Brush Or Brushless Motor For A Mini/midi Lathe?

[TonyL]

I was wondering if it matters. I like the HiTorque 8.5 X, Jet 920, and the PM. They will all cost me the same once they are tooled. (Enco has 25% off and free shipping on the Jet920).

Thank you for any feedback.

 

[Ulma Doctor]

they are both good machines.
i personally, would get the largest swing and bed that could fit into my workspace.

the brushless motor and brushed motors will both work for the purpose of driving a lathe.
a brushless motor will be maintenance free, they are usually AC powered.
whereas as brushed motor may require the changing of carbon brushes and the cleaning of the motor's commutator when the brushes wear out.
i may add that, in my experience, a brushless motor in- the same given specification envelope- will wear out or fail before the brushless motor
brushed motors are either AC, DC or universal
most brushed motors may be a little less efficient than their brushless counterparts.
variable speed control is a lot easier to accomplish with a brushed motor, but can be accomplished on small AC motors with a PWM board (Pulse Width Modulation).

 

[TonyL]

Wow! That's an excellent explanation; I even understood it. Thank you.

 

[Wreck™Wreck]

A bit of information about brushed and brushless motors may help.

Alternating current, especially 3 phase will produce a rotating magnetic field causing a motor to rotate, the drawback is that it will always try and rotate at the same speed as the frequency dependent on the number of coils (or fields) in the motor, a VFD (Variable Frequency Drive) alters the frequency to control speed. An AC induction motors speed is generally not effected by voltage up to the point of very high or very low values.

Direct current has no frequency as such so a switching device is employed to create a rotating field, many use a commutator on the rotor with brushes and commutator as switches. Changing the voltage will change the speed, the starter motor in a car is a perfect example, these are simple permanent magnet devices however.
A brushless DC or AC motor is externally commutated which means that the switching is done by a control outside of the motor in place of a fixed commutator.
The advantages of this are speed control and torque control at a given speed in a field wired motor.

To answer your question a synchronous motor (commom AC induction motor) is by far the least expensive, as controls and other devices are added it becomes considerably more expensive so it is not a matter of which is better but what you are willing to spend to achieve the performance that you require.

You may have noticed that your corded 110 VAC hand drill has brushes as well, it will also run on DC power. This is often called a universal motor

 

[John Hasler]

they are both good machines.
i personally, would get the largest swing and bed that could fit into my workspace.

the brushless motor and brushed motors will both work for the purpose of driving a lathe.
a brushless motor will be maintenance free, they are usually AC powered.
whereas as brushed motor may require the changing of carbon brushes and the cleaning of the motor's commutator when the brushes wear out.
i may add that, in my experience, a brushless motor in- the same given specification envelope- will wear out or fail before the brushless motor
brushed motors are either AC, DC or universal
most brushed motors may be a little less efficient than their brushless counterparts.
variable speed control is a lot easier to accomplish with a brushed motor, but can be accomplished on small AC motors with a PWM board (Pulse Width Modulation).

Brushless DC motors (which are actually synchronous AC motors with PM fields) are capable of very good speed control over a very wide range but require much more complex controllers than do DC motors. In a hobby lathe the brushes and commutator in a DC motor will last for decades.

 

[TonyL]

Thank you. I want to turn, cut tbread, bore, and part off 304L , 303, ss rod that is .75 inches in diameter I don't know it that helps. But I apprecite your comprehensive response.

 

[Wreck™Wreck]

they are both good machines.
i personally, would get the largest swing and bed that could fit into my workspace.

the brushless motor and brushed motors will both work for the purpose of driving a lathe.
a brushless motor will be maintenance free, they are usually AC powered.
whereas as brushed motor may require the changing of carbon brushes and the cleaning of the motor's commutator when the brushes wear out.
i may add that, in my experience, a brushless motor in- the same given specification envelope- will wear out or fail before the brushless motor
brushed motors are either AC, DC or universal
most brushed motors may be a little less efficient than their brushless counterparts.
variable speed control is a lot easier to accomplish with a brushed motor, but can be accomplished on small AC motors with a PWM board (Pulse Width Modulation).

I also work in the automation industry and can not even count the number of times that I have had the same conversation with customers.

Customer: We need to control the speed of this conveyor

Wreck™: Easy, I will install a VFD linked to the input device and the speed will be perfectly coordinated

Customer: $2500.00, you are crazy, I can buy an entire new conveyor for less

Wreck™: Not with speed control linked to the previous process or device

Six Months Later

Customer: When can you install that control that you quoted $1500.00 for 6 months ago, we need it ASAP.

 

[John Hasler]

Customer: When can you install that control that you quoted $1500.00 for 6 months ago, we need it ASAP.

I like the way you quote them $2500 and six months later they remember it as $1500. That's real.

Just recently I had a guy show interest in an old hay conveyor I had out behind the shed. I quoted him $500 and he said he'd think about it. Since he had shown interest and it is the season to sell such things I dragged it out, overhauled the motor, put air in the tires, put a drawbar and a stand on it, and greased and oiled it. The other day he came back and asked if I'd stll be willing to let it go for $300.

 

[TonyL]

This is why I ask:

http://littlemachineshop.com/products/product_view.php?ProductID=3540&category=1271799306

Can I expect to have problems with a brushless variable speed motor?

Versus this:

http://precisionmatthews.com/PM1027Lathe.html

 

[John Hasler]

Can I expect to have problems with a brushless variable speed motor?

If it's a properly specified good quality motor with a properly specified good quality controller, no. The simple induction motor will, of course, be more reliable because it is simpler but will also not be variable speed.