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Making a Rotary Table

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NormanV:
Pekka, you may well be right, I do not mind the criticism. I had planned for the table to sit on the top plate and to be clamped to it. This would be fine for indexing but not for cutting curved parts. I could add a bridge piece with a bearing below the worm wheel, this would brace it. Any comments or ideas are welcome, I am no expert.

Arbalist:
That's a nice chunky looking casting Norman, looking forward to seeing how you progress!

PekkaNF:
I have normal #6 size rotab and it's fine with drilling and even light milling, but it is not happy when I  feed work against the mill, if it is even close to circumfrence of the rotab table. It looks like that the table is lifting or moving sideways.

If you only use the table for indexing, you may consider dimenssioning parts such way, that the bearing keeps everything in close contact and then you use clamps or dogs to pull the top (rotab table) into the body. If you can imobolize them for a cut, I believe it all would be fine for drilling and such.

The problem with bearings is that they are all designed to very spesific purposes and need some getting used to. Here you have short bearing distance and you need some rigidy in all directions. It would be simple if major forces would work only one or two directions.

Professional rotabs have very elaborate bearing arragements, simplest form is something like this on top:
http://www.wd-bearing.com/en/WD-YRT-Rotary-Table-Bearings/WD-YRT-Rotary-Table-Bearings.htm#.VAq2hmMsHOg

We hoppyist find it very difficuts to machine parts to make use of this kind of stuff and must hope that robot joint falls on front yard from e-bay or just make it the way it has been made in last 100 years - plain bearings:
http://www.deansphotographica.com/machining/projects/mill/rotary/50.jpg

The bottom bearing (surface) just pulls it all together. This does not look very different from yours:
http://www.deansphotographica.com/machining/projects/mill/rotary/rotary3.html

Maybe you'll find it useful.

Pekka
* fixed mass of typos, I wonder if anybody made any use of this. I got new mini laptop and keyboard is very different from the old one. Aso, I'm blind as a bat and this display is small. I allready got time on optometris. I need separate glasses for driving, work, reading and soon for a computer display. What next? A guide dog or white cane?

NormanV:
Thank you Pekka for your detailed comments, the Taig design is similar to what I intend to do including clamping the table to the body whilst making a cut. This of course does not enable me to make a cut whilst rotating the table. This is something that I had not given enough thought to as it is a facility that would be useful. There may be enough space under the worm wheel to fit a bearing that would give the support needed, but I do have a piece of equipment that may contain a ring bearing that would support the table. I'll only know this if I can work out how to dismantle it!
Today I machined the remaining sides of the body casting and faced off the top plate. I am really pleased with these two castings as they have no bubbles or inclusions where it matters. I am confused at the talk of the need to degass the molten metal, I do nothing other than skim the top of the melt before I do the pour. Forty years ago I did some aluminium casting at evening school and that metal was degassed but still had bubbles in it.
The milling machine does throw the swarf around all over the place, I had to spend a lot of time vacuuming it all up as I found it quite irritating crunching underfoot.

NormanV:
By the way, does anybody have any suggestions as to the cause of the rings on the top plate? The feed was done by hand but the rings are equally spaced.

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