Which machine to get / build

[Doddy]

Does the WM16 work-area/table suit your CNC requirement?, do you use it rarely as a manual mill? Is the spindle suited to the work that you're looking to do? If the answer to any of these is no, then look elsewhere (but you'll struggle on your budget).

I converted a SX2.7 (It's a Trigger's Broom - so little left of the original now I refuse to call it a Sieg) having got bored of spinning little wheels by hand - they can be made into reasonable bench mills with little effort. Besides, the conversion can be fun. But you'll be on the edge of your budget. Manual wheels?, you'll suffer the commutating forces of a stepper, you can get by with a MPG / electronics. To be honest, other than the quill control (which I retained) I don't miss the manual wheels at all.

The 3040 might polish a bit of steel, but probably not much else.

[JAZZCNC]

Forget the 3040 type rubbish they are only just good enough to cut MDF and can't do that correctly.!

To me with your budget your only option is to convert the Mill and even then you'll have to buy wisely. If it was me I'd do it in phases and improve it as you go along and get a better fell for CNC.
Start by using the leadscrews that are fitted and just connect steppers to them, this is simple and cheap with minimal to no impact on the manual machine.

Controller wise then It's a perfect candidate for using Linux CNC because it's free and is scalable. By this I mean you can start simple with a Cheap £5 Breakout board and throw some half decent Closed-loop steppers on it which will be in £300 region and away you go, you'll just about do it with £500. Then as you have the money and learn you can build up the system and improve it with ballscrews and more advanced Mesa cards.
With Mesa cards and Linux CNC you can do just about anything, including using hand wheels for semi manual control(still need PC on). Clive S is the man for Linux CNC and he's converted the same machine using Linux CNC and it used handwheels.

I wouldn't look at any other route unless you substancialy increase the budget.

[GeorgeS]

Thanks for all the advice, I'll deffinately be converting my mill.

Would I still be able to get half decent results using the stock leadscrews? Also (posibly a stupid question) should the steppers be directly attached to the leadscrews where the hand wheels are, or can they be connected using belts to pulleys mounted where the hand wheels are (seems a lot easier to do)?

[JAZZCNC]

Thanks for all the advice, I'll deffinately be converting my mill.

Would I still be able to get half decent results using the stock leadscrews? Also (posibly a stupid question) should the steppers be directly attached to the leadscrews where the hand wheels are, or can they be connected using belts to pulleys mounted where the hand wheels are (seems a lot easier to do)?

Like Doddy says you will have some backlash but how much depends on your machine but it can be lessened by using backlash compensation which is a software work around. It's not perfect but can help a little and will certainly get you going.

You'll probably find using belts will be required because won't be able to directly mount easily. But that said it's a good thing to do any way because it lowers the resonance on the motors and makes them run smoother. If was Me I'd be fitting belts regardless for this reason alone.