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torker
01-16-2009, 01:42 AM
Hey guys...I'm bagged...been working on moving my Ohio mill into my too small machine room. Getting it set up for when my helper comes back so she can start learning how to cut gears.
Had to tear the table off and move a million things about 4 times each ...moving engine hoist around and thru etc etc etc . I ended up with the mill sitting right beside the monster old dividing head I got with my VN. It's a Cincy head if i recall.
Anyway I got monkeying around with it...it's a pretty cool old head.
I need to cut a 10.82" gear with 204 teeth(6tpi).
so..I've decided to do it with this old head.
However..I'm lost with the calculations.
I can follow the formulas easy enough for small gears but this big tooth count has my tired noodle all buggered up.
The dividing head is a 40 to 1. The only plate on it has from 24 to 43 holes.
How in the heck do I figure the right row on the plates...and how many hole spaces etc?
I need one of them fancy Decimal to fraction calculators. I found an excellent program for that...I don't have the right calculator. What am I missing?
I can figure out 33 or 28 or whatever...small gears...no problem...not this high tooth count..
Thanks!
Russ

doctor demo
01-16-2009, 02:07 AM
Hey guys...I'm bagged...been working on moving my Ohio mill into my too small machine room. Getting it set up for when my helper comes back so she can start learning how to cut gears.
Had to tear the table off and move a million things about 4 times each ...moving engine hoist around and thru etc etc etc . I ended up with the mill sitting right beside the monster old dividing head I got with my VN. It's a Cincy head if i recall.
Anyway I got monkeying around with it...it's a pretty cool old head.
I need to cut a 10.82" gear with 204 teeth(6tpi).
so..I've decided to do it with this old head.
However..I'm lost with the calculations.
I can follow the formulas easy enough for small gears but this big tooth count has my tired noodle all buggered up.
The dividing head is a 40 to 1. The only plate on it has from 24 to 43 holes.
How in the heck do I figure the right row on the plates...and how many hole spaces etc?
I need one of them fancy Decimal to fraction calculators. I found an excellent program for that...I don't have the right calculator. What am I missing?
I can figure out 33 or 28 or whatever...small gears...no problem...not this high tooth count..
Thanks!
Russ
Russ, I'm no help on the deviding head math.What helper You got coming back? The Girl, or Her Son or Your drill press slave-er Wife?

Steve

torker
01-16-2009, 02:13 AM
Yup...we're trying to find a place back in the shop for the gurl. She needs a second, part time deal...problem is...she's not interested in the things she used to do before she came to work here.
She's hooked on chips!
This whole thing is (hoping) going to be a kick in the arse for me...to get some cnc equipment in the shop finally.
Nothing in stone yet...we both have a lot to learn..
Russ

Pherdie
01-16-2009, 02:28 AM
Hi Russ,

I figure you need a 51 division plate for plain indexing. With such a plate you would generate a tooth every 10 divisions (40/204 = 10/51). Thus you would generate 5.1 teeth per crank rotation, x 40 cranks =204 teeth.

Time to make a plate?? Or can you do differential dividing with your head?

Hope this helps.

Optics Curmudgeon
01-16-2009, 02:30 AM
204 spaces on a Cincy head, you need a 51 hole plate, 10 holes per space. Cincinnati plates had a different set of holes than B&S, there wasn't a 51 hole circle on any of the B&S plates.

Joe

Optics Curmudgeon
01-16-2009, 02:36 AM
Can't seem to get edit to work, Pherdie's quicker than me.

Joe

doctor demo
01-16-2009, 02:39 AM
I hope it works out for both of You. Russ I hope You know....that Monarch is not C N C:D .
Good luck and all the best to both of you.

Steve

Oldbrock
01-16-2009, 03:00 AM
Now you have to make a plate with a 51 hole circle. Easy enough done a la Gingery and if you are careful quite accurate. If you have room between one of the circles or on the outside, half your work is done. Get a strip of paper, (not too thin), the width of the thickness of the plate and make it long enough to more than reach the circumference of the plate. Now wrap it around the plate, get it tight and use a razor knife and cut through where they overlap. Tape it to a sheet of drawing paper.mark a line along the middle of the strip. sharp pencil needed for this and subsiqent lines. Make a strip about 2" longer and mark a line along the middle of this one. Make a vertical line from the right end of the first strip. Use deviders and mark off 51 spaces along the second strip, experiment until you use up most or all of the length. Now mark off 51 spaces along the second strip ACCURATELY. Put a pin in the "0" of the long strip and the "0" of the main strip and swing the long strip up until it lines up with your vertical line. Drop verticals from each point to the circumference strip. When the strip is taped to your plate the cut line will be "0" and 51. Now you have to devise a method to line up each line with a pointer and drill your 51 circle. I do it in my lathe with a dremel in the toolpost and a pointer mounted on the headstock. Be sure the pointer is exactly on each line as you drill. I use a 1/8" center drill for this op and drill to the pin size after. I have made four plates this for my dividing head and you can't hear any variation when the gear is running at high speed. Long winded I know but it works if youre stuck, Good luck, Peter

Pherdie
01-16-2009, 03:07 AM
....or have a good buddy pop out a CAD generated 51 hole pattern for your size plate, e-mail you the pattern, print, paste the pattern on the plate and drill.

Bguns
01-16-2009, 03:20 AM
Set it on Plate and Rub just the 51 Circle... :) Or all of the Circles and Plates......

Get busy with a Centerpunch and Drill :)

Give Us the OD and ID of your existing Plate.

Make up a Couple Blank Plates...

My 2 Sets of Plates are ~ 5 1/8 OD and 4 7/8 OD Probably small for your Head tho...

Sorry for Wasted Frame size.I poked around and was able to enlarge it on Photobucket. Looks like this Image if blown up, is good enough...

53 51 49 47 46 hole Plate

http://i95.photobucket.com/albums/l142/m37b1/Scan10019.jpg

You can go direct to Photobucket page to get in Full Res...

Oldbrock
01-16-2009, 03:20 AM
The good buddy must know what diameter is available on Russ's plate.

JCHannum
01-16-2009, 09:09 AM
Look at the back side of the plate. A lot of Cincinatti dividing heads had double sided plates with different hole counts on each side.

Evan
01-16-2009, 09:26 AM
I'll make you a plate Russ. What are the specs? Yeah, I know, 51 holes.

torker
01-16-2009, 09:38 AM
Holy Smoke! Thanks guys!
Maybe I should tell you what I'm up to first...you may see a hole in my game.
I'm making a hillbilly worm gear to rotate my welding positioner.
I have an acme worm...it's 6tpi. About a 10 " gear will give me really good mechanical advantage. 6tpi yeilds the size of gear given previously.
I'm going to make this out of 1/2" plate...it won't be a full circle. I only need a bit more than 1/4 of the gear to get the head from verticle to horizontal.
This doesn't have to be perfect either...henceforth and dewwith..I've decided to set the helix angle for the worm with the dividing head set on the table at an angle (3*).
Then...LOL..after the gear was machined...I was going to grind an aproximation of the arc into the middle of the gear so it would more closely match the diameter of the worm. I know, I know...it may not work...but I will learn from my mistake... :D
So...it doesn't HAVE to be 204 teeth...
Russ

Evan
01-16-2009, 09:43 AM
Here is a pattern taken from the image above.

http://metalshopborealis.ca/pics5/divplate.jpg

torker
01-16-2009, 09:59 AM
Evan...LOL! That's almost exactly the size of the plate on that ol' head...the center hole is too big is all.
I had already calculated the 51 hole deal last night but thought there was a way of using another plate. Now i'm seeing the math will not add up.
I'm going to look in the base of my Ohio after I eat...there's whole pile of drive gears in there for a dividing head. There may be one with 51 teeth...I can just use it to index a new plate.

John Stevenson
01-16-2009, 10:22 AM
Why not cut a few corners then and not bother with the division plate etc .

What about getting a rack off one of the window extenders, old lathe etc and bending it round a segment of plate for what you want.

Another dodge is to get a length of Acme rod, cut a piece off for the worm and then bend and weld the rest round a segment.

This way you will have both axis in the same line as the helix angles cancel out.

I know it's rough and ready but it well suits the application.

Lew Hartswick
01-16-2009, 10:59 AM
OR. :-) Just use tha angle measure on a rotary table and make a tooth
every 1 deg 45 min 53 sec . Especially if you dont have to do the
full circle. :-)
...lew...

torker
01-16-2009, 11:26 AM
Look at the back side of the plate. A lot of Cincinatti dividing heads had double sided plates with different hole counts on each side.
OK...someone here is smarter than the average bear :D
Jim...bingo...I took the plate off and flipped it over.
the other side has divisions from 46 to 66...including 51....lol! I'm thinking i'm going to like this ol' dividing head. It even swivels up...has a whole bunch of other gadgets on it that I have no idea how or what they are for.
Now...I just wish it didn't weigh so damm much. It's gotta be over 200 pounds. Makes for a tough lift up onto the table. Might have to make one of those crane deals... Thankyou gentlemen!
Russ

torker
01-16-2009, 11:28 AM
Why not cut a few corners then and not bother with the division plate etc .

What about getting a rack off one of the window extenders, old lathe etc and bending it round a segment of plate for what you want.

Another dodge is to get a length of Acme rod, cut a piece off for the worm and then bend and weld the rest round a segment.

This way you will have both axis in the same line as the helix angles cancel out.

I know it's rough and ready but it well suits the application. John...that's just too simple. Geez...ok..if my bright idea doesn't work..I've got a simple fix. Thanks hey!

camdigger
01-16-2009, 12:07 PM
If the gear is for a new design, would it be possible to reduce the tooth count to something a little friendlier to the machinist like 200 teeth? From what I remember from gear theory class that would change the OD of the gear 2% or 0.200" on a 10" gear.....

Paul Alciatore
01-16-2009, 12:26 PM
See my response to the Thirty-Nine Tooth Splines thread. It will work for any number of divisions.

Oldbrock
01-16-2009, 02:09 PM
****, I knew that about Cinci. plates, just forgot. Peter