Tips on Using a Rotary Table

[Smifffy]

Today, I was lucky enough to take delivery of a 6" rotary table, meaning I can now crack on and generate more swarf in the production of my Crank Axle webs.

However, I'm a little perplexed on how to use it. My webs have radii off the axle centre and the journal centre, so I will need to ensure that each is centered for the cutting of them.

My current thought is to turn a piece of bar to fit the (say) axle hole and put an MT2 taper on this (I'm not sure that will be so easy!) so that it can be centered in the table and then the work piece clamped accordingly.

As always, any suggestions will be very much appreciated.

Mark

[AndrewP]

If that's the Soba one snap! - heavy aren't they
How about starting with a blank MT2 arbor and turning the soft end down for your say axle hole (biggest one first obviously).

Cheaper still - just clamp it to the table oriented with say the Y axis (we are talking about working on a vertical mill I assume), chuck a piece of bar that is a good fit in the relevant hole and move the table till it fits - zero your dials and go from there.

Added the following morning - this only works of course if you centre the table first and move the workpiece before clamping.

Why is the second idea always better than the first?

Cheers, Andy

[circlip]

In industry we used to have the rotary table fastened to the miller bed with known dial co-ordinates for the centre of it. We then had a two axis co-ordinate table centred and fastened to the top of the rotary table. This ensured that once a job was centred on the "top" table, we could do square cuts using the main slides of the miller, and by re-centreing the main slides and off setting the top table onto the centre of the required bore we could then machine a radius as you want to do. The reason for this "stack" was that the Bridgeports used in this operation were CONSTANTLY used for co-ordinate milling of press tool punches,(noticed my post name?)
Your operation don't need to go to these lengths,question is why do you need to machine a Morse taper setting bar? If you centralize the miller table left to right, clamp the rotary table to the middle slot and use a DTI on the bore of the rotary to put it central under the spindle and then clamp it to the miller table. Your work piece is then centred and clamped to the rotary again picking up with a DTI before clamping. You then need to "Zero" your dials without moving the slides.
Don't know what your spindle cutter tooling is like, but it shouldn't be too difficult to make a cone centre, bit like a fixed centre, to locate the rotary table centre under the spindle quickly by impressing into the centre location, then "clock". The work piece can also be quickly centred by the same method. Only problem is then having to tap the work piece central, clocking with the DTI and not disturbing the main slides.
This little epistle has taken about a hundred times longer to type than it takes to physically set the job up. Difficult to imagine how to do it the first time but you don't have to think about it the second and successive times. Good luck, Ian.

[havoc]

Why use a taper? I would put in a collet with a piece of ground silver steel that fits the axle you want to center.

[modeng2000]

That is how I do it, a collet and a piece of silver steel.

John

[steam4ian]

G'day Mark

A variety of Sir Ian's input. put a 2MT centre in the rotary table. And use the dial indicator in the spindle to run on the 60 deg, cone. Rotate the spindle by hand and move the rotary table to where there is no deflection.

If you have a piece of rod with a 60 deg taper on the end you can grasp the same in a collet chuck in the spindle. Hold thin blade between the point of the MT centre and the point in the collet and move the RT to where the blade is level in all directions. This could be a quick set up before using the dial indicator.

A rough way is a drill chuck 2MT arbor. Don't fix the RT to the mill table. Put the arbor in the RT and loosely grip the Jacobs taper with a collet chuck in the spindle. the bolt down the RT.

[Smifffy]

OK guys, lots of good advice here, but it takes some thought to translate the words in to "pictures" in my head.

Centering the table under the spindle is not an issue and I can do that easy enough. The tough bit is to centre the Axle and Journal holes on the table - sadly all my collets are MT3. However, I think the easist thing to do, is to clamp my crank web to the table with a piece of appropriately sized bar in the relevant hole and just use my Dial Guage to centre it.

Longer term, I'll follow Andy's suggestion and get an MT2 Arbor with a soft end and turn it down accordingly.

Thanks for your suggestions and help.

Mark

Regards

Mark

[circlip]

If setting the rotary table is no problem then thats half the battle solved. For setting the crank webs, setting pins. Have a look at the link radiusing table in the early MEW. It used a stepped pin in the centre of the table. Ian.

[AndrewP]

If you are happy centering the table the workpiece is the easy bit.
Admittedly the dial gauge is potentially more accurate but what about just chucking a piece of bar in the spindle that is a good fit in the workpiece's hole - a slow taper would work just as well, lower the head till it's located the workpiece and then clamp the work to the RT.

I have turned up several such pieces which fit in my most used collets and use them whenever the dial gauge would be overkill for accuracy.

I know what you mean about a "picture" in the head, hopefully this isn't completely blurred.

Cheers, Andy

[circlip]

Wow, double posted at the same time, haven't seen that one before. OK. Mark you got the choice, centred from the top or the bottom. Can you or Andy tell us what the centre of the rotary table is like?

[AndrewP]

Well mine is round with a MT2 taper.

[Smifffy]

...well guys, I turned down a piece of bar to fit the journal hole(s) in the web(s), then turned my top slide round to 1.5 deg and turned a taper. It fitted snug as a bug into the MT2 taper on the Rotary Table. I was a happy man :-)

Then, I found out I had been a overly keen in my generation of swarf (see Satisfaction thread in the general forum) and had to bin what I have so far done on the webs. It's funny how the 2nd attempt at any given operation (boring the axle and journal holes in the webs in this case) is soooooo much easier than the first!

D'Oh!

Hoepfull tomorrow, I'll be milling those radii on the webs.....

[circlip]

OK, rather than turn a pin onto the end of the plug, if you bore a standard size blind HOLE, be it metric or imperial to fit a pin into, you can then make a series of stepped pins to locate whatever sizes required. Plug needs to be flush with table top. I have a series of 6MM dia pins with different ends turned onto them. Just slept on it, don't forget, you can only cut radii generated from the centre you're putting on the rotary table centre. That's why the compound table was mounted on top of the rotary table. Regards Ian.

[Tel]

Agreed Ian, but when you do it, drill a little vent hole from the top of the hole out thru the side - makes life much easier. Even easier would be to drill the hole from the side, in to the top of the 'ole - but you know wot I mean

[circlip]

Dead right Tel, my table is the above mentioned MEW design which has a flat faced screw in the bottom of the table and all made from stainless - it dont rust and always looks clean and shiney. Why stainless? Cos it cost me bu**er all for the raw material. Regards Ian.

[Tel]

Now that's my kind of price ;D