Need help using my dividing head

[DeereGuy]

Hello everyone. I have a 40 tooth worm wheel dividing head. I am trying to cut 31 teeth for a sprocket. I have a 31 hole dividing head and the first time around I turned the crank one full turn plus one hole in the dividing plate for each tooth.....well ...this didn't work out so well. I am pretty confused to say the least.

So now I have gone back to the manual and read that I need to divide 40 by 31 which equals 1 and 29/31. From what I am understanding I need to turn the crank one full turn and 29 holes in the 31 hole plate each time I make a tooth. Is this correct? I sure hope so if not I am totally lost. I greatly apprecitate any help I can get.

TIA
Bob

[agrip]

bob

40/31 = 1 plus 9/31 or one turn plus 9 SPACES on a 31 plate.
To get the 9 spaces, the original hole is counted as zero plus nine more holes.
i.e., There will be ten holes visible between the reference stops.

Hth Ag

[LES A W HARRIS]

Bob, you should be underway by now, having had your question answered, but here is a visual anyway, as this crops up from time to time.

[John Stevenson]

Good picture Les.
The common mistake most people make is that they start at the row of numbered holes.
In this case the hole marked 31 is the 31st hole in the circle.
The first hole you start counting from is the one to the right of it.

You can't have the same hole being the first and the thirty first.

BTW What CAD program is that ?

.

[DeereGuy]

Guys, thanks a bunch for your responses. I was a little numskulled on this one. I have had this dividing head since spring and have a few days off so I thought I would try to get a grip on it. Right now I am just duplicating some plastic gears I had laying around. The 24 tooth were easy to do and came out ok for my use.

One other question I have is how do you determine the diameter you need for a blank. Just in case I decide to make up a few that I don't already have others to copy from.

[John Stevenson]

Outside diameter is the number of teeth plus two divided by the Diametrical Pitch.

So a 24 tooth gear with a DP of 20 will be 24 + 2 = 26
26 / 20 DP = 1.300"

.

[vmil3]

Bob,
You state you are trying to cut a "sprocket", and not a gear as some here have thought, we need to know the pitch of the roller chain, and roller size to answer your question.. (eg: 40, 41, 50, 60 chain) look on the side of the chain links on some makes the size will be stamped there.

[DeereGuy]

Gear is what a should have said. Just a loose term of words that I should have known better. Been on Percoset all week for my shoulder and I think it has my mind a little numb..)). Only thing is no machining this week for me..((

[LES A W HARRIS]

BTW What CAD program is that ?

.

John, Its my old Visual Cadd 4.0.3. Successor to the old Generic Cadd.

The plate was of an Old 'Ellis' Dividing Head I refurbished in 2003, I had it already drawn, other than blacking in the ref holes on the 31 hole circle, & move & rotate the sector arms which are on diferent layers, then I did a screen capture with IrfanView. Got SolidWorks in 2004, (The only way to fly) the old VCD files can quickly be saved as DXF & Imported as the sketch into SolidWorks saving a lot of time on updating.

[bill4227]

Les,

Would you be willing to email the dxf file to me?

Bill