Thread: rotary table

Maybe 16 fullturns and 112.5 divisions on your dial.

thanks pete how did you get that ??

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

Originally Posted by tanii51

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

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

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.

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.

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

Originally Posted by tanii51

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

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

well i found the torch and went and counted the teeth 3 times
72 sounds a
bit more realistic
'

joe stop making me think about more projects im 10 years behind already

Originally Posted by tanii51

well i found the torch and went and counted the teeth 3 times
72 sounds a bit more realistic

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.xls

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

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.

Michael

Thanks michael
oh i should add pics i suppose this is before i cleaned it up a little
ROTAB.jpg