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Dividing With a Rotary Table

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Bryan:
Attached is a zip file containing an Excel spreadsheet. Below is a copy of the readme. If you are prompted about macros when opening, you can disable them.


--- Quote ---
This spreadsheet is intended to enable divisions with only a rotary table and no division plates. If you want to divide a circle into, say, 16 equal parts, select the sheet labeled 16 and print the page. The last 3 columns are the degrees, minutes and seconds to set on your rotary table for each consecutive step. You may want to tick each one off as you go.

Tables are only included for divisions up to 127, that being the highest number commonly used for lathe change gears. If you need higher numbers it's easy to do.

At the bottom left of the screen, click this  >|  to go to the far right of the tabs. Right click the 360 tab and insert a new worksheet. If for example you're doing 153 divisions, name the sheet 153.

Go to the 360 tab, select all and copy. Paste to your new sheet. Now there are two small edits  needed. First, cell B2 will say =360/360. Change the last number to your divisor, in this case 153. Now just delete all the rows below that number. In our example, delete rows 155-361 inclusive. (There's an offset because of the title row.)

Check that the last row says 360 degrees, 0 minutes, 0 seconds. If it doesn't, something went wrong. Make sure B2 is correct.

Errors, suggestions, comments etc may be addressed to: shed at ptmedia dot com dot au.

This file may be freely distributed.


--- End quote ---

Artie:
Thanks mate, saved... while I do have the plates for my RT... its still 'black magic' at this point, one of the to do list items, learn how to use the plates!  :(

mklotz:
Alternatively, download the ROTARY program from my page and run it.  It will produce a file that looks like this example...


--- Code: ---Number of divisions = 13

DIVISION      degdec     deg     min     sec
       0      0.0000       0       0       0
       1     27.6923      27      41      32
       2     55.3846      55      23       5
       3     83.0769      83       4      37
       4    110.7692     110      46       9
       5    138.4615     138      27      42
       6    166.1538     166       9      14
       7    193.8462     193      50      46
       8    221.5385     221      32      18
       9    249.2308     249      13      51
      10    276.9231     276      55      23
      11    304.6154     304      36      55
      12    332.3077     332      18      28
      13    360.0000       0       0       0

--- End code ---

Print the file and carry it to the shop. 

RichardShute:

--- Quote from: Artie on March 08, 2011, 08:20:47 PM ---Thanks mate, saved... while I do have the plates for my RT... its still 'black magic' at this point, one of the to do list items, learn how to use the plates!  :(

--- End quote ---

Artie,
using the plates is actually not as difficult as it seems at first and for 'direct indexing' you can do the calculation in your head, because there is none, once you know the rule. An example first, then the rule.

Say your rotary table ratio is 60:1 - many are. You turn the handle 60 times to get one table rotation

I'll pick a deliberately peculiar division, say 17. You want the table to turn 1/17 turn for one index, so the handle will move 60/17 per index.

Now, 60/17 is an inconvenient angle of degrees, but if you have a disc with 17 holes, each hole is 1/17 turn and you want 60/17 so you simply count 60 holes round the 17 hole ring. Job done

Soooo... The Rule:
for n divisions, count the number of holes equal to the table ratio round the n-hole ring, that's it.

If you haven't got a disc with n holes then look for one with 2n and count twice as many holes, so in the above example 120 holes on a 34 hole ring. Or if necessary 3n and three times as many.

You set the forks, if you have them, so that the edges indicate the 'extra' holes. Say you were going to do 120 holes on a 34 hole ring. That's 3 turns (=102holes) and 18 extra holes. Set the forks 18 holes apart, bring the trailing fork against the pin, wind round 3 turns and then up to the leading fork, drop the pin in the hole. Before the next move, slide the forks round so the trailing one is again kissing the back of the pin etc.

Hope that helps
Richard

Artie:
Hi Richard, yes it does help and thank you. Ive actually worked out how to use them...just havent taken that 'step' yet.... have had jobs that need the dividing head but have put those jobs to one side.

Lots of excuses.... im in the last 5 days of an extended work trip (jayzus...I left home last month...!!)... get home late Wednesday night and back on the plane Thursday afternoon.....aaaahhhh.....

Be a while before I get cutting fluid in my veins again.... :loco: :palm:

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