Rotary Table

[tornitore45]

The MT hole is very useful. I have a set of MT2 collet and if not used to old a part in a normal way it can be used to hold a cylindrical pin that may or my not have a an OD thread or an ID thread. I accumulated a box of such adapters. I would not try to machine that taper out.

[pete]

That Yuasa will probably be more to a lot more accurate than my 6" Vertex. With mine there's at least a few 10ths run out between the tables center of rotation and it's MT 2 bore. Maybe for most things that might not matter. But with shop tooling I still think it's well worth checking what that equipment already has for accuracy before trying to do any modifications. Mine looks to have a press fit spindle and there's not a whole lot of spare metal around to do any modifications. For mine the worm is attached to the bottom of the table and not to the spindle, but yours might be different.If it were me? I'd do a full disassembly to see what you actually have before trying to do irreversible modifications. As others have said, those MT 2 blank end shanks are a good option. If accuracy is important, I think I'd spend the extra and buy the hardened and ground that still come with machinable ends.

There's very good reasons why most rotary tables and dividing heads use some type of spindle taper. It's much more accurate and repeatable than any straight bore and slip fit part locator. Those machinable MT shanks are made for exactly this type of requirement. I look at these tables having that MT taper as the much better design choice and not a deficit. Like Mauro I have MT 2 collets, but there a lot easier to use when the tables in a vertical orientation since they require some type of draw bar to close them. With the table in the horizontal position it's still not impossible, but you'd have to add some type of blocking under the table to gain access to the draw bar end. Adding part locators to any RT is no different than building fixtures for a lathe or mill. There's no single method that's going to work for everything. Check the riveted on tag that Yuasa should have, it will probably indicate what the spindle taper really is. Choprboy's right, not all of them have a MT spindle. MSC doesn't list a 6" but the rest of them all seem to come with MT's. That may not be reliable information for an older one though.

[tornitore45]

you'd have to add some type of blocking under the table to gain access

That was my first solution but then I figured that there was enough space to turn an insert that allowed the short drawbar (A Socket Head Cap Screw) to fit flush.

Basically, think of an old fashion cylinder hat. The screw head fits inside the hat and the hat inside the MT2 bore, the brim act as a flange thick enough to fit in the recess without protruding.
Still the drawback is that one has to tighten the collet before clamping the RT to the bed. This is where the adapters to transition from collet hole to whatever one need come handy.

[pete]

that's funny since that's exactly what I did with mine Mauro. And when I was making it I even thought it had the same shape as one of those old Top Hats. Maybe all R/T's are like what I have, but mine has the spindle a little shorter and doesn't protrude to the full depth of the table. So that flanged cylindrical spacer idea works well as you said with an Allen bolt. For a single part it works just fine, for multiple parts then blocking the table up and using a standard hex head bolt and shop built heavy spacer might be a bit easier I think.

Troyke, Advance and a few others made R/T's with a built in X,Y table mounted on top of the table that does away with all this pita adapting. So mounting anything fairly close and using that X,Y table you can zero your parts or off set it to where you want. But even with used one's there not cheap. Average prices that I've been seeing is around $800. The smallest I know of has a 9"x9" top I think, and with it's extra height may not work at all on a smaller mill. There also heavy. I still wish I had one.

[tornitore45]

Great minds think alike.
I did not even think of multiple parts because rarely is my case. Again, inserting some adapter in the collet makes the access from the top.

[liveaboard]

I just checked the hole on mine; MT3.

It's 8" Taiwanese.