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David S Newman
10-11-2007, 03:49 PM
I have a dividing head 60 to 1 ratio I need to divide 125 divisions, the two plates I have are 60,46,38,34,31,29 and 78,66,42,32,27. My old brain can't seem to work it out or is it impossible with these two plates ? Can't seem to find a common denomenator with these. David

oldtiffie
10-11-2007, 04:06 PM
Deleted by author

dm1try
10-11-2007, 04:21 PM
I have a dividing head 60 to 1 ratio I need to divide 125 divisions, the two plates I have are 60,46,38,34,31,29 and 78,66,42,32,27. My old brain can't seem to work it out or is it impossible with these two plates ? Can't seem to find a common denomenator with these. David
it's not possible. with your plates you can't do

37 41 43 47 49 53 59 61 67 71 73 74 77 79 82 83 86 89 91 94 97 98 101 103 106 107 109 111 112 113 118 119 121 122 123 125 127 129 131 133 134 137 139 141 142 143 146 147 148 149 ...

i have a little calculator at http://mmcd.meditprofi.ru/machining/dh.html you can save the html code to a hard disk if you like, it will work from there just fine.

SGW
10-11-2007, 04:23 PM
I think you're dividing the wrong way. It's 60/125, or 12/25, so you need a 25-hole circle (or some multiple of 25) to do it.

lynnl
10-11-2007, 04:33 PM
Oldtiffie, I think you have your fraction inverted, ie. should be 60/125.

With a 60:1 ratio 60 turns will yield one round-trip. And we want to DIVIDE that into 125 pieces. ergo, 60/125 or 12/25. So we'd go 12 spaces on a 25 hole plate (or 24 spaces on a 50 hole plate, etc).
But alas, to David's great disappointment, he doesn't have one with a factor of 25.

David S Newman
10-11-2007, 04:43 PM
Thanks for your replies. made me quite happy, thought I had signs of my brain needing a rebuild. David

John Stevenson
10-11-2007, 04:44 PM
One reason why on our division plates we put three extra hole sets, 25, 63 and 127.

125 division is a common one if you want a dial for an 8 tpi screw.

Failing this Evan has posted a way using a sticky label strip.

.
[edit] And before anyone asks, yes I am doing the special 5" plates once we get this last show out of the way this weekend.

.

oldtiffie
10-11-2007, 04:55 PM
Deleted by author.

David S Newman
10-11-2007, 05:06 PM
One reason why on our division plates we put three extra hole sets, 25, 63 and 127.

125 division is a common one if you want a dial for an 8 tpi screw.

Failing this Evan has posted a way using a sticky label strip.

.
[edit] And before anyone asks, yes I am doing the special 5" plates once we get this last show out of the way this weekend.

.
Yes John, that's what I need to do , make a dial for a 8 tpi feedscrew. David

oldtiffie
10-11-2007, 05:24 PM
Sorry.

You are right and I am wrong.

Thanks for the check and advice - appreciated.

I sure am glad that David did not proceed on my advice!!!

I have "re-worked" the figures which confirms my error and that everyone else is correct:

1/125 = N/60 (N = number of turns of indexing arm)

60/125 = N/1

12/25 = N

So to use indexing arm requires row/s with multiple/s of 25 holes. So cannot be done with existing set of plates.

oldtiffie
10-11-2007, 05:47 PM
Deleted by author

John Stevenson
10-11-2007, 06:05 PM
Tiffie, About halfway down, there is a mis print ..


.

Lew Hartswick
10-11-2007, 06:34 PM
oldtiffe, That is the way "real" machinists do it. :-) Or is that engineers??
...lew...

oldtiffie
10-11-2007, 11:18 PM
Deleted by author

oldtiffie
10-11-2007, 11:24 PM
Deleted by author

Bob G
10-12-2007, 06:50 AM
It's been a long time, I'm 78 years old, but I would consider adding a 25 hole circle to one plate using the 60 hole circle on the other plate.
2 Turns + 24 Holes = 25 spaces
Have fun,
Bob G

DICKEYBIRD
10-12-2007, 10:11 AM
Thanks John.

I don't doubt that;
a. your are correct; and
b. that yout eyes are better than mine.

Please advise/post and I'll either re-try Marv's software or re-run and re-post it.Methinks Sir John was "takin' the p!$$" (Respectfully of course!)

David S Newman
10-12-2007, 12:12 PM
It's been a long time, I'm 78 years old, but I would consider adding a 25 hole circle to one plate using the 60 hole circle on the other plate.
2 Turns + 24 Holes = 25 spaces
Have fun,
Bob G

Thanks Bob, thats what I shall do this evening, better than watching television !!!!!!! David