Rotary table problem.

I just acquired a small rotary table (Warco) and am now trying to put it into good use but have hit a problem.

I'm trying to drill radially spaced holes into the face of a disc. The disc has been turned in the lathe and so is mounted in the 3-jaw. Along with the table I got a 3-jaw mounting plate so I stacked table, mounting plate, 3-jaw and workpiece on the mill (Centec 2a with 3" VH raising block). Problem then arises I have no headspace remaining for a chuck and drill! Shift it to the drilling machine (small bench Draper) and similar problem!

The chuck and its mounting plate take up nearly 4 inches of headspace. I could just about get a drill in if I mounted it in an ER collet but it seems a weak solution to what is probably going to be a fairly frequently used setup. There is plenty of room if you mount work directly on the table but that would need a different machining and mounting strategy. How do people get round this? Is there a simpler way of working that I'm not aware of? It seems that the chuck and its plate must go, but then I lose the job concentricity. A bigger mill is not an option I'm afraid!

What size holes do you need to drill, would a morse taper drill bit solve the problem? I also keep a selection of stub drills when things get a bit tight for head space.

Not sure there an easy answer to this. I found the same thing while using the rotary table + mounting plate+chuck+job=no space left ! also no room to change drills.

Welcome to the club .

Put the disk straight on the face of the rotary table. If possible have a hole in the middle machined whilst still in the lathe so you can set it on a spike from the table centre, otherwise you'll have to clock it true, but it doesn't take long. All you have to remember then is not to drill right through, or put some packing underneath. Agricultural people like me use MDF

Stub drills held in an ER chuck helps.

Rod

1) Next time can you make a mount for your faceplate on the rotab and mount your workpiece on the faceplate for the lathe operation. Perhaps making a range of faceplate dogs that make it chuck-like.

2) Use a centre drill to pick out the hole positions and then open out on the pillar drill. If not enough room even for this mount a dremel-like additional spindle on the Centec head to hold the centre drill.

3) make a mount for the rotab on the back of the lathe spindle, yes it has been done before, so you can spot the holes on the lathe.

4) mount your pillar drill so it can be swung over the mill table with a bit of extra bracing to firm it all up.

Stub drill in a MT collet works for me when head room gets tight, even a custom bush to hold an odd dia drill in a MT collet.

My 4 jaw independent chuck is significantly thinner than my self centering 3 jaw chuck. Might be a future option if the needed space is not too much more than you have now. Otherwise collets straight into the mill spindle as stated earlier is a possible solution if you can do it.

If you have a DRO then fit the plate on the machine and drill holes using coordinates (Zeus book has details) or built in bolt hole circle function on the DRO controller.

Martin C

Next time you could consider drilling the holes first, using the co-ordinates method, and then setting up the work in a 4-jaw on the lathe so that the ring of holes runs true, and then turning the face etc. Perhaps I should have said this earlier ... ?

Cheers, Tim

A bigger mill is not an option I'm afraid!

Make or purchase a taller raising block instead!

If you could arrange for a short 2MT drill, they could also be drilled horizontally. It won't help now (a short 2MT drill should suffice as you are), but if your disc happenned to exceed Centec throat depth, the disc could be up to twice the listed horizontal clearance?

A location might help, as you might live close to someone with a taller riser block.

Not sure if the Centec is a horizontal mill with a vertical head attachment but if it is mount the drill chuck in an arbour and mount the rotary table in the vertical position.

Thanks, some useful ideas here. It looks as though one of the most useful accessories for the table is going to be a collection of concentric stubs that fit in the centre hole, together with some clamping dogs - reasonably delicate so that they obscure the workpiece as little as possible. Fortunately the present item has a centre hole that I can use for location. It looks like mounting the chuck as planned is a bit of a non-starter. I have a small lever scroll chuck on my Perris lathe that I could make an adaptor for, although the capacity of that is rather limited. I think I will keep an eye open for a thin 3-jaw chuck with a Myford thread, and work out a way of mounting it that doesn't require an additional backplate.

Can you mount the rotary table to an angle plate on the cross-slide of your lathe (or even bolt it to a bar clamped in the toolpost)? Even without a vertical slide it may be possible to offset the table to a position that lets you drill the holes, and the lathe bed may allow you more (horizontal) headroom than the mill.

Brian

Do them on a lathe. Plenty of examples of using a lathe spindle as an indexer. Would need a live spindle to use as a drill but a Dremel will create a small hole. Or another alternative mark the hole positions out, centre punch and drill. Probably all as accurate as your stack build up.

You could perhaps drill the holes in the cylinder head, then use that as a template to drill the cylinder.

Ian S C