif ]

John S.

[torker]

John...I just got back from the shop. I put the thing together and tried it. I guess I did it right except I was using the inside of the arms...not the outside. The only thing is some of the attaching bits don't fit. The holes are drilled wrong in the plates for the mount but I got two out of three to work. Must need to make a spacer for the "U" clip that is supposed to hold the arms in place. I bought the dividing set from a different company who told me they where all the same...they aren't http://bbs.homeshopmachinist.net//frown.gif. Yes...I will make a couple of trial runs. Thanks a lot guys! I should have asked you all this morning and saved myself the new ulcer I developed today http://bbs.homeshopmachinist.net//biggrin.gif
Russ

[John Garner]

A point of semantics: When setting the sector arms for, in this example, 13/16 of a turn you want to have 13 SPACES-between-holes between the sector arms . . . which means you should have 14 holes between the arms.

John

[WJHartson]

John, that is a great set of instructions.

Joe

[torker]

John G...Does that add up in the end though? There are 16 holes in the plate. You have to use 13 holes right?

[Arcane]

John Garner is quite correct about the number of spaces and the hole count.

[torker]

Ahhh...I just went down and looked...lol! The holes are all the same.....the SPACES are the determining factor! John G...you are right of course. Thanks for the lesson http://bbs.homeshopmachinist.net//biggrin.gif!!
Russ

[vmil3]

When counting off the holes in the sector plate "NEVER" count the hole your sector pin is in. This is the First rule in setting up a dividing head or rotary table. A fellow worker didn't remember the rule, He machined a ring gear with 257-1/2 teeth. The air was blue for a week in the shop!!!!!!!!!!!

------------------
Doug

[bobbybeef]

John Stevenson,
What a great reply to a question we all need to have answered. I have been creeping around my vertex dividing head looking for a way to overcome the need for a 12 hole circle on a plate when I dont have one. Is the only solution to make one. I have the standard three plates which work fine.They are 15,16,17,18,19,20.21,23,27,29,31,33.and37,39,41,43 ,47,and 49. It is a simple vertex not the differential divider with twelve gears.The ratio of the indirect drive is 40:1.
Its a nice bit of kit but it has limitations.
Any comment will bec helpful.

I am making a chiming clock.
Regards Bob.

[vmil3]

Hi Bob,
For 12 divisions on a 40:1 ratio 40/12= 3turns and 4/12 of a turn, take the fraction to it's lowest denominator (1/3). Look for a hole circle that is a multiple of 3, in your case 15,18,21,27,33,39 hole circles can be used. Let's take the 27 HC you would neeed 9 holes in 27 hole circle, another example 39 hole circle, in it you would use 13 holes in a 39 hole circle. In both cases they are 1/3 of a hole circle. From experience I use the largest hole circle on the plate, it's easier to hit the hole with the sector pin. So for your 12 divisions I would use the 39 hole circle 3 full turns and 13 holes on a 39 hole circle for each one of your 12 divisions.

------------------
Doug

[John Stevenson]

John G and Vmil are both correct and I was misleading.

I should have put don't count the hole you are in.
Sorry it was after midnight here and I did throw the do a dummy run in.

It's very easy to be one hole out, be rushing and get it wrong.
That's one reason why you should have a routine , wind turns plus holes, Move quadrants.
It doesn't matter whether you use inside or outside the arms as long as you are concistant, in fact when you get large hole counts like 15 on a 16 circle you have to go outside, no other way for it.

Dividing is regarded as a bit of a black art but it's a lot like screwcutting, seems offputting until you dive in and them it all comes together.

John S.

[Thrud]

Russ
Next time you are in town getting your hair permed with the girls stop by and I will show you how to use the table the easy way - hands on. , You have to call first - I can't hear the doorbells in the basement where I snore/and/or blow up stuff. I will email it to you...

[bobbybeef]

Sorry vmil3,I was so unclear in my rush to get involved in a solution to my problem I failed to tell you that the wheel I wish to cut has 96 teeth. The 12 is the factor. I cannot see how to achieve the 96 teeth without the 12 hole disc and without a differential gearbox for the dividing head.
Any suggestions would be helpful.
Regards Bob.

[pgp001]

I have a variety of different dividing heads and rotary tables, rather than having to work out the maths every time I use a different one, I keep a set of charts handy in the workshop with all available divisions listed.
I use a system of factors to achieve this, if you draw up a table with the columns being factors of your main ratio, and the rows being factors of all the available holes.
Multiply all the rows and all the columns and you will end up with a chart showing every division availble to you on that set-up.

Below is a typical example.

Alexander Dividing Head - Ratio 40:1

Holes available
27,31,33,34,36,37,38,39,40,41,42,43,46,58

Factors 1 2 4 5 8 10 20 40

1 1 2 4 5 8 10 20 40
2 2 4 8 10 16 20 40 80
3 3 6 12 15 24 30 60 120
4 4 8 16 20 32 40 80 160
5 5 10 20 25 40 50 100 200
6 6 12 24 30 48 60 120 240
7 7 14 28 35 56 70 140 280
8 8 16 32 40 64 80 160 320
9 9 18 36 45 72 90 180 360
10 10 20 40 50 80 100 200 400
11 11 22 44 55 88 110 220 440
12 12 24 48 60 96 120 240 480
13 13 26 52 65 104 130 260 520
14 14 28 56 70 112 140 280 560
17 17 34 68 85 136 170 340 680
18 18 36 72 90 144 180 360 720
19 19 38 76 95 152 190 380 760
20 20 40 80 100 160 200 400 800
21 21 42 84 105 168 210 420 840
23 23 46 92 115 184 230 460 920
27 27 54 108 135 216 270 540 1080
29 29 58 116 145 232 290 580 1160
31 31 62 124 155 248 310 620 1240
33 33 66 132 165 264 330 660 1320
36 36 72 144 180 288 360 720 1440
37 37 74 148 185 296 370 740 1480
38 38 76 152 190 304 380 760 1520
39 39 78 156 195 312 390 780 1560
40 40 80 160 200 320 400 800 1600
41 41 82 164 205 328 410 820 1640
42 42 84 168 210 336 420 840 1680
43 43 86 172 215 344 430 860 1720
46 46 92 184 230 368 460 920 1840
58 58 116 232 290 464 580 1160 2320

Hope you find this useful

I will attempt to try and format the columns so they are more readable.

Phil


[This message has been edited by pgp001 (edited 01-20-2005).]

[pgp001]

Alexander Dividing Head

Ratio of wormwheel is 40:1

Holes available 27,31,33,34,36,37,38,39,40,41,42,43,46,58

Factors 1 2 4 5 8 10 20 40

1 1 2 4 5 8 10 20 40
2 2 4 8 10 16 20 40 80
3 3 6 12 15 24 30 60 120
4 4 8 16 20 32 40 80 160
5 5 10 20 25 40 50 100 200
6 6 12 24 30 48 60 120 240
7 7 14 28 35 56 70 140 280
8 8 16 32 40 64 80 160 320
9 9 18 36 45 72 90 180 360
10 10 20 40 50 80 100 200 400
11 11 22 44 55 88 110 220 440
12 12 24 48 60 96 120 240 480
13 13 26 52 65 104 130 260 520
14 14 28 56 70 112 140 280 560
17 17 34 68 85 136 170 340 680
18 18 36 72 90 144 180 360 720
19 19 38 76 95 152 190 380 760
20 20 40 80 100 160 200 400 800
21 21 42 84 105 168 210 420 840
23 23 46 92 115 184 230 460 920
27 27 54 108 135 216 270 540 1080
29 29 58 116 145 232 290 580 1160
31 31 62 124 155 248 310 620 1240
33 33 66 132 165 264 330 660 1320
36 36 72 144 180 288 360 720 1440
37 37 74 148 185 296 370 740 1480
38 38 76 152 190 304 380 760 1520
39 39 78 156 195 312 390 780 1560
40 40 80 160 200 320 400 800 1600
41 41 82 164 205 328 410 820 1640
42 42 84 168 210 336 420 840 1680
43 43 86 172 215 344 430 860 1720
46 46 92 184 230 368 460 920 1840
58 58 116 232 290 464 580 1160 2320

[John Stevenson]

Bobby,
Sorry you have lucked out with a standard set of plates.
One way would be to make a new plate.
12 divisions is 3 turns and 9 holes on the 27 circle.

There are some division plates listed on ebay that cater for watchmakers who need weird numbers of holes, 96 being one of them.

As you can't advertise here, do a search on ebay for watchmakers under business, office and industrial.

John S.

[torker]

John...I figured you must have been up awful late! No problem! You guys this is a fantastic lot of info! There is so much of this stuff that I have trouble finding information about. This sure helps! Thanks again to you all!
Russ

[lynnl]

<font face="Verdana, Arial" size="2">Originally posted by Thrud:
Russ
Next time you are in town getting your hair permed with the girls stop by ...., You have to call first - I can't hear the doorbells in the basement where I snore/and/or blow up stuff. I will email it to you...</font>

http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif ...stop it Thrud! You're killing me! http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

It's no fun to snort coffee thru your nose you know.

[mklotz]

John's instructions are excellent and to the point. Nevertheless, my
experience suggests that there are a number of folks who will still be
challenged by the arithmetic involved. If that sounds familiar, you may want
to get a copy of the DIVHEAD program on my site.

By entering the gear ratio and available hole plates into a simple ASCII data
file, you will have customized the program to whatever dividing head you happen
to own. Then, when you run the program, you merely enter the number of
divisions required and the program produces a printout that looks like:

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

DIVIDING HEAD CALCULATIONS

Number of workpiece divisions [14] ? 32

DH Worm Gear Ratio = 90:1
No rapid indexing plate available
Divisions of Workpiece = 32
Ratio/Divisions = 90/32 = 2.8125
Turns required = 45/16 = 2 & 13/16

2 full turns of crank
and 13 holes on 16 hole plate

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

The program is free to anyone who wants it. Only about 65Kbytes to download.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

[pgp001]

Here is a link to an Excel spreadsheet I did for all the factors on my various dividing heads and rotary tables.

http://homepage.ntlworld.com/phil.procter/Division%20Data/

Phil

[torker]

Phil...I guess I don't have anything that will open that. I just checked with Microsoft and am not sure what I'd have to download to read this file. Thanks!
Russ

[3 Phase Lightbulb]

Thanks for the table Phil,

I converted it to .PDF format for those that don't have Excel (or Star Office):

Here is Phil's table in PDF format:

http://www.gnuxtools.com/source/dividing-head.pdf

-3Ph

[bobbybeef]

Thank you John S and Doug for your useful input to my problem.Thank you also to all the others who started and continued this thread.
I guess I will just make a twelve hole plate. I do not need to use the 27 hole circle plate as I have this on the direct division plate which is applied after the 40:1 ratio.
I no doubt will need this 96 tooth configuration frequently in the clock work.
Regards to all,
Bobbybeef.

[pgp001]

bobbybeef

If you are going to make a new plate with 12 holes for just one job, can I suggest that you make a 36 hole plate instead.

In addition to the divisions available from a 12 hole plate, this will give you the following extra numbers of divisions.

9, 18, 36, 45, 72, 90, 144, 180, 288, 360, 720, 1440.

If you are doing clock work some of those might be very handy to have in my experience.
You may well already be able to do some of them with your existing plates, but 36 is a more usual count than 12 on a dividing plate, and not much more work is involved in making it.

Regards
Phil

[bobbybeef]

Hi Phil,
What a really good suggestion.36 it will be.Thank you very much.
I had a vague memory that someone on this board suggested making extra plates from discarded disc brake discs. does anyone know if this is a prospect or are they too hard.
At the rate I go through them on the truck they must be fairly soft.Comment anyone.
Regards,
Bobbybeef

[torker]

Bobby...I don't remember that but I do know that Thrud made some from weights for barbells. He was really happy with the result. A few months ago I went up to a small town not far from here to buy an engine for my 4wld project. The fellow (a wierd little hippy type guy) had a big stack of these old cast iron weights sitting outside in the snow. I wanted them of course and offered to take them off his hands. He laughed at me...."Oh no...I'll be hitting the old weights again real soon. Gotta stay in shape you know". I bet they are still out in the snow!
Russ

[torker]

I might also mention two other sources that I've seen recently. I use old cast pots to melt lead in. My wife picked me up an old cast iron cooking set from a garage sale. Some of these seem to have heavy enough bottoms in them for that. Also, there was a fellow here who used to repair old wood cook stoves. Some of the lids would have worked for plates. seems to me I was in a plumbing supply house and saw some cast plugs for floor drains as well. I can't remember if these had holes in them that might be in the way though.

[pgp001]

bobbybeef
I am not wanting to break any rules here, but you might want to try a google search for "Watchmakers & Clockmakers dividing plates"
The first result at the top of the page might be very much to your advantage !!

A well known previous contributor to this topic may be able to give more info on these.

Phil

[mklotz]

One of the items supplied as part of my DIVHEAD package (mentioned above) is
a program called DPLATES. Supplied with the gear ratio of the DH in question,
it will tell you which hole plates are required to obtain all divisions up to
some input maximum. For example, with a 40:1 DH, it reports:

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

REQUIRED DIVIDING HEAD HOLE PLATES

DH worm gear ratio [40] ?
Maximum number of divisions needed [50] ? 100

Hole plates required for all divisions up to 100
8,12,15,37,39,41,43,47,49,51,53,57,59,61,63,67,69, 71,73,77,79,81,
83,87,89,91,93,97,99,

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

Note that the smallest number of holes is reported by the program. Any plate
with an integer multiple of the hole counts indicated above could be used,
e.g., a 24 or 36 hole plate could serve in lieu of the 12 hole plate.

I've found that having this information to hand when you go searching for (or
building) hole plates can be very helpful.

Regards, Marv

Home Shop Freeware - Tools for People Who Build Things
http://www.geocities.com/mklotz.geo

[Paul Alciatore]

The plates are a nice shortcut but you can do any number of divisions or any angular separation between holes with a RT that has calibrated scales. Just divide 360 by the number of holes (teeth) you want and make a table in increments. Excel would be a great help.

Then crank to each setting in turn.


Paul A.