Page 1 of 3 123 LastLast
Results 1 to 15 of 37
  1. #1
    Join Date
    Jul 2013
    Location
    BRISBANE BAYSIDE
    Posts
    90

    Default Lathe motor runs in forward but not reverse

    The single phase motor on my AL320G lathe runs just fine in forward but just hums when switched to reverse.
    I was parting off in reverse with an inverted parting tool when it jammed. Interestingly, it didn't break the parting blade, just locked up solid. It took me no more than a second to kill the power but after clearing the jam the motor only hums when switched to reverse. I would suspect that something got a fright but I am at a loss to know what. As far as I am aware, two wires only need to be reversed to run a 240v motor in reverse, so that should be a simple switching arrangement. However the forward/reverse switch on the lathe looks anything but simple.
    Unfortunately the motor rewinding specialist I have used in the past (and trusted - he was old school and knew it all backwards ) has retired, so I can't run it past him.
    Anyone run across this before or have any clues as to the problem?

  2. #2
    Join Date
    Jul 2006
    Location
    Athelstone, SA 5076
    Posts
    4,255

    Default

    Guessing that that seizure caused a faulty wire connection or most likely contact of the lever switch. It was probably crap to begin with and just needed a few more amps to kill it.

    Also when using the switch do not go slow on the lever. Do it deliberately and swiftly. A slow moving action on the contacts of switch can burn them out .....so to speak.

    You have most likely turned a light switch off and heard it crackle...same thing...burns the contacts. Eventually it fails.

  3. #3
    Join Date
    Aug 2011
    Location
    Melbourne
    Posts
    4,779

    Default

    Hi there, swapping the active and neutral wiring on an induction motor will have no effect on the direction the motor turns. Assuming your lathe has an induction motor of course....

    Remember, it's AC so the current is alternating at 50Hz anyway so swapping changes nothing.

    Reversible motors (I think) have several windings. This is why your direction selection switch is not as simple as you expected.

    Your motor will most likely have 2 start caps. Now im not sure if these motors have two start circuits (one for each direction) but i would check those first off.

    Also, another test, try spinning the chuck with the motor humming in reverse and see if you can get it going. Select a lowish speed to reduce load on the motor. If you get it running that would also indicate that something is up with the start circuit, likely the caps.

    Simon

    Sent from my SM-G970F using Tapatalk
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  4. #4
    Join Date
    Mar 2011
    Location
    Southern Flinders Ranges
    Posts
    1,536

    Default

    Like Eskimo said, you most likely lunched one or more contacts in the switch.
    Thats where I would start looking anyway.

  5. #5
    Join Date
    Aug 2012
    Location
    Greenmount, W.A.
    Age
    70
    Posts
    272

    Default

    If the motor runs in one direction, and not the other it indicates there is nothing wrong with the motor!

    The problem you have is that the reversing switch is not making a contact with either the "start" or "run" winding when it is reversed. This is signified by the "humming."

    A check of the connections to the reversing switch would be in order. Look for charred or hardened insulation (on the conductors) at the switch, or signs of overheating on the switch's outer case. This indicates a (or several) connection(s) / contact(s) has/ have been hot. A good tug on them (while the lathe is NOT connected to the 240 volt mains!) may reveal the culprit.

    I have had brand new Chinese made start / stop switches fail in the first hour or two of use. Charred conductor insulation was obvious. Unfortuneately Quality Control is not a high priority for some Chinese suppliers.

    When all else fails, get a new switch.

    Hope this helps.

  6. #6
    Join Date
    Jun 2012
    Location
    melbourne
    Posts
    341

    Default

    You could always try what engineers do when something stops working. Go to the breaker box and give it a sharp thump. Seriously, its what I do when my lathe won't start and sits and hums. In my case, I could replace the breakers, or do what I do and every 6 months to a year when it refuses to start - I give it a thump.

  7. #7
    Join Date
    Jul 2013
    Location
    BRISBANE BAYSIDE
    Posts
    90

    Default

    Thanks for all the replies and suggestions. I have checked all the connections to the forward/reverse switch. They were all good with no sign of overheating. I stripped all the insulation off the forked connector ends to the switch to check that there were no broken or fried wires. All good. (replaced the insulation stripped off with heat shrink). The forward/reverse switch is a sealed unit, you can't get into it, so if there are fried contacts inside, then it's a new switch. I will check with Hairy Forbes tomorrow to see if they can supply a replacement. I also checked all the connections at the motor input and all were good.
    simonl, it is a 2 cap motor and I did as you suggested and turned the chuck while it was just humming in reverse, it ran, but very slowly. I'd assume that this indicates that it's obviously not getting the starting input it needs to get up to run speed. I had previously visually inspected the caps and both looked ok. No sign or smell of anything untoward. I'm inclined to try the switch first, but if that doesn't fix the problem then the caps are the next on the list.

  8. #8
    Join Date
    Feb 2014
    Location
    Werribee, Melbourne
    Posts
    177

    Default

    There is an old thread regarding an AL320G only running in reverse and that mentions the forward and reverse switching being done via relays so a faulty contact also be in the reverse relay?

    https://metalworkforums.com/f65/t199137

    I don't have any first hand AL320G experience so don't know what sort of relays they have but might be worth a look?

    Ray

  9. #9
    Join Date
    May 2020
    Location
    Willowbank QLD
    Posts
    517

    Default

    Before I spent any money on a new switch I would swap the forward and reverse wires. Once swapped the motor should run in reverse in the forward selection and visa versa. If the fault changes the switch is at fault. If the fault remains the same the wires or motor is at fault.

    Steve

  10. #10
    Join Date
    Jun 2012
    Location
    melbourne
    Posts
    341

    Default

    Surely you have an ohmmeter? you can check the switch with that. Save you buying something on spec.
    I have a hafco lathe as well. Hafco use screw on wire connectors, which in my opinion are complete crap. They basically twist two wires together, and wind on one of these covers to cover the connection. https://www.ebay.com.au/itm/180x-Ele...c4c774b75ee57e The wires are still just connected, its not welded like in wirewound. Its bound to cause problems with corrosion eventually. I unscrewed mine, soldered the wires and screwed it back on so it was insulated. Its now been two years since I had to thump anything.

    If you are going to look at this be careful. They used them to connect on the capacitors (which is why you have problems starting) The issue being you will come across up to 380V on those capacitors, for days after you switch it off at the mains. I'd bet good money thats your problem. Clean those connections. Far more likely than the switch.

  11. #11
    Join Date
    Aug 2008
    Location
    Adelaide
    Age
    68
    Posts
    1,373

    Default

    Quote Originally Posted by Ray-s View Post
    There is an old thread regarding an AL320G only running in reverse and that mentions the forward and reverse switching being done via relays so a faulty contact also be in the reverse relay?

    https://metalworkforums.com/f65/t199137

    I don't have any first hand AL320G experience so don't know what sort of relays they have but might be worth a look?

    Ray
    That thread refers to relays in relation to a 335, not the 320. From memory the 320 I had many years ago had no relays, just a switch.

  12. #12
    Join Date
    Mar 2011
    Location
    Southern Flinders Ranges
    Posts
    1,536

    Default

    Quote Originally Posted by sossity View Post
    ...
    If you are going to look at this be careful. They used them to connect on the capacitors (which is why you have problems starting) The issue being you will come across up to 380V on those capacitors, for days after you switch it off at the mains. I'd bet good money thats your problem. Clean those connections. Far more likely than the switch.

  13. #13
    Join Date
    Feb 2014
    Location
    Werribee, Melbourne
    Posts
    177

    Default

    Gavin, yes that was my mistake going by the thread title and not reading the details closely enough.

    I see that H&F have the AL320G manual online and the circuit diagram (as rough as it is) shows only an On/Off switch and a reversing switch and no separate relays.

  14. #14
    Join Date
    Jun 2012
    Location
    melbourne
    Posts
    341

    Default

    Quote Originally Posted by racingtadpole View Post
    So whats root2 x's 240? Ok so its 340. You obviously haven't done much fault finding on motors if you think you can't get that voltage on motor capacitors if there's a fault.

  15. #15
    Join Date
    Jun 2012
    Location
    melbourne
    Posts
    341

    Default

    Quote Originally Posted by racingtadpole View Post
    Like Eskimo said, you most likely lunched one or more contacts in the switch.
    Thats where I would start looking anyway.
    Just how different do you think the start current is to the stall current? Don't you perhaps think the switch will be rated for that?

Page 1 of 3 123 LastLast

Similar Threads

  1. reverse/ forward on mill
    By China in forum METALWORK GENERAL
    Replies: 12
    Last Post: 3rd Feb 2020, 09:30 PM
  2. Replies: 0
    Last Post: 25th Mar 2018, 06:58 PM
  3. Replies: 28
    Last Post: 23rd Mar 2015, 04:16 PM
  4. Turning lathe motor from forward to reverse
    By Jim Ferrous in forum METALWORK GENERAL
    Replies: 13
    Last Post: 19th Sep 2013, 03:34 PM
  5. SOLD: 415v motor with forward reverse
    By Ch4iS in forum METALWORK - Machinery, Equipment, MARKET
    Replies: 2
    Last Post: 19th Apr 2012, 09:42 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •