Indexing plate calculator / indexing plate generator

[Henrik]

The use of indexing heads / plates (or are they called dividing heads?) has always been a bit of a mystery to me, until I started playing with some numbers in Excel on the computer.

Anyway, one way led to another, and now I've written a couple of small online programs (no download necessary) to calculate how many revs / holes have to be skipped for a given number of divisions for a given set of plates.

Link to the programs is here: http://bilar.co.uk/engineering

The first link lets you calculate either one specific division, or generates a list of possible combinations from 1 - 128 holes.

The second link is a bit more interesting, for me, at least. Basically, my own rotary table doesn't have any indexing plates with it, and my solution to this is to make some myself. To that avail, I've written a piece of software that will generate an *image* of a plate, which can be printed out and basically glued to something solid, and then drilled in the relevant places.

Obviously, a printed plate will not be exact, but I reckon it will be pretty close, given that the accuracy basically increases by the ratio of the table (i.e. an error of 1 degree on the plate, gives a 1/ratio error on the final division).


Anyway, hope someone finds it useful

 

[Rudi McAnichal]

It sounds as though you have just an indexing rotary table, rather than a dividing head. A dividing head has perforated plates and also a worm gear (typically 40/1 or 60/1 ratio) that will allow a much greater range of divisions.

For anybody who does have a dividing head, there was an interesting article “Dividing on the lathe” written by Roy Smalley and published in Model Engineers’ Workshop November 2009. It explained how you can make a dividing plate with holes in roughly the right places, and then use the dividing head to produce a second generation plate. If the worm gear on the dividing head has a 60 to 1 ratio, errors in the second plate with be reduced to 1/60th of those in the original plate, and a third generation plate would further reduce errors in the same way. The author made blank plates by using two or three old CDs glued together.

 

[Henrik]

It sounds as though you have just an indexing rotary table, rather than a dividing head. A dividing head has perforated plates and also a worm gear (typically 40/1 or 60/1 ratio) that will allow a much greater range of divisions.

For anybody who does have a dividing head, there was an interesting article “Dividing on the lathe” written by Roy Smalley and published in Model Engineers’ Workshop November 2009. It explained how you can make a dividing plate with holes in roughly the right places, and then use the dividing head to produce a second generation plate. If the worm gear on the dividing head has a 60 to 1 ratio, errors in the second plate with be reduced to 1/60th of those in the original plate, and a third generation plate would further reduce errors in the same way. The author made blank plates by using two or three old CDs glued together.

Yes, that's correct, I only have a rotary table (worm gear style). The images generated by the above program will be used to generate a set of indexing plates for it

I like the idea of using the CD's as a blank, though, as it's much quicker and easier to drill them than it is to drill steel plates.