Work holding on a rotary table

What is the best way of holding something on a rotary table (I haven't got the rotary table yet!).

I need to mill the outside diameter of 83mm diameter aluminium round bar to make a flange. What is the best way to hold this, do I need to buy a chuck?

David

Edited By David Brown 9 on 12/12/2015 08:28:23

Just make some clamping blocks, second picture down

Alos buy the biggest rotary table you can fit on your mill. Clamps take up a surprising amount of room.

Hard to use clamps round the outside to mill an OD! Might be easier to start by drilling the bolt holes first (assuming that it's that sort of flange) then using those to clamp to the table slots. But you might either need to get a 3 slot table if there are six holes, or drill 8 or 12 holes for a 4 slot table. If you buy a 3 slot table though you may regret it later, IMHO 4 slots better.

As a previous thread a slave plate with lots of tapped holes clamped to the rotary works well. I have two 10" tables and find even at that size clamping some jobs is a challenge without the slave plate. Any bigger rotary and I would struggle to lift it !

Or just cut the hole in the middle first and pass the hold down clamps through that to do the outside dia.

Is this a round bar you are working with or a bit of plate?

It is 83mm diameter aluminium round bar, T6.

David

If you could give more information it would help, for example a sketch of what you are trying to make showing what needs machining. Will it have bolt holes? Will there be a hole through the middle? Do you need to actually machine the OD or face round one end, or what? Do you have access to a lathe?

If you make up a set of tee-section lengths that fit the tee slots in the table, you could extend them outside the diameter of the table and use them to clamp to. Not as rigid as clamping within the table limits but by definition we seem to have exceeded them anyway.

I need to make something very roughly like this, except this is a picture of a bearing not a flange, but it is approximately the right shape.

A 11/2 inch steel shaft will fit inside the flange, secured by set screws. The flange will then be bolted to a 15 inches diameter wooden pulley.

David

I think I would describe that as a flanged boss or bush. If the 1.5" shaft and 15" pulley signify quite high power transmission you may need something more than set screws to hold it - at least a flat on the shaft or better a key.

I assume the plan is to bore the boss out on the mill - how do you get the ends flat and parallel first? But back to your original question, using a mill I think the best approach is to face the ends, drill the centre hole to a suitable diameter for a big bolt to clamp to a rotary table (M12?) so the hole is concentric with the table (would need a threaded fitting for the bolt in the centre of the table), mill the boss down to the flange, spot drill the bolt holes in the right position, remove from table, drill out bolt holes, refit to mill and finally centre the spindle over the hole and bore to size. Not a natural job for the mill (except the bolt hole circle), would be trivial on a lathe. Are you sure this is the right approach for what you are trying to do?

If you have the room on your mill a 4 jaw chuck mounted on the rotary table will cover most of your work holding needs.
Using a dial indicator you can center up a part perfectly. the same way as on the lathe.
By reversing the jaws you can even cheat a little and work over the edge of the rotary table itself.
Odd shaped parts are not a problem.

Make sure you get one with the correct number of through hole mounting points designed for front mounting on a face plate for your particular rotary table.

Regards
John

Why not make life simple for yourself, rather than buy a rotary table or use a boring head to do the outer diameters as per your other thread just make the part more suitable for production on the mill.

Clamp as I suggested on the 83mm OD with shims between the sawn end and MILL table to set the billets sides vertical and then maching the top face flat.

Turn it over with the newly machined face on some parallel packing to raise it off the mill table again clamping against the 83mm OD. Drill and bore the internal hole and then simply mill the sides square as there is no reason for them to be round. While set up like this drill the 4 mounting holes.

The 83mm OD of the flange is not critical so can be left unmachined.

Even simpler would be to just leave it all 83mm dia, drill and bore the hole but tap the four mounting holes so you can pass bolts through with their heads on teh timber disc side

Edited By JasonB on 13/12/2015 07:52:00

I must be missing something as this seems more like a turning job just finished on the mill/drill?

Vertex make some of the better RT's but sadly they only have three slots so you don't have a choice. The answer as mentioned by others is to use adaptor plates. Where there's a will.

No lathe available

There you go! Thought I was missing something. Like many I assume folks buy a Lathe first then a Mill.

Vic, my 6" Vertex has 4 T slots, it's been at work this afternoon as I carved out the spokes of a flywheel.

Ian S C

Spent Saturday afternoon, milling a piece of Aluminium some 14 inches dia on a HV6 Rotary table.

(Job was too big to fit into the lathe, and am too idle to remove the gap!)

Having centred the Rotary Table under the Mill, the centre of the Aluminium was found by scribing lines, off centre, to form a square. Scribing diagonals, marked the centre which was then centre drilled. At the same time two holes 8.5mm dia , on a centreline, were marked out and drilled 2.5 inches each side of the centre.

The Aluminium was centred on the Table, using the centre drill to locate it while nuts were tightened onto the M8 studs in Tee Nuts in two diametrically opposed slots in the Rotary Table. The Mill Table was locked in the Y axis and the X axis traversed until an End Mill , held in an ER collet could be used to mill the periphery to clean it up.

I found that the best method was to take a number of wide, but shallow cuts, to bring the Aluminium to the required size. The Table clamps were lightly applied, to reduce vibration.

Possibly needless to say, but the Rotary Table rotation opposed that of the End Mill.

Similar clamping techniques, or Finger Clamps, can be used for other smaller jobs.

Howard

Thanks for all the advice. I should have realised that I can mill the sides square. In which case I don't need a rotary table to do this. On the other hand I think I may need a rotary table for something else,

I will hopefully get this done over the Christmas holidays. Most probably I will cut keyways in the shaft and flange to secure the shaft better. I will write again when (if!) I get the flange finished,

David