Myford VM-B CNC Conversion.

[John S]

Mark,
Should be plenty of photos as Grandson needs all this for his project CV thingy.

Done a few of these previously and quick run down is to strip the motor and take measurements mainly where the rotor needs to sit.
Then draw up a new front cover to take the bigger bearing and that will then define where everything goes.

Old shaft is pressed out of the rotor and a keyway broached in. New shaft will be made a slip fit and rely on the keyway and a retaining nut on the tail side of the rotor.

New shaft roughed out of a piece of EN19 steel, couple of mm left on all over.

Hold by long diameter and machine where the ER20 fitting goes all at one setting, bore at 8 degrees and blue fit to suit collet, screwcut M25 x 1.5 p to suit nut.
Remove from chuck, replace with lump of Scrapbinium [ TM ] and turn down to 13mm by 40mm long, polish for good finish.
Then very carefully insert 13mm collect into the nut and tighten up onto the shaft you have just turned. running at low speed ~150 rpm, carefully centre drill the opposite end, use low revs so it doesn't whip.

Once the centre is in then the rest of the bearing diameters, rotor diameter and retaining thread can be finish turned and polished to size.

Do a build up and spin by hand checking the runout of a test bar held in the collet, should be minimum run out.

Strip and send new spindle for Tuftriding this is a heat treatment that is done at about 400 degrees and not hot enough to cause distorsion. it only puts a very thin skin of hardness on but enough to protect it against normal wear and tear, EN19 suits this process very well. Another plus is that it's virtually rust proof.

Short of hardening full out and then having all surfaces ground afterwards to ensure they are true this is the easiest / best way to produce a spindle.

[Jonathan]

Where do you get the EN19 steel from? I'm guessing it would be the right stuff to use for ATC holders.