Rotary table Chuck mounting.

[John Gray 7Participant @johngray7]

I bought a rotary table and had it delivered to my campsite as I’m away at the moment. It’s still in the box unopened until I go home, no point in getting grease and oil all over my caravan and incurring the wrath of SWMBO. Whilst “armchair engineering” I got to thinking that I should have bought a chuck with this, as I think my lathe chucks might be too big to be practical. The RT is a Soba HV4 which it says is actually 4inch and 5/16ths diameter with 4 slots. I was exploring on line methods of connecting the two parts and came across a post on a forum where the guy had bolted a front fixture chuck with 4 bolts directly into tnuts in the four slots, ie no backing or fixture plate. The chuck would have to be centred either with a mandrel into the mt2 hole in the centre or clocked in in some other way before the bolts are tightened. It may seem a daft question but I really am not sure of the answer, but is this process ok? It seems to me that the potential lateral movement of the Chuck is being held only by the downward force of 4 m6 or m8 bolts. Not having an extra plate will of course give a little more space under the head of my SX2P mill. In the course of my internet wanderings I discovered the Chronos where I bought the RT from actually do both a 3 and 4 jaw self centering Chuck bolted to a backplate to fit the Soba 4 inch RT. If a 4 jaw Chuck could be bolted directly to the RT then why would Chronos supply this kit? The original post I saw using this no back plate method, centred the RT by clocking the inside edge of the MT hole and then after locking everything off and zeroing his dro, a rod was fixed in the jaws of the Chuck, he used I think the shank of an endmill, and then tapped the loosely fixed Chuck into concentricity before tightening down the Chuck mounting screws. What do you think is this viable ??

[John HinkleyParticipant @johnhinkley26699]

Short answer: yes.

Long answer: yes, absolutely.

John

 

[DiogenesParticipant @diogenes]

..why would Chronos..? ..because their 3J front mount only has three holes and their small 4Js are rear mount, I think.

 

[Peter Cook 6Participant @petercook6]

I personally find a fixture plate like this

much more useful on my 4″ rotary table than a chuck. It’s a 6″ diameter slice of aluminium 25mm thick, with a pattern of M6 threaded holes (same size as my T slots). A 10mm hole in the centre gives location for a centre, and I made a few threaded pins, which with standard clamps let me mount all sorts of shapes on the table.

It’s held down by four T nuts in the table slots. If you are careful with the placement of the holes for bolting it down, it will also bolt directly to the mill table if needed.

The only reason for using a chuck on the rotary table would be to allow you to move work from the lathe to the mill without disturbing the concentricity, but that means mounting the lathe chuck on the table, rather than a separate item.

[John Gray 7Participant @johngray7]

Thank you for your replies. I thought that I was missing some vital point as it seemed too simple to just bolt the chuck to the RT surface when everybody I could see was faffing around with adapter plates. It is my intention to use a self centering 4 jaw which mostly have a 4 bolt fixing. Both Chronos and RDG sell suitable chucks of this design, but I now realise that I have a good quality Rohm front fixing 4 jaw from my lathe that doesn’t get much use, and provided it’s not actually too big may well fit the job.

Peter Cook 6, a fixture plate was to be the first task I will complete. I agree whole heartedly that this would certainly be the most useful fixturing device and likely to get most use. I made a small one a while ago that fits in my vice and which allows me to fixture small odd shaped component’s under a cutter. Yours looks a super job. Thank you for sharing.

[Peter Cook 6]

On Peter Cook 6 Said:

[…]

The only reason for using a chuck on the rotary table would be to allow you to move work from the lathe to the mill without disturbing the concentricity, but that means mounting the lathe chuck on the table, rather than a separate item.

I beg to differ, slightly
An independent 4-jaw can be useful for holding and positioning small items

… sometimes easier than using clamps.

MichaelG.

[Nigel Graham 2Participant @nigelgraham2]

The big drawback with using a lathe chuck on a rotary-table is the significant loss of headroom.

For screw-on chucks transferred between lathe and mill, the usual way is a mounting-plate with a register on the underside for the centre of the RT, and a boss threaded as with the lathe on the top. The plate has holes to take Tee-nut screws or studs, for clamping to the rotary-table.

NB: arrange some form of locking for the chuck, as milling the work’s periphery will try to unscrew such a chuck from the mounting.

…….

It may be worth making the mounting-plate compatible with not only the rotary-table but also the milling-machine table, allowing direct mounting there.

For a chuck used solely on the mill, directly and on the RT, machine and fit the mounting-plate to replace the usual back-plate.

[Nigel Graham 2]

On Nigel Graham 2 Said:

The big drawback with using a lathe chuck on a rotary-table is the significant loss of headroom.

That’s an “interesting” generalisation, Nigel

Last time I looked, chucks were available in many sizes, as were rotary tables

.. in some use-cases the loss of headroom might be considered trivial

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

On Nigel Graham 2 Said:

The big drawback with using a lathe chuck on a rotary-table is the significant loss of headroom.

That’s an “interesting” generalisation, Nigel

Last time I looked, chucks were available in many sizes, as were rotary tables

.. in some use-cases the loss of headroom might be considered trivial

MichaelG.

You’re both right!  It depends on the “Use Case”: a combination of work type and machine size. An HV6 with full chuck fits on a WM18 mill, but an HV8 would be a squeeze.  Likewise, I suspect an HV6 and chuck would be uncomfortably big on a WM16, and monstrous on a WM14.

My use case is like Nigel’s example.   Mostly easier for me to hold work in a full-profile chuck bolted to the table, and, though it eats headroom, the mill is generally big enough to cope.  Full-size chucks hold longer work, which happens to be handy for me.  That I rarely clamp stuff direct to my rotary table and have no call for a low chuck is circumstantial – I’m sure others are the other way round!

Dave

 

[JasonBModerator @jasonb]

Must admit that 90% of the time when I’m using a rotary table it will have a 3 jaw on it, mounted with a backplate so the screws are outside the OD of the chuck.

Mostly gets used to hold small diameters <12mm where a fixture plate would not offer much of an advantage.

Yes they can eat into headroom or even table length when being used vertically but you can shop around for short chucks or use finger collets though I have not found the need for a shorter chuck. A collet chuck is another option if not holding large diameters, 3 & 4 hole ones are available to suit your R/T slots

I ctr the rotary table under the mill’s quill and then depending on which one I’m using will either hold a ground rod in a collet an close the chuck onto that then bolt chuck to R/T. The other one I use more often has a spigot on the back of the backplate that locate sinto a recess in teh R/T so only need to clock in the R/T

[Author]

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