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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: 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

Thread: Using the faceplate and dog on a Sherline lathe
19/08/2019 13:55:59
Posted by Christopher judd on 19/08/2019 12:26:25:

Not sure I understand are you saying just centre using the 3 jaw chuck after checking alignment?... Also what then is the purpose of the faceplate and dog as the 3 jaw can be used instead/

Chris

Yes, because - within reason - the exact placing of the centre holes may not matter much. When turning between centres with a dog the axis of rotation is the line between the two centre points, nearly independent of any chuck run-out. If top accuracy or a known taper is to be cut it can be achieved by nudging the tail-stock sideways while testing with a DTI.

How easy it is to set and reset a tail-stock may be the sign of a quality lathe. The adjustment on my mini-lathe was distinctly crude and could take ages to get right. Not sure what a Sherline is like, but many lathe owners avoid altering tail-stock alignment if they can!

On a big lathe, centre drills are the best way of drilling the holes. They put a chamfer on the end of the hole that the well-greased centre runs on. Watchmaking may be too tiny for a centre drill in which case the centre is caught with the sharp point of a graver. As the centre of axis has no rotational velocity, the graver tends to find it.

Personally I've yet to use a face-place or a dog on any of my adventures. Much quicker to use a chuck or collet unless there's good reason not to!

Dave

Thread: This weeks offer at Lidl
19/08/2019 09:18:51
Posted by Hacksaw on 18/08/2019 20:04:46:

Umm ...I've read that the electronics in mig welders dislike being run from a generator , or rather the generator needs to be a much larger kw for it to work ? Well , today i used my newish Lidls variable speed 1200w angle grinder with my Honda EX500 genny...( 500w ) It ran it ok to start with, I didn't overload it , as obviously it wasn't making much power running on 500w ..and i was only using a 1mm disc to cut off a 8mm bolt so i wanted it to keep spinning fast . When i went to cut off a second bolt , the grinder wouldn't work.. Nor on mains .. Fetching my second Lidls grinder , that worked ok with genny power and i finished the job .. Do you think i've damaged the variable speed board ? I can't see that I could have burnt out the motor windings...

Small generators are notorious for poor voltage regulation and mucky output. The waveform can be non-sinusoidal and spiky, while the output voltage swings wildly with the load. A simple generator won't be good at handling intermittent loads - like an angle grinder - and is likely to over-volt the angle-grinders electronics.

Root cause is the motor's throttle reacts too slowly, first failing to accelerate fast enough and then failing to slow down quickly when the load drops. Older generators are particularly prone to voltage swings because their regulators are slow acting, perhaps even a mechanical cut-out.

Apart from the cheap basic models, modern generators are better regulated with the posh ones putting an inverter between the generator and user to clean up the output. They still don't like being overloaded, but they're less likely to damage electronics.

An oversized generator is recommended for a varying loads like an angle grinder because the larger mass of it's spinning parts store enough inertial energy to smooth out peaks and troughs.

Dave

Thread: Grinding your own lathe cutters
18/08/2019 16:08:05
Posted by Christopher judd on 18/08/2019 15:26:57:

...

To an extent tools used are like one's politics deeply believed right but at the end of the day we are all but bigots.

Regards

Chris

I hope not Chris! Evidence based choices are the foundation of engineering, not personal opinion.

As advice often depends on context don't be afraid to test ideas and reject them but never reject advice simply because it doesn't happen to align with what you believe. People are often wrong, especially me!

It takes time and experience to filter good from bad - the important thing with machining is to try it and see. Actually using HSS and Carbide for a few weeks will make the issues much clearer.

Dave

Thread: TTFN
18/08/2019 11:35:22
Posted by Andrew Johnston on 18/08/2019 11:29:17:

After my interregnum I have decided to return to the forum.

...

Andrew

Hooray! Welcome back...

smiley

Thread: Grinding your own lathe cutters
18/08/2019 10:41:27
Posted by Christopher judd on 18/08/2019 09:33:10:

...

The person giving this advice is a world renowned craftsman so you can see why at this stage in my lathe experience I will be sticking with it as all my work will also be horological. Suffice to say though I will at some point try aluminium to gauge the results.

Regards

Chris

I think you may be missing the point slightly: what a world renowned craftsman does may not be the best place for a beginner to start! Learner drivers shouldn't begin by asking Lewis Hamilton which oil is best for Formula 1.

Correctly sharpened HSS is very suitable for small lathes and - as lathes go - the Sherline is tiny. So the obvious answer is use HSS, and why not? The main objection is a beginner might find he doesn't have the skills or equipment needed to correctly sharpen HSS. The equipment is easy enough - a grinding wheel - but learning to use it may not be.

As is often the case, the operator is more important than the equipment. If Christopher Judd happens to be a grinding natural, and some people are, then all is well with HSS. But if he's cack-handed like me, then frustration ensues. In that case carbide inserts remove the need for the operator to develop grinding skills. Eliminating causes is useful at the early stages when it's not clear if the lathe, material, cutter-type, set-up, speed, depth of cut or feed-rate are wrong.

In practice I use both carbide and HSS. It's allowed! Mostly carbide because it's convenient - there's no point me wasting time sharpening HSS when carbide will do the job. When carbide fails, mostly by not getting a good finish or something very delicate is in hand, out comes HSS and a short fight with my grinder. It's possible to buy HSS inserts to fit carbide holders, but I'm not that clumsy. A good alternative to HSS for fine hobby use is the carbide inserts used by the grown-ups on non-ferrous metals like Aluminium. Like HSS they're sharp and polished, simple as that.

Part of the fun is developing the skills needed to get the best out of tools and materials. What suits other people doing other types of work on different equipment can be highly misleading. The best way to find out is to grind some HSS tools and cut metal: if the advice works for you, hurrah. If results are poor, try carbide.

You also said 'Regarding quality brazed carbon cutters as they have been recommended they can be used as they come needing no setting up.' That's a booby trap because brazed carbide tools often come unsharpened. The advantage of brazed carbide over inserts is they're cheap and can be ground to shape like HSS and resharpened. A special grinding wheel is needed. I never use them.

Dave

Thread: Clarke CL251mh Milling Attachment Wiring Help
18/08/2019 09:22:06

In support of Les, the circuit diagram in the CL250 Manual identifies the output of the lathe's control board as 220VDC.

clwiring.jpg

The output of the reversing switch under the legend OUT DC 220V on terminals 10 & 11 connect invisibly to terminals 10 & 11 on the motor select switch bottom right above Motor M1. The manual also refers to the motor brushes, which are also characteristic of DC motors.

The easiest way to power the milling head would be to buy a spare controller board for the lathe from Clarke's Service Department and box it up.

So far from best practice I hesitate to mention it, but you could rectify the output of the SCR controller with a diode or bridge rectifier and apply that to the motor. Apart from serious safety concerns it would put too many volts on the motor. Some solutions are too simple!

Dave

Thread: What Did You Do Today 2019
17/08/2019 20:35:27
Posted by Les Jones 1 on 17/08/2019 17:31:20:

Cut a helix on the mill using the rotary table and a right angle drill attachment. The right angle drill attachment was a lazy way to get a right angle drive.

img_1615 (medium).jpg

...

Les.

Ingenious - I'm impressed, and not just by the right-angle drive!

Dave

Thread: Superheat or not?
17/08/2019 10:08:31
Posted by fizzy on 17/08/2019 09:05:39:

... But there are good superheaters and bad ones...another story.

Fizzy's comment is spot on I think.

Though I'm never likely to build a boiler, I've always been interested in how they work. In theory superheat is without doubt a good thing, and - from about 1890 - full-size locomotives adopted it almost universally. As well as being more fuel efficient superheat also makes the engine more powerful.

Superheaters don't scale down well. The problem is small engines leak heat far faster than a big one. One reason is the ratio of surface area to boiler volume increases rapidly as diameter of the boiler reduces. Another is full-size boilers have space for a few inches of cladding, while little one's don't. Same issue with pipes, valves, and cylinders - all waste heat. The first problem with superheating a small engine is ensuring superheated steam actually reaches the pistons in enough volume to make a difference. Not easy.

A second problem is wet steam acts as a lubricant helping pistons and valves to run freely. Superheat dries the steam out removing this benefit. I think it likely that an engine might have enough superheat to lose the lube effect whilst not having enough heat to improve performance. The effects balance out.

I don't believe water splashing into a superheater tube would make enough steam to make an engine uncontrollable. Anyone seen a runaway happen in practice?

If you fancy being controversial, tell the 'knowledgeable' that they're completely wrong. Superheating does work, it's just too difficult for bad builders!

More helpfully, I suspect the layout may be more critical than builder skills. A design than conserves heat by minimising the length of passages and keeping the cylinders warm might take superheat better than one with long or exposed steam surfaces. Just a thought, but LBSC specialised in engines that ran rather than being accurate models of prototypes. Possibly his designs are a bit more superheater friendly than others?

There's a parallel between the failure of superheating on small engines and compounding. In theory compounding is also 'a good thing'. In practice, so much heat is lost in the first cylinder there isn't enough left to effectively drive a second. Due to severe shortage of space, compounding on full-size locomotives hasn't worked well either - the extra complexity doesn't deliver enough benefit. Different story on marine steam engines where relaxed space and weight limits meant engineers could work with much higher boiler pressures and layout efficient triple or quadruple expansion engines.

Dave

Thread: Class 22 Diesel (next project)
17/08/2019 09:10:21
Posted by Ron Laden on 17/08/2019 08:22:28:

The 4 motor assy,s are completed, just starting on the bogie frames.

dsc06890.jpg

Very good! I like the way you go neatly from concept to reality. But could you slow down by about 2000% please? Your rate of progress has got my inferiority complex into meltdown!

smiley

Dave

Thread: Can Anyone Help Me to Identify This Very Old Boiler Please?
17/08/2019 08:50:11
Posted by JasonB on 16/08/2019 15:50:35:
Posted by SillyOldDuffer on 16/08/2019 15:32:43:

The 'mud-hole' is opened and the items to be treated are placed on a shelf inside. Once the mud-hole replaced the fire is lit. The spigot underneath the fire door may be a gas inlet, perhaps used to ignite a solid fuel with minimum fuss.

The mudhole is as I stated earlier the small access cover under the firebox door used to clear sediment, how you would get anything usefuul in there I don't know. It is also not a spigot.

If by mudhole you mean the larger manhole then that would very much depend on the gap between the top of the firebox and the top of the boiler. If the firebox is below the manhole then possible, if it is above then it is purely for cleaning the boiler.

The upper test cock is also above the level of the manhole so you could not fill to that then open the manhole unless you wanted wet feet

Hattie, are you able to measure the height inside the boiler so we can get an idea of the distance the inner top is to the outer top.

Typical man hole is the large one on the side of the boiler, mudholes are the small ones on the corners of teh firebox placed just above the foundation ring for clearing sediment

...

Good points Jason, I am not claiming to have proved it's an Autoclave. As you say much depends on the geometry.

manhole.jpg

By mud-hole, I meant the large entrance at the top and my naming of boiler parts is likely amiss. Normally they're for inspection and cleaning, as there's no steam outlet on Hattie's device, I suggest it's used as a door.

My information on boilers comes mainly from POULTNEY. E, C., Steam Locomotives, Caxton, 1951. He calls the hose inputs for flushing boilers 'wash-plugs' or 'mud-plugs'. They're physically similar to what I think may be a gas input. Hard to tell from the pictures. May be elsewhere in the book but Mr Poultney fails to mention what those clamped man-holes are called; during maintenance he jumps straight inside the boiler without bothering to remove them! (Still a good book though.)

Dave

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