Gallery, Projects and General > How to's

Dividing With a Rotary Table

<< < (2/4) > >>

wildman692:

--- Quote from: RichardShute on March 12, 2011, 04:55:20 AM ---
--- 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

--- End quote ---
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.

Fergus OMore:
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?

Bryan:
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.

Fergus OMore:
Sorry- maybe it is me- but I didn't get anywhere!

Regards

FOM

Bryan:
Fergus, can you elaborate?

Navigation

[0] Message Index

[#] Next page

[*] Previous page