# Optimum mill ndrawbar mmod.



## th62 (Jan 10, 2021)

For anyone with an Optimum mill.  As you've already found, the mill comes with  a whitworth threaded drawbar and most arbors have metric threads.  You can use a long M12x1.75 pitch bolt and knock the arbor out by tapping on the head of  the drawbar, however be  careful as the quill gear, apparently is plastic.  Or, you can  do as I've done:  I bought a long M12 x 1.75 pitch bolt, turned the head down to 17mm and  drilled a 5mm hole through the head to a few mm.  I turn down a piece of 19mmm stock to 17mm, then turned down one end to 5mm long enough to fit in the hole in the head of the bolt.  The other  end I turned down to 9.5mm and milled flats on either side to fit a  spanner.  The 17mm section needs to be no longer than 24mm so it will fit  under the cap nut.   I then inserted the 5mm spigot into the hole in the bolt head, welded them together then turned the welded area down to 17mm.  It came out a little under 17mm, but that's not critical.  That done then it was just a matter of dropping the drawbar down the spindle, screwing on the cap nut and fitting the arbor.  To remove the arbor just fit a spanner over the flats on the new drawbar and turn anti clockwise.  In retrospect I should have turned a 5mm spigot on one end  of the 19mm stock,, welded that to the bolt head  and then turned down  the hole lot to 17mm.  As it turned out the bit I welded onto the head turned out spot on, but that's called a fluke I think.


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## sycle1 (Jan 10, 2021)

Your remedy is so much more skookum (elegant) than mine.
 I just drilled out the cup nut with the flats on it for 12mm and cut a 12mm threaded rod to suit, locked two nuts on the end and it works.
I do need to make a better drawbar one day.


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## ClintNZ (May 3, 2022)

Here's my take on an Optimum BV20 metric drawbar, not as tidy as th62's but maybe a little more refined than sycle1. This was my first project using the new BV20.




I turned & milled the end of some high tensile threaded rod to match the top then machined a round nut that was loctited & pinned on. Drilled & tapped a hole in some some alu square to index it around while milling the flats:




Cheers
Clint


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## sycle1 (May 3, 2022)

Nice job Clint 
 I am lazy.
 I really should make a new drawbar one day.
But for now it works.
Cheers


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