# Rotary Table



## Coomba (May 2, 2017)

Looking to buy one of two rotary tables. One is a  6 inch, and the other an 8 inch. The 6 inch has three division plates, and the eight has two. Is this because the eight is larger and has more room for the holes? Does anyone have any experience or knowledge of these tables?

http://www.ebay.com/itm/311611757244?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT


http://www.ebay.com/itm/311611906010?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT


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## DAT510 (May 3, 2017)

I'm not familiar with the two you listed. They look similar to the RT sets that Grizzly sells. The individual HV Rotary Tables Grizzly sells look similar to the 6" Vertex I just picked up.  I've been happy with it so far. Not sure what size mill you have, I have a medium sized bench mill, and for me an 8" RT would have been too big when used in the vertical position. 

As for the Division plates, from the images, yes it looks like you are correct.  The 6" plates have 6-7 rows/rings of holes per plate and the 8" plates have 9-10 rows.


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## Coomba (May 3, 2017)

DAT510 said:


> I'm not familiar with the two you listed. They look similar to the RT sets that Grizzly sells. The individual HV Rotary Tables Grizzly sells look similar to the 6" Vertex I just picked up.  I've been happy with it so far. Not sure what size mill you have, I have a medium sized bench mill, and for me an 8" RT would have been too big when used in the vertical position.
> 
> As for the Division plates, from the images, yes it looks like you are correct.  The 6" plates have 6-7 rows/rings of holes per plate and the 8" plates have 9-10 rows.



Thanks for bring that up, I didn't even think that the 8 inch may be to tall for my mill.


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## umahunter (May 7, 2017)

Looks just like the grizzly 6 inch that sells for 350 precision matthews  sells vertex which are made in Taiwan and supposed to be better I think the 6 inch is around 350 for the rotary table and nothing  else


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## mikey (May 7, 2017)

Just to add, the Vertex 6" table is a close clone of the very expensive Yuasa 6" rotary table. Construction is nearly identical except for some of the oil groove patterns. The Vertex tailstock is also a close clone of the Yuasa construct so the Vertex is pretty well made and seems to be worth the cost.


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## umahunter (May 11, 2017)

Actually I think the vertex is a lil closer to 269 not 350


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## ezduzit (May 11, 2017)

Get the biggest one your machine can handle. Mine is the 12" Troyke. My first fabrication on a milling machine (end fitting for 4" sailboat boom) really required that much table. You need room for hold-downs, etc.


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## darkzero (May 12, 2017)

Coomba said:


> Thanks for bring that up, I didn't even think that the 8 inch may be to tall for my mill.



What mill do you have?


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## Coomba (May 12, 2017)

darkzero said:


> What mill do you have?



I have the PM450G


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## darkzero (May 12, 2017)

Coomba said:


> I have the PM450G



I'm not familiar with all the new model PM mills but a quick search online shows that the PM450G has a 8-1/4" wide table. That may be borderline between a 6" & 8" RT. Here's what I mean.

I have a PM45M which is the predecessor of the PM932. My table is 9-1/2" wide. I originally bought a 6" Vertex/Yuasa style RT & it was too small for my table. In order to clear the handwheel of the RT, since it sits lower than the surface of the RT base, I had to use outermost T-slot on my table to mount it & I did not like that cause my mill does not have an adjustable ram. With the RT mounted that far out, there may be cases where I can't move the table in Y axis enough to reach. In addition, with the RT in the vertical position, the slots on the RT would not line up with my table T-slots so it would need to be clamped down. Not a big deal but I did not like that either.

So I sold the 6" & got me an 8" Vertex RT from Matt. Now this one was well suited for my mill. I could mount the RT using the middle T-slot & the handwheel clears the edge of the table. In the vertical position, the slots on the RT lines up with with my T-slots, no clamps needed. In addition, the 8" RT has 14mm slots & so does my mill table so I could use the same clamping kit that I use for my mill table on the RT.

Here's a post showing what I mean. http://www.hobby-machinist.com/threads/rotary-tables.34634/#post-292983

I would recommend comparing the measurements of the 6" RT with your mill table so you don't make the same mistake I did if what I mentioned matters to you. Luckily my mistake did not cost me anything, I actually came out well on top but it still not a good feeling!


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## Wreck™Wreck (May 23, 2017)

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?


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## JR49 (May 24, 2017)

Wreck™Wreck said:


> 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


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## Wreck™Wreck (May 24, 2017)

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.


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## JR49 (May 25, 2017)

Wreck™Wreck said:


> 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


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## catsparadise (May 25, 2017)

JR49 said:


> 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


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## Wreck™Wreck (May 25, 2017)

JR49 said:


> 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.


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## Reeltor (May 25, 2017)

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.


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