You can buy packs of single-edge razor blades at just about any hardware store.

You can also get scalpels for really intricate work.

Neither of these items is essential, IMHO, at least for someone who is just starting out, and I would be reluctant to recommend them to younger builders. (This comes from painful personal experience - several experiences, in fact.) It's good to reach adulthood with all of your fingers intact. (I eventually learned that, and did manage somehow to keep all of mine.)

Once the builder has learned to exercise appropriate care (and manual dexterity, too), these tools can be real handy to have around when the right situations come up, such as in the ones that you mentioned.

I wouldn't recommend breaking apart a shaver to salvage the blade, though. You have no margin for error with that, and you are using the blade for something that it was never designed to do. Other tools are available to do the same thing, such as the previously mentioned scalpels. They at least are actually designed to be used as hand tools, and therefore possess some safety features.

Mark

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SAM # 0011