The Home Machinist!

Hi
I'm considering building a dividing head. I don't intend to "reinvent the wheel" and I'm sure that it was done before by member(s) of the forum. I hope that you can offer me advise, based on your experience and maybe even building plans/drawings. one more thing that I wanted to ask is where I can purchase decent dividing plates, what I've seen on a Chinese site - they claim that its made of cast iron and it weights 29grams! I find it hard to believe that they are serious.

KBC has a few dividing head plates for different models (I was browsing them yesterday thinking about getting some replacements for the missing plates on mine). Shars has some as well. If you don't need all the different combinations, collet spin-dexes with 24 locking positions are pretty cheap as well.

Instrad of getting plates, why not make it electronic with an arsuino based deviding setup. There are a couple of ready made programs available on the net with all the nescescary turorials

I do believe one of Dave Gingery's "Build a workshop from scrap" series included a book on dividing heads. He laid out and drilled the plates by hand on a drill press.

Hi
Thanx for your comments.
Rhynardt - perhaps you know where I can look for more info regarding the Arduino setup?
Mihit - I've searched Dave Gingery's publication. found how to to build a lathe (which I already have ) and how to build a mill (which I have as well and for it I need the dividing head) but unfortunately, I haven't found anything regarding the dividing head. I'll keep on searching.

The hole circles you need on the plates are a function of the dividing head's internal gear ratio. When I wrote the programs available under the DIVHEAD archive on my webpage, I included a program, DPLATES, which can be used to determine which hole circles are required to perform all divisions up to N, where N is an input to the program. The extract below from the text file that is included in the archive shows some example output from the program.

All programs on my webpage are available for free should you care to download and use them.

-----------------------------------------------------------------------------
REQUIRED DIVIDING HEAD HOLE PLATES

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

Hole plates required for all divisions up to 50
4,5,6,17,19,21,23,27,29,31,33,37,39,41,43,47,49,

It would appear that the 15 and 16 hole circles normally supplied with
commonly available devices aren't really needed to get the advertised "all
possible divisions up to 50". Maybe it's done to make the low number plate
look better. (You need the 20 hole plate for 4 and 5 and the 18 hole plate
supplies the 6.)

REQUIRED DIVIDING HEAD HOLE PLATES

DH worm gear ratio [40] ? 90
Maximum number of divisions needed [50] ?

Hole plates required for all divisions up to 50
3,5,13,14,16,17,19,22,23,29,31,37,41,43,47,49,

One less plate with a 90:1 ratio to get everything up to 50.

REQUIRED DIVIDING HEAD HOLE PLATES

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

Hole plates required for all divisions up to 50
8,12,17,19,21,23,27,29,31,33,37,39,41,43,47,49,

A 100:1 ratio doesn't save a lot of drilling effort.

REQUIRED DIVIDING HEAD HOLE PLATES

DH worm gear ratio [40] ? 60
Maximum number of divisions needed [50] ?

Hole plates required for all divisions up to 50
5,8,9,11,13,17,19,23,29,31,37,41,43,47,49,

A 60:1 ratio is good because 60 is evenly divisible by a lot of
integers.

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

How large a dividing head, required number of divisions your looking for, what machine tools do you have access to for building it etc? Gingery's DH build is ok, I'm no fan of his using the far less durable aluminum castings though. Fwiw in the Village Press book The Shop Wisdom of Philip Duclos https://secure.villagepress.com/store/i ... l/item/819 is the reprinted series that was in the Home Shop Machinist magazine for about a 4" swing model makers dividing head and most of the design was lifted from an Ellis dividing head once made in California. That one is 40 - 1 ratio. George Thomas in his book Work Shop Techniques https://www.teepublishing.co.uk/books/i ... echniques/ goes into lengthy detail about building a very capable and fairly small dividing head that uses two worms and wheels so it can sub divide to 1/1,000 of a degree for divisions the standard plates with there fixed number of holes can't do. So it's a bit like a semi universal dividing head that can do compound indexing. That one does use some castings available from Hemingway Kit's though. http://www.hemingwaykits.com/acatalog/V ... _Head.html Thomas used a 60 -1 ratio.

Making the dividing plates isn't all that tough and do so quite accurately. Both books give good details for doing just that. It's just a bit tedious, but I'd tend to trust something I made than buying anything at the cheapest possible price out of China. Even though any inaccuracy is also divided by the wheel ratio. While it could be done in a home shop with a great deal of skill and care, if it were me I think I'd just buy a decent worm and wheel from someone like Boston Gear or Browning since no matter how well made the rest of the dividing head is it's ultimate accuracy directly depends on the worm and wheel being accurate. There wheels would be cnc hobbed and it's more than doubtful most home shops could come close to that level of off the shelf accuracy. While there's some variations, almost all dividing heads and the easy to find dividing tables to get the required number of divisions are almost are based on a 40 -1 worm and wheel ratio. But Thomas also gives a table of divisions in his book.