Questions on Holding Items on A Rotary Table

[Pmedic828]

I feel like I am pestering everyone because I ask so many questions, but here's another.....
I recently purchased a 6" Phase II rotary table - I want to make a round base from a square piece of 1/2' plate - (I want to make the cylindrical portion of a ball turner - How do you mount this plate when it is bigger than the table. I drilled a thru hole and was going to put a bolt with a washer in the pre-drilled hole, going down the center of the table with a nut and washer on the underside - I don't have enough clearance under the rotary table to secure anything - the "hole" in the table runs from the top plate to the base - no room for a nut or anything - thought about turning a piece the inside diameter of the hole in the rotary table but it passes right thru the hole without anything to grab.
I other words, i have a plate that hangs over the side of the rotary table - I wanted to cut a portion of this plate round with an end mill but don't know how to secure it without using t-nuts which in my opinion, would be hit by the end mill. I can't afford a chuck and don't have another plate to drill holes in it so I can use the t-nuts.

 

[caster]

The rotary table has a mt2 taper in the center and t-slots on the face. I turned a mt2 taper and drilled/tapped a 3/8-16 hole on the wider side and 1/4-20 on the thinner side. I thinned the head of a bolt and secure the taper from the bottom, like a draw bar. Then I have a threaded hole in the center to mount to. You can make variation of this with a mandrel or a threaded rod extending out the top. If you are looking to round a square why not mount it on the lathe with a mandrel and turn.

 

[Pmedic828]

The plate that I wanted to cut a cylinder out of is about 18 X 18 - I wanted to cut the cylinder from one of the corners - otherwise, I guess I could cut a square out of one of the corners and then bore and mount on a mandrel. As I am new to this, I am afraid that the stock would start spinning and not be clamped hard enough in the mandrel, especially attempting to do an interrupted cut to make a square into a circle. Don't you need to make a hole with a key to keep the work from slipping - it is all new to me and need lots of help!
When making a mt2 taper, how would I hold this into the table since the "mt-2 hole" is flush with the base - there is no room for a washer or nut? maybe I am mis-understanding.

 

[dave2176]

You can clean the table and work piece with acetone or such to remove any oil and then use double sided carpet tape to hold the piece to the table. It is pressure sensitive so apply pressure for a minute or two.

Dave

 

[GK1918]

Absoulty not a pest thats a good question. Is your thru hole tapered? Do you care if you drill a holes in your square plate as to use countersunk allens into Tee nuts? Then a lot of
tables have table locks that gets into the way. I try to visualize the bottom to top hole and yours is straight. I may be off key, but I think I would put the table upside down on the
mill and counter bore deep enought for a thick washer for a bolt and drill one hole throught the plate and put one bolt through plate into the table T slot like a lathe dog. Or four holes
in the plate with equal packing under and just tee bolt it. I got the same problem with a 12" table and a 12" chuck. What ever, you will still need packing under the plate.
sam Only If I was there I'm not a good story author


Daves method will work just go easy

 

[dave2176]

On the lathe clamp a nut or two in the three jaw and screw a bolt through the piece to hold it. As it turns against the pressure of the tool it will keep it tight.

Dave

 

[caster]

My 6" rotary table has a small space allowing me to have a thinned bolt. It you don't want to mill the rotary table you may consider placing spacers underneath the table creating the space needed for the bolt. There are mandrels that are .001 oversized and can be pressed to the work, otherwise expanding mandrels, or a threaded rod with nuts on both sides, or two nuts in the chuck and bolt through the work... you have many options.

 

[JimDawson]

What I did was to make a plug that loosely fit the center hole, tapped both ends, and in the bottom I use a flat head cap screw to secure the plug. My RT has about 1/8 inch relief on the center hole, so plenty of clearance for the flat head screw. This gives me a tapped hole on top to use to secure the work.

If this is not clear, I'll take a couple of pictures and post them.

EDIT Here is a few pics:

A 3/8 flat head cap screw fits mine perfectly, yours may vary.

 

[mzayd3]

Sounds like you are trying to make a 1/2" thick disc out of a much larger plate? I would try to rough it out a little closer to size rather than mount an entire 18 x 18 plate on a rotary table and cut a circle out of the corner.

 

[NEL957]

I believe you started out in the right direction turning a plug for the center of the RT. Instead of cutting a straight cut, try to cut a slight taper that will insert easily to about 3/4 the length and get slightly larger. When drawn in or pressed in with a arbor press, then press it out when finished.
Good luck
Nelson Collar