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 4940 members
Re: [GrizHFMinimill] Rotary Table Book or PDF
 Hello Alan,Thank you for that link, I too have found it very useful.All the best,Malc.
From: Alan Reinhart <avr@...>
To: GrizHFMinimill@yahoogroups.com
Sent: Thursday, 19 September 2013, 2:00
Subject: RE: [GrizHFMinimill] Rotary Table Book or PDF
Yet another – few pages but may be helpful:From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of clevinski@...
Sent: Wednesday, September 18, 2013 8:42 PM
To: GrizHFMinimill@yahoogroups.com
Subject: [GrizHFMinimill] Rotary Table Book or PDFHi,
Besides the LMS document (which IS helpful), does anyone know of a book or, even better because it's free, a PDF on rotary tables?
Many thanks!
Charlie
New Jersey, US Hi, Herb,
Thanks for the link, but I have no trouble at all reading a normal vernier scale. What throws me about this one is that...
1. It goes from 60 to +60 with a 0 in the middle.
2. The resolution for each graduation seems to be a very odd number.
So I can identify the right graduation, but I'm not sure how to interpret it.
Thanks,
Charlie
New Jersey, US Thank you for all the informations. This days I am looking for a
rotaty table, but I did not understand the upset
Jorgen Denmark
Sendt fra min iPad Charlie – try this link:
http://www.homemodelenginemachinist.com/f13/rotarytableminutesseconds14527/
I’ll send more later – on the phone now…
=A.
From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of clevinski@...
Sent: Wednesday, September 18, 2013 11:11 PM
To: GrizHFMinimill@yahoogroups.com
Subject: [GrizHFMinimill] RE: Rotary Table Book or PDFThanks, Alan... that helps, especially the Sherline info. I'm having a heck of a time figuring out how to read the vernier on mine; it's kind of strange, or I just don't know how to read it. You can see the dial here.
Each division on the moving dial is 5 minutes (12 divisions between degrees). But how to read the vernier? There are + and  six increments, so the total range is dividing the 5 minutes of the main dial into 12 parts, or .4166667 minutes per graduation. That happens to be 25 seconds per graduation, but that doesn't really help much, does it? If you get alignment with either of the "60" marks on the vernier, that would be 2.5 minutes. But what about the others? And why is the 2.5 minute mark on the vernier labeled "60"?
Anyway, I'll figure it out eventually...
Thanks for the links!
Charlie
New Jersey, USOn 9/18/2013 11:10 PM, clevinski@... wrote:
Thanks, Alan... that helps, especially the Sherline info. I'm having a heck of a time figuring out how to read the vernier on mine; it's kind of strange, or I just don't know how to read it. You can see the dial here.
Did you or can you get dividing plates with your rotary table? Since I do not work with astronomy or other applications where minutes and seconds apply, my main consideration is *divisions* like perhaps a 6 hole circle, a 50 division dial or for cutting some number of teeth into a gear blank disk.
http://www.atmsite.org/contrib/JSAPP/divide/divhead.html
What is the ratio of the internal worm gear on your R/T? Mine does 5 degrees per handcrank revolution (0 thru 4 to 0 again) . There are 360 degrees in a circle so 360 / 5 = 72. My worm gear ration is 72:1. Knowing this I can look at other more expensive rotary tables and find which dividing plates are available for them, as mine only came with one dividing plate.
For your degrees/minutes/seconds, I would say simply ignore the minus (left) 60 part of the vernier when cranking clockwise and focus only on the positive (right) +60 increments. 10 second increments means you are going to have to roughly guesstimate anything less than 5 seconds or so. Again, I normally go by divisions not degrees/minutes/seconds so the whole degree/minute dial is usually removed and replaced with a dividing plate.
I bought the LMS 2183 kit, back when U.S. dollars were much more valuable than they are now.
http://lmscnc.com/2183
which is the 1810 precision R/T with dividing plate and a tailstock. You may have some luck with reading the instructions for the R/T:
http://www.littlemachineshop.com/instructions/RotaryTable.pdf
and perhaps most especially, for the dividing plate that comes with it.
http://www.littlemachineshop.com/instructions/1811DividingPlates.pdf
Without dividing plate(s) a rotary table is severely limited in use whenever divisions are needed as opposed to degree/minute/second use (and even for degree/minute/second use it is hard to set for less than the nearest whole 10 or maybe 5 second increment).
Search online for how easy it is to convert from decimal degrees to degrees/minutes/seconds and vice versa. I could also post more about working out which dividing plate hole circle is needed for whatever division as may be needed, but as usual my post is already turning into a book so I'll stop it here for now. If it turns out your handcrank is 5 degrees per revolution, meaning your R/T is a 72:1 ratio, I can post back with all the bolt hole circles on the standard set of 3 dividing plates sold with the much more expensive units. You can see what hole circles are on the single plate that comes with my unit on the above LMS dividing plate link as well.
Cheers,
John Z.
 I will post this information assuming that any interested readers will
know that a dividing plate replaces the degree/minute dial and seconds
vernier scale under the handle of a typical rotary table, and that they
will also understand that there are adjustable sector arms over the
dividing plate which can be easily set to select any set number of holes
in any selected circle, so doing divisions becomes very quick and easy
to do repeatedly.
Book Title:
Gears And Gear Cutting' by Ivan Law, #17 of the Workshop Practice Series
     Excerpt from Chapter 8, Dividing Heads, page 63     
The author never likes to have to rely solely on tables or data charts
for information as they usually get torn or covered with oil and dirt,
making them difficult to read. It is always prudent to be able to work
things out for oneself. There is nothing magical about determining the
number of holes or which circle to use in the dividing plate, as the
following example shows.
Supposing that one wishes to cut a gear having 33 teeth using a
dividing head with a worm and wheel ratio of 60:1. The first step is to
divide the number of divisions required into the worm and wheel ratio 
in this case 60 divided by 33. This gives an answer of 127/33, which
indicates that each division is one complete turn of the handle plus a
further addition of 27/33 of a turn. The 27/33 of a turn can be achieved
by using 27 holes in a 33hole circle of the division plate.
If a 33hole circle is available then the problem is solved, but it is
unlikely that a 33hole circle will be on the division plate so the next
step is to look at the fraction 27/33 and see if it can be factorized.
And the answer is, yes it can as both top and bottom are divisible by 3,
resulting in a new fraction of the same value 9/11. If the division
plate does not have a 33hole circle then it certainly will not have an
11hole one but it is most likely to to have a circle that is a multiple
of 11 and this will in all probability be a 77hole circle. If we now
return to our 9/11 fraction and multiply both top and bottom by 7 we
arrive at 63/77. The division for producing a 33tooth gear is therefore
one complete turn of the handle plus 63 holes on a 77hole circle of the
division plate. Once this example is understood it is a simple matter to
substitute any division as required.
The occasion may arise when the division plate does not possess a
circle with the requisite number of holes. This is a most unlikely
occurrence as the plates are carefully planned to give a very wide range
of divisions but, if a makeshift division plate has to be made do not
worry about positioning the holes to very fine limits as any error in
the division plate is not passed on directly to the workpiece, but is
divided by the wormwheel ratio so the actual error becomes very tiny indeed.
  End Excerpt  
A lot of people are going to buy the increasingly common 72:1 ratio
rotary tables (R/T's) that either do not come with any dividing plates,
or in my case, only comes with one dividing plate when more than that
would be world's better.
With that said, looking around at more expensive R/T's with 72:1
ratios, I found that the best ones come with 3 dividing plates, A, B,
and C. They have hole circles as follows:
A Plate  15,16,17,18,19,20
B Plate  21,23,27,29,31,33
C Plate  37,39,41,43,47,49
Save this message if you have a rotary table that goes 5 degrees per
full revolution of the handle. That would be 0 through 4, and then back
to 0 again making it 5 degrees. A 72:1 worm wheel ratio. Also, a lot of
people are going to have to search way back in memory to when they last
had to work in oddball fractions outside of the usual inch system. For
folks used to metric that may be an extra long time. :)
To repeat the above 33tooth gear example on a 72:1 R/T with the above
A, B and C dividing plates, that would be:
72 divided by 33 = 2.181818182 on the calculator.
So you know that is 2 full turns, mark that down and subtract 2 from
the reading on your calculator to leave only the decimal portion
showing. To turn that decimal remainder into a whole remainder, multiply
it by the same divisor just used above, in this case 33.
.181818182 X 33 = 6, as in 6/33 of a turn left over. (Always round to
nearest whole number when necessary, like when a result shows .999999999
round up, or .00000006 then round down, etc,).
So each division would be 2 full turns plus 6 holes in the 33 hole
circle on plate B. Set up the sector arms so they leave 6 holes open
between them and adjust the arm plunger to engage with the holes in the
33hole circle. 2 full turns plus 6 holes, 33 times and done. Using a
dividing plate is easy  repetitious but easy  as long as you simply
keep track of where you are. Mainly that means don't get side tracked or
interrupted to where you forget what you were doing. Turn off the phone,
etc. :)
How about making a dial with 40 divisions like on the cross slide of
the minilathe:
72 divided by 40 = 1.8, so there is 1 full turn plus
.8 times 40 = 32, as in 32/40 of a turn left over.
There is no 40 hole circle, but 32/40 can be factored down by dividing
both top and bottom by 2, so 32/40 becomes 16/20. There IS a 20 circle
hole on plate A above.
So 1 full turn plus 16 holes in the 20 hole circle. Set up the sector
arms and have at it, 20 times and done, although in making the dial you
would probably make some indicator marks longer than others, like an
extra long mark every 10th and medium long every 5th as per most dials.
Make up some more divisions to do as practice and you should hopefully
find this gets easy pretty fast. If you have an R/T with dividing plates
and a table of divisions you can double check your math that way too.
Now somebody bright is going to want to do 25, 50 or 100 divisions and
quickly find they need a 50 or 25 hole circle. Time to make a new hole
circle in another dividing plate! That would be another post, too.
Reread the last paragraph in the excerpt above. :)
The two circles in my LMS 1810 rotary table's sole dividing plate are
15 and 28. They cover a wide range but skip way more than I'd like. The
3 plate set as per above would be much better, along with an additional
plate with a 25 hole circle. (There are reasons why 40:1 and 60:1 ratios
used to be so much more common. but if people can get little minimill
sized 72:1 R/T's cheap then all of the above becomes important.)
Cheers,
John Z. Hi, John,
I finally realized that it is what I originally thought; 25 seconds per vernier division. It's just not terribly convenient.
No, I didn't get dividing plates for it, but I'm planning to make some in the future.
The table is a 72:1 ratio (the main crank goes 012340), as does yours. The difference is how the scale is graduated. The main scale has only 12 divisions between degrees, making each graduation 5 minutes (300 seconds). With a vernier with a total of 12 divisions, that makes each vernier division 300 seconds / 12 divisions = 25 seconds /division.
I'd appreciate any info you'd like to share on dividing plates, etc.
Thanks,
Charlie
New Jersey, US In grizhfminimill@yahoogroups.com, <steelchipper@...> wrote:
On 9/18/2013 11:10 PM, clevinski@... wrote:
Thanks, Alan... that helps, especially the Sherline info. I'm having a heck of a time figuring out how to read the vernier on mine; it's kind of strange, or I just don't know how to read it. You can see the dial here.
Did you or can you get dividing plates with your rotary table? Since I do not work with astronomy or other applications where minutes and seconds apply, my main consideration is *divisions* like perhaps a 6 hole circle, a 50 division dial or for cutting some number of teeth into a gear blank disk.
http://www.atmsite.org/contrib/JSAPP/divide/divhead.html
What is the ratio of the internal worm gear on your R/T? Mine does 5 degrees per handcrank revolution (0 thru 4 to 0 again) . There are 360 degrees in a circle so 360 / 5 = 72. My worm gear ration is 72:1. Knowing this I can look at other more expensive rotary tables and find which dividing plates are available for them, as mine only came with one dividing plate.
For your degrees/minutes/seconds, I would say simply ignore the minus (left) 60 part of the vernier when cranking clockwise and focus only on the positive (right) +60 increments. 10 second increments means you are going to have to roughly guesstimate anything less than 5 seconds or so. Again, I normally go by divisions not degrees/minutes/seconds so the whole degree/minute dial is usually removed and replaced with a dividing plate.
I bought the LMS 2183 kit, back when U.S. dollars were much more valuable than they are now.
http://lmscnc.com/2183
which is the 1810 precision R/T with dividing plate and a tailstock. You may have some luck with reading the instructions for the R/T:
http://www.littlemachineshop.com/instructions/RotaryTable.pdf
and perhaps most especially, for the dividing plate that comes with it.
http://www.littlemachineshop.com/instructions/1811DividingPlates.pdf
Without dividing plate(s) a rotary table is severely limited in use whenever divisions are needed as opposed to degree/minute/second use (and even for degree/minute/second use it is hard to set for less than the nearest whole 10 or maybe 5 second increment).
Search online for how easy it is to convert from decimal degrees to degrees/minutes/seconds and vice versa. I could also post more about working out which dividing plate hole circle is needed for whatever division as may be needed, but as usual my post is already turning into a book so I'll stop it here for now. If it turns out your handcrank is 5 degrees per revolution, meaning your R/T is a 72:1 ratio, I can post back with all the bolt hole circles on the standard set of 3 dividing plates sold with the much more expensive units. You can see what hole circles are on the single plate that comes with my unit on the above LMS dividing plate link as well.
Cheers,
John Z.
 Awesome link AlanThanks for posting it.Barry Young
From: Alan Reinhart <avr@...>
To: GrizHFMinimill@yahoogroups.com
Sent: Wednesday, September 18, 2013 5:55 PM
Subject: RE: [GrizHFMinimill] Rotary Table Book or PDF
Hi Charlie – have you seen this from Sherline?From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of clevinski@...
Sent: Wednesday, September 18, 2013 8:42 PM
To: GrizHFMinimill@yahoogroups.com
Subject: [GrizHFMinimill] Rotary Table Book or PDFHi,
Besides the LMS document (which IS helpful), does anyone know of a book or, even better because it's free, a PDF on rotary tables?
Many thanks!
Charlie
New Jersey, US  Thanks for sharing this great link Herb.Barry Young
From: Herb Walke <herbwalke@...>
To: Griz MiniMill <grizhfminimill@yahoogroups.com>
Sent: Wednesday, September 18, 2013 8:30 PM
Subject: RE: [GrizHFMinimill] RE: Rotary Table Book or PDF
http://biology.clc.uc.edu/fankhauser/labs/anatomy_&_physiology/a&p203/circulatory_system/vernier_scale/vernier_scales.htm
This may help
To: GrizHFMinimill@yahoogroups.com
From: clevinski@...
Date: Wed, 18 Sep 2013 20:10:51 0700
Subject: [GrizHFMinimill] RE: Rotary Table Book or PDF
Thanks, Alan... that helps, especially the Sherline info. I'm having a heck of a time figuring out how to read the vernier on mine; it's kind of strange, or I just don't know how to read it. You can see the dial here.
Each division on the moving dial is 5 minutes (12 divisions between degrees). But how to read the vernier? There are + and  six increments, so the total range is dividing the 5 minutes of the main dial into 12 parts, or .4166667 minutes per graduation. That happens to be 25 seconds per graduation, but that doesn't really help much, does it? If you get alignment with either of the "60" marks on the vernier, that would be 2.5 minutes. But what about the others? And why is the 2.5 minute mark on the vernier labeled "60"?
Anyway, I'll figure it out eventually...
Thanks for the links!
Charlie
New Jersey, US  Thanks to everyone who commented, and a special thanks to Sir John for the detailed information on dividing plates!
As mentioned above, it looks like my particular table works out to 25 seconds / vernier division; I just don't know why the vernier is labeled "60..0..60". I suspect that this vernier is also used on tables where the moving dial is 2 minutes/graduation; in that case, the labeling would mean 60 minutes to +60 minutes.
Thanks,
Charlie
New Jersey, US