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A Look at The Differences Between The "Flat Prong" and "Round Pin" Plugs

For the black Featherweights, Singer had two different connection types.  They aren't interchangeable, so this article can be a reference when checking the compatibility of the machine and cord.  

Round Pin Plug and Terminal:

The round pin terminals and plugs were used exclusively in the USA, but they can also be seen on most Featherweights sold in Canada, and Featherweights marketed to Europe prior to about 1951.


The photos above show how the cords come out of the top of the plug, and the two halves of the plug are held together by two screws and nuts.

A look inside the plug shows the intricacies of the wiring and the components that make connection to the terminal.   

Flat Prong Plug and Terminal:

The flat prong terminals and plugs were used on most black Featherweights sold in the UK, Europe, and Australia.  In the UK and Europe Singer started using this configuration in 1951 just prior to the release of the 222K Featherweight in 1953.    

It is common to see these terminals equipped with either bakelite nuts or brass slotted nuts at the connection points in the back.

To open the flat prong plug for rewiring, these small metal rings must first be removed.  

The cords on the flat prong plugs do come out the side, and the wires on the inside are held in place by small screws instead of the brass caps and nuts in the round pin plug.  Singer uses the same wiring pattern for both the round pin and flat prong plugs.

This oddly-shaped flat prong plug can be sometimes be seen with the 221 and 222; it is designed with an extra spot for a grounding wire.

Most all flat prong plugs were used in conjunction with machines fitted with the top light switch shown in the "221K4" diagram above.

Broken Terminals:

It is a fairly common occurrence that the terminal on the machine will be broken.  That is almost always caused by the machine being hit against the case as it is put away.  Click here to read how to properly pack and store the Featherweight in its case.

Click here to order a replacement terminal.

The Featherweight 221 machines manufactured from 1933 into 1936 had an opening in the base below the terminal, so they are more susceptible to this damage.

This article can quickly help match the proper cord set to the correct machine terminal.  To see how to wire the machine to its terminal, use the following links to our video tutorial and the Featherweight service manual:

How to Replace the Electrical Components of a Singer Featherweight

Featherweight 221 Service Manual

Further reading:

How to Fix Terminal Pins for a Better Connection