# Purpose of having Reverse



## Kroll (May 19, 2013)

Guys couple weeks ago I ask bout the wiring of my motor over on the elec section and thanks to John and other there I am ready to more to the next step,but before I do-----
What is the purpose of having reverse,won't the chuck come off running in reverse?Is this a function that the average person needs?
I have a Sears 101.28900 that came with a drum switch that has For/Stop/Rev,I am getting to the point of wiring the motor and figuring out if I need reverse,if not then I'm just going to install ON/OFF switch,but if there is some benefits that I may come across in the future of having reverse than I would like to make plans for that.
So,is it worth having reverse and please give examples and pics would be nice for this simple minded person.Thanks----kroll


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## Chucketn (May 19, 2013)

I use reverse during threading, both for returning the carriage to the starting point when single pointing, and for backing the tap out of internal threads.

Chuck


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## itsme_Bernie (May 19, 2013)

More important option using collets, since they won't spin out.  Also for tapered spindles instead of threaded.

Be really careful if your spindle is threaded, like all Atlas machines (?), even reversing the carriage feed etc with a chuck in the spindle, depending on what the startup is like.  You could still spin it off, or worse, loosen it and not notice it is loose until you go into a fast forward speed.


Bernie


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## rdhem2 (May 19, 2013)

Purpose of reverse?  Tapping and threading mostly.  Drill chuck MT spins in tail stock?  Slide back on Morse taper and bump reverse.  Comes right off.   Break a bolt or screw?  Use a left hand drill to remove.  Worried about accidently going past stop and right into reverse?  Easy, throw away the drum switch and use a motor starter rated for the load controlled by pushbuttons.  This will bring your lathe up to current code by giving the motor overload protection and you peace of mind of not creating a potential accident.  Good old American lathes used drum switches because it was CHEAP at the time and legal.  But not now.  Pop the covers off those HF and Grizzly lathes and you will find contactors and overload relays.  Why?  Because they would not be allowed to sell them otherwise.  This is also why it is so easy for an electrician to add a VFD controller.  Except for the controller itself, a motor and a switch or two, he is COMPLETE.


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## pdentrem (May 19, 2013)

One is not likely to be running in top rpm in reverse. Usually it is a threading operating and low rpm. I had an Atlas and my current lathe is threaded as well, and this is the way I have run my lathes. 

You can use a shot pin to hold the chuck in place by simply drilling a hole into the face of the flange and a slot to the outside for a handle to retract the pin that is pushed by a spring into a matching hole on the spindle. this is just one method found on the net.
Pierre


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## Tony Wells (May 19, 2013)

I use it whenever it suits me and the job in the machine. I face down to an external boss shoulder by working a boring bar on the "far" side of the spindle, and I can turn the OD with a bar too. Sometimes cutting bevels and chamfers is done in reverse with tools on the far side. Just depends on what tool is in the holder and what I want to cut. I don't generally do the reversing method for threading, but once in a while I do power tap, so it gets reversed then. 

If you happen to have left handed bars, either boring, threading, or grooving bars, nothing wrong with working the "other side" of the hole. I'd feel handicapped not to have reverse available.


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## VSAncona (May 19, 2013)

Another reason for running the lathe in reverse is when using a tool post grinder.


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## Jimsehr (May 20, 2013)

One good reason is if you some day want to use collets . And there are also other good reasons for running parts in reverse.  Cutting left hand threads is one good reason. And in  production shops I have ran thousands of parts in reverse in collets and cutting tools upside down in back side of crosslide using only the bottom two rollers of a steadyrest with cycle times less then 30 seconds and never stopping spindle. It can save lots of time.

jimsehr


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## gheumann (May 20, 2013)

I routinely make a part that involves cutting a .425 deep pocket in 2.5" diameter .750 thick aluminum. The rough cuts are fast and deep - much faster than any auto-feed option so it is done manually. I do it in reverse because it is so much easier to see the tool approaching the far side of the pocket.


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## hosinsky (May 20, 2013)

There is a danger with it too, as with all things mechanical if you are  not careful. Yesterday I was threading some M6 blind holes on the lathe,  turning the lathe manually when going in, using the motor in reverse  going out. Went fine until I forgot to switch back to reverse after  drilling the hole to be threaded. The tap was in the bottom of the hole  and could not go in further when I started the motor to bring it out.  The cross bar of the tap holder cut a deep slash in my middle finger  when it started rotating. According to the doctor I had luck. A deep and  broad cut but it did not touch the bone or the tendons. It will be some  time though, before I can finish the mounting of the new telescope.

Goran
Canary Islands

written with my left hand


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## swatson144 (May 20, 2013)

> Worried about accidently going past stop and right into reverse?  Easy,  throw away the drum switch and use a motor starter rated for the load  controlled by pushbuttons.



Actually you have no worries about rolling the barrel switch past stop into reverse or vice versa as the motor will continue to run in the direction it is going. The reversing function is controlled by the starter windings which are already disconnected by the centrifugal switch with the motor already running.

Steve


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## jbollman (May 20, 2013)

Kroll said:


> Guys couple weeks ago I ask bout the wiring of my motor over on the elec section and thanks to John and other there I am ready to more to the next step,but before I do-----
> What is the purpose of having reverse,won't the chuck come off running in reverse?Is this a function that the average person needs?
> I have a Sears 101.28900 that came with a drum switch that has For/Stop/Rev,I am getting to the point of wiring the motor and figuring out if I need reverse,if not then I'm just going to install ON/OFF switch,but if there is some benefits that I may come across in the future of having reverse than I would like to make plans for that.
> So,is it worth having reverse and please give examples and pics would be nice for this simple minded person.Thanks----kroll



Hi Kroll:

Many (not all) single phase motors rotation can be reversed*.  The "start winding"  must be reversed in regard to the "run winding"  Making this change causes the rotor
to rotate in the opposite direction. The "start winding"  will have a centrifical switch which turns off when the rotor comes up to name plate speed.    

"Induction" single phase motors are unlikely reversable.  An induction motor for any machine tool is not compatable since the "overal start torque" is rather weak  Most machines in a machine shop have an inertia factor such as lathe parts & a 3 or 4 jaw chuck or a face plate. These items require additional torque to get them moving. 

 I have a bench grinder ( 1/3 HP which can be reversed - however I have to take the rotor out and change a wire to another lug.  Obviously this type would not be compatable with a lathe.  Some motors have a "start capacitor" in the "start" winding which increases the "start torque" until the motor gets up to speed and then the centrifical switch shuts of the "starting scenario.

If needed I have both single and three phase wiring diagrams & can send you a diagram on this site. this will take a couple of days or so since I have another issue to resolve.

In the interim you might want to get on the internet and call up "Single Phase Motor Windings" and review the diagrams.

Regards,

jbollman


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## BRIAN (May 21, 2013)

A while ago I fitted my 7x12 with a 1 ph motor with reverse. 






I used the existing toggle switch, It ts rated at 15 A. and put a circut breaker in the feed.






The start/stop switch has a interlock that drops out if you cut the power,So if you turn from  F to R you have to push the start button again





Under the cover I have a 12v power supply for the saftey switches including a saddle limit switch these operate thro a relay to cut the power.



I think all the reasons for having reverse have been covered so I wont repeat that good advice,


 A lathe without reverse is like a fridge with no beer.

I hope this helps.

Brian.


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## Codered741 (May 21, 2013)

jbollman said:


> Hi Kroll:
> 
> Many (not all) single phase motors rotation can be reversed*.  The "start winding"  must be reversed in regard to the "run winding"  Making this change causes the rotor
> to rotate in the opposite direction. The "start winding"  will have a centrifical switch which turns off when the rotor comes up to name plate speed.
> ...



Part of what you are saying is true, but a little clarification is needed. 

You are correct in that many but not all single phase motors can be reversed. For most types of machine tool motors, this is possible, if the motor manufacturer left you access to both windings of the motor. Eg. If your motor only has two wires accessible, it is not reversible. However if you have four or more wires, then it is most likely possible to reverse the direction of the motor. 

However, almost all single phase motors are induction motors.  Exceptions would be a "universal" motor, which will run on AC or DC, using a combination of brushes and induction. 

And induction motors actually have very high starting torque, usually at least double their rated torque, which makes them perfect for starting large, high inertia machines, like lathes, mills and air compressors. 

The capacitor usually found in single phase motors, is used to create a phase differential between the start and the run windings, which makes the motor start to spin, and once spinning, the centrifugal switch shuts it off. Without this differential, you would just create a large electro-magnet, and get a loud buzz from the motor.  A three phase motor does not need such capacitors, as the phase differential already exists between the phases naturally. 

If you really study how an induction motor works, you soon realize that there is a bit of magic to it.  You have to use electricity to create magnetism, which then creates electricity, which then creates magnetism, and having several of these fluctuating magnetic fields rotating at a specific frequency and timing, creates a rotational force (torque) which causes a shaft to spin.  

If there is interest, I would be happy to expound on the intricacies of motors, and their various types, though I think it would be best served in a separate thread, for fear of hijacking this one. 

Sorry if I hijacked! 

-Cody

Sent from my iPad using Tapatalk HD


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