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Member postings for SillyOldDuffer

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: Trouble Cutting Silver steel
25/08/2019 15:22:01
Posted by Chris TickTock on 25/08/2019 13:57:34:

OK More detail but not sure I haven't given enough already...

...

Chris

Don't worry Chris, engineers like to have all the details. Long painful experience has taught us that even carefully drawn and double-checked drawings can mislead. As we haven't read your project book and don't have access what's in your mind's eye it's really easy for chaps to get confused and give misleading answers! A picture is worth a thousand words; I reckon you mean one of these:

scribe.jpg

This object's a difficult challenge because long thin rods bend easily. You have to plan how the rod will be supported whilst being cut to shape : it's not as simple as gripping one end in a chuck and shouting 'tally-ho'. At least on a Sherline there's no risk of the rod kinking and whipping into the operator at high-speed. Many nasty accidents on big machines where several horse-power at high rpm can instantly convert a long steel rod into a lethal flail.

The answer is to plan some way of supporting the job during the cut. A fixed or travelling steady will be too big. Bob's suggestion of making a female centre is a good one. The idea is to put a short section of taper on one end whilst most of the rod is safely held by the chuck, then to extend the job out so the point runs in a female centre held by the tail-stock. A rod supported at both ends is much stiffer. Still needs a sharp HSS tool running at high rpm exactly at centre height (See Howard.)

Another method might be to support the rod with a block of wood opposite to the cutting edge.

Planning is an important skill because the order of operations can make life easy or impossible. I often rehearse various methods and sleep on ideas to make sure they're sound before trying it. Being self-taught is a disadvantage; apprentices get told stuff and lots of on-the-job training. The rest of us bumble about! A good trick is to delay cutting objects to final size for as long as possible because the base stock can often be used for gripping and support during manufacture. In other words don't start by cutting 1.25" of silver-steel off and then struggling to hold a small bit of metal. For the same reason, finishing the taper should be left late because a taper is much harder to hold than a cylinder. Also, avoid weakening the job until the last moment.

As Neil suggests, a good plan should look for ways for simplifying the job, in this example avoiding turning down to 2.5mm by drilling a 1/8" hole instead. Don't do that - at this stage of the game it's more useful to learn how to make the difficult object. Cheating comes later in the curriculum!

Dave

PS Must learn to type faster.  Jason made one and posted photos while I was dithering.  My work-rate is  depressing...

 

 

 

 

Edited By SillyOldDuffer on 25/08/2019 15:29:14

Thread: Current leakage om CNC
25/08/2019 10:13:04
Posted by fizzy on 24/08/2019 23:24:16:

... I dont think there is a workshop wiring fault as it is installed to Iee regs.

May have been OK when installed but there's always the possibility of wear and tear later. I've had the neutral connection inside a well-used wall socket lose enough spring to spark due to a fatigue crack.

A socket tester would confirm all is well with the workshop wiring, this example is £7.99 from Screwfix.

Though I trust nothing I agree faulty workshop wiring is unlikely. A more likely cause is damage to the CNC machine's power lead, perhaps the earth connection in the plug has been strained or the wire pulled off inside the machine. Or a manufacturing problem left the earth disconnected.

Easy enough to test with a multimeter as Joe described. There should be close to zero ohms resistance between the plug's earth pin and all the CNC machine's exposed metal work.

Most likely the cause is simple.

Dave

Thread: Ultrasonic toothbrushes
23/08/2019 15:12:28
Posted by pgk pgk on 23/08/2019 14:00:38:
Posted by JasonB on 23/08/2019 11:43:25:

Don't go putting human toothpaste into your dogs mouth,see item 3

Mine like Malt flavour, not the whisky type.

I would be very sceptical about that and suspect it's some sort of veterinary myth otherwise all dogs in naturally or artifically flouridated water areas would be toast.

...

pgk

My Humphreys Veterinary Toxicology says a dusting powder containing 40% Sodium Fluoride caused poisoning in a dog in 1946. I'm not surprised, that's strong stuff compared with toothpaste!

Also mentions castrated pigs bleeding to death after dosing with Sodium Fluoride - those poor animals certainly had a bad day. I can warn sheep owning members of the forum to beware of volcanic eruptions - acute fluoride poisoning is caused by high levels of fluorine in ash.

Reading on, I see I share most of the symptoms of sheep poisoned by Sodium Fluorosilicate pesticide: salivation, inappetence, dullness, dyspnoea and recumbency! Can't wait to tell my GP about it. She's always delighted to hear all the details of my latest self-diagnosed ilness...

Dave

PS. I picked the toxicology book up for 50p in a charity shop and everything else I know about Veterinary Science comes from watching the works of James Herriot on TV. I think that makes me an expert.

Thread: Outrageous?
22/08/2019 19:36:46

Got to say ""Paid instantly, seller said item not in stock & refunded - OUTRAGEOUS!!!" is over the top feedback in my book. Getting your money back rather than the item ordered is IRRITATING. OUTRAGEOUS!!!" is when someone sends you a turd instead.

Dozens of reasons why items might not be available. Gosh, Tesco's no longer stock my favourite coffee (Cafe Imperial) and they ran out of Peanut Butter one week. Last ebay item I bought was American made, ordered from a seller in Madrid, and delivered from Poland. Genuine item, works perfectly, and less than half Catalogue price : that's globalisation for you!

Chaps have short memories - remember 'Allow 28 Days for Delivery' and 'POA - Send Stamp Addressed Envelope'.

Dave

Thread: Simple table of potential hardness of metals
22/08/2019 14:30:36

Ifs and buts off the scale on this question because there are so many variables. Roughly though, and with many overlaps, softest first:

Lead
Tin
Copper
Aluminium
Magnesium
Dead mild steel (Car Bodies)
Black Mild Steel (Holding up buildings)
Cast Iron (varies)
Soft Brass (plumbing)
Hard Brass (cartridges)
Medium Carbon Steels (stronger than mild-steel, not so easy to work)
High Carbon Steels (Files and Razors, heat treatment essential)
Ultra-high Carbon Steels (punches)
Alloy steels, HSS, & camshafts etc
Tungsten


Hardness is a bit like Easter though - it moves about! Try stretching a length of solid copper core from a mains cable. Starts soft, then goes hard. Many materials can be softened by heat - annealing. Some, especially the high-carbon steels, can be hardened by heating and rapidly cooling - quenching. Metals like bronze and stainless steel work harden. Some types of stainless are vicious, going from usable to glass hard the instant a cutting tool is allowed to rub.

Hardness isn't the whole story. Though soft, pure aluminium is nasty to work with because it's sticky and highly likely to weld itself to a tool's cutting edge. Quenching steel for maximum hardness is rarely done because the process leaves the steel brittle to the point it can shatter like glass. Balancing Heat treatment for hardness versus toughness can be rather complicated. O1 (aka Gauge Plate) and W1 are favoured in workshops because they are easy to heat treat. O1 is designed to be quenched in oil, a slow process that strikes a good balance between hardness and toughness, as is needed in knife blades. W1 (aka silver steel) is designed to be quenched in water without cracking. The result is a bit harder for making drills, punches, and screw-taps, and it often benefits from being tempered (cooked in an oven) to reduce brittleness. The two alloys are similar.

When buying metal look for mention of machinability in the description. Many alloys are tuned to make them more suitable for turning and drilling etc. and life is made easier by buying them. Ordinary mild-steel is neither awful nor nice to machine but it's well worth spending a little extra on EN1APb, aka EN1A Leaded, or 230M07PB. Most Brasses machine well, but the Bronzes can be a pig, especially Phosphor Bronze.

Dave

 

Edited By SillyOldDuffer on 22/08/2019 14:31:02

Thread: Scale gauges
22/08/2019 10:44:15
Posted by 34046 on 21/08/2019 19:47:56:

...

7,25 inch locos and rolling stock are built to a scale of 1.5 inches equals 1 foot.

...

Bill

 

Like Merlin I'm confused slightly by scale and gauge.

A scale of 1½" to 1' is 1:8 so standard gauge ( 4'8½" ) rail track should be modelled 7¹⁄₁₆" apart. Not that it makes any difference, but why jump to 7¼" or even 7½" as is popular in the USA?

Dave

 

Edited By SillyOldDuffer on 22/08/2019 10:45:12

Thread: How can this work?
22/08/2019 10:24:13

I think that's an advertising photo - wow, look! 2 more belt ratios. It's not showing how the lathe was operated in practice. Easy enough to swap belts over when needed. The user photos on lathes.co.uk show only one belt in position.

Dave

Thread: Garmin sat nav
22/08/2019 09:22:44

One of my Uncle's told a story about his contribution to WW2 and he may have been pulling my leg. Aged 18 in 1945 he was too young to see any fighting and found himself allocated to the Royal Army Service Corps as a driver, a skill he didn't have.

On arrival at Bicester instead of being taught to drive he was ordered into the cab of a large lorry, shown the controls, and told he was driving it in convoy to Greece! No map, street names, towns, or road numbers - the instructions for navigating across war-torn Europe consisted of a long mimeographed list of distances and turns:

  • At main gate turn right drive 100 yards.
  • At junction turn left drive 6 miles.
  • And so on all the way to Athens.

I like to think the jeep leading the convoy had a map, but perhaps it was just following a well defined military route, no civilians allowed to get in the way.

Uncle's memory of his journey across a recent battlefield was probably censored to save my delicate sensibilities. (Soldiers don't like describing what they went through to people who can't understand because they weren't there.) He mentioned being constantly shouted at by Military Policemen racing up and down the convoy on motorbikes, the fact that the convoy rarely exceeded a fast walking pace, and that the lorries whining gears gave him splitting headaches. Other than that, it might have been a picnic.

Dave

Thread: Piston/Cylinder Materials
22/08/2019 08:41:59
Posted by Steve Crow on 20/08/2019 22:23:24:

... I've never heard of graphite being used as a material in an engineering context. Is it a material that's readily available and used?

...

Graphite is fairly easy to buy - I got mine from Noggin End, other sources are available including ebay.

Many applications for it; good lubricating properties (unless it's mixed with something else); conducts electricity (motor brushes, electrodes and resistors); highly temperature resistant - it melts at about 3600°C, much better than steel at 1500°C, making it ideal for rocket venturi and crucibles. Also used to make high-strength exotics like carbon-fibre, carbon-nanotubes and aerogels (see 'Frozen Smoke' )

As a piston material, Graphite has the advantage of being about a third of the density of cast-iron. Light pistons are better than heavy ones in an engine. Downsides of graphite are it's brittle and burns in air. Being brittle means it doesn't scale up well for making bigger pistons, but it's an interesting alternative for small engines and Stirlings.

Dave

Edited By SillyOldDuffer on 22/08/2019 08:48:21

Thread: Torx head variant or faulty batch?
21/08/2019 16:10:57
Posted by Barrie Lever on 21/08/2019 15:24:26:
Posted by Neil Wyatt on 21/08/2019 14:23:14:
Posted by not done it yet on 21/08/2019 10:30:12:...

Just cheap chinese rubbish. No quality control. Slave labour production.

...

...

 

...

Whilst NDIY was a bit blunt, what he said was correct.

B.

 

Apart from NDIY not knowing:

  1. The Country of Origin - assumed to be China, maybe not.
  2. What Quality Control is in place - assumed to be none, maybe wrongly
  3. The Terms and Conditions of the workforce - assumed to be 'Slave Labour', maybe not.

Three generalised assumptions from a commentator not involved in the purchase can hardly be described as 'correct' in the sense they are 'free from error; true; right'. Ironic that a criticism of a faulty product should itself be an intellectual quality failure. (A conclusion drawn in the absence of evidence.)

Personally I think it's a waste of time moaning about Chinese quality in the absence of affordable British alternatives. Whinging may be easy but it's also ineffective. The real challenge is to outperform foreign competition by doing the same thing better and/or cheaper here. Possibly it's not happening in the UK because there are better ways of making a living than making nuts and bolts, possibly it's because some mistakenly fail to believe other folk are just as clever and hard-working as them and go immediately bankrupt. Anyone wanting to bash China should look at their unpleasant foreign and domestic policies. Both are much better targets than cheapo ebay goods, but not really appropriate to this forum.

Dave

PS Jason asked for a shut-up while I was typing - sorry.

 

Edited By SillyOldDuffer on 21/08/2019 16:13:02

Thread: Profiling tools
21/08/2019 08:56:56

Posted by Robin Graham on 20/08/2019 00:36:57:.

...

Question is - how big a profiling tool can one run on a 'domestic' lathe? ...

I have a 12x36 lathe and I'm working in brass.

Robin.

 

 

 

Looking at it another way, what would stop a domestic lathe using wide form cutters?

  • The ultimate limit is the power of the lathe's motor. How much energy is needed to cut a particular metal is determined by the metal's tensile strength, and, although brass is weaker than steel, the difference in tensile strength isn't massive. Therefore the rule of thumb 1HP will remove one cubic inch of steel per minute can be used as a guide to guestimate the HP needed to achieve a particular depth of cut and feed-rate. The minimum power motor needed to drive a form-tool can be calculated from the minimum feed-rate needed to take a satisfactory cut along the edge, say 0.001", while the maximum theoretical feed rate would be the one where the motor is just powerful enough to meet the demand. (You can't remove more than a cubic inch per horse power per minute).
  • BUT a second limit will be more important on a hobby machine. The amount of power that can be put into a cut depends on the machines ability to absorb the forces involved without vibrating or distorting. With heavy cuts the tool and tool-post are the first features likely to bend, but the saddle and other parts can move as well. A heavy industrial lathe will do better than a hobby machine because it's more rigid.
  • Other issues are the shape of the form and the strength of the work-piece. A form shape that clears swarf naturally will do better than one that tends to trap it, as parting tools do. And a thin or poorly supported work-piece might bend away from the cutting edge, or break.

In practice a hobby lathe should work reasonably well with larger form tools than might be expected especially if light cuts only are taken. I'd experiment to find out the maximum a particular lathe can do because so much depends on the machine and how fast you need to work. To find the limits start small and move up in stages. As an index Jason's encouraging example shows what can be done on a WM280, a lathe heavier and more powerful than a Super7, but smaller than a Boxford. Form tools on a mini-lathe would be more restricted, but scaled to suit they should still be usable.

Dave

Edited By SillyOldDuffer on 21/08/2019 09:03:09

Thread: Piston/Cylinder Materials
20/08/2019 21:12:20

Bump really, as I'm no expert.

My feeling:

  • No need for Bronze unless the engine is expected to work hard.
  • Cast Iron is good for cylinders and pistons because it's self-lubricating. Ditto Graphite for an air engine. (Graphite is light-weight, but not satisfactory for IC engines because it burns in an oxidizing flame.)
  • Usual to have one material softer than the other when they rub together. The piston is generally the softer metal, mainly I think because it's easier to replace a piston (or rings) than to fix a damaged bore. But either way round will work.
  • With an air-driven piston no need to worry about temperature coefficient expansion of the metals used. For example an engine fitted with a pair where where the piston expanded much faster than the cylinder would tend to seize.

I think a Silver steel piston in a brass cylinder would work fine. Most engines I've built have used brass pistons in mild-steel cylinders. Also used graphite in brass and brass in aluminium. They all worked.

Dave

Thread: Need a lot of help from you good people
20/08/2019 19:09:36
Posted by Tim Stevens on 20/08/2019 18:01:10:

SoD says (above) - A 15 Ah battery can deliver 15 Amps for an hour.

Sorry, but this is based on a misunderstanding. It is true that a 15 Ah battery willl (should) deliver 1 Amp for 15 hours, but that is not the same thing. 15 Amps would overload a small battery, causing overheating, and likely damage to the plates, if continued more than a few minutes.

It is just one of life's (many) swindles, sorry.

Cheers, Tim

Not quite, Terry mentioned using an ebilke battery. They're Lithium Ion high current batteries capable of delivering quite a wallop. This ebay example claims to be good up to 1200W.

Dave

Thread: my knowledge of steel needs improving
20/08/2019 16:09:06

Silver Steel is usually sold as Silver Steel, aka Drill Rod in the US, with no magic number needed.

O1 is an American specification for a Tool Steel, not an Engineering or Structural Steel. It's European Specification is 100MnCrW4, but it's often called O1 in the UK, for example as sold by Metal Supermarkets.

For historical reasons steel specifications are a confusing muddle. Nationally, internationally, commercially and over time. Following old plans can have you frantically searching for apparently exotic materials simply because the terminology has changed. Not many know what Muirkirk No 1 is, nor is it likely to matter much, because mild-steel is better!

Fortunately most of us only use a few common alloys and it gets easier once you know what 's needed in your workshop and stocked up, perhaps from a Horological specialist. However it's rarely necessary to use exactly the steel specified : for making a clock I'd think 4130, 4140, and En19 are so similar as to be indistinguishable.

Dave

Thread: Anyone good at fault finding with amplifiers here?
20/08/2019 15:14:46

Posted by Joseph Noci 1 on 20/08/2019 14:54:29:

...

What intrigues me is ( assuming the amp's original offset was 'good' ) what causes it to change? Unless the transistor is abused, over-voltaged, overheated, etc, hfe should not really change much in years, and in a matched pair, the changes should be similar in both.

...

But,boy, did it now make nice ocean sounds....

Joe

Maybe the can's seal gradually failed over the years and the innards are exposed to dirt and moisture. Perhaps Neil's transistor has gone rusty.

Ocean sounds invariably produced by my amplifier efforts too. Motorboating...

Dave

Thread: All things Beaver Mill
20/08/2019 14:38:21
Posted by Peter_H on 20/08/2019 13:40:25:

Here is an uncompleted QCAD drawing/tracing ...

Yes, I know the perspective of the caphead screws is wrong, nothing looks right however I do them!

Peter

beaver_mill_carriage_gbox.jpg

Now that is impressive! Despite being a committed Qcad fanboy I've never attempted any that complicated. Just shows what can be done.

Dave

Thread: Need a lot of help from you good people
20/08/2019 14:13:57
Posted by terry callaghan on 20/08/2019 11:21:00:

Hi. Thanks for all the physics. I have a question. Would fitting a motor from an electric bike and a 48v 15ah battery with new controller work. These motors come in 350w 500w and 1000w. But getting information on the torque they produce is hard to get. Surely there must be an answer to this.

An electric bike motor and controller would certainly work. The power needed is decided as per earlier physics by:

  • the need to overcome friction in the bearings, drive train and motion work (in good condition). This can be gauged by pushing the engine by hand. A man working steadily can deliver about 250W, up to say 500W in ten minute bursts, and Olympic athlete up to 1500W for a few minutes. If the engine is easy to move 350W should drive it, otherwise 500W. If it's very stiff, check the bearings etc.
  • How fast the train needs to accelerate in service. A 100W motor can do the same amount of work as a 500W motor, but it needs 5 times longer to do it. That might be too time-wasting for comfort! If it wasn't for friction, a 1W motor and gearbox could move your engine, but it would be incredibly slow. You're looking for a reasonable balance between power and performance. Having plenty of power is exhilarating, but it's not necessary on a track model. Steam engines don't accelerate quickly in full-size and an electric model pulling wheelies down the track might not be popular!
  • Any hills the engine needs to climb. Once it's moving, pulling a train around a flat track doesn't do much work, but going up hill does! As railways are built flat, I think in practice this would just limit the weight of carriages and passengers that could be pulled at a particular site. This is echoed in full-size practice: railway freight engines are sized powerful enough to restart their load in the event the train is forced to stop on the journey's steepest incline. Engines for passenger trains are sized to accelerate to meet the timetable.

Other issue that might suggest a big motor is whether or not the engine is to be run continuously. A 350W motor run flat-out for hours will have a shorter life than a 1000W motor run at 350W simply because the big motor stays cooler. So motor size matters less on an engine run intermittently for fun at the track by the driver and a few bystanders than the same engine expected to haul hundreds of paying passengers continuously over a Bank Holiday weekend event.

A 15Ah battery can deliver 15 amps for an hour. That's 48V*15A = 750W for an hour. Actually, because deep discharging is undesirable, it would be unwise to assume more than about 75% of that, say 750W for 45 minutes, which isn't unreasonable for fun use. A 350W motor would use half the power and run for about 90 minutes, 500W about an hour. In practice because the motor probably wouldn't be run at full power all the time, it would likely last longer per session. But so much depends on stops, starts, how hard the driver accelerates, the rolling resistance of stock, slopes and the state of the track it's hard to predict.

I bet the original builder would have used a modern electric bike motor and batteries if they'd been available at the time.

Dave

Edited By SillyOldDuffer on 20/08/2019 14:21:55

Thread: What coating/grease for long term tool storage
20/08/2019 10:32:33

Trivia: the proper name for the 'bunch of hay' is Excelsior.

The best known preservative used for long term storage of guns is Cosmoline. It's a family of similar products, all based on an oily wax. Cosmoline in an American trade-name and similar mixes under other names were used by the rest of the world.

I think Cosmoline is remembered because it's a right pig to clean off. No-one who ever had to apply or remove it forgot! A whole range of protective products are available today ranging from heavy waxes to light silicone spray-ons.

Dave

Thread: Need a lot of help from you good people
20/08/2019 09:29:08
Posted by Les Jones 1 on 19/08/2019 21:50:52:

I think those motors are WW2 vintage motor/generators. ...

Les.

+1 for that; When I was growing up WW2 surplus was my playground. Motor/generators were the best way to produce the multitude of voltages needed in large aircraft, less desirable second-hand than motors and cheaper.

Frances suggests the control system is pre-electronic and I think she's right. It may even be cruder than a field-winding control system - big wire-wound resistors straight off the 'regulator'!

resistors.jpg

Except the potentiometer top right hints at electronics somewhere!

Dave

19/08/2019 16:59:31

I'd give it a try before ripping it apart. The two doubled black wires ending in eyelets look like battery connections to me. One of them is marked Blue for negative. (Circled in Blue), the other will be Positive (circled in Red)

enginewires.jpg

With the wheels free to turn, I'd try dabbing the eyelets on a car battery to see if there's any sign of life. Provided they've not been soaked electric motors are tough old birds. Any markings on the motors? I'd guess they're 24V or more rather than 12V, which effects the battery configuration.

Only a guess about the small motor dangling bottom right off a choc bloc; it might be belt driven off the shaft as a generator to drive a speedo in the cab. Or perhaps it drives an oil-pump.

Dave

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