Before you throw those audio or video cassettes away, take some time to remove the screws that hold most of them together. Trust me, some day you will need one or more of them. jerry
Waste not, want not. Good idea
When you go to inquire or buy these 'little screws' - all 347 gazillion required to MR - how do you tell the guy at a fastener store, "it's only about this big" as he looks at you thinking "why doesn't he want 10,000 SAE 1 inch machine bolts 6 inches long so I can make some money?"
What sizes are these little buggers, seriously!?
Okie
No, no, it's...waste not, want LOTS.
To tell the size of screws, you need three things - a digital caliper to measure diameter, a thread gauge to measure pitch and a table of thread sizes to figure out what you have.
Metric machine screws are usually a bit smaller than their nominal size, for example an M4 or 4 mm machine screw is typically about 3.8 mm in diameter. Their pitch is given as the number of mm between adjacent threads. For example, an M4x0.7 is a metric machine screw nominally 4 mm in diameter with the threads .7 mm apart.
In the imperial system, machine screws are designated by a number related to diameter and a pitch expressed as threads per inch. Some examples are #2-56, #4-40, #6-32, #8-32 and #10-32. The diameter in inches is .06 plus .013 times the number. For example, a #6-32 is .06 + .013 * 6 = .138 inches in diameter.
Some metric machine screws look similar to imperial machine screws. For example, an M5x0.8 is virtually indistinguishable by the naked eye from an imperial #10-32, but they are not interchangeable.
Self tapping machine screws are generally specified only by diameter in metric or # in imperial measure. They are similar in size to wood screws but not identical. In addition, wood screws are tapered, self tapping screws may be straight or slightly tapered at the lead end.
But if you really want to buy screws, then you also need to specify head style, slot type, material and finish. It really is not a simple subject.
Jim
2-56 phillips machine screws for trucks/couplers, low as 59 cents per 100.
http://tinyurl.com/kjmcdu
Try Micro Fasteners - (800) 892-6917
Jim Banner is right, it is not a simple subject. Whenever I need more screws to finish a repair, I usually "mike " the screw in Imperial and metric units and then look it up in the Machinery Handbook. Works OK for machine screws , but it does not work for woodscrews
Fastener Manufacturers have their reference Manuals for many of their products. I usually end up going down the aisles of Ace , Menards , Home Depot , Woodcraft or industrial Supply stores on a quest . Sometimes I Think the "Grail Quest " is easier. John II
I love this thread, I made my wife read it so she understands I am not a nut and why I stop and pick up every discarded boom box, vcr and dvd player and then spend an hour disassembling these things, they have a great amount of tiny nuts bolts screws pulleys belts arms sprockets springs and motors which I use to animate stuff and model.
Jeff
As usual, great info from all 'cept me. It's bookmarked as . . .
HOW TO SCREW - BY THE PROs
Okie
Go to "boltdepot.com". They have charts and tables to identify what you are looking for. All you will need is a set of calipers.