MadModder
Gallery, Projects and General => How to's => Topic started by: Bryan on March 08, 2011, 07:48:01 PM
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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.
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.
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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! :(
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Alternatively, download the ROTARY program from my page and run it. It will produce a file that looks like this example...
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
Print the file and carry it to the shop.
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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! :(
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
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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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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! :(
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
sorry but that read incorrectly as the locating pin will already be against the left hand fork you then need to move it 18 holes so the arms are actually set 19 holes showing (number required plus existing location) I am surprised no one has pointed this out yet.
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One of the most informative( my opinion) articles is the book by GH Thomas called Workshop Techniques. OK, it's a brit book and all that jazz but it takes the reader through not only building a dividing head but actually how to make division plates.
It takes a lot of believing but this guy had at one point, a division plate with ONE hole. He generated -with increasing accuracy, how each plate etc was made.
And - yes- I have one. But, GHT -as usuual- wrote up in his other book- Model Engineers Workshop Manual how to make a small rotary table- without gears. His had, however, a set of degree graduations - around the outer edge. Mine has them but has gears as well.
Couple of good books for the Christmas- eh?
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It has come to my attention that the file in my original post has become corrupted somehow, so I am reposting it. Please let me know if this doesn't work. Thanks.
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Sorry- maybe it is me- but I didn't get anywhere!
Regards
FOM
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Fergus, can you elaborate?
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It's doing everything it should for me. At what stage does it fail? Download? Unzip? Launch? What error messages appear?
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All I got was a jumble of a few letters on the first and a front piece on the second. Mebbe me- but others will comment.
Whatever, it is a very useful tool to have for most people to use.
Cheers
FOM
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Seems to open OK here,
.xls file with lots of sheets ..
??
Running Office 2007
BC
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Works fine for me Bryan :thumbup:
Rob
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No-go! Sorry.
No matter, my maths is still good enough :smart:
Can still do Trachtenburg Maths.
Cheers
N
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It has come to my attention that the file in my original post has become corrupted somehow, so I am reposting it. Please let me know if this doesn't work. Thanks.
Thanks Bryan,
this one worked for me. It's just the sort of thing I need!
( Modification! I to am a Linux user, opened with open office)
Regards Matthew
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Thanks for sharing that Bryan! The reposted file opens and works fine in OpenOffice. (I'm a Linux user...)