ER40 by MT3 collet chuck

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blockmanjohn

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Hi,

I have a Vertex rotary table with an MT3 bore. I would like to use my ER40 collets to hold work on this table. I saw on E-bay a Shars CNC milling holder that took ER-40 collets, and had an MT3 taper on the other side. Do you think that this would work on my table without using a drawbar to keep it from spinning? It doesn't seem to have a tang on the end. Thanks, John.
 
Personally I would consider something like this
https://www.arceurotrade.co.uk/Catalogue/Collets/ER-Lathe-Collet-Chucks/ER40-Lathe-Collet-Chucks

An MT tanged ER40 sounds like a good idea in that it plugs into the RT socket, becomes concentric and ready to go. But also a few downsides
- the tang filled hole now prevents you from holding longer work that could otherwise extend down into the hole, whereas the plate system has a hole so can facilitate this
- in reality the assembly may still have a bit of runout & you are stuck with it vs the plate can be dialed in. (Always indicate the RT hole first, then the chuck second.)
- the plate system is pretty low profile vs some of the shaked tools have an extended body. thi smight rob some headroom depending on the size of your mill & RT thickness
- the ER-40 plate can still have utility value in other environments. 1) your lathe with some fixturing depending on spindle nose 2) bolted directly to your mill table +/- existing hole pattern to suite 3) held in your mill vise by milling opposing flats on the plate
- ER-40 actually require a bit of torque for proper gripping if you read the specs. I guess the MT should provide enough friction so it doesn't spin in the RT socket but I think the plate bolts would be better
 
The plate looks like a good option. My RT has 4slots so I am not quite sure how I would mount it to the table. Maybe drill new holes? Thanks, John
 
That's a good point. I assume the boss plate will be hard. The question is how hard as in 'drill-able' hard. Maybe someone has experience. I made a plate to hold a chuck I also use on the lathe from cast aluminum plate. If push comes to shove you could do something similar with an intermediary plate. It would just be nicer if you didn't have the 'wedding cake' stack up.

The way to dial it in is just grip an accurate blank in the ER chuck like a ground dowel pin & indicate around it with a dial test indicator.
 

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Can drill or use clamps, the base seems small enough to leave room for the clamps.
My ER32 collet chuck was purchased to screws on the lathe spindle. I made a plate to mount on the rotary table. The plate has 2 holes for the North-South slots and two slots running North to South for the East-West slots. The chuck has limited movement East-West, just enough to move on center. The plate can move North or South as much as the slot allow for centering or offsetting.
 
Another approach that has max flexibility is to find a flat-back 4-jaw chuck that is slightly larger than your RT. Turn a shallow recess in the back of the chuck to fit snugly on your RT. Drill the body of the chuck between jaws for a couple of countersunk cap screws to mate with T-nuts in the RT slots. You can now dial-in any shape work piece to zero with ease.

WOB
 
WOB,
Thanks for the tip. It seems to me that any size 4 jaw would work as long as it can be secured firmly to the RT.
John
 
John what did you end up with for your ER 40 to rotary table setup ?
animal
 
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