Rotary table with MT3 center

[Maplehead]

Hi All
I bought a MT3 arbor with a threaded top to hold down some 16 gauge sheet metal so that I can spin a circle out of it. However, even after tapping in the arbor with a metal hammer the part is spinning under the cutter, and I was only taking .005" cuts.
How do I secure the arbor?

 

[mikey]

I would first check the fit of that MT3 arbor. It should not slip under such slight forces so if it is spinning then the fit is either poor or there is some debris or burr in there that is preventing it from seating. You might want to blue the arbor and check.

The other thing you can do is use a drawbar to lock the arbor in place. Most rotary tables will allow this.

 

[C-Bag]

The other thing you can do is use a drawbar to lock the arbor in place. Most rotary tables will allow this.

Yup, mine is just a bolt with a big washer.

 

[cathead]

The center isn't really designed to take the torque of milling. I use it mostly for positioning and rely on the
table's keyed slots to do the work holding. The farther you get from the center, the better for work holding.
It's easy to mount your work on a piece of plywood with maybe 3 to 4 small wood screws. Then affix the
plywood to the table slots with bolts. The wood screws are placed outside of where the cutter passes
so you don't end up with holes in the work piece.

 

[Maplehead]

The center isn't really designed to take the torque of milling. I use it mostly for positioning and rely on the
table's keyed slots to do the work holding. The farther you get from the center, the better for work holding.
It's easy to mount your work on a piece of plywood with maybe 3 to 4 small wood screws. Then affix the
plywood to the table slots with bolts. The wood screws are placed outside of where the cutter passes
so you don't end up with holes in the work piece.

That's like the old jig I had with my smaller rt and mill. Guess I'm going back to that method.

 

[C-Bag]

I am in no way an expert so maybe that’s why I got away with it, but my brother took one of those mt3 with a machinable ends on it and threaded it so I could put my 4” chuck on it to mount my 4” chuck on my RT. I used it to make 4.5” OD holding collar for my antique screw press. Worked great.