I seem to remember a similar problem back when I was using my Dore-Westbury years ago. I made up a little plug for the morse taper, male M10 to screw into the taper and extended, drilled and tapped to take the 3/8 male drawbar. This pushed the drawbar a little higher so I made a simple spacer to go under the head of the drawbar – plenty of room above on a mill with no top cover! Those does depend on space available inside the spindle but given that it will probably have room to take a taper with tang, it might work for you. I suggest well-fixing the plug into the taper as if that thread unscrews you might find yourself in an embarrassing position. Don’t ask…

As you don’t need to put silly tightening loads into a drawbar just cut a M10 thread on a bit of 3/8″ bar, should be enough engagement

Why not open up the hole in the spindle to take M10

What I did on my Emco mill was hold a longish 10.2 drill vertically in a machine vice (very loosely fastened to the table so it self aligned) and bored out the milling machine spindle. I dont recall it being tough but it drilled easily enough.

IanP

Take a length of 10mm threaded rod and reduce dia to suit by lathe or file, it only needs a few thou off.  Noel

William, as you’ve shown, the Centec drawbar is good in that it’s captive and also self ejects the MT2 arbor.
When I pulled my own drawbar out, the thread was well chewed, so i made a new pair, one 3/8″BSW and the other M10.
It’s not just about the ER25 chuck, but it also allows me to use other imported stuff, such as shell mill arbors etc.

As well as the extra draw bar, for the vertical head anyway, I knocked up a quick peg socket for easy removal of the top hat nut/drawbar retainer.
The gas bottle spanner fits the drawbar, and the hex on the peg socket is 17mm, as that’s the size of my clamping set nuts

Bill

You can buy a parallel shank ER25 collet holder, cut to length, plug the end if required (I tapped it and screwed in a bit off a bolt with Loctite), centre drill it and thread the outside diameter to fit in an AutoLock chuck. This is a 16mm shank ER16

Martin C

A storm in a teacup or a mountain out of a molehill?

3/8” drawbar will have some clearance in the spindle.  That means the spindle will have a bore greater than 9.52mm – only a mere 20thou (in old money) as maximum difference.  It may well be very close to 10mm.  A 10mm drawbar reduced by less than 0.5mm does not exactly present a huge problem – only the 10mm thread needs to be reduced to pass through the 3/8” + clearance.  The rest of the drawbar could be reduced by some arbitrary amount.  So I basically agree with JB, but with the absolute minimum 10mm thread diameter reduction.  TBH, IIRC, I didn’t have any great problem with 10mm drawbars in my Centec.

Thus, like I said, a mountain out of a molehill.  Theory over practicality.