View Full Version : Size motors for Mill Drill

06-17-2005, 04:02 PM
i am currently debating on whether to go with a servo motor or a stepper motor for my home mill/drill conversion. i have a 12 speed mill that has been converted to variable speed. i will do the ball screw conversion using parts from McMaster Carr. (5/8) screws. i am all new to this so speed is not really important but i want it to be upgradeable.

i found a starter kit with 150 oz in stepper motors. will these be enough to run this mill? its not the mini mill. i guess its similar to the G1005. a conversion that i saw done online seems to use the same 150 oz in stepper motors as are available in the kit.

i have found some electric motors that are clifton and have 2000 rpm at 23 volts. at 3 amp draw they put out 46.5 oz per inch. how do you compare stepper motor and servo motor output power? also how do you know how much you need for your mill?

sorry for all the questions but i don't want to buy the wrong stuff. anyone have some stuff that works they want to sell and possibly upgrade?

06-18-2005, 12:44 AM
Do you have any pictures of this mill? I have an industrial hobbies mill how does it compare? Does it have adjusting gibs in the table? There is a lot of things to know and I will admit that I don't know everything but I do know that the stronger the motor the more energy you can transmit to your work in cutting force. I will be using 750 oz for the x y and a 1200 for the z and I question if I should go higher on the x y but I will find out soon enough.

06-18-2005, 07:50 AM
this is a round column mill. i will not be using the z axis to adjust the entire head. it will be used only to extend and retract teh quill. yes i do you have gibs on the table.

06-19-2005, 12:28 AM
Hi, welcome aboard...

The ratings for motors whether it be steppers or servos can be confusing.

There are "peak" or maximum current ratings and continuous ratings. And then it gets even more confusing when you mix the ratings of servos VS steppers.

Servos produce their "power" differently than steppers. Basically as I understand it, servos produce their maximum torque at a higher RPM than steppers. They need to get the current flowing (torque) through high RPM relative to steppers. Steppers get the current flowing via low resistance (impedance) windings and do not need the rotational speed to produce a comparable torque rating.

So, what did I say...and does it help you ....

Your mill looks to be about the same size as most round/square column mills of the 8"x20" table size. That being said 46 oz/in continuous would be sufficient. The peak ratings of 300-600 oz/in for similar motors is less important, contrary to what the sales-person would want you to believe. Continuous torque is where you will be doing your machining, not the peak. The "sales speak" of "peak" numbers are not realistic.

For your setup it's basically a monetary issue. Servos will cost more because of the higher cost of the motors and the feedback circuit (encoders, tachs, scales) but may give you more speed (IPM) and reliability as far as positioning. Steppers are less expensive and can be very reliable as long as you stay within the load limits of the motor to keep outta the "missed steps" range.

Anyway, sorry for the long winded reply, either way you will be in the CNC arena and lovin it...JRouche

06-19-2005, 02:09 AM
You might also want to take a look at this thread http://www.cnczone.com/forums/showthread.php?t=11197&goto=newpost
This site is full of information look in the wood routers forums and bechtop mills. Please post your progress and some pictures. You will find that everyone here would like to help and by doing so you may help someone trying to do the same.