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Posted By Topic: Antique Sewing Machine

Jan 21 2019 14:26

A mate wants me to test n tag a sewing machine that was made in the 1950s. No earth pin, and no data plate stating double insulated (has volt/current ratings), and small ac motor. What he has described to me is a class II appliance. The casing is metal. How do I confirm what I'm actually testing is a classII without confirmation from an OEM data plate? I have found the manual online as well which doesn't mention anything.

Jan 21 2019 15:26

There is likely no way that you are going to be able to get compliance with AS/NZS3760.

The next question is why does he want it tagged?

If it hasn’t Killed anyone yet and looks to be in good condition (electrically) what is his need for tag.

If it is an antique perhaps it should be retired.

Jan 22 2019 13:15

It'll be what's known as Class 0.


Jan 22 2019 13:41

Just stick a new mains cable with moulded plug and earth on it.

Jan 22 2019 18:34

Yep that’ll work but then you have modified it so it’s no longer an antique. And more importantly as the modifier who certified it you can be held responsible if something goes wrong. Then you will have to prove that it wasn’t your mod that caused the bad thing to happen.
And so it goes on.

And given the track record of both the board and Worksafe do you want their attention.


Jan 22 2019 19:46

Double Insulation seems to be a concept that came into being about 1968, if this item was made in the 1950's it's almost certainly not a double insulated item.

Is it an industrial sewing machine? Makers name? I have a client that has a bunch of these in captivity, some certainly look like they were made in the 1950s, they are all earthed appliances.

Have found more than a few appliances that someone has fitted a two core lead to an item that isn't a Class 2 appliance over the years

Port Appliance Test & Tag

Jan 23 2019 07:21

The machine s/n is EG294197
[This is model 201K and made in December 1950 iaw google s/n database.]
The motor is CAT.No.BRK.12-S s/n K6083889
The Singer manufacturing Co.

Jan 23 2019 16:02

I couldn't find a good picture online, but I'm fairly this is the machine my mum had when I was a kid, and - from very faded memory - there is a connector attached to the motor that is like an oversized old kettle connector with three pins, neutral, live (for the light) and motor, and there is a spring body connector for earth. The mains lead and the cable to the foot rheostat go into the connector.

Does that look right? Spring things for earths on kettles were a thing back then.

Jan 23 2019 18:32

Found some pix of connector on Ebay of 201 Singer, appears to show 3 posts, which would suggest Phase Neutral and Earth.

Looks very much like the connector that my client has on two Electric Tailors Knives.

Vendor of Ebay machine has restored it, so I've asked him Class 1 or 2, will post his response, if I get one.

Port Appliance Test & Tag

Jan 23 2019 20:56

And the response is:

"Hi. This is a vintage machine the wire system is two wire. Not 3. The motor wires leads into the motor are double jacket. Plus soldered into place. Thanks. Matt




Jan 24 2019 09:00

Like Sarmajor, I wonder why the mate wants it tested. The T&T regime is intended for units that are in service. But i don't agree with the attitude of "it hasn't killed anyone yet". If it's in service; it needs to be definitely safe. NOT just maybe safe.

For museum pieces; "4701" provides guidance. That's also the one that tells us how to properly "disable & label" if appliances fail the safety testing after repair.

As for OP's question of how to apply "3760"; since there are clearly exposed conductive parts that are not earthed, the basic problem is whether to treat it as Class I or as Class II. In my view, the absence of a clear and definite indication of being Class II, ie labelling, means it has to be treated as Class I. Either decision could be wrong, but only one can be both wrong and release an unsafe unit into circulation. And i believe ESR 23 (1)(c) backs that view - without clear evidence that the insulation level is equivalent to double insulation, it's electrically unsafe.

WRT the light, many older sewing machines used a tapping off the motor to get an "ELV" supply, basically an auto-transformer. The risk with that is if the tapping is close to the active end of the winding - either as-built or by polarity reversal - the "ELV" supply will be at LV to earth. Very dangerous; and banned by R 110 in the 1976 Regs. ESR 23(1)(b) would cover that particular issue, as well as a lot of other scenarios.


Jan 24 2019 11:09

Pointer to eBay was a good one, and a memory refresh confirms my memory from nearly sixty years ago, three pole connector, no earth pin. There are two live pins, one always live, for the light,l and one that is fed through the foot controller to the motor.

Jan 24 2019 18:54

Of course there is always the possibility that the earth pin has been snapped off the plug.


Jan 25 2019 02:02

A quick google gives some pictures of one in Aussie. Making it safe is not a simple job.

Aside from that, he's obviously not electrically knowledgeable - Using unearthed metal shrouded audio DIN connectors!

There is enough info to determine there was never any earth to the machine and no provision to add one on the original connector. Notably he had to loop around that connector to add one.

The original arrangement with the foot pedal dangling on the power cable is horrid. And he failed to earth the foot pedal too.

Jan 26 2019 00:30

There are a couple of possibilities why OP's mate might want this item TnT'ed, he might be wanting to offer it for sale, or could be intending to take it to a show/convention where the venue owner requires all electrical appliances taken on site to be TnT'ed. Of course, he might be one of the rare breed that wants to discharge his duty of care WRT E(S) reg 15.

Wiring diagram for this machine shows light to be connected across Active and Neutral, with one side of motor windings connected to Active other side of motor windings series connected in series with Foot to Neutral. Google "Singer 201 Service Adjusters Manual" for pdf copy.

Some research reveals that AEG produced a double Insulated drill in the late 1930's, reading through Evan's link, an ex Singer engineer comments that these machines were newer earthed, and there does seem to be at least two layers of insulation between live components and the user- what's a poor boy to do.

Some of our clients wives are keen quilters, and ask us to test & tag their sewing machines, desk lamps, extension leads and power boards before they to head of to their annual symposium- being such nice guys we do this gratis, haven't been asked to test a vintage puppy though.

Port Appliance Test & Tag

Jan 26 2019 06:59


The info you have found is as I recalled by my late mother's sewing machine, I had to fix it a couple of times by reterminating the incoming power cord and also the foot control cord on the 3 pin connector. I also had to replace the radio interference but was able to use a modern type unit inside the old enclosure screw fixed to the motor.

I consider that those old sewing machines are NOT "DOUBLE INSULATED" but are "ALL INSULATED" this being so, the need to be earthed goes away.

Jan 26 2019 07:29

Would fiting a permanent 1:1 isolation tranny get around all of the complexities?

Jan 26 2019 08:32

yes, provided the construction of the isolating transformer was of all insulated or double insulated.

Jan 26 2019 08:50

Yes there are a number of reasons someone might request T&T; but the actual reason would allow relevant advice to be provided. Speculation is much use.

True there were appliances away back that had exposed conductive parts and no earth. Whether they were double insulated, all insulated,or whatever doesn't really matter.
The OP was how to apply today's T&T regime as set by "3760"; which, while not the only way of being electrically safe, is the only way to get "deemed electrically safe" under ESR26 use by an employee.

And the t&T regime of 3760 only allows for Class I & Class II, and to use Class II methods you need a Class II marking; not just the knowledge that the item might possibly be equ9ivalent of Class II. Clause 1.4.3 acknowleges the possibility of a conductive enclosure, but requires a marking before we can apply Class II methods. Remember "3760" is deliberately designed not to require dismantling, and is intended for use by semi-skilled people who do not necessarily have much electrical training.

So I don't believe an appliance with conductive case, no PEC, and no "DI" label can be validly issued with a test tag under "3760". The Standard simply doesn't allow for this situation.

That's not to say it can't be used safely; for example by fitting an PRCD plug top; which would certainly be safe enough for all practical purposes. Under ESR 26, itt would get to "deemed safe" for hire gear, but not for employees' use.


Jan 28 2019 21:51

So Chau, have you quizzed your mate as to why he want's the Sewing MC tested & tagged.

We've coll anectively established that this item was never made as an earthed/CL1 appliance, can't have a 3760 pass tag because it isn't marked as a DI appliance.

The EWRB used supply books of "Electrical Safety Certificates", this could be a case where you could, as a Registered Electrical Worker open this item up, verify that all connections, components and wiring are OK, perform an Insulation Resistance Test and Current Leakage (given it's construction 1mA max would be all I'd be happy with) and issued one of those.

I like Aleck's idea of fitting an Inline RCD, but as pointed out above, depends on why it needs to be tested

Port Appliance Test & Tag

Jan 29 2019 08:33

Thanks guys for all your replies. Much appreciated. I've been busy and don't do a lot of T&T. I'll catch up with him and get some more details.