Questions on Holding Items on A Rotary Table

[Starlight Tools]

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.

What diameter do you want to cut from the corner of the 18x18 plate?

I would be looking at either a hole saw, or a trepanning tool to cut out the rough size of the disc first. Then finish up by either turning on the lathe or using the rotary table to finish up the disc.

As for mandrels, there are a few different types. Plain mandrels, that have a very slight taper that are pressed into the hole, Expansion mandrels, held between centres, that consist of an externally tapered mandrel with an internally tapered sleeve that expands as it is pressed onto the mandrel, then there is the plug style, where the mandrel is split and a tapered screw is threaded into it, which expands the mandrel in the hole, then the simple mandrel which is just a bar with a stepped diameter and a threaded end which the part to be turned is bolted on (think saw blades). They do not generally have a key, they rely totally on the expansion, or compression to hold the part.

Walter

 

[kwoodhands]

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.

I am assuming the round base will be under 4" diameter for your ball turner. Cut a piece from the corner of the large plate, round or square but oversize. Bore with a center drill at center of the piece. Install a faceplate on the lathe.
Push tailstock with a center up to the faceplate. Hold the work with the center and then clamp the work to the faceplate.
You may have to drill extra holes in the faceplate to accomadate the work. You could also use an adhesive plus the center instead of boring holes. Shellac or hot hide glue removes easily but holds well with a center.
You can trepan the perimeter. Also if you rough cut it round an interrupted cut will also work.
The lathe is better suited for turning a disk. If you must use the mill then I would make a sacrificial plate for the rotary table. Hold it down with flathead counter sunk screws into the t-nuts. Then clamp or bolt the work to the sacrificial plate with spacers in between.

mike

 

[Silverbullet]

Need more specs, plate material , aluminum you can cut with a jigsaw to ruff it out. A little spray of water displacer 40 , will help with the cutting. Are you going to drill any holes in the round plate? You should back it with a piece of scrap , so you don't cut your new table. As Dave said double sided tape holds very well. Even super glue will do it . Oxtool has a vid doing cuts on a lathe with only glue holding the discs . Just go lightly on every cut feed and depth. I'd keep a little lock pressure on the table rotation so it can't jump. Pics lots of pics.

 

[Tony Wells]

Mount your RT up on 123 blocks or parallels and you should have ample room for a bolt, the larger, the better. I am assuming you will be ok with a hole in the center of the finished disc.

 

[higgite]

All good advice (I hope, cause I'm taking notes), but hopefully he has solved his problem since his original post.
Don't you hate it when an OP abandons their own thread? Would be nice to know how or if he worked it out.

Tom

 

[talvare]

Don't you hate it when an OP abandons their own thread? Would be nice to know how or if he worked it out.Tom

I agree Tom, but unfortunately this is a two year old post that got kind of re-opened. I've been lured into responding to old posts myself before looking at the post dates.

Ted

 

[Tony Wells]

No harm in it. Who knows whether someone else is pondering the same problem and could use a hint or two.