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Thread: rotary table
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8th June 2014, 07:28 PM #1SENIOR MEMBER
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rotary table
just recently bought a second hand ( but appears unused) rotary table of unknown origin came with a chuck and dividing plates 23 25 28 31 39 43 and 19 27 30 33 41 47.
the confusing part for me is its 67: 1 turns for 360 degrees and each revolution of the handle is divided into 150 divisions
how do you work out say marking out a 4 hole back plate for a chuck back plate??
the unit is unsealed but covered in grease the lub points have those little ball type for oiling should i clean grease off and use oil
john
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8th June 2014 07:28 PM # ADSGoogle Adsense Advertisement
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8th June 2014, 07:51 PM #2GOLD MEMBER
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Maybe 16 fullturns and 112.5 divisions on your dial.
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8th June 2014, 08:05 PM #3SENIOR MEMBER
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thanks pete how did you get that ??
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8th June 2014, 08:12 PM #4SENIOR MEMBER
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doooh i might have known use your head and calculator john before pipeclay wraps you on the knuckles
67/4 =16.75
so 16 turns+150*.75=112.5
16+112,5
hmm not so hard,
can this be done using the given indexing plates supplied seems a bit harder
john
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8th June 2014, 08:20 PM #5
Pick a dividing plate that is divisible by 4 when multiplied by 67.. like 28*67=1876, 1876/4 = 469.. 469/67=7
So, mount up the 28 hole plate, that gives you 28*67 (1876) holes per table revolution, 1876/4 = 469 holes for each 90 degrees of table rotation. 469/28 = 16 turns of 28 plus 21 holes..
Most rotary tables are 90:1 ratio. Unusual to get one that's 67:1..
Ray
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8th June 2014, 08:50 PM #6Senior Member
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Could the rotab ratio be more like 66.666 turns per full revolution rather than 67? That gives a sort of rational 5.4° per turn of the handle, whereas the reasoning behind a genuine 67 turns for 360° is a bit of a head scratcher.
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8th June 2014, 08:51 PM #7
If you REALLY want to use this for dividing, I suggest you build a digital divider for it and drive it with a stepper motor..... then you can stop counting turns and doing mental arrithmatic and just type in the number of divisions you want
If that tickles your fancy, then have a look at the thread https://www.woodworkforums.com/showth...48#post1673648 to see what I'm talking about. I think SimonL also built one since then.Cheers,
Joe
9"thicknesser/planer, 12" bench saw, 2Hp Dusty, 5/8" Drill press, 10" Makita drop saw, 2Hp Makita outer, the usual power tools and carpentry hand tools...
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8th June 2014, 08:55 PM #8SENIOR MEMBER
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thanks ray yes i was surprised when i counted the turns , atm its dismantled to clean off all the grease so ill recheck it when its back together
john
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8th June 2014, 09:00 PM #9Philomath in training
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The grease would be protective. The oil nipples are for oil.
67:1 is weird. I would have expected a divisible number (for example 60 or 90) rather than a prime number (? I think). Is the ratio what you have physically measured or what you have been told?
Indexing half a division is not good practice, so while indexing 112.5 divisions may be the answer technically, accurately getting that 1/2 division can be troublesome.
Apart from winding the handle a lot, one way to check the ratio is to count the teeth on the worm gear wheel. If you have a single start worm and 67 teeth on the worm gear wheel then you do have a 67:1 R/T.
I notice you are in Adelaide. Shoot me a PM if you want to bring it over for a dissection (or other analysis).
Michael
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8th June 2014, 09:12 PM #10SENIOR MEMBER
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well i found the torch and went and counted the teeth 3 times
72 sounds a
bit more realistic
'
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8th June 2014, 09:19 PM #11SENIOR MEMBER
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joe stop making me think about more projects im 10 years behind already
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8th June 2014, 09:30 PM #12Philomath in training
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Sounds much better. 1 turn = 5 degrees. Easier to work out too.
Michael
This spreadsheet may help - I haven't double checked the results so a spot check is warranted but it should be a start anyway.
RT.xlsLast edited by Michael G; 8th June 2014 at 09:35 PM. Reason: added spreadsheet
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8th June 2014, 09:43 PM #13SENIOR MEMBER
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Thanks for that Michael that certainly makes a difference and yes we had better catch up one day id love to see some of your achievements i live way out north near gawler so mutual free time may be the hard part
thanks every one for your input
john
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8th June 2014, 09:49 PM #14Philomath in training
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Forgot to say - the spreadsheet calculates out depending on the numbers across the top. That means you can insert a column and see what combinations it would give you - so if you put in a wheel with 34 divisions it will solve the inability to divide by 17 and 34 for example. (remembering to adjust the formula in column C)
If you change the ratio up in the top left corner it will also work for other tables too.
MichaelLast edited by Michael G; 8th June 2014 at 09:55 PM. Reason: Lots of corrections - brain not in gear
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8th June 2014, 10:07 PM #15SENIOR MEMBER
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Thanks michael
oh i should add pics i suppose this is before i cleaned it up a little
ROTAB.jpg
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