# Thread: how to convert a mill to cnc?

1. Im thinking about converting a fairly big mill that ive got with lead screws (i would say that the xyz axis are fairley easy to move). It has quite a lot of backlash at the moment so am going to see if i can reduse it but is good for its age (i realise it wont be super accurate). I have used hass mills before but know very little about converting mills. I have been looking at this system 4 kit http://www.diycnc.co.uk/html/cnc_systems.html and woundered if it would have enough power with 3nm steppers geared down 2:1. so i just want to know everything i need to know and if its worth doing.

Thanks

2. A Newton is about 100 grams and motors are usually rated by holding torque rather than pull in torque. You need to see a torque against speed graph to know if you are in the right ball park. If the mill is of any size then you'd want NEMA 34 steppers or servo's for speed.

Suggest you wind some kind of tape around one of the handles and then see what weight you have to lift on the end of it before you feel the kind of torque you reckon would make a cut.

3. Ok, so can i get a simular system for nema 34s without costing a fourtune. I do not particually want it to be very fast, so dont mind if its a bit slow.

4. I tryed pulling on the handels and measuring the weight and at about 2" away from the centre it took 4 kilograms and at 6" it to under 1 with no load to move the table. like i said i would say it has very low friction and have used smaller mills with more friction. so dont know how much power i need?

Thanks

5. Interesting choice of units

I calculate 1 kgf inch = 0.25 Nm or thereabouts.

4kgf at 2 inches = 8kgf inches = 2Nm
1kgf at 6 inches = 6kgf inches = 1.5Nm

Table's kind of stiff if that's at no load.

You can get more Nm out of a motor with a belt reduction but that doesn't do your top speed any favours.

Q1: Can you free the table up?
Q2: Does it matter if it's kind of slow?
Q3: Could your budget stretch to servo motors?

best

Robin

6. Ok, i dont mind if its slow, dont think i can free up the table anymore. I dont know how much a servo system would cost, so dont know about budget. I thourght they were a lot more so dont know anything about them.

Thanks

7. What type of Miller?

Bill

8. Hi, ive got a thiel 158 tollroom mill. Ive seen this kit http://www.rhonmac-cnc.co.uk/index.htm and woundered if the one with the 5.8nm steppers would be enough to power it geared down 2:1, but dont quite understand about the driver, as it appears to me that it can run 4.2 amp but the motor takes 7?

Thanks

9. I used to have a couple of Thiel 158's, excellent machines. I remember the X axis being nice and free flowing, but the Y axis was always stiff. The Y axis is created by an overarm coming forward and backward with the spindle is attached, this all added to the weight and stiffness. Have you thought how you will get the stepper/servo drive to the Y axis? I am assuming you have a fixed table and not the XY fancy one.

Mike

10. Hi, i have the fixed one i think, its the same as the one that you attached a pic of. The y axis is surprisingly free moving with little backlash but can see how it could be hard to move. My x axis is the one that is harder to move and also has a bit of backlash so i need to find a way to reduce that first.

Thanks

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