Question about an Oscilloscope

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I bought an analog oscilloscope the other day (Elenco S-1325) and I forgot to get a ground plug for it. This particular ground port doesn't take banana plugs, so I have a couple of questions to anyone with more oscilloscope (or electronics in general) experience than me:

1. Is a ground wire absolutely necessary? The breadboard projects I'm doing don't use anything higher than +6Vdc and I'm already using a chassis ground (the AC>DC converter)

2. If 1 is "yes" does the ground wire I use matter? I have an audio plug (which will fit witha little help) and some 24 awg speaker wire I can solder together, will that make a suitable ground, or should I wait until I can find an actual ground wire / plug.

I'll leave the scope for the holidays if there's a chance I'll ruin it without the proper ground wire.

Congratulations! A real oscilloscope is a great tool to have!

Your ground connection should be via the grounding connection on the scope probe--typically, you want to measure the voltages between the input of the probe and the ground of the probe.

You need to relearn the definition of ground--in real life, it isn't an infinite sink. You can and do pick up unwanted signals if you were to use a ground connection, as opposed to making the connections I suggested with the probe.

Have fun with your new scope!

you wont ruin the scope by leaving out the reference probe(ground probe)

essentially you measure between the reference and common probe and it doesnt serve as a grounded conection for the scope itself, that said a scope aint worth much without the reference probe.
i know there are plenty of cheap probes on ebay, i got a 10x-100x probe for some 25 dollars and it works well enough to read unamplified piezo speakers as a microphone.

Thanks guys, I can now enjoy a weekend of waveform tracking (and finding).