[dbruins]

In my new build wish list thread there's a sub-discussion about the size of the 4th axis rotary table.

This topic deserves it's own thread as I've read about it in numerous other threads and we can shed light with a simple pros and cons list of the smaller vs larger rotary tables.

Please comment and add to the list and by the end we'll have a solid reference.

6" Rotary Table (30290)

Pros

• $235.18 cheaper (and cheaper to ship)
  
  • $1,287.83 for 6" 4th axis kit (30290)
  • $118.80 for 6" tailstock (30272)
  • $272.80 for 6" 3 jaw chuck (30292)
  • $1,679.43 total for 6"er

• $1,447.11 for 8" 4th axis kit (30289)
• $157.30 for 8" tailstock (30197)
• $310.20 for 8" 3 jaw chuck (30291)
• $1,914.61 total for 8"er

• 25 lbs lighter (weights are shipping weights but since we're taking the difference the packing materials cancel out, roughly)
  
  • 70# for 6" table only (30267)
  • 28# for 6" 3 jaw chuck (30292)
  • 98# total for 6"er

• 89# for 8" table only (30194)
• 34# for 8" 3 jaw chuck (30291)
• 123# total for 8"er

• Compatible with the ATC (32279).

Cons

• Not as rigid as the 8"er.
• Cannot hold as large a work piece.

8" Rotary Table (30289)

Pros

• More rigid than 6"er.
• Can hold larger work pieces.

Cons

• $235.18 more expensive (+ higher cost of shipping)
• 25# heavier
• Not easily compatible with ATC (32279).

[philbur]

If you have a need to attached odd shaped work-pieces then buy the 8" because the extra real-estate will be useful, for absolutely all other purposes buy the 6".

Phil

[mioduz]

I use the 8 inch super saver. It is more pricey but I think it's worth it. Not using the atc is not an option in my mind. Also I needed the larger through hole of the 8". I hate buying equipment and not being able to do something because I didn't get the bigger version so I try and get what I think I may need in the future

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[mountaindew]

I know its not a big concern for many users but weight is also something to consider in cost and use.
I installed a medium duty trolley crane to move 4th axis on and off the mill. the 8" super spacer with 3 jaw chuck is 145 lbs.
This added 200$ to the cost of the 4th axis for my use. long term this solved other lifting problems also, so it does have more use around the shop. md

[mioduz]

I agree with mountain dew. Consider how you will get it on and off. It is a real batch to get the 8 in super spacer on and off.

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[Don Clement]

I have both a manual 6" RT and a Tormach 8" RT. Since I don't have an ATC, the 8" RT works well for me in my applications with no cons. As for getting the 8" RT on and off (which I do regularly) I built a shelf just behind the mill at the same height as the mill table so that I need only lift the RT slightly just enough to clear the mill table turn around and set the RT down on the shelf with no bending. The 6 months of strength training at the gym has really helped with this effort ;-)

Don C.

[pickled]

I have both PCNC models as well as the 6" and 8" rotary tables in my shop. I must say that I favor the 8" in every aspect, but moving it around and the amount of table space left after mounting it. The newest 6" tables are much better than the old style that I had. They have much more reserve torque and seem to be built a little tighter.

I personally like to leave my 4th axis (with a 4 jaw chuk) and a vise on the machine unless it is absolutely necessary to remove it. My projects typically require the use of both during part runs so I want to minimize set-up times, errors and gouges to my machine tables. In my opinion mounting an 8" table and chuck on a PCNC 770 would definitely crowd the table and limit the location of a vise for doing any other work. The 6" RT on the 770 table fills it up pretty good, but still leaves you enough room to run a 5" plus part envelope in a vise hanging out somewhere in + X land. Also realize that the 770 has less Z travel than an 1100 so if you are planning on index drilling larger diameter stock in your 4th axis using the 8" table is going to make things pretty tight from a Z perspective. If you do get the 8" for a 770 be sure to get a set of machine screw drills to conserve your Z real estate. The 8" is great for my 1100, but I wouldn't burden the 770 with it. Good luck with your set-up!

[dbruins]

So in the end our pros and cons list looks like this ...

6" Rotary Table (30290)

Pros

• $235.18 cheaper (and cheaper to ship)
  
  • $1,287.83 for 6" 4th axis kit (30290)
  • $118.80 for 6" tailstock (30272)
  • $272.80 for 6" 3 jaw chuck (30292)
  • $1,679.43 total for 6"er

• $1,447.11 for 8" 4th axis kit (30289)
• $157.30 for 8" tailstock (30197)
• $310.20 for 8" 3 jaw chuck (30291)
• $1,914.61 total for 8"er

• 25 lbs lighter (weights are shipping weights but since we're taking the difference the packing materials cancel out, roughly)
  
  • 70# for 6" table only (30267)
  • 28# for 6" 3 jaw chuck (30292)
  • 98# total for 6"er

• 89# for 8" table only (30194)
• 34# for 8" 3 jaw chuck (30291)
• 123# total for 8"er

• Compatible with the ATC (32279).
• Does not crowd table space.

Cons

• Not as rigid as the 8"er.
• Cannot hold as large a work piece.

8" Rotary Table (30289)

Pros

• More rigid than 6"er.
• Can hold larger work pieces.

Cons

• $235.18 more expensive (+ higher cost of shipping)
• 25# heavier
• Not easily compatible with ATC (32279). (Requires either the 8" Tilting Table or the 8" Super Spacer Table. Both of which are heavier and more expensive.)
• Crowds table space: esp in X and Z directions.

[Don Clement]

Déjà vu all over again :-)