Restoration Progress On My 1952 ER10

[bucksaw]

Por qué? I was thinking that because the entire headstock / motor assembly is connected and it's all metal, it wouldn't matter. Lay it on me.

I agree with you Mike. Check the resistance between the headstock and the motor casing to verify there is a good connection.

[JPG]

I agree with you Mike. Check the resistance between the headstock and the motor casing to verify there is a good connection.

You and Mike have too much 'faith' in the guaranteed(long term) conductivity of the connective devices(Mike knows what they are). They may be screws or they may be bolts(a screw is a more fancy smanchy bolt[finer surface finish under the head]). Our demise will be caused by rust interrupting the conductive path(not likely, but possible). Since the third wire(grounding conductor) is a safety device(protection in the event of another unlikely though possible event) ALL bases MUST be covered! Actually since another device(electrical - switch) is mounted on the headstock it should also be grounded - hence the jumper is needed regardless of which the linecord grounding conductor is connected to. Use external tooth lock washers and closed ring terminals. Also the grounding conductor must be longer than the 'working' conductors so as to be the last to break loose if the strain relief fails.

The 'safe' way is rarely the easiest most logical way!

BTW - Two lockwashers/ring terminal(one on each side). Two ring terminals on a single screw may share a lockwasher positioned between them.

There will be a quiz in this material covered today(date/time TBA)!:D

[mickyd]

You and Mike have too much 'faith' in the guaranteed(long term) conductivity of the connective devices(Mike knows what they are). They may be screws or they may be bolts(a screw is a more fancy smanchy bolt[finer surface finish under the head]). Our demise will be caused by rust interrupting the conductive path(not likely, but possible). Since the third wire(grounding conductor) is a safety device(protection in the event of another unlikely though possible event) ALL bases MUST be covered! Actually since another device(electrical - switch) is mounted on the headstock it should also be grounded - hence the jumper is needed regardless of which the linecord grounding conductor is connected to. Use external tooth lock washers and closed ring terminals. Also the grounding conductor must be longer than the 'working' conductors so as to be the last to break loose if the strain relief fails.

The 'safe' way is rarely the easiest most logical way!

BTW - Two lockwashers/ring terminal(one on each side). Two ring terminals on a single screw may share a lockwasher positioned between them.

There will be a quiz in this material covered today(date/time TBA)!:D

I thought (knew) that was your logic. The conductivity path from the headstock to motor does have about 5 metal to metal (some painted)contact points that would need to be functioning properly for the "assmebly" to be grounded.

Excellent point on the length of the ground wire being the longest in the event that the cable gets pulled. Often overlooked if inexperienced.

I'll ground the motor too.

[JPG]

I am all excited at the prospect of seeing your improved strain relief!:D Ref: Earlier manual pix!:eek:

[bucksaw]

If I had the choice of grounding only 1, I'd pick the head stock. The user will rarely be in contact with the motor and the chance that the ground failing (multiple routes are present) between the motor and saw frame/headstock is not likely. The head stock where the on/off switch is mounted and poses the greatest risk to the user. To be really safe, you should probably run the jumper to the motor, but the headstock needs to be grounded. I'm not sure how SS grounds the new head stocks. I've always attached the ground to the motor and have relied on the motor mountings to take care of the headstock grounding.

[dusty]

PROTECTING AGAINST ELECTRICAL SHOCK

The Mark V is adequately grounded without adding a ground wire to the headstock. If wired per instructions, the ground wire (green wire n the power cable) is to be connected to the motor housing. The motor is connected by 4 screws to the motor cover and the motor cover is connected to the headstock by at least 5 screws.

I just measured the resistance from the ground wire in the Mark V ac plug and about fifteen different contact points on the Mark V. These contacts points included the rip fence, the rails, the main table, the headstock, the extension table and others.

The highest reading was 2.76 ohms and the majority of the readings were on the order of 1.3 ohms. The Mark V is adequately guarded for your safety without adding a ground wire.

Adding a ground wire will not lessen the protection against electrical shock already provided but it also will not improve it.

[mickyd]

PROTECTING AGAINST ELECTRICAL SHOCK

The Mark V is .........

Hey we don't discuss Mark V's in this thread. This is reserved for ER stuff only. (just kidding!!)

[dusty]

Hey we don't discuss Mark V's in this thread. This is reserved for ER stuff only. (just kidding!!)

Actually, you are absolutely correct and my assumptions may not apply at all to the ER. To rely on mechanical interconnections (without verifying their effectiveness) for electrical shock protection would not be wise.

However, I still doubt that extra grounding is required for the ER to be safe.

[JPG]

Actually, you are absolutely correct and my assumptions may not apply at all to the ER. To rely on mechanical interconnections (without verifying their effectiveness) for electrical shock protection would not be wise.

However, I still doubt that extra grounding is required for the ER to be safe.

I agree from a 'practical' viewpoint, but, this is about safety(prevent shock) and a method(grounding) to provide protection against it.

The measurements though informative, are not sufficient to provide protection against any faults(electrical) no matter how remote their possible occurence may be. Multiple 'possible' conductive paths are better than 'one' since the multiple paths must all be compromised to create a 'hazard'. However, we are discussing a safety 'issue' and therefore probability is only relevant if not Zero.

The mounting of any device in which a fault can occur on a conductive surface should be included in any attempt to preclude electrical shock by 'grounding' all exposed areas of those conductive surfaces.

All this rambling is relative to as we understand the issue today. When the 10 e/r was produced NONE of this was a concern(not universally accepted anyway).

Since the linecord terminates on the switch(recommend both white(neutral) and black(hot) wires be terminated one on each pole of a two pole switch). The wiring to the motor then is run from the switch to the motor. A common attachment point (through hole with nut(s) and lockwashers) on the headstock of the linecord and the motor 'jumper' becomes adequate. By using two nuts, the linecord may be secured to the headstock first(with nut and two external tooth lock washers) and the jumper secured with two more lockwashers and nut. This allows removal of the motor jumper without disturbing the linecord grounding conductor.

A more practical(and still effective) set of 'hardware' is a tapped hole with a screw tightly inserted, an external tooth lockwasher the closed ring terminal of the grounding conductor(linecord) followed by either another lockwasher and nut or a nut with a captive external tooth lockwasher. On top of that, repeat for the motor jumper.

[dusty]

Whatever, JPG. You do it your way!