Rod,

If I understand correctly what you have in mind …

I would probably not use a drawbar, but simply Loctite the collet adapter into/onto the drill shaft, using 638 [yes, I am a great advocate of the stuff ]

If you ever change your mind and want to revert to the original fitting, the Loctite can be softened at about 200°C or "destroyed" at somewhat higher temperature.

What's the present chuck fitting arrangement ?

MichaelG.

The mill I own had an 8mm diameter drawbar for its MT2 socket (Its not MT2 now but that's a long story). Also supplied was an M8 to M10 adapter to fit in the end of whichever tool was being held.

Your 19mm or so splined shaft should easily accommodate a 5/16" or M8 clearance hole and if you can get suitably long drills you could drill the hole in-situ just feeding with the quill.onto a drill held vertically. You might need more than one length of drill.

Ian P

I have just checked the spindle that was in my Emco mill. It was drilled through for an 8mm drawbar but I actually opened it up to take a 10mm one. The upper part of the spindle has a keyway (no proper splines on this example of a precision Barvarian machine!) is 16mm OD and the keyway is 1.5mm deep giving originally a 2.5mm wall thickness.

At 3/4" your shaft will comfortably stand a 10mm drawbar which gives you the flexibility of changing collets or tooling with the bonus of saving the Loctite for something that really need it!

Ian P