4 inch rotary table

DanGraves said:
I am thinking about buying this for small work. I know this is a cheapie has anyone used this one? Wondering if it will hold up for light duty work.Here is a link to the e-bay seller

http://www.ebay.com/itm/230768653517?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648
Click to expand...

I have one. I am happy with it. The rotation is smooth. There is about 2 degrees of play in the turntable, but it has a thumb screw to lock the turntable tight.
If you are using to position parts on the mill, it will work fine. Heavy cutting while rotating will have a bit of chatter.
It only weighs a few pounds, so I use it a lot for small bolt patterns on my manual mill. My other rotary turntable weighs about 110 and I avoid lifting it as much a possible.
I bought this little unit because I can use it on my lathe to turn very long radius of curvature spheres.

P1000273.JPG

The turntable is set a few degrees angled to the face of the work and as the turntable is rotated, the tool bit creates a sphere.
The greater the angle, the shorter the radius.
Turn the angle the other way and you get a convex rather than a concave sphere.
If you set the turntable to the horizontal position, it can be configured to be a ball end turner.
At the $72 price, it is a worthwhile tool.
Dennis

P1000273.JPG
 
Dan, may I hijack your thread for a moment? I know I shouldn't but you brought up such a valuable question about that very inexpensive little rotary table.

Here goes:
Dennis, would you show this lunkhead (me) what you're doing with the rotary table at that moment in the photo? I can get the horizontal position of making ball ends notion (I thought to myself once I figured it out, "Duh, that's too cool and easy!") but for the life of me I can't get the notion in my head what you are making with the lathe and table in that pic. Would you help me out?

Dan, that table is super cute. Doggone it's cheap (inexpensive) too! Bah, I'd just take it all apart and clean it like a gent here does with his foreign lathe chucks.
Now I want one bad. Real bad. I do think ahead as it were..... i.e. Four or five lathes (already have three [2 US and 1 Chinaman] and waiting on the fourth [US]...) here with specific purposes. And when the mill comes along, well I have a small rotary table ready to go but can I spare it from that lathe? Get another.
 
Just remember the higher the ratio the closer you can control the degrees of movement. So a 72:1 is better than a 40:1 . The teeth are finer and usually have less loose play that the bigger toothed 40:1's just about every time.

Bob
 
Duey C said:
Dan, may I hijack your thread for a moment? I know I shouldn't but you brought up such a valuable question about that very inexpensive little rotary table.

Here goes:
Dennis, would you show this lunkhead (me) what you're doing with the rotary table at that moment in the photo? I can get the horizontal position of making ball ends notion (I thought to myself once I figured it out, "Duh, that's too cool and easy!") but for the life of me I can't get the notion in my head what you are making with the lathe and table in that pic. Would you help me out?
Click to expand...

The Picture below should show you the theory of making curves with a fly cutter on a milling machine.
Using a rotary table set at some small angle, one can use a fly cutter to make a convex or concave dish in the material on the turntable.
As the turntable is rotated, a spherical curve is formed.
The exact angle can be done with sin bars or just trial and error shimming or by setting the angle so that the desired saggita (depression) can be measured by the clearance of the fly cutter at the workpiece edge versus the center.

Spherical Generation 001.jpg
I have made numerous curved tools for mirror making using this method.

17 inch flycut tool 2.jpg

In this example, the turntable is tilted about 3 degrees and a 200 inch convex radius of curvature is being generated.
You can see the curve in the reflection on the aluminum platter.
The more tilt, the shorter the radius is.
If the turntable is positioned so that the center of the work is lower than the edge in relation to fly cutter, the curve will be concave.

In the previous lathe photo, the turntable is vertical and by setting it at an angle, a curve will be formed when a cutting bit sticking out on the turntable is rotated cutting a curved path through the face of the rotating work. You can also use a four jaw chuck to hold an offset (1/2 the diameter of the material) cutting bit * now basically a fly cutter) and cut a sphere into a piece of work attached to the rotating turntable.

The milling machine and fly cutter method is best, and the 17 inch aluminum platter (a pitch lap of a 24 inch telescope mirror) was generated in about 15 minutes.
It is by far the best way to make long radius spherical curves that I have found.

Hope this helps,
Dennis

Spherical Generation 001.jpg 17 inch flycut tool 2.jpg
 
Awesome ideas on lathe and mill Dennis- I have never seen that on a lathe before- I guessed you were making telescope mirrors!

Bernie
 
Now I remember why my post isn't here!
I feel asleep at the wheel (this old computer) and must have touched a button and poof! The next morning all of my (potential) post was gone.
Dan, thank you for posting this question. Did you get the table yet? How do you like it so far? Etc, etc....
Dennis, that was a BIG help! Super simple ways of doing cool things with machines!
Thank you both!
 
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