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| Thread ID: 35141 | 2003-07-03 08:38:00 | Screw You | bardin (1950) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 157207 | 2003-07-04 00:07:00 | Machine Screws have 6 main things about them, diameter, thread pitch, head, strength, type of steel and length. Well that's what I think is important about them, in different industries and different places around the world they use different types of screws, now some industries use the different standards, most common standards is UNC, UNF, and Metric ISO, these standards can still be varied by whether you are wanting a finer or coarse pitch, their a many advantages/disavantages in using certain types of screws. A big disadvantage is if the standard is considered obsolete BSW, BSF, etc, although BSW is the same as UNC except for 1/2" diameter (not likely you'll get a screw for a computer that big though, I use to work in an engineering supply company) because you'll find it hard to replace a lost screw, easiest way is to retap a new thread. Finer thread screws are more likely to stay on longer than a coarser threaded screw due to vibration, automotive bolts use finer threads. With computers though, the metal for the case is pretty weak, you can tap your own thread with any screw as long as diameter is similar, just requires a bit more effort to get the screw in but once in, you've probably retapped it. |
Kame (312) | ||
| 157208 | 2003-07-04 01:45:00 | Well...er... BSW and UNC are not the same. BSW has a 55 degree thread angle with radiused crests and roots, whereas UNC and UNF are basically truncated threads with a 60 degree thread angle. They are most definitely not interchangeable. My brain cells seem to remember there may be a radius option for the roots of Unified thread series. If you are really old, you will easily remember that UNC and UNF were derived from ANC and ANF, American National Coarse and Fine. UNC and UNF came about to UNIFY the manufacture and specs for these threads manufactured in Europe ( mainly in UK) and America, driven by the car and aircraft industries, so as to be fully interchangeable. Whilst on the subject of threads, the other popular screw thread was/is the British Association or BA screw threads for instrument type applications. These are a funny mixture of metric and imperial with a 47 degree thread and radiused roots and crests. |
Terry Porritt (14) | ||
| 157209 | 2003-07-04 03:00:00 | Terry, I'm not that old (20 this month :P), and I only understand the basics required in the sales position of an engineering supply store, not the manufacturing of it. As I understand from 1/4" and up UNC and BSW have the same thread per inch except for 1/2". If they asked for BSW and as long as it wasn't 1/2" I could supply them with UNC fasteners. Now I don't know if it's because these people were use to calling it BSW when infact what they were using was UNC but my boss was the one who explained to me they were just the same and he's got over 35 years experience in Engineering, I had none at the time. Explain this 55 degree thread angle and 60 degree thread angle, as if BSW couldn't be used in conjunction with UNC as this degree seems it would at least make it difficult for fastening those two together. |
Kame (312) | ||
| 157210 | 2003-07-04 05:11:00 | There's a simple answer to all this, know as the "Microsoft Solution" Put your screws in place with a H uge A ll-purpose M assive M ultipurpose E ntropic R ammer (All those who didn't recoil in horror must now stop reading this thread. There is no hope for you.) Now, my point (part one). Paste this into Google. BSW BSF thread diameter metric pitch flat history Who's copying whom? My point (part two). I know there's much, much more on this topic on the web, because I've been there, read that, got the Alzheimer's T-Shirt, but I can't find it again. I'm VERY interested. Good links, anyone? (REALLY off topic) alt.binaries.sounds.mp3.classical and other classical music newsgroups are currently enjoying a flood of Bach's Chacconne and the Goldberg Variations done by different performers. (That's the Chaconne from the Partita for Solo violin in D Minor BWV 1005 in case you need a driver for it.) I'd never heard Kurt Rodermeyer play it on guitar before. Now I have, and have a compulsion to share with otheres who haven't heard him. I still like Radiohead, Filter, Placebo... others, bat Bach is KING. (Or not. You listen to whatever you like.) OK, OK. I must not go off topic. I must not go off topic. I must not go off topic. Cheers, Alan Carpenter |
Alan Carpenter (540) | ||
| 157211 | 2003-07-04 05:32:00 | (... I must typo-check my posts.) The links on this page, to do with Screw Threads and Tapping Drills Pages homepages.tesco.net may be of interest. Cheers, Alan Carpenter |
Alan Carpenter (540) | ||
| 157212 | 2003-07-04 05:38:00 | At last! members.lycos.co.uk Cheers, Alan Carpenter |
Alan Carpenter (540) | ||
| 157213 | 2003-07-04 05:41:00 | So Bardin,does this help at all? | Thomas (1820) | ||
| 157214 | 2003-07-04 07:08:00 | A couple of good reference sites there Alan. Most is explained. The thread angle of a screw is interesting as it is defined as measured along the axis of the screw, but screw threads have an helix angle and if large the flanks can obscure each other.... read on. If you are all sitting comfortably, here begins a little lesson on thread measurement, it is not as straight forward as it may appear, for example how do you measure the thread angle inside a nut? Except for very special screw threads (eg certain aircraft screws like ACME screw jack threads), every day screw threads are checked against GO/NOT GO screw thread gauges which are certified to be within the size tolerances specified in screw thread gauge standards. These gauges are plug and ring, and can be parallel or taper. So how is a gauge measured? Classically, the profile is measured with an optical projector with the screw tilted through its helix angle so as to see each flank of the screw. A small arithmetical correction is then made to the measured thread angle to get the angle in the axial plane. The root and crest radii and sizes are also measured optically and also sometimes the pitch (distance between consecutive threads in the axial direction) though pitch measuring machines are usually used. The pitch diameter of the screw which is the diameter of the screw measured at half the height of the theoretical full form of the screw, ie no truncation etc, is measured using calibrated precision thread wires sitting in the thread nominally at the pitch diameter, and using a high resolution "floating carriage" bench micrometer. Ring gauges which have an internal thread are checked for angle and form using plaster casts, and the casts are measured optically. Axial pitch and pitch diameter are measured using thread measuring machines as above but with internal measuring probes or "feelers" instead of external attachments. So, where does all this come from? Well I used to work in one of my incarnations for Horstman Gauge and Metrology, a now defunct, but once maybe the leading screw gauge manufacturer in the UK (together with Coventry Tool and Gauge). In another incarnation more recently thread measurement was part of the job at DSIR. As those references show there are heaps of thread forms for all sorts of different trades, model makers, horology(clocks and watches), oil drilling threads (API, very very special), hydraulic and pipe threads, etc, etc. |
Terry Porritt (14) | ||
| 157215 | 2003-07-04 07:18:00 | >Okay I've determinded that there's two different size screws ..... So you see bardin,aren't you glad you asked;) |
Thomas (1820) | ||
| 157216 | 2003-07-06 04:56:00 | And cycle threads. | Graham L (2) | ||
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