Grounding, furnas switch


Tom Harrold
 

So, I have wired up my 9" model C, just waiting for a flat belt.  At some point a previous owned had used a 3-prong plug, and it raised the question:  how are you grounding your lathes?


I can try to fasten the ground wire to the furnas switch, or I can just leave it unused. 


Wondering how good of a ground it would be, since the motor is separated from the lathe (I have a horizontal drive system).


Anyone else find a way to deal with ground? Or just run it like it was run back in 1954?


-Tom


DJ Delorie
 

Speaking from an electrical background....

(and this is all 100% AFAIK so feel free to argue facts ;)

There are a couple purposes of the "ground" wire. One is protection -
by keeping everything at "earth potential" you avoid stuff from
(small) static zaps to (big) electrocution due to bad conductors.
Another is fusing - by providing a really good alternate return path,
it ensures that shorts from broken wires blow the circuit breaker
before they harm humans or cause fires.

These needs can be bypassed by providing alternate methods. For
example, "double insulated" tools need not be grounded because
protection is provided via alternate needs. Likewise, plastic tools
(or electrical boxes) need not worry about electrocution risk :-)

So, as for grounding the lathe, there are two considerations...

First, grounding the electrical portions. The motor itself is likely
grounded internally. Any boxes the wiring goes through should either
be plastic, or grounded. Any electrical switches or outlets should be
grounded, etc. While home building code doesn't cover these unless
the tool is hard-wired into the house, code provides useful guidance
here.

As for grounding the lathe itself - the only consideration here is if
you find that you're getting static buildup on the lathe. If you turn
plastics, you might want to ground it. In wood shops, dust collectors
are often grounded for this reason. Note: the tool does NOT count as
a ground wire when I say "the electrical boxes should be grounded".
Grounding means connecting an actual ground wire.

If you think grounding the lathe to avoid electrocution is a good
idea, consider what this means - it implies that the wired ground is
insufficient in the electrical portions! Also, if a fault happens you
might weld your gears together. Also, oil isn't a good conductor
(relatively speaking, and it might burn or explode) so a grounded tool
might still have dangerous potential across it. Ground the electrical
portions correctly and don't rely on your tool to be a wire.

So... ground the electrical portions as well as you can, and IMHO let
the machine fend for itself ;-)


John Gallo
 

If the switch has a metal housing and is grounded and connected to the lathe, doesn't that make the lathe itself grounded also?


Tom Harrold
 

 I guess I'm curious as to what most people have done.  Clearly the US electrical standards have changed since the mid-1900's, and we've added ground wires to our outlets.  Now I have a 1954 lathe, which probably never came with a 3-prong plug, and I have the ability to "improve" safety...just wondering what others have done.

My setup has the 3-wire power cord coming into my (metal) furnas switch. (forward reverse switch).  The ground wire is not connected to anything.  I could certainly wire it to the furnas switch box, but wondering if there's a better option. (like extending it to the motor, etc)

-Tom


Sent from Yahoo Mail. Get the app


On Monday, August 15, 2016 2:36 PM, "johnnyblock1@... [SOUTHBENDLATHE]" wrote:


 
If the switch has a metal housing and is grounded and connected to the lathe, doesn't that make the lathe itself grounded also?



ww_big_al
 

Myself, I grounded mine. It’s not hard. If you look on the back of your furnace switch, depending when it was built, there might be a thread hole doing nothing. If so, use a machine screw and bond you green wire there. If there isn’t just drill a small hole for a 10-32 or 8-32 and use a nut and bolt to tie it down. Your motor should have a 3 conductor wire going to it. If the motor doesn’t have a dedicated bonding screw spot, common practice is to use the cover plate screw. Not ideal but functional. The other end of the motor cord should then be tied to the same grounding screw in the furnas switch. There is no need to bond the lathe since there isn’t any other source of electrical shorting device on it.

 

From: SOUTHBENDLATHE@... [mailto:SOUTHBENDLATHE@...]
Sent: Monday, August 15, 2016 2:38 PM
To: SOUTHBENDLATHE@...
Subject: [SOUTHBENDLATHE] Grounding, furnas switch

 

 

So, I have wired up my 9" model C, just waiting for a flat belt.  At some point a previous owned had used a 3-prong plug, and it raised the question:  how are you grounding your lathes?

 

I can try to fasten the ground wire to the furnas switch, or I can just leave it unused. 

 

Wondering how good of a ground it would be, since the motor is separated from the lathe (I have a horizontal drive system).

 

Anyone else find a way to deal with ground? Or just run it like it was run back in 1954?

 

-Tom


DJ Delorie
 

If the switch has a metal housing and is grounded and connected to
the lathe, doesn't that make the lathe itself grounded also?
Like I said, don't rely on your lathe to be a wire. "Happens to be
connected to ground" is not the same as "grounded".

Every electrical part of your lathe - switches, metal electrical
boxes, motors - should have a ground wire of suitable gauge connecting
it to earth ground through the power cord's ground wire (which is
"grounded" via suitable buried copper conductors, eventually).

If other metal parts happen to connect to these grounded electrical
components, that's only "happens to be connected to ground". Rust and
paint are pretty good insulators.

If you decide you want to ground your lathe, you'd connect a suitable
wire to the lathe itself, and connect that to earth ground somehow.

Note that code does NOT allow multiple earth grounds in one building.


john kling
 

Question: The early motors that came with the lathe did not use 2 prong plugs. Indeed the ads show them connected to overhead light sockets. Any opinopns on grounding these motors?


Gary Johnson
 

Regardless of age, ALL motors must be properly grounded for the safety reasons previously stated. A very old one may not have a designed-in ground screw. In that case, you may add one in a sensible location at the terminal box. Alternatively, you can run a bonding conductor to the frame of the motor and connect that directly to another properly-grounded item such as a switch box. 

Modern safety standards are written in blood. Grounding is really simple to do and there is no reason to skimp in this area. "If there's power running to it or through it, ground it."

Gary NA6O
(Retired EE)


Jefferson Tomlinson
 

I recommend that any other electrical equipment you use around any equipment that has a safety ground on it that all other  eletrical equipment including lights small electric power tools unless double insulated be grounded. I have magnetfied florescent light I use around my 3in1 and I have grounded it for safety reasons. I also leaned the importance of grounding everything when I had a ametuer radio license. His just a little food for thought.

Jeff Tomlinson


On Monday, August 15, 2016, gwj@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 

Regardless of age, ALL motors must be properly grounded for the safety reasons previously stated. A very old one may not have a designed-in ground screw. In that case, you may add one in a sensible location at the terminal box. Alternatively, you can run a bonding conductor to the frame of the motor and connect that directly to another properly-grounded item such as a switch box. 


Modern safety standards are written in blood. Grounding is really simple to do and there is no reason to skimp in this area. "If there's power running to it or through it, ground it."

Gary NA6O
(Retired EE)


eddie.draper@btinternet.com
 

I would just add that if your ancient terminal box on the motor is not actually part of the motor, i.e. cast or welded to it, but bolted or riveted on, then you should earth the motor as well.
 
From what I understand, USA wiring regs are designed more around preventing fires as the domestic voltage is 110V, with commensurately high currents, whereas in Europe, single phase domestic is 230V and the corresponding 3 phase is 410, so the regs are more about preventing electrocution.
 
Do you have earth leakage circuit breakers on distribution boards or consumer units feeding sockets in the US?  They're mandatory in the UK.  These trip when as little as 10mA ends up going to earth, and I believe they work just by comparing outgoing and returning current on the live & neutral.
 
What tends to happen when a row of houses is built, is that each in turn is fed from a different phase, so by co-operation with the neighbours, you can cobble up 3 phase, but don't try to parallel it!
 
Eddie



From: "gwj@... [SOUTHBENDLATHE]"
To: SOUTHBENDLATHE@...
Sent: Tuesday, 16 August 2016, 6:41
Subject: Re: [SOUTHBENDLATHE] Grounding, furnas switch

 
Regardless of age, ALL motors must be properly grounded for the safety reasons previously stated. A very old one may not have a designed-in ground screw. In that case, you may add one in a sensible location at the terminal box. Alternatively, you can run a bonding conductor to the frame of the motor and connect that directly to another properly-grounded item such as a switch box. 

Modern safety standards are written in blood. Grounding is really simple to do and there is no reason to skimp in this area. "If there's power running to it or through it, ground it."

Gary NA6O
(Retired EE)