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Thread: 7x14 mini lathe with electical short

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    Default 7x14 mini lathe with electical short

    I used my lathe for the first time since last Fall and it has a short somewhere.

    It runs but if I touch it with my bare hands I get a mild shock.

    Is this a common problem?

    If so what causes it and what can I do about it?

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    Community Moderator Al_The_Man's Avatar
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    The machine is not grounded properly.
    check continuity from the lathe frame to the service ground at the supply socket.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    That's a good idea and I will check it when I get home.

    But if so I wonder how it became ungrounded just sitting on the bench?



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    It has been shown here before that ROC electrical standards sometimes leave alot to be desired.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    Lol, I didn't know ROC even had electrical standards. Still, I would think that they would be required to meet standards of the country to which they are being imported.

    Problem may not be in the lathe, but maybe something happened to your outlet or wiring.

    Daystar Development didn't build your house, did they?



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    Quote Originally Posted by blades View Post
    Lol, I didn't know ROC even had electrical standards. Still, I would think that they would be required to meet standards of the country to which they are being imported.

    Problem may not be in the lathe, but maybe something happened to your outlet or wiring.

    Daystar Development didn't build your house, did they?
    I second Blades' suggestion to check the outlet first. Go to Home Depot, Lowes or even Harbor Freight and buy an outlet tester:

    http://acmehowto.com/howto/homemaint...outlettest.php

    BTW: Electrical conduction depends on skin resistance. That mild shock from touching with a dry hand could become quite serious if touched with a wet or sweaty hand--And DEADLY if there is also, say a bare foot touching ground.

    This problem needs IMMEDIATE attention before plugging in the lathe again.

    CR.

    http://crevicereamer.com
    Too many PMs. Email me to my name plus At A O L dot com.


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    Community Moderator Al_The_Man's Avatar
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    Very simple to test the ground path on the outlet, use a 60w~100w lamp and use a couple of jumper/test prods to go between hot side to ground pin, the lamp should light at full brilliance with 120v across it.
    Old electricians trick.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
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    Lol, I didn't know ROC even had electrical standards.
    They actually have very strict electrical standards. Easy to understand too. 1. If you build something that burns down your factory, you will be executed and your family persecuted. 2. All bets are off once it ships

    You can also check your outlet with a volt meter. If the outlet is right-side-up, HOT is on the left, NEUTRAL on the right, GROUND on bottom. HOT is also the slightly taller blade/slot. Volt meter to volts AC at a range over 120 (usually that is the 200 volt range, cheap meters it's often 2000 volt range).

    HOT to NEUTRAL = 110 to 120 VAC
    HOT to GROUND = 110 to 120 VAC
    NEUTRAL to GROUND = 0 VAC

    You must check all three, even for a ground problem. I wire with grounded metal outlet boxes, so I also verify HOT to the switch plate screw or the box itself = 120 VAC. This is the best test. In fact, I wouldn't have one of those plug in circuit checkers in my home/shop. I would through it at whoever put it there. Years back, I would recommend a xenon bulb tester if you couldn't afford a meter, but now you can get a decent meter at HF for under $5. Back-lit LED for under $10. A clamp meter for load balancing your circuits for $15. A very nice meter for $30. Al, hire a new electrician, your old one's a tight (_!_)

    WARNING: Consider all the connections HOT. Unlikely that ground will become hot at the outlet, unless miss-wired, but neutral passes current and can most certainly kill you. True, neutral ties to ground at the circuit breaker box, and normally has no potential in reference to ground, but get a hold of it while an appliance downstream passes the current to neutral, and it will make your day.

    Now, if we use a Chinese volt meter and all seems OK, is it really OK?



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    Quote Originally Posted by knudsen View Post
    They actually have very strict electrical standards. Easy to understand too. 1. If you build something that burns down your factory, you will be executed and your family persecuted. 2. All bets are off once it ships
    I seem to remember an issue in previous post where the ROC manuf had a 120v outlet on the machine using a male pins socket instead of female?? .

    Quote Originally Posted by rcr22b View Post
    It runs but if I touch it with my bare hands I get a mild shock.
    If so what causes it and what can I do about it?
    What is the verdict?
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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    I surprised we don't frequently hear of people buying an imported gizmo at (fill in the blank) ____-mart, plugging it in and getting their socks zapped off or burning their house down. Probably our saving grace is plastic doesn't conduct electricity well.

    Unrelated, but still regulatory, I saw a thing on Energy Start the other day. Manufacturers claim compliance, add the sticker, and no one follows up on it or does any testing. At my last company, way too small to afford real UL testing, we just bought UL listed power cords and used those We came in under the radar and/or claimed prototype status so we didn't need to comply with much. When CE came out, we freaked out thinking we would loose 30% of our biz because if we couldn't comply, we couldn't ship to EU. After looking into it we found CE is self certification that doesn't mean squat. So we bought CE stickers



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    Quote Originally Posted by rcr22b View Post
    I used my lathe for the first time since last Fall and it has a short somewhere.

    It runs but if I touch it with my bare hands I get a mild shock.

    Is this a common problem?

    If so what causes it and what can I do about it?
    Best bet is one of the motor wires has frayed, and is now grounding out to the machine.

    Start with the switch face plate(pull it) and check the wires behind it so see if one of them has a fray or strand of wire touching the metal, then chase the wires down to the motor and check them out as well (pull the cap cover on the motor).

    Granted that the ground on your Home outlet ground may not be connected correctly and causing the problem (feed back if someone just used a neutral wire for the ground circuit instead of a dictated ground wire circuit), but the off/off switch on the machine is only amp over load rated to trip, and not a GFI device.

    Also, take a good look at the cap and it wires as well. The energized cap can put out some major voltage, and if allowed to ground out to the metal, will cook the cap in no time at all (read no joy finding a replacement cap since the US models are all larger than the one on the motor that fits under the cover).



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    Quote Originally Posted by Dano523 View Post
    Best bet is one of the motor wires has frayed, and is now grounding out to the machine.
    It is possible, but if the machine is properly grounded then it should have either blown free or tripped the breaker.
    With AC you do not need a direct resistive connection to pass current to ground, if the machine is not grounded and you are standing on a damp floor etc, the path can be capacitive or inductive, very small current but enough to feel a slight tingle.
    Especially if not used since last fall, dampness in the motor and other wiring could be the cause of leakage.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


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