Excel sheet to calculate divisions on a BS0 dividing head

[Norppu]

I was working for three years in a German bank. During that time I learned to fill an excel sheet. Now, let's put that skill into proper use.
I have prepared an excel sheet that contains all possible divisions between 3 and 200 for a BS0 dividing head. The sheet can be adopted to other type of dividing head simply by inputting the number of direct division steps and the worm gear ratio. Also, the number of holes in the dividing disks can be changed to adopt to some other division plate schema.
The sheet calculates the number of turns and the number of holes to add for each division.
The leftmost column that contains the division will be green if the division is possible, if not then it will be dark grey.
Enjoy !

 

[benmychree]

Why bother? every machinist's handbook and B&S milling book has the tables already published.

 

[Lo-Fi]

Why bother? every machinist's handbook and B&S milling book has the tables already published.

For me, there's two reasons not to bother with published tables:

1) I don't believe published tables are ever complete. This may be important for a hobbyist that has limited plates.
2) Why swim through thousands of entries when you can filter to the exact entry you want based on what you actually have available? You can't search or filter paper tables, nor feed them your particular capability and have them compute what you can achieve, leaving out what you can't.

 

[benmychree]

Brown & Sharpe designed and built these devices and published tables in their publication "Practical Treatise on Milling and Milling Machines" the tables were copied by others, and they contain information on every possible division that the device is capable of. What more does anyone need? Other companies have done the same for equipment that they have manufactured that may differ, either by ratio or available dividing plates.

 

[Norppu]

Why bother doing something like this?

First of all, it took something like half an hour to produce the base code for the excel and maybe one hour to make it readable and looking decent. I also enjoyed every 90 minutes of doing it. The process of creating this also deepened my understanding on the subject.
My chinese copy of BS0 came with a paper that was really hard to read and when You finally understood what was printed on that paper, it contained errors so I used it to start the fire in our sauna heater.
The printed tables are probably not complete because the number of possible divisions is so large. In the case of BS0 it is 1960. I have never seen the B&S documentation nor have I seen the Machinists Handbook but I suspect that they left out the impossible divisions just to save space. That makes such tables more readable too.
Then there is the obvious, this table can be altered which is somewhat difficult with a printed table.

 

[benmychree]

Indeed, on the information given in the tables, the impossible divisions are left out, for larger B&S dividing heads such as my 10" universal, all possibilities are listed, some requiring change gears for differential indexing which allows indexing prime numbers, something not possible with the smaller dividing heads of their manufacture. One limiting factor with the B&S heads is the relatively small diameter of their dividing plates so that larger numbers of holes can be drilled; the Cincinnati plates were about twice the diameter so large numbers of divisions could be drilled including prime numbers, also their plates were drilled on both sides, so only one plate was required. For the sake of convenience, B&S also made a sheet metal printed wall chart that went from 2 to 320 divisions, not including prime numbers, I was lucky to find one on E Bay. for simple indexing, it saves pulling the book out of the drawer and going to the pages that have all the "mechanic's tan". Using the change gears, I have been able to index gear teeth of several prime number change gears that I made for cutting metric threads on my 19" lathe. The real B&S d8ividing heads have a feature that I have not seen on any other dividing heads, including the knock offs; In their tables there is a column marked (graduation) this refers to graduations on the sector arms on the dividing plates; you set the arms to the graduation and it automatically sets the correct number of holes and eliminates all counting errors and the resultant partial thickness gear teeth or slots, etc. The B&S tables in the book that I mentioned go up to 1008 divisions and also lists all spiral leads possible with the standard change gears that come with a universal dividing head and the short lead attachment which comes with additional change gears. The handbook that I mentioned is "Machinery's Handbook" originally published by the Machinery Publishing Company of Great Britain, they also published a monthly magazine, "Machinery".