Looking For 90-1 Dividing Head Chart

[Sandia]

I have a Phase II that is 90 -1 ratio. The paperwork that came with it has some charts, I will try to take a pic tomorrow and send it to you.

 

[brino]

cathead,

Since starting this endeavor I can easily see why most dividing heads use a smaller ratio worm gear. With a 90:1 ratio, you only get 4 degrees per rotation of the handle (360/90 = 4) since it takes 90 rotations of the input handle to get one rotation (360 deg) of the output.

So for many useful divisions it may take many, many rotations of the handle to get there!
However, it also means that any error of your dividing plate will be reduced by the worm ratio, too.

For any given division there are also sometimes a few right answers....for instance, to get 36 divisions (or 360/36 = 10 degrees) you could use either:
1) 2 full rotations and 17 additional holes on the 34 hole circle plate ((2+17/34)*4 deg) = 10 deg. _or_
2) 2 full rotations and 22 additional holes on the 44 hole circle plate ((2+22/44)*4 deg) = 10 deg. _or_
3) 2 full rotations and 32 additional holes on the 64 hole circle plate ((2+32/64)*4 deg) = 10deg.

Another interesting point.....for any row where the "Number of additional holes" is zero there are only full rotations so it doesn't really matter what dividing plate you use!

I'll post back with something useful soon....

-brino

 

[Mark_f]

Mark,

Thanks for the interest. I want to thank everyone who has responded. It's really great to have you all helping me out like this.

Cathead,

I have a chart for 90:1 ratio and all the hole patters you said. It gives all possible divisions for the hole patterns. It is a text file so I can send it to yo if you PM me your email address. I can't figure out how to post it here.

 

[brino]

cathead,

I misjudged the effort.
Doing a fully configurable one was a little more work than I thought.

Attached here is a basic one for your 90:1 worm ratio and the dividing plates you have.

I'll keep working to:
1) add a few more ratios to yours, and
2) try to work out the remaining issues with the full version.

Interesting project in itself.......

-brino

edit: it might be a good idea to check this against Mark's!

 

[coffmajt]

I have an Excel spreadsheet that will let you set any worm ratio and then find divisions that you need for a variety of division plate circles. Send me an e mail coffmajt@cox.net and I will send you a copy -- Jack

 

[cathead]

cathead,

I misjudged the effort.
Doing a fully configurable one was a little more work than I thought.

Attached here is a basic one for your 90:1 worm ratio and the dividing plates you have.

I'll keep working to:
1) add a few more ratios to yours, and
2) try to work out the remaining issues with the full version.

Interesting project in itself.......

-brino

edit: it might be a good idea to check this against Mark's!

OK, I was able to save the file and print it too and made several copies for the shop. I can see where just the math part to make the chart would be a big undertaking.
I'm not too good with computers so was happy that I was able to download and print without any glitches.

I appreciate your efforts! THANK YOU Burt

 

[hman]

Just for fun, here's a pretty complete table for my own 90:1 rotab, which uses the same dividing plates you have.
Note 1 - All my holes are on two disks, which I've called A and B. Your diskss may differ, but all your hole sets are there
Note 2 - The 51 and 57 hole patterns aren't of any use that I can come up with
Note 3 - You CAN make a 127 tooth gear with minimal error (0.065 degree) by following the "recipe" on the third page. Just gotta pay attention, and do "something different" every 16th tooth.

 

[brino]

I appreciate your efforts!

Just for fun, here's a pretty complete table for my own 90:1 rotab, which uses the same dividing plates you have.

Hi Guys,

Thanks to hman, I had something to check mine against......and I found an error in the one hman posted!!!!

For a 90:1 worm gear we get 360/90 = 4 degrees per rotation.
For 19 divisions the step angle is 360/19 = 18.94736 deg.

In hman's copy for 19 divisions it claims 4 full turns plus 8 more holes on the 38 hole circle.
In numbers that is: (4 + 8/38) x 4 deg/rotation = 16.8421 deg.

In my version 2(attached) for 19 divisions I give 4 full turns plus 28 more holes on the 38 hole circle.
In numbers that is (4 +28/38) x 4 deg/rotation = 18.94736 deg.

Therefore mine is correct!!!!!!
In hman's version it looks like they dropped the "2"; must be a typo.

-brino

edit: to be clear I know of NO errors in my version 1. the only reason for my version 2 is to add more divisions that I figured out since the first version......there still be more updates to come.

 

[seasicksteve]

I have a copy of the 90:1 table for a bridgeport rotary table. I would be happy to send you a copy if you would like it, send me a PM with your address and Ill get it in the mail

 

[seasicksteve]

Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

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