A small dividing head

[steamer]

I was going to throw some math out there, but as is usual, someones done it already

https://www.cgtk.co.uk/metalwork/calculators/dividing

Set this spreadsheet to " custom" and 30 for the gear ratio.  Then set out the plates you want to make or have.....

It will tell you what divisions are obtainable....

[steamer]

and here is an example of the math

https://www.bing.com/videos/search?q=dividing+head+formuala%27s&docid=608038928227046131&mid=95B19BB63B9B79AC12EB95B19BB63B9B79AC12EB&view=detail&FORM=VIRE

Dave

[RReid]

Thanks Dave. I've bookmarked that calculator, it will be handy.

[steamer]

If you start with a 1 hole plate, then a 2, you can add hole counts using the dividing head...if you plan it out with that calculator, you can get nearly all divisions up to 50 with only a handful of holes....though prime numbers will need to be laid out I think..

Enjoy..

Dave

[steamer]

For the prime  holes, you can calculate the BC, and the XY positions with this calculator....

http://theoreticalmachinist.com/BoltCircleCalc

Dave

[Thor]

Hi Ron,

 If you have access to a 2D CAD program you can draw the (prime number) hole circles for the division plate(s) and print the drawing on paper and glue the paper to the division plate blank and then drill the holes. If you get it slightly wrong, use the first plate to generate a second one, then any erros will become much smaller.
 Here is a webpage that generate dials: https://www.cgtk.co.uk/metalwork/calculators/divider
 It will at least give you one hole circle.

Thor

[RReid]

Thanks Thor, Thanks Dave. Clearly there is more than one way to skin the division plate cat!

Going back to my earlier example of a 30 hole division circle, I said that it could be used to cut any number of teeth or segments that is a factor of 30. But in fact the possibilities go beyond that. It will also cut any number that divides into 30 with a Remainder that is a factor of 30.

As an example, imagine wanting to cut flats in bar stock to form the basis of crankcases for a series of radial engines of 5, 7, an 9 cylinders, with only a 30 hole division plate to work with.

The 5 cylinder case is easiest, 6 full turns of the crank for each flat (5 into 30 = 6).

For 7 cylinders, 7 goes into 30 4 times, with a remainder of 2. So each flat would take 4 full turns plus 2 additional holes.

9 cylinders is similar, 9 into 30 = 3 plus remainder 3. So 3 full turns plus 3 holes. Nifty huh?

An 11 cylinder radial wouldn't work though. 11 into 30 is 2 with remainder 8. Eight is not a factor of 30, so we would need a new hole circle. 24 holes would work, and that could be generated from the 30 hole circle. Also nifty.

[RReid]

Using the partially completed dividing head, as discussed in the previous posts, I made a 30 hole division plate today. First off I lined up the spindle with the mill spindle and locked down the X and Y gibs.


I have a 3” diameter aluminum face plate that I had used in the past on my wood turning lathe. I chose to make that my “blank”. Conveniently, it has a 3/4-16 threaded hub, so I could screw it directly onto the spindle.


That plate already has some holes drilled in it, four of which are at the same 0.8125” radius as I want my hole circle to be. So I lined up on one of the existing holes. Their diameter is too large though, so I then  turned and pressed in some ali rod to plug them. I marked the end of the crank with a fine Sharpie and taped on a piece of parting tool blade to serve as a pointer, to give me a reference for “one full turn”. Cheesy I know, but sometimes you just have to make do and get on with the job.


Then it was just a matter of going around once with a center drill, then again with the final 1/8” drill.






Still enough real estate left for up to 3 additional circles outside of this one. Later I'll remove the existing hub, since I expect to screw this plate directly to the side of the diving head. But the shop thermometer says it's 105 F out there, so I quit for today. I don't get paid enough to work when it's that hot.

[Kim]

Great looking index plate, Ron!  And nice work on the dividing head/RT too.  Looks like a great tool!

Kim

[RReid]

Thanks Kim! I hope you're finding time to at least think about your A3!

[steamer]

ok....GOOD   you're thinking about it.........

[Kim]

Thanks Kim! I hope you're finding time to at least think about your A3!

Yes, definitely thinking about it!  Just not getting a lot of time to actually work on it.  Should have some time this weekend?  (He says optimistically!)

What is that people say about having less time once you retire? 
Kim

[simplyloco]

What is that people say about having less time once you retire? 
Kim

I've been retired now for 15 years and I don't know how I EVER found time for work!

[RReid]

What is that people say about having less time once you retire?

I've been retired now for 15 years and I don't know how I EVER found time for work!

I agree, but I still say it's the best job I ever had!

[RReid]

A relative asked me to make a pair of door mirror clamps for his vintage pick-up truck, to replace an original (in front in the first pic) that is cracked and stripped. He also wanted them slightly larger and stronger. They are offset turned, bored, then the larger diameter was partially milled away. That has diverted me off of the DH project for a few days, but I want to try to finish them off using the DH as a rotary table.



To do that, I'll need the DH mounted to the mill table, along with both the 4J chuck and the lathe tailstock. And to do that, I need a riser block that's a bit over 1” thick. The half disc of aluminum that I have the lathe mounted to has enough thickness, and I can spare part of it, so that's what I'm using. I cut a chunk off on the bandsaw, then squared it all up on the mill with a flycutter. Mounting holes have been drilled, so all that's left is to flycut it down to the exact thickness needed for the spindle center and the tailstock center to line up.


What's wrong with this picture? No, I don't try to flycut loose parts, it's an “after thought" photo.