Here is a list of all the postings SillyOldDuffer has made in our forums. Click on a thread name to jump to the thread.
|Thread: Stuart S50 (Want to cry)|
First off, chilled cast-iron can be hard enough to give HSS a hard time. Cast-iron is on my list of difficult materials because it's anything between lovely to machine and awful. Usually the hardness is just a skin, but it can go several mm deep and a small casting might be hard throughout. As Carbide has no trouble with hard cast-iron, I always start with a carbide end-mill, only switching to HSS when through the skin.
Secondly,an important part of my learning curve was being told that tools last far longer when made to cut rather than allowed to rub. Rubbing is ruinous because it rapidly blunts the tool without removing metal. And once the edge is blunt, game over - carrying on with a blunt cutter results in poor finish, slow progress, ruined work and bad language. Rubbing is an easy trap to fall into when working with hard materials and a low powered machine. Blunt cutters due to rubbing may be the root cause behind this bad experience.
Ideally, the cutting edge should be forced deep into the material and then moved at a rate that slices steadily through the metal. Small milling machines may struggle and cause the operator to back off and blunt the tool when he should attack. After Andrew Johnson of this forum told me to stop pussy-footing, all my cutting tools suddenly stayed sharp for far longer. To avoid premature loss of edge it's also important to remove swarf and keep HSS cutters cool - flood cooling may be necessary.
Thirdly, £70 for a set of 12 end mills isn't either dirt cheap or very costly. You seem to be buying the same sort of mid-range end-mills as me, and - though I've ruined a few - mine generally give good service. I've not found it necessary to go up-market yet. Just as well, a single 20mm 4-flute end-mill from Cutwel is nearly £40 (not the dearest in the world) and expensive cutters can be blunted by rubbing too...
Glad to hear Stuart have sorted you out with a new casting. Well done them!
|Thread: Digital Phase converter...|
I've been looking at various Digital Phase Converters on the web and none of them describe how they actually work. I'm with Robert: my guess is they're beefed up VFD's with better voltage regulation and load tolerance, ie electronics not discombobulated by multiple devices on the output. Price, weight and power output suggest industrial rather than hobby users.
I note the linked 5HP unit takes 240V single phase up to 415V 3-phase - it's a brute! The blurb says this unit will take a 7.5HP starting overload which is in the same range as a similar USA device claiming a 60% startup margin. So withstanding a 50% overload may be typical. Dunno if that helps -no idea what the start load of a Hardinge lathe is, or a cheap way of measuring it.
|Thread: Hardening and Tempering for the hobbyist|
Um, yeah but no but yeah. The main objection is that any tempering effect is accidental and this flies in the face of heat treating under control to achieve a defined result.
Heating to a particular red-heat temperature and then cooling rapidly aims to capture a particular chemical state inside the steel. Get either temperature or time wrong and the steel won't harden properly or might be burnt.
After successful hardening, tempering relieves strains and improves toughness. It's done at a much lower temperature over a much longer period - the metal takes time to adapt and needs to soak.
In both hardening and tempering, time and temperature are managed for best results. Some steels like HSS are unforgiving if the operator gets it even slightly wrong. Silver-steel is formulated to be straightforward to harden and temper without fuss or elaborate equipment. As such heating the remote end of a hardened silver steel rod might not do much harm or good either way. Might be slightly worse, might be slightly better.
|Thread: Plumbing question|
That must be right. So me saying 'While the presence of a choke in the pipe makes no difference to the flow, or to the movement of either piston, it does make a difference to the pressure!' must be wrong. Oh dear, now I'm confusing myself as well as everybody else.
Sackcloth and ashes AGAIN! Or I could go into politics...
|Thread: Hardening and Tempering for the hobbyist|
I only harden what needs hardening. Hard and brittle often go hand-in-hand, so not good to hammer or snap hardened steel.
This commercial cold-chisel has a hardened tip and soft end. The soft-end has mushroomed out and needs trimming back, but even like that the soft metal is less likely to spray shrapnel about.
For the same reason it's not recommended to bang hammer heads together. As both are hardened, any splinters formed are likely to come off at high-speed. Not funny if a shard goes in your eyes. (Not that hammers are particularly inclined to splinter. I've accidentally clashed them many times without ill-effect. But why risk it...)
|Thread: Plumbing question|
As a picture is worth a thousand words:
If the tap on the open tank is cracked open, the amount of water flowing out of the tank will be constrained. If the tap is fully opened, then more water flows but the volume is limited by the water pressure and the diameter of the outlet pipe.
In the pressured tank, something rather different happens. If the piston in the large cylinder is pushed down a fixed volume of water is transferred to the small piston, which moves much further inside its cylinder. And in reverse, pushing the small piston down moves a fixed volume of water back into the large cylinder, which pisto moves a small distance. While the presence of a choke in the pipe makes no difference to the flow, or to the movement of either piston, it does make a difference to the pressure!
Open tanks are typical of domestic water systems: water pressure at the tap is usually obtained by gravity feed from a reservoir on higher ground, not from a directly connected force pump. As a system gravity fed water is cheaper and more controllable. Most of the system runs at low pressure, up to about 10bar.
Pressured systems are typical of heating systems and Hydraulic systems like power steering and road diggers. In a hydraulic system small pipes are used to transfer energy as high-pressure water. The high-pressure is easily produced by a force pump, and the relative movement of different diameter pistons can be exploited to multiply force at the expense of movement or vice versa. The small pump on my Hydraulic engine crane allows me to lift a 1/3rd ton lathe with no trouble at all. Hydraulic systems run at much higher pressures, say 500 or 600 bar. The very high water pressure available from a simple force pump - little more than a lever operated ram in a plain cylinder - is excellent for testing boilers. Although the pressure is much higher than that produced by steam, there is very little energy stored in it. If a water pressured boiler gives way, it won't explode.
Testing a boiler by pressurising a gas is very dangerous because gas acts like a spring. If the boiler breaks, it could well explode because compressed gas contains stored energy that can be released almost instantaneously.
Gases and liquids follow the same basic rules, but the compressibility of gases cause considerable side effects compared with liquids. But designing a ship's propeller is much the same mathematically (I'm told) as designing an air-screw. They're not interchangeable though - large bladed ship propellers turn slowly in a thick fluid, while slim aircraft propellers spin fast in a thin fluid. Propellers have to be optimised to the working fluid.
Edited By SillyOldDuffer on 11/12/2019 15:24:49
Well, it depends. I prefer Einstein's 'Make everything as simple as possible but not simpler'. He also said 'If you can’t explain it, you don’t understand it well enough.'
Personally I incline to argue there is no such thing as common sense. Here's a few definitions to choose from. Common Sense is:
I'm not sure John's question has been answered correctly, though I think Hopper and Robert both correctly identify the main consideration, which is the difference between a tender that's just a tank, and one containing a pump. One assumption is the tender gravity feeds water to an injector, equally valid is a tender containing a force pump for directly injecting high-pressure water into the boiler. Maybe both are wrong, could be the tender is used to fill a tea-urn on the back.
If John wanted a simple practical answer to the effect of a choke on water flowing under gravity, easy enough to do the experiment. The experiment would also find the actual relationship between choke and output volume, useful for answering a question like 'will the choked pipe enough flow to allow an injector to fill the boiler'? A rather harder question is, 'how much longer will it take to fill a boiler with a force pump if the pipe is constrained?' In the latter case, the smaller pipe may be necessary to manage the high-pressure involved, not just a casual feature.
While practical skills are high value, they are strongly reinforced by effective theory. I'm impressed by Lord Kelvin, (physicist as smart as Newton and Einstein) who is alleged to have said: 'if you can't put numbers on it, it ain't worth sh1t!'
|Thread: Broken drill bit in hole|
There are many 'Alums'! In chemistry Alums are a family of related compounds. They have different chemical properties, as unlike as cast-iron is from mild-steel, tool-steel, or stainless.
The word is also used loosely by various historic trades. The 'Alum' in tanning, may not be the 'Alum' used in Dyeing, nor is it the 'Alum' used in cookery, or as a fertilizer. Or perhaps they are! Alum might be the most misleading name in common use, only slightly more precise than 'thingy'.
The Alum needed for removing broken taps and drills is NDIY's Potassium Aluminium Sulphate. Although other Alum's are likely to have some corrosive effect on steel, so does water given long enough. My advice: accept no substitutes! Potassium Aluminium Sulphate is widely available, for example from Amazon.
|Thread: Plumbing question|
Too late! I thought of asking a moderator to change the thread's title from 'Plumbing Question' to 'Rocket Science', because it's about Hydrodynamics rather than pipework. For example, these constrictions all behave much the same at low pressure and very differently at high pressures:
Even in plumbing it can matter because it costs money to pump large masses of water through badly designed pipes. Ever more critical to get flow right in a ship's hull, aircraft wing, jet-engine, and rocket engine. The latter really is complicated. For a given energy content, what is the best form of output nozzle? For example, an over tight nozzle in an ordinary Guy Fawkes rocket will cause it to explode rather than fly, and an over wide nozzle will have it burn out without moving.
Firework rockets can be made 'about right' in a shed by experiment, crude methods are good enough. Designing a rocket motor for a guided missile or a space-craft is much more demanding - truly rocket science!
|Thread: my first lathe.|
I agree. My guess is it's an unsuccessful quick-change tool-post and those angled slots are meant to take a tool-holder which holds the cutter at a normal angle. My other thought was it's angled to take a tangential cutter, or both sides are used with a missing ball-cutting attachment. Doesn't make much sense though.
Buying second-hand can be confusing. Not unknown for lathes to come with accessories meant for different machines entirely. Although Jamie's strange tool-post looks as if goes with his lathe, perhaps that's just coincidental!
|Thread: BSP vs NPT vs "PT"|
Comprehensive list of threads here on The Engineering Toolbox. I hope no-one expects a short simple list!
PT was a Japanese Industrial Standard thread. It's interchangable with BSPT.
PF was the JIS thread interchangable with BSPP (parallel), and later called 'G'
Edited By SillyOldDuffer on 10/12/2019 21:29:25
|Thread: a good quality milling vise for sale|
I'm not surprised it has no dings - it's for sale as 'A brand-new, unused, unopened and undamaged item in original retail packaging'
The design is common, I have a very similar vice made in the Far East. It's OK. Old Mart's find is a good price but can quality ever be judged from a photo?
|Thread: Keigan Motor|
Not sure I'd be quite so dismissive. Most of the website is in Japanese, so it's not completely clear what you get. However the motor spec is 0.3Nm. and 0.1 to 250rpm, almost certainly a stepper, but it might be hybrid or closed loop.
On the software side, the video shows the motors being controlled by via Bluetooth or USB by a Smartphone application. This is basic get-you-started stuff, good fun on xmas day, but also for learning about more serious possibilities.
Digging clues out of the Japanese website though, the motors also have grown-up control capability, with support for rolling your own on Arduino, RaspberryPi and Obniz. Probably others. I'm impressed by anyone who thinks Internet of Things applications require low technical skill!
I'm reminded of Meccano. Easy to dismiss as a children's toy, but used by adults to make superb models, and prototypes. This 6-speed gearbox isn't a plaything!
My school had a working seismograph built from Meccano. Main problem was it detected heavy footed boys more often than earthquakes.
|Thread: my first lathe.|
Beware of plastics and metals difficult to machine! My start as a total beginner was dogged with problems caused by me assuming a metal-working lathe would obviously cope with anything. Not true! Plastics are usually gummy, pliable and easily damaged by heat. Many metals from finished products will have been carefully selected to suit a particular purpose and manufacturing process; zero consideration is given to chaps wanting to turn it on a small lathe! For example, aluminium window frames are made from an alloy intended to be extruded, too soft to machine well. There's a lot to learn about machining different materials.
I wasted months as a beginner. I may have been unlucky because my entire collection of scrap metal turned out to be carp. Buying EN1A was a revelation - it's a mild-steel specifically formulated for machining. Plenty of suppliers other than Metal Supermarkets, but their description is worth repeating:
EN1A is a low carbon-manganese free cutting steel suitable for machining using both automatic and CNC machines. EN1A is used for turned components, such as nuts, bolts, studs and hydraulic fittings.
EN1A, also known as 230M07, can be case hardened to produce components with enhanced wear resistance.
EN1A can also be supplied in a leaded grade, EN1A Pb, 230M07pb.
The leaded grade is particularly good for turning, it's about twice as machinable as ordinary mild steel.
Same advice when buying other metals especially Stainless Steel, Aluminium and Bronze: look for 'free-cutting' or 'suitable for machining' in the specification. Brasses are also somewhat variable, but they all seem to turn OK in a lathe. Plastics too need research.
The ground steel rods from old printers and scanners mostly turn well, but I have one that's incredibly hard. Tricky for beginners to identify if problems are down to the lathe, tool, material, or the operator. In the absence of a tutor, this forum, books, and YouTube all help, but be prepared to experiment.
Tools are another controversial subject. Personally I see little point in buying expensive high-end industrial cutters for occasional light use in my garage! Nor do I like the risk of buying from unknown web-sellers because there's more risk of factory rejects, 'too cheap' and counterfeit. (But people do get genuine bargains off ebay!)
I prefer established UK based sellers. Mostly ArcEuroTrade, Warco and Tracy Tools (for Drills, Taps & Dies), but I've also used RDG, MachineMart and several others without grief. While hobby vendors rarely sell the best possible tools they're OK for my purposes. (The reason the best possible tools aren't carried is probably economic. While Model Engineers are keen to own good tools they are rarely prepared to pay full price for them! Impossible, I think, to profit selling good tools to hobbyists because most of 'em have tiny budgets.)
I guess anyone starting with a second-hand MD65 isn't a serious professional machinist intending to make a living from it. Compromise is the order of the day. As a beginner my advice is avoid cheap and nasty, and don't get hung up on 'quality'.
There's debate about HSS vs Carbide. HSS is more general purpose, but it needs to be kept sharp. That means buying a grinder and learning how to use it! There are chaps who find grinding easy, others - like me - struggle. Carbide inserts avoid sharpening problems: tad expensive to buy but very easy to use. I mostly use Carbide for convenience (at least 80% of the time) but switch to HSS when carbide doesn't produce a good finish(rare), or when a specially shaped tool is needed for awkward corners or fine work. Depends on what you're doing. Owners of powerful fast lathes turning big lumps will likely prefer carbide, small lathes used for delicate work will probably do better with HSS, as will big slow lathes. I used carbide OK on a mini-lathe, which is similar size/speed to the MD65, but I wasn't making clocks!
Carbide inserts are available in a deeply confusing multitude of sizes and shapes. Hobby suppliers like ArcEuroTrade tend to stock the types useful to hobbyists, and you won't go far wrong buying them. Chaps who know what they're doing never recommend sets, but I recommend sets for beginners because beginners seldom know what they need or even exactly what they want a lathe for. Though I'm unlikely to buy a set now, I found sets invaluable for learning.
The December issue of Model Engineer's Workshop Magazine includes a printed ArcEuroTrade Catalogue. Buy one! Both magazine and catalogue give a good idea of what's available and who sells it.
|Thread: Tool steel - Beginners guide ?|
Whilst mild steel isn't ideal for chuck keys because it's a little soft and bendy, I would have thought it would be 'good enough' strength-wise. Is the chuck particularly stiff? The scroll might need cleaning because it's full of swarf.
Or are you an enthusiastic tightener? I've known a few chaps who habitually overdid it! One couldn't stop himself stripping RS232 fixings, and a friend is convinced it's essential to finish off tightening nuts by hammering on the spanner.
|Thread: Beginners models|
Not sure most people use collets on the lathe, though they can be very useful I don't use mine much.
If the work can be turned in one go, three jaw chucks are quick and easy to use. But, it's difficult to reset work in them with any accuracy, for example when you start a job in the lathe, move to a mill or vice, and then return to finish off on the lathe. With a 3-jaw, it's highly unlikely the second axis will align with the first.
Four jaw chucks are slower to set up but, ideally with a DTI, can be adjusted to restore the original axis. Bit fiddly, takes practice, and slow. But not a problem unless speed is of the essence.
Collets allow work to be moved between machines with speed and accuracy. For general use they have a few disadvantages: cost of chuck and individual collets, limited range grip range per collet means many have to be bought, and they aren't handy for jobs involving several different diameters.
My guess is most of us use three and four jaw chucks most of time because they're well-suited to most work. Apart from being resettable, collets are also good for delicate accurate work like clock making because the absence of jaws means the cutter and operator can get much closer to the job, and run-out is much reduced. For general purpose work, chucks have the edge.
Your big old 3- and 4-jaw may need to be complemented with smaller newer chucks if they're too big to grip the items you want to turn. Chucks would be more use to me than collets.
|Thread: my first lathe.|
Just a guess as I've never looked closely at the MD65, but they're probably locking bolts. If so, (and believe an MD65 owner if he contradicts me ), then the gibs are set with them slackened,using only the screws with lock-nuts. May be a bit of a fiddle to set the gibs evenly with these so the slides don't bind at one end or in the middle of their travel. The gibs should be tight enough to stop the slides slopping about but not tight enough to make it hard to turn the controls.
Lock bolts on gibs aren't an adjustment. Rather they can be tightened to lock a slide in a fixed position as a way of eliminating accidental movement whenever that particular slide doesn't need to move. For example it's worth stopping the top-slide moving right-left when facing off front-to-back. Not sure about the MD65 but there may be a bolt or Allen Key on the saddle that locks it to the bed, again useful to reduce accidental movement.
Good practice to check locks are on or off correctly before using the lathe to take a cut. Lathes don't like cutting under power with the saddle locked!
A photo of the tool and work would help. Though I doubt it's the problem the temporary mounting balanced on boards may not be helping. Shouldn't be necessary to tighten the gibs until they actually grip. Bolting down my mini-lathe didn't make any difference - it was OK on rubber feet.
One thing that jumps out at me is the tool-post with angled slots:
How are you holding the tool in it?
Tool blunt or wrongly angled.
Edited By SillyOldDuffer on 08/12/2019 14:09:56
|Thread: Beginners models|
I always recommend Stewart Hart's Potty Mill engine : no castings, simple, but challenging enough to make you think!
Stewart is active on the forum and his engine is discussed in a number of threads, for example this one.
Plans available without bother: I used this found on the web without finding any mistakes. As technical drawings go it's rather cramped, and I believe Stewart provides better laid out drawings?
Possible negative for some, it's a metric design.
As a training exercise, I built one in Fusion 360, this image being when I was struggling to learn moving joints!
Edited By SillyOldDuffer on 08/12/2019 09:44:49
|Thread: Cannon or Carronade?|
+1! Scotland was a major producer of Iron, perhaps 25% of all UK production, and there were many firms making and using Iron there.
Not all cast-iron back then was equally suitable for all purposes. Much depended on what was in the ore - unknown impurities - and tricks the Iron-founder knew that improved it. It happens that Scottish iron-ore produces a cast-iron well suited to cannon making, and - at a time when gun-making was hit and miss - guns made from Scottish cast-iron were reliable. Some English ores were also suitable, and both benefited from the Industrial Revolution. On average, British guns were safer than foreign ones, though the best foreign guns were as good as anything made in the UK.
British guns sold like hot cakes, Carronades being popular on merchant ships because they can be fired by an unskilled team of four and are effective against pirates. Pirates can't blast victims at long range - they want cargo and ship intact, which means they have to get up close and personal with the gun. Most preferred not to risk it.
Cast-iron improved significantly after 1841 due to advancing chemistry and metallurgy. The Artillery entry in Dr Ure's Dictionary of Arts, Manufactures and Mines quotes a US Government analysis of Cast Iron guns showing wide variances in density, tenacity, transverse strength, torsional strength, compressive strength, and hardness in the metal tested. The best cast-iron sampled was 5 times stronger than the worst. No surprise that guns often burst!
Dr Ure mentions purity (achieved by better chemistry), melt control (achieved with air-blowers driven by a Watt Steam engine), and cooling methods as making significant improvements to British cast-iron between 1841 and 1851. Controlled heat and cooling are important because they effect crystallisation, understanding which demanded a microscope and scientists. British cast-iron guns made before 1841: average density 7.148, tenacity 23,638. Guns cast in 1851: average density 7.289, tenacity 37,774.
Once their chemistry is understood, the special properties of local ore become less important. By tweaking the process, metal producers can accommodate a wide range of impurities and reliably churn out large quantities of metal to almost any specification.
Top quality cast-iron didn't last long as a gun-metal. By 1851, gun makers were moving to more promising alternatives released by science and technology, first Wrought-Iron, then Cast Steel. The carronade was more-or-less obsolete by 1850, pushed aside by faster firing more powerful weapons. Wrought-iron was rejected fairly quickly because it's expensive to make and has a grain structure like wood - strong and weak depending on direction. Took about 30 years to get cast-steel consistently right in large volumes, but that's what we've used since.
Artillery itself has a wobbly future. Guns are easily detected, for example by tracking the shell with radar, and they aren't easy to move quickly. Highly vulnerable to aircraft and guided missiles...
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