Rotary table

[mike4]

Sometime ago there were several discussions regarding how to put a four jaw chuck onto a rotary table with only three slots.
http://s1127.photobucket.com/albums/l626/Mike4uni/
The photo above shows how i did it ,I mounted an adaptor plate which then had the chuck bolted to it , makes work centering easier.
Michael

[dp]

I haven't done this yet. I use a 4-jaw and made some t-nuts for it to attach directly to the RT. But it is unsatisfactory. How do you center the plate on the RT? Mine has 4 slots which allows for some slop. I considered a center hole and tapered pin. Here's my setup:

http://metalworkingathome.com/?p=156

[Ian B]

DP,

Does your R/T have a parallel centre hole, or a taper? Mine has a 20mm dia parallel hole. I just machined up a 'mushroom' that fith in the 20mm hole, and has a spigot to match the register in the back of the chuck - centres it straight away.

Ian

[A.K. Boomer]

yes that's the way to go I think - it's what I did on mine and it works great.



I drilled a hole directly through the pin to allow for a one bolt cinch up for lighter jobs - any time I install my RT on the mill I have a special nut Between it and the table for this and other options.





If it's heavier work then I use the four slot holders.




The little 5" three jaw is an r-8 milling/lathe chuck and is very versatile now..

The raised section on the plate fits perfectly inside the recess in the chuck so no alignment issues there - and the bore of the plate fits perfectly on the taper arbor... so it's dial indicate the rotary table in and then bolt up all your crap to it and all is good...

[Paul Alciatore]

I faced the same problem, four jaw chuck and a RT with six slots which is really the same problem as three slots.

My first realization was that with a four jaw chuck the work will be centered on the table using the chuck jaws after the chuck is mounted. It does not matter one wit if the chuck is perfectly centered on the table and centering the chuck does not save you any time. I deliberately did not choose to use a three jaw on the RT due to the centering errors of those chucks or at least of those that I could afford. So I abandoned any thought of a central plug for centering and decided to just use a caliper set to a predetermined and distance that I keep recorded to quickly and roughly (+/- 0.005" or so) center it by checking between the ODs of the table and the chuck. I set the caliper to this dimension and use it to push the chuck to the center from two orthogonal directions. This only takes seconds and is easily good enough.

As for mounting it, I didn't want to lose any vertical space under the quill so I did not use any adapter plates. I have a 10" table and a 6" four jaw chuck that I bought for it so I looked at the casting of the chuck body and found three locations that were about 3/8" or 1/2" from the outer edge and that were spaced at 120 degree intervals to match three of the six table slots. I then drilled three 13/32" holes clear through the chuck, face to back. In a four jaw it is easy to find locations for this: a three jaw might be more problematic. Three long 3/8", grade 8 bolts and three tee nuts and the chuck is mounted flat on the table. The end of the holes on the face of the chuck can be countersunk or counter-bored if you do not want the heads of the bolts to protrude above the face of the chuck.

With the above centering trick, installation of the chuck is fast and easy and no space is lost to adapter plates. But, to be on the safe side, do check the thickness of the metal casting at all points before doing any drilling or countersinking or counter-boring.

These three holes do not in any way interfere with other uses of the chuck. It can be easily attached to other tables of to a face plate for use in the lathe.

Sorry but I do not have any photos and my shop is still in storage so I can not take one.

[oldtiffie]

Sometime ago there were several discussions regarding how to put a four jaw chuck onto a rotary table with only three slots.
http://s1127.photobucket.com/albums/l626/Mike4uni/
The photo above shows how i did it ,I mounted an adaptor plate which then had the chuck bolted to it , makes work centering easier.
Michael

Nice job Mike.

I notice that you have a front-face fastening chuck which sure makes it easier to bolt the chuck directly to the rotary table if you had four slots in your rotary table but as you have got three slots the adaptor plate is the best or only realistic option.

https://www.machineryhouse.com.au/C250

I have 3 slots in my rotary table and so use a 3-hole 3 jaw front face fastenting directly to the table.

https://www.machineryhouse.com.au/C280

http://i200.photobucket.com/albums/a...isc/HF45-5.jpg

I have never needed an "adaptor plate" as such but if I did I would not be relying on the table taper, the plate and the chuck (all of which will have concentricity errors) for "location".

There is that much "slop" in my assembly that it is very easy to centre a job to the table axis even with a 3-jaw chuck. Once set up it relocates very accurately.

[mike4]

I haven't done this yet. I use a 4-jaw and made some t-nuts for it to attach directly to the RT. But it is unsatisfactory. How do you center the plate on the RT? Mine has 4 slots which allows for some slop. I considered a center hole and tapered pin. Here's my setup:

http://metalworkingathome.com/?p=156

I machined it so that there is a raised section which fits into the centre of the R/T and there is a ridge under the chuck to aid alignment , also there is a mark on the outside of the plat with a matching mark on the R/T .
I have purchased a three jaw chuck and am in the process of cleaning it up and will fit it in a similar manner .
Michael

[Ian B]

Michael,

If your next chuck is a 3 jaw, does it have 3 equispaced holes? If so, why not skip the adaptor plate, just use an alignment 'mushroom' and bolt the back of the chuck straight to the RT with tee slot nuts and cap screws?

Ian

[mike4]

The chuck has three holes in the back so its a bit hard to mount without the plate ,I am trying to make the plate adaptable to hopefully save some time setting up for a future project .
It will involve transferring from mill to lathe and back again ,I am making a steel replacement for a moulded plastic partwhich is no longer manufactured.
Rest of machine still working but the plastic part is in five pieces which will be epoxied back together for use as a pattern.
Possibly planned obselescence?
Michael

[Ian B]

Ah, holes in the back - yes, that does make it awkward. I thought you were buying chucks for the purpose. 3 jaws with through holes are a bit unusual, but they're around: http://www.ebay.co.uk/itm/100MM-3-JA...item43a4143c75

If the chuck is the same diameter as the RT, you could make long tee section bars that slide into the tee slots and act as 'outriggers' - drill the flange for these, then slot the holes out to the edge. Fit studs & nuts to the outer ends of the outriggers, slide them into the 3 tee slots & tighten - should do it.

Ian