Rotary Table Dividing Question

[chucketn]

I’m trying to set up to cut a gear using my Vertex 4” Rotary Table. The table is 90:1. I’m using the Lathemaster 6” and 8” dividing table located here:
http://www.lathemaster.com/images/6%20and%208%20Inch%20Rotary%20Table%20Charts.pdf
I’m using this table because Lathemaster says they are 90:1.
According to the table, I should use the 23 hole circle, advancing 1full turn and 22 holes. On my 4” Vertex. It is impossible to set the sector arms to select 22 holes. I have tried reversing the arms and still cannot space them where I can select 22 holes. How do I select 22 holes? Any experienced folks out there with a 4” Vertex with Dividing plates? From what I understand, the plates I have are the same as used on the 6” Vertex if not also the 8” Blogwitch, if you’re seeing this, I’m the guy that got the tailstock and plate set from you a while back.
Chuck

 

[Blogwitch]

Hi Chuck,
It's very dark outside at the moment and the boogie man might get me, but if you can wait until tomorrow, I will scan the Vertex manual for the setup figures for number of divisions required.
It would be good if you could tell us how many teeth you are trying to cut.
You might be better trying to set up a larger sized plate. BTW, what you normally do is ignore the first hole and count your 22 holes from that, so in fact, there should be 23 holes showing between your fingers.

Or do as I did, buy a Division master, I can get 9,999 divisions if needed at the press of a couple of buttons.

John

 

[chucketn]

I wish I could afford the DivisionMaster, John.
The gear I'm cutting is 46 teeth, 16DP, 14.5 PA. The Lathemaster chart for 90:1 says 22 out of 23 holes. If I skip one and then go 22, that would be 23 holes. Why not just cut a tooth every 2 turns?
My big issue is how to set the sector arms. Do I set them to cover 23 holes, or 1? If I set them to cover 1 hole, I can't get the locking pin into the holes.

Chuck

 

[///]

It's very dark outside at the moment and the boogie man might get me

Haha!
I literally choked on my coffee reading this, thanks for the morning laugh John!

 

[RichD]

Chuck,
Here's my calculations for your situation. If you need more let me know. My program gives results for a range of divisions, in this case 2 to 46 using a 90:1 ratio and a 23 hole plate. So it looks like one turn plus 22 more holes for each tooth you cut. You never count the hole the plunger is in. Without a picture I'd just be guessing on how to use the sector arms so I'll let someone else answer that part.
Rich

 

[///]

I could have sworn I edited my original post to include the below... Dunno what happened there :shrug:

Chuck, have you seen Chuck's thread on his DIY Dividing Head?
It uses an Arduino which are quite cheap, pretty sure it would be easily adapted for a HV4 (have been toying with the idea myself)
http://www.homemodelenginemachinist.com/showthread.php?t=17896

There was another similar Arduino 'Divisionmaster' clone that is very popular, tho I now can't find the link.


EDIT: I just noticed in the above link that John has covered the Vertex stepper conversion on madmodder, tho the images are now missing
http://madmodder.net/index.php?topic=4040.0

 

[RichD]

This is from the "LittleMachineShop" reference area. It basically says to adjust the sector arms so only the two holes needed are trapped between the sector arms. Their example is for 27 holes on a 28 hole plate. See the attachment...

View attachment 1811dividingplates.pdf

 

[kiwi2]

Hi Chuck,
I can't visualise why you can't set the sheaves on adjacent holes and can't get the pin in. The top of the sheaves taper down to the selected hole so shouldn't interfere with the pin. Can you post a picture?
Rich - DOS!!!! What a trip down memory lane.
Regards,
Alan C.

 

[kiwi2]

Hi again Chuck,
I think I've just realised what the problem is. You seem to be trying to set the sheaves to cover 22 holes in a 23 hole plate. Don't do this. Set them to cover a 1 hole gap and move the sheaves anticlockwise instead of clockwise.
Consider the case where you want to advance 11 holes in a 12 hole plate.
Put the pin in the #12 hole. Set the right hand sheave against the pin. Set the left hand sheave against the #11 hole. Make your cut and advance the pin clockwise to the #11 hole which is against the left hand sheave. Rotate the sheaves anticlockwise until the right hand sheave is against the pin and the left hand sheave is against pin #10. Make your next cut etc.

Hope this is useful.

Regards,
Alan C.

 

[Ken I]

Sorry if I'm stating the obvious but you are trying to get 46 divisions in 360° or 90 turns of the handwheel.

90 doesn't divide by 46 but by using the 23 hole plate we now have 90x23 which equals 2070 divisions which does divide by 46 to give us 45 "holes" or one full revolution followed by almost one more = 23 + 22 holes.

So to keep track you set the sheaves as a "reminder" (the sheaves serve no purpose other than as reminders - you'll get lost without them) - in this case you would set them over two holes (one divison) so starting from the one sheaf we go round one turn, then another but stop short the one hole. Before doing anything else push the sheaves back against the pin to set your next reminder & carry on.

Just to continue - tables are all good and well but its best if you understand what you are doing - you can then calculate it yourself and better understand the process.

In your case 46 divisions = 360/46 = 7.826086956...°

Since 90 revoultions is 360° / 90 = 4° per turn of the handwheel. (R.T.s are typically 90 turns dividing heads typically 40 turns)

Then 7.826086956° equals (divide by 4°) =1.956521739 turns of the handwheel.

Subtract from the next highest interger (in this case 2) and we get 0.04347826087 of a revolution (short or remainder).
Use the reciprocal 1 / 0.043478..... = 23

So we use the 23 hole disk.

Before proceeding check your maths 90x23÷46 = 45 a valid result.

For a regular number of teeth there is always a solution - for odd angles however you might have to settle for the nearest aproximation (with a dividing head you can go to a process called differential gearing which I'm not going to go into here.)

John, the boogyman really did pay you a visit and stranded a dirty great big ship on your beach.

Regards,

 

[chucketn]

I do understand the concept of dividing using the plates. My problem was how to set the sector arms. I will follow Alan's suggestion, and take a picture.
I had tried to set up that way, but I think the sector arms are to wide to allow setting one hole on the 23 hole circle.

Chuck

 

[Ken I]

Sorry - tend to go into lecture mode - bad habits die hard etc.

Below my Vertex 6" 23 hole plate (not mounted).

Showing the sheaves set for a one pitch gap on the 23 hole plate.

Assuming you are going clockwise from here - go around twice but on the second go one hole short.

You normally set the sheave up for long or short - if you wanted 1 rev plus 10 holes you would set the sheaves to cover 10 and work forward "long" (ie add the 10) if you wanted 15 holes it would be more common to set to 8 and work backward "short" (less than ie subtract).

Typically you add when you are less than 1/2 the number of holes and subtract when you are more than 1/2 the number. My sheaves won't open past 3/4 way in any case.

I hope that clears it up.

Regards,
Ken

 

[chucketn]

Thanks, Ken. You're explanation does help a lot. You must be a teacher... LOL, I was a tech instructor for 10 years in the USAF. Best job I ever had!
Got to go light the heater in the shop. Very cold today in Tennessee.

Chuck

 

[chucketn]

Another question as to charts. I can use Lathemaster's charts referenced in my original post, for the 6" and 8" Rotary tables, as they are the same 90:1 worm ratio as my 4" Vertex, right?
Thanks again for all the help folks.

Chuck

 

[Ken I]

Yup - as long as the turns are the same, the same tables will work just fine.

Last time I was in Tennessee was June 98 on my way down to Pulaski and drove smack through the centre of a tornado in the Old Hickory Boulevard area just outside of Nashville airport.

Stupid, dangerous, exciting, memorable.

Regards,
Ken

 

[Blogwitch]

Chuck,
I have uploaded the relevent parts of the Vertex manual for you to peruse at your leisure.

Anyone else who has seen any of my post without pictures, then I have every picture I have ever put onto any site on my computer, except some very early ones on here that were lost because of a foul up by photobucket.
So if you see an article by myself (usually Bogstandard) that takes your fancy, copy the text from the site then contact me by email and the missing pictures should soon be winging their way to you.

John

 

[bb218]

One thing that has always helped me with dividing heads is to look at it this way.

On a 90 to 1 head the 90 is Constance, for instance if you have a 46 hole plate stopping every 90 holes will equal 46 divisions. So in Chuck case he had a 23 hole plate so every 45 holes would give him 23 divisions " One full turn + 22 holes.

Same thing is true for a 40 to 1 head the 40 is the Constance number, if you have a 46 hole plate stopping every 40 holes would give your 46 divisions. Since you have a 23 hole plate every 20 holes would give you the 23 divisions.

Makes it a little easier to figure what plate you need to have for the divisions you want to index.

Mike

 

[chucketn]

Chuck,
I have uploaded the relevent parts of the Vertex manual for you to peruse at your leisure...

John

Thank you, John. Downloaded and printed.

Chuck

 

[chucketn]

...
Last time I was in Tennessee was June 98 on my way down to Pulaski and drove smack through the centre of a tornado in the Old Hickory Boulevard area just outside of Nashville airport.

Regards,
Ken

Next time you're in the area Ken, stop by for a cuppa! I promise to arrange better weather...

Chuck