What I hate is those really crazy 'heads' you get on various domestic appliances and automotive bits and bobs, where ytou need a 'key' (for want of a better word) shaped like a witches hat, or a pyramid, or a tricorn hat etc. Apparently this is to stop people opening said equipment up, and electrocuting themselves.
OR in my cynical view, to stop people opening it up, and realising the equipment can be fixed with a modic of technical knowledge, and a blob of solder...
On the motoring side, i remember a story (probably apocryphal) that certain British cars built in the 70s had many bolts, nuts etc which were metric, and many which were imperial, neccesitating TWO sets of spanners!
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It's true, Ian. I've come across mixtures of imperial and metric on the same 70's car. Can't remember what it was though.
I still think whitworth is the best, if only for the name. I remember fondly a 1962 Rover 100 P4 I owned a few years ago. The fasteners on that were superb quality, they never seemed to rust seroisly and always came apart easily even after 30 years. They were all 'parkerised', presumably a coating process. Can anyone enlighten me as to what 'parkerising' actually is?
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IIRC Parkerising is a chemical treatment process where steel or ferrous metals are coated with manganese phosphate. There is a further process which can be carried out referred to as prkolubing where an oil coating is applied to the parkerised finish.
Commonly used on long and short barrelled weapons to reduce glare and prevent corossion.
Open to correction on this one.....
Leon
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On the ball exactly Leon. Process was invented and developed by Birmingham gunsmiths Parker-Hale Ltd. Is a chemical bath. I have no idea what the constituent chemicals are - was considered super trade secret by people who ran PH at the time (early 50's) PH were still in business on the site of the old BSA factory in Small Heath a few years ago. They were taken over by some firm of wholesalers and are now at Petersfield just as a marketing firm since 2000.
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The car having a mixture of threads was the later version of the Ford Cortina. This had imperial, metric and imperial-with-metric-heads. Removing and replacing the gearbox brought you into contact with all of these.
There is a major difference between UNF and Metric threads that hasn't been mentioned. The ISO (International Standards Organisation) specifies that the Metric standard thread is Coarse, with fine threads being approved only for special purposes, whereas the standard Unified thread was UNF (fine-thread). The drawback with Metric Coarse bolts is that they vibrate loose more easily than UNF. On the other hand, Metric Coarse doesn't cross-thread as readily as UNF and it needs less turns with the spanner.
Whitworth was fine (no it wasn't - it was coarse!) and was reckoned to be the first attempt at standardisation. However the heads are quite large so they take up more space. They also tend to be less strong than modern bolts which are usually made from a higher grade steel. Modern bolts also usually have cold-rolled threads which are a bit stronger than machined threads.
I reckon to handle Whitworth bolts at least once a week (on railway locomotives). I worked for many years in an engine specifications position with Metric threads, and one of my cars has UNF threads. There isn't much in it but I think Metric is the overall best.
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Funny you should mention the Ford Cortina Dizzy, the Mk1 Escort of 1968-1974 vintage also had a mixture of imperial and metric threads. It was Imperial (AF) everywhere with a smattering of Whitworth EXCEPT for the gearbox and bell housing which were metric. (Large warnings in the \ford workshop manuals).
Having started car maintenance late in life (first car at 25 in 1990) I acquired all my tools to work on the Escort....all Imperial then at a critical point one weekend I had to splash out on a set of Metric spanners for that one job.
regards
Ian L.
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Metric standard thread is Coarse, with fine threads being approved only for special purposes, whereas the standard Unified thread was UNF (fine-thread). The drawback with Metric Coarse bolts is that they vibrate loose more easily than UNF.
The factors taken into consideration by the designer when he is choosing between UNC and UNF are just the same as when he is choosing between "standard" (coarse) metric and metric fine, namely the required bolt load, the tensile strength of the material of the bolt and that of the corresponding internal thread, and any special factors. If vibration is a factor, then this is taken into account accordingly.
The torque specified also takes into account the surface finish of the mating items, i.e. plain, zinc plated, Parkerised, Sheradised, etc, etc, and whether lubrication is present. (It is not universally known by the hoi polloi that the surface finish affects how much of the applied torque is expended in overcoming friction and that the use of items that have a different surface finish from the original should be avoided.)
The use of "shakeproof" and serrated washers (intended to prevent loosening) has largely been abandonded because at best they are ineffective, and at worst they are detrimental. Modern practice is to have (at most) a plain (flat) washer and to specify a torque that is just sufficient to produce "yield" or permanent stretch of the bolt. Incidentally (although I personally would never condone the practice) it is said that an experienced fitter can tell when yield has just started to occur without using a torque wrench.
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L'escargot by name, but not by nature.
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I quite agree, Ian.
By chance one day whilst out shopping, I was however able, for the princely sum of a fiver to purchase a set of tool heads designed to undo all commonly used 'tamperproof' screws and bolts, so prompted by your post, have just added up the value of replacing devices repaired through use of the tool since purchased last year. I'm sure there are more, but these are the ones I recall:
Household iron
Replacement cost saved: £40
Cost to fix: Forty five minutes plus a piece of emery paper to clean the bi-metallic switch.
Food mixer
Replacement cost saved: £60
Cost to fix: Thirty minutes plus some hot water to wash encrusted flour from the plastic gear train.
Motorcycle intercom
Replacement cost saved: £75
Cost to fix: Thirty minutes with a multimeter, plus a blob of solder on a dry joint.
Plastic laminator
Replacement cost saved: £80
Cost to fix: Twenty minutes of my time, and hot water to clean the rollers.
VCR
Replacement cost saved: £149
Cost to fix: Ninety minutes and a blob of graphite grease.
So, spending that fiver saved five otherwise sound items from the scrap head, and my wallet £404. I don't count my time as cost, because I repaired all the items whilst enjoying my passion for music. The best fiver I ever spent, I think!
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I've got a set of bits to unlock these "puzzle screws" and the ability to undo them and use the absolute minimum of repair skills and a blob of solder is now contributing to my new career as Home Facilities Management - General Repairer.
Hawkeye
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Stranger in a strange land
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What I hate is those really crazy 'heads' you get on various domestic appliances and automotive bits and bobs, where ytou need a 'key' (for want of a better word) shaped like a witches hat, or a pyramid, or a tricorn hat etc.
Then of course you get "Torx" socket heads which require a special "Torx" key.
Anyone know the advantage of these over the ubiquitous hexagon socket heads which require an equally ubiquitous Allen key?
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L'escargot by name, but not by nature.
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Then of course you get "Torx" socket heads which require a special "Torx" key. Anyone know the advantage of these over the ubiquitous hexagon socket heads which require an equally ubiquitous Allen key? >>
Torx has huge advantages over Allan socket heads. The following is a repeat of what I said on the subject in an earlier thread:
Allen screws are becoming obsolescent now, mainly because of their high cost. This is due to the fact that they need to be made of a high grade steel (at least 10,9) because of the tendency for the heads to crack across the corners. A high grade steel is more expensive to buy and forming the head is also costlier.
Torx screws are now far more popular because the heads are inherently stronger, so the screws can be made from a cheaper steel (typically 8,8) and the heads are easier to form. However, because Torx has a stronger head, the socket depth has been reduced in comparison with Allen screws (to ease head forming) so it is equally important to make sure that the socket is clean and the tool fully seated.
I'll just add that a respected maker of Torx screws claims that the production tooling used for tightening Torx screws can last 1200 times longer than for the equivalent Allan screws.
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L'escargot; Well, thanx 4 starting this off old chap.
No probs, NitroBurner.
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L'escargot by name, but not by nature.
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