3

My Apple IIc is what appears to be the first US model: A2S4000 with version 255 ROMs. The upper half of the case is held to the base with six Phillips drive button-head 2 cm screws with a very wide thread, of which I'm missing two. They look like this:

Larger images: bit, head.

The front four screws going through the keyboard tap straight into plastic sleeeves molded into the case, so there's a danger of destroying the existing threads of I use the wrong screw (which obviously I want to avoid). The rear two screws go through a hole in a plastic tab with a small piece of thin sheet metal, with two similar holes, folded around it, so I am guessing that this would conform with screws with a different pitch.

What are these screws called, or what terms should I use when searching for replacements? What are the dimensions I should be confirming (I'm likely to be ordering these over the Internet) and, if you don't already know what dimensions Apple specified for this screw, how ought I measure them?

7

What are these screws called

Exact term may depend on manufacturer, but usually they are classed as single threaded, self-tapping with thread-forming as sub-class. The tip shown is close (*1) to a Type B Tip indicating that it's meant to be used with a predrilled hole of about the same diameter as the inner one of the screw.

Applicable standards are DIN 7981 / ISO 7049 (old) or DIN/ISO 1478..1483 (new).

If your intention is to get exact replacement to avoid recutting, it may need some luck and a good way to measure the valid parameters (inner/outer diameter, thread inclination, thread form), as these screws are usually odered in a more relaxed manners than bolts are. After all, their counterpart is a metal/plastic hole, it'll cut the way it needs on its own and it's not intended to be opened or used again - or at least not many times.


*1 - Close, as there is almost no cone at the tip - still within the definition.

|improve this answer|||||
5

They are self-tapping but not self-drilling (the tip is also blunt.)

|improve this answer|||||

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.