Rotary Table – Mini Mill Accessory
A rotary table is a really nice accessory to have for your mill, but one that you can delay purchasing for a while until you master the basic milling operations. The rotary table is driven by a worm-gear and is accurately calibrated in degrees and fractions of a degree.
It is used to mill or drill accurately positioned holes around a bolt circle, for milling arc-shaped grooves or slots and many other operations. Most, but not all, can be mounted in a vertical as well as a horizontal orientation; a very desirable feature.
Finding a rotary table of the right size for the mini-mill has been a lille problematic. 8-inch tables are really much too big. Even a 6-inch is pushing the limits. I have one from Grizzly. It is well made and works well, but mounting it to the table was a little bit of a challenge.
Sherline offers a very nice 4-inch model, and more recently LittleMachineShop.com has listed a 4-inch model as well. These are very nice, but a little smaller than I would like. In my view, a 5-inch model would be ideal, but I don’t know of one in that size.
The first rotary table I purchased was made in India and was of really poor quality. I returned it to the vendor for a refund. Unfortunately, the return shipping on a heavy object like this is not cheap, so be careful what you buy!
Sherline makes a beautifully finished 4″ rotary table which I got to see first hand at Cabin Fever 2001. I was very impressed by the high quality of this item, but It was a little small for my needs.
Grizzly 6-inch G1049
The table I currently use is a Grizzly G1049 6-inch model. As of 03/02 it sells for $199 plus shipping. It is well-made, and I have been very satisfied with it, although it is a little large for the mini-lathe as you will see in the photos below.
The Grizzly RT is shipped in a cardboard box with molded styrofoam packing. I received it quickly and damage-free.
After cleaning off the packing grease with kerosene, a painbrush and a rag, I mounted it on the mini-mill table using 3/8″ carriage bolts that I also use for my 3 1/2″ Grizzly milling vise. The center hole is a #2 Morse taper.
The RT is really a little oversize for the mini-mill, but still provides enough clearance to be practical. I did not feel that the weight was beyond the capabilities of the mini-mill table.
Here’s a picture showing the table with a 12″ rule and a 1/2″ mill in an end mill adaptor. Mounting the mill in a collet would provide another 2″ or so of working room. The head is at the top of the column. Also shown is the 3″ chuck from the 7×10 mini lathe. As you can see, there is adequate clearance for most operations.
The casting has mounting lugs for both horizontal or vertical mounting. This makes it potentially much more flexlible, but the table of the mini mill is small compared to the RT which makes mounting the rotary table in the vertical orientation a little tricky.
It can be aligned either parallel or perpendicular to the table x-dimension but either orientation has some difficulties.
One problem is that the lower edge of the handwheel for the RT is lower than the base of the RT, so it must be positioned off the edge of the table. If the RT is positioned perpendicular to the X-axis, the mounting holes in the RT are outside the limits of the T-slots in the mill table.
These problems can presumably easily be overcome by using custom-made riser blocks and clamps, though. I have not yet attempted to make these items, but would not expect them to be very difficult to make.
For the price, I was pretty impressed by the quality of the table. I would rate it somewhat lower in quality than the Sherline 4″, but much better than the Victor 6″.
The base is painted with wrinkle-finish black paint. Fortuitously, the T-slots in the RT are about the same width as those on the mini-mill, so the same T-nuts can be used on both.
The handwheel is satin-finish steel with cleanly etched divisions. Each full rotation of the handwheel rotates the table by 4 degrees. A brochure included with the RT illustrates an indexing plate accessory which can apparently be attached to the RT, but I’m not sure whether or not Grizzly sells this accessory.
An eccentric cam between the handwheel and the table permits you adjust the meshing of the worm-screw to minimize backlash. A screw with a T-handle locks the cam in place once it is set.
Heres a closeup of the divisions on the periphery of the table before the packing grease was removed:
Once rotated to the desired setting, the table can be locked in place by means of two locking clamps on opposite sides of the table.
LittleMachineShop 4-inch, SKU 1627 (Discontinued)
Here’s a nice little 4″ imported rotary table offered by LMS for $134.95. They offer several other models, including the Sherline 4″. I don’t have any first-hand experience with this one, so I can’t really comment on quality or capabilities.