Rotary Table

[Wreck™Wreck]

You do not need dividing plates, I have never seen a rotary table without marks that resolve to degrees and minutes of arc. A dividing plate makes it easy for an operator/employee to reach a particular position with less error when making hundreds or thousands of the same part. As a hobby you are probably not making 100 copies of the same part, do a little math and rotate it in Degrees and Minutes to the proper location.

Do you think that a dividing plate is inherently more "accurate" then the vernier scale?

 

[JR49]

do a little math and rotate it in Degrees and Minutes to the proper location.

Hey Wreck, any chance you could give the newbees (myself included) a quick lesson on doing the math to convert some random number of divisions into degrees and minutes ? Please be thorough, as I only had 1 semester of algebra about 54 years ago. Thanks, JR49

 

[Wreck™Wreck]

The angle is 360 divided by the number of divisions, a 4 hole bolt circle is 360/4 or 90 deg. and so on.

The decimal degrees X 60 will yield the minutes and a decimal

20.5 degrees would be .5 X 60 or 20 Deg. 30 Min. (this is not an equal number of divisions) but would apply to 2 or more features that need to be 20.5 degrees apart, like so.


The decimal minutes divided by 60 then multiplied by 3600 will give seconds.

Every rotary table that I have used has a whole degree scale and a minute vernier scale.

 

[JR49]

The decimal minutes divided by 60 then multiplied by 3600 will give seconds.

So, what do you do if you still have a decimal left when you've divided by 60, then multiplied by 3600 to get the seconds??? I tried it using 21 divisions, and came up with 17 degrees, 8 minutes, and 34.28496 seconds. Now what??? JR49

 

[catsparadise]

So, what do you do if you still have a decimal left when you've divided by 60, then multiplied by 3600 to get the seconds??? I tried it using 21 divisions, and came up with 17 degrees, 8 minutes, and 34.28496 seconds. Now what??? JR49

You need to round up/down to the nearest sensible setting. If you're indexing a 1" dia workpiece, 1 degree of arc is a distance of 8.7 thou around the circumference. 1 minute of arc is 0.14 thou and 1 second is 0.0024 thou. So even if your workpiece is 10" diameter, the error from ignoring the seconds will make no difference. For what I do the minutes of arc aren't going to affect the final result either!

Rob

 

[Wreck™Wreck]

So, what do you do if you still have a decimal left when you've divided by 60, then multiplied by 3600 to get the seconds??? I tried it using 21 divisions, and came up with 17 degrees, 8 minutes, and 34.28496 seconds. Now what??? JR49

17 degrees, 8 1/2"

Ignore the seconds for practical purposes as you likely lack a method of measuring such a thing anyway. If you had a dividing plate with 21 divisions how would you measure 34.28406 seconds of arc to verify the accuracy?

The same is true of linear measurements, if you were to turn a part in a lathe aiming for say 1", you get out the trusty tenth reading Starrett micrometer and measure it at 1.0006, is it actually
1.00063 or 1.00067. You now buy a .000001 reading tool and measure it at 1.0006403. There is no end in sight. Do not worry about dimensions that you lack the equipment to measure for obvious reasons.

 

[Reeltor]

I would contact your ebay seller and ask what hole patterns are on each plate for each of the two units that you are looking at. Should be pretty easy since the same seller is marketing both. Just because one has 3 plates and one has 2 plates doesn't mean that they will have the same numbered hole pattern.