reversing a milling machine

[James fortinParticipant @jamesfortin46829]

i am at the start of putting a reversing switch on my mill using a DPDT switch. (so i can reverse taps e.c.t)

 

the diagram goes like this

 

 

 

 

 

am i right in thinking that this should reverse an AC motor or will it still run in the same direction- because i know most motors have capacitors on them but don’t know if this affects the direction

 

any help would be appreciated

 

many thanks

james 

[James fortinParticipant @jamesfortin46829]

trying to reverse a milling machine but unsure of obstacles

[john swift 1Participant @johnswift1]

Hi James ,

 

what type of motor do you have ?

 

your circuit will only work if used to reverse the connections to the armature or field winding of a universal motor , as in a mains power black and decker type of drill

 

or reverse the connections to the main or start winding of a single phase

capacitor start , ac motor

 

   John

 

ps – if you need , i’ll upload a diagram for you

Edited By john swift 1 on 01/12/2010 13:09:05

[Nicholas FarrParticipant @nicholasfarr14254]

Hi James, I doubt that your idea will work on a single phase ac motor. Like John has said, you need to change the armature/field winding relationship. Most motors allow you to do this inside the connection box. To do this with a remout switch you will have to bring extra wires out of the motor to the switch.

 

Regards Nick

[James fortinParticipant @jamesfortin46829]

hi thanks for the advise

 

a diagram would be appreciated john-its a 4pole induction motor if this helps

 

 

many thanks james 

 

 

[Jeff DaymanParticipant @jeffdayman43397]

Hi James,

 

Your switch wiring will work perfectly for a DC motor but will not work for an AC motor.

 

You need to ID the type of AC motor you have to be able to figure out how to phase shift the field  to reverse the motor.

 

If it is a shaded pole AC motor it will be difficult or impossible to do this, as these motors have a heavy copper shunt winding that influences the direction, which is built onto the stator lamination pack.

 

If it is a common general purpose AC motor for washing machines etc. which reverses the field by altering connections in the wiring box, a simple drum switch will be able to reverse it. The key is to find an AC motor with a wiring box and 4 to 6 connections in it.

 

JD

[James fortinParticipant @jamesfortin46829]

when i got it and rewired the mill it did have 4 connexions. ill post a pic when i get in the shop.

 

many thanks 

[James fortinParticipant @jamesfortin46829]

 ive put some pictures up and i also found a diagram inside the cover that looks like this but unfortunately couldn’t photograph it because it is to small.— the 1234 are the connections to the 4 poles and the 2 wires going towards them is the supply- i don’t fully understand this diagram, any opinion on it is welcome.

 

 clockwise      anti clockwise

  CW                     CCW

 

  1  2  3  4         1  2  3  4    

   I   I   I   I           I   I   I   I    

     /     /             /     U

     I       I               I       I

 

 

 

many thanks

 

james 

 

[James fortinParticipant @jamesfortin46829]

sorry the formatting has changed maybe this is better

 

 

clockwise       anti clockwise

     CW                 CCW

 

  1   2   3   4         1  2   3   4    

   I   I   I   I           I   I   I   I    

     /     /             /      U

     I       I                I       I

  

Edited By James fortin on 01/12/2010 14:44:42

Edited By James fortin on 01/12/2010 14:45:09

Edited By James fortin on 01/12/2010 14:45:28

Edited By James fortin on 01/12/2010 14:45:43

[NJHParticipant @njh]

Hi All

 

This is a probably a really silly question – Why is there a need to reverse the motor?

 

Regards

Norman 

[James fortinParticipant @jamesfortin46829]

its not a silly question 

 

i need i reverse it because in the future i am going to us it as a tapping machine and for other things that require reversing 

 

by the way its single phase. 

 

many thanks

 

james 

Edited By James fortin on 01/12/2010 14:58:17

[Jeff DaymanParticipant @jeffdayman43397]

James I don’t want to burst your bubble, but unless your mill has LOTS of torque and very low speeds, you may find you will not be able to tap much under power. For non powered alignments ie tapping immediately after drilling without moving the table, you can’t beat doing that in the mill.

 

In my experience  taps larger than say 1/4″-20 need a LOT of torque, and taps below #10-32 will break easily in steel if power tapping.  I have not had much luck power tapping in my RF30 Taiwan mill. My old South Bend lathe is great for tapping though.

 

When I first started work the shop I was in had a jig borer with a 20 HP motor and spindle speed down to 2 rpm. On that unit, we tapped from #2-56 up to 3/4″-10 under power regularly. It weighed about 8 tons and was super heavy cast iron construction though.

 

JD

[KWILParticipant @kwil]

I would not use it as a tapping machine without the use of a properly constructed tapping drive unit. How would you stop the rotation instantly?

[James fortinParticipant @jamesfortin46829]

thanks for the advice – i think i should be able to tap quite things easy as in the lowest gear the reduction is 1450 / 120 . the torque is 12 time more than at the motor(hence 12 times less speed)- thats a total of 12 horsepower 

 

when i am out in the shed next i will try my biggest tap and see how it copes

 

many thanks

 

james 

Edited By James fortin on 01/12/2010 16:23:05

[Jeff DaymanParticipant @jeffdayman43397]

Sorry KWIL, I assumed James would be using a tapping head like a Procunier unit or a Tapmatic. These are driven by the spindle James and are instantly reversible for tapping by means of internal cone clutches. You will need something like these units for power tapping or at least a clutch on the motor or spindle.

 

JD

[James fortinParticipant @jamesfortin46829]

thanks ill look this up and buy one of these instead

 

many thanks

 

james 

[john swift 1Participant @johnswift1]

Hi James ,

 

does this diagram help with the wiring ?

 

 

as I understand tapping machines have two counter rotating drives

 

when you pull down on the handle

one clutch is engauged to drive the tap in

 

when you release the downward presure the drive stops

 

letting the handle up engauges  the reverse drive to remove the tap

 

  John

[James fortinParticipant @jamesfortin46829]

thanks for the diagram john, it makes sense now  , i might still use this method if i cant afford a tapping head. but at the moment the the tapping clutch sounds sensible.

 

thank you all for your input 

 

many thanks

 

james 

[Anonymous]

Errr, assuming that the motor in question is 1hp, you’ll still have 1hp at the spindle, whatever the speed reduction? It’d be a neat trick otherwise, and would have the Nobel prize committee winging it’s way to your door post haste!

 

Power is torque times angular velocity, so if the speed is reduced by 12 then, as you say, the torque goes up by 12, but the power stays the same.

 

Regards,

 

Andrew

[James fortinParticipant @jamesfortin46829]

oh, thanks for that. now i think of it horse power isn’t torque at all its just another unit of power as torque is in ft/lbs and n/m

 

many thanks

 

james 

[Author]

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