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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: What has happened to this die to cause this ?
29/04/2016 21:05:56
Posted by JasonB on 29/04/2016 20:43:28:

Dave, option 4. Find a bit of bar that will slide into the hollow small end and hold that in the drill chuck. With work rotating at slowest speed, tailstock clamped to bed hold die holder in finger and thumb and slide along bar until it engages on the work and cuts thread, just loosen your grip when desired length of thread cut, stop lathe and then wind the die off either by hand or under reversed power.

J

Thanks Jason! It's easy when you know how. I would never ever have thought of that and it's just so obvious...

Cheers,

Dave

29/04/2016 20:19:51
Posted by Brian John on 29/04/2016 12:07:17:

I have checked the die with an M3 screw it threads okay.

I opened up the die a bit and applied some tap magic to the die : the result is still a mess. It just will not cut.

I think we can assume that the die has become blunt so I will order a new one tonight. That is the only way to find out for sure. When the new die arrives I will use tap magic every time. The lack of a cutting compound might explain why it has become blunt.

If the new die does not cut then I have a problem.

I also tried the die holder. I ordered this months ago but when it arrived it did not fit in my tailstock drill chuck. I then ordered a larger drill chuck which arrived many weeks later. At the time I was busy with something else and I never actually got a chance to use the two of them together until now. It still did not solve my problem

I am 99% certain that a new die is required. I cut a thread on this material only yesterday with no problem.

die problem 2.jpg

Edited By Brian John on 29/04/2016 12:14:17

Edited By Brian John on 29/04/2016 12:15:18

Edited By Brian John on 29/04/2016 12:27:48

Can anyone advise on the correct way to cut a thread using the set-up shown in Brian's picture? I have the same type of die holder and am not clear on how it is meant to be used.

The die holder simply consists of a wide tube at one end to hold the die with a hollow narrow tube or shank at the other. The die holder doesn't have any arrangement that allows the die holder to move forward as the thread is cut. Nor is the holder obviously intended to be hand held.

A few ways of using the tool occur to me none of which seem quite right.

1. The drill chuck is wedged into the tail-stock so that it can't turn. The shank of the die holder is firmly gripped by the drill chuck. The tail-stock is unlocked and free to slide on the ways. Whilst the lathe chuck is rotating, possibly under power, the die is engaged with the end of the rod and the whole tail-stock pushed towards the lathe as the thread cuts.

2. Exactly as above except the tail-stock is locked and pressure applied by winding in the quill.

3. The shank of the die holder is loosely aligned by the drill chuck but not gripped by it. The die holder is held by hand and pressed on to the rod by moving the tail-stock. As the lathe chuck is turned by hand to cut the thread the die holder slides out of the drill chuck.

Methods 1 and 2 in my hands are likely to mangle the thread. Method 3 works but doesn't feel like "industry best practice"

I now use a more conventional sliding die holder. The way that's used on the lathe seems obvious in comparison to the simple type.

Thanks in anticipation,

Dave

Thread: electric - measuring the kwh for my workshop
25/04/2016 18:18:09

Why is it as soon as you want it the pesky thing disappears?

My monitor is easy to set up because it doesn't attempt to calculate cost or do anything clever. You just push a button to select what you want to measure. I can't find it to confirm the model but from memory it's like this one from Maplin's.

Cheers,

Dave

Thread: indexable carbide tools
25/04/2016 16:07:43

When first starting out as a Model Engineer there's a lot to take in: materials, tools, measuring, dials, cutting speeds, coolants, work holding, reading drawings, suppliers, setting up a workshop, what to buy first: there's an almost endless list of new things to explore.

An advantage of indexable carbide for the beginner is that it eliminates the need to develop a rather difficult new skill, that is how to correctly sharpen HSS with a grinding wheel. It's well worth joining the HSS club but these days newcomers can choose to do it as and when it suits them.

You won't go far wrong with indexable carbide. In my experience it's rather well matched to a small lathe run fast.

Cheers,

Dave

Thread: Arduino 555 watchdog timer
23/04/2016 11:39:03

Hi Steve,

Now I'm jealous! You have the scope I wanted. And a ESR70. I wonder what other goodies? It took me a long time to realise that having a decent set of tools saves a lot of frustration and false leads. Making do with a multimeter and a slightly faulty set ot second hand test equipment held me back I'm sure. It's why I'm the sort of person who diagnoses electronic faults best when the broken bit is actually smoking.

Last night I was able to write a simple sketch to prove that an Arduino really can reset the 555. The code was harder than I expected, but it does work.

I had to use a 30mS LOW pulse to reliably discharge the capacitor. One thing I hadn't thought of is that the Arduino and 555 aren't synchronised. If the 555 has only just started to recharge the capacitor, a very short pulse from the Arduino will discharge it. On the other hand the same LOW pulse arriving when the capacitor is nearly fully charged won't fully discharge it, and the Arduino gets an unwanted reset shortly after.

This screen-shot shows a successful heartbeat followed by a reset. I pulled the heartbeat lead on the Arduino immediately after the successful heartbeat tick and then watched the 555 reset the Arduino when it didn't get another heartbeat. The blue line is the reset line and the yellow line is the capacitor.

tick.jpg

I'm pretty sure that you were right early on when you suggested that something simple is wrong with the circuit, or perhaps with the code. It's odd that 47k works when 1M doesn't. On the code side I had to do a bit of a hack to stop the heartbeat back charging the capacitor. You can't let the heartbeat pin go HIGH after you've forced it LOW, which is what normally happens with digitalWrite(). Here's how I did it, there may be a better way!

void heartbeat()
{
// Sends a LOW pulse to discharge the 555's timing capacitor.
// Note the pin is reset to be an input at the end, ie neither high nor low.
// Done because making the pin HIGH rather than LOW charges the capacitor
// and messes up the 555's timing!!!

pinMode(HeartbeatPin,OUTPUT);
digitalWrite( HeartbeatPin, LOW ); // Start the pulse
Serial.print("Tick\n"; // only needed to show heartbeat is working
delay(30); // 30mS needed to reliably discharge 22uF via 560 ohms
pinMode(HeartbeatPin,INPUT); // End the pulse
}

I like helping people too. At the moment I've had much more help from the forum than I've returned. It's not only that my direct questions get good answers, it's the wealth of knowledge I've harvested from all the other threads. I'm pleased you found my comments useful and you sound exactly to be the kind of guy who helps solve my multitudinous mechanical issues.

By the way I found this example of fun with an SDS1102CML on the web. I wish I knew how he did it!

Cheers,

Dave

Edited By SillyOldDuffer on 23/04/2016 11:39:34

22/04/2016 16:05:52
Posted by John Fielding on 22/04/2016 12:52:20:

Hi Silly Old Duffer,

The 1N4148 is typically 4pF and the 1N4000 series is about 50pF, but these are much too small to cause a problem. It can only be one of two things. Either the asserted reset pulse is not going low enough, as Neill pointed out, or more likely to be the reset low duration is not long enough. Most uPs need a minimum duration of the reset pulse to provide a reliable rest pulse to be recognised. If they could be triggered by nano-second long pulses then they would be forever resetting, which would keep the uP out of running.

I didn't notice a POR capacitor on the original schematic? Normally one is needed to hold the uP off until the supply rail has stabilised after initial switch on. It can either use an external or internal pull-up resistor and a smallish capacitor, preferably a tantalum for low leakage. On the Motorola GP32 processors the recommended reset circuit is via a 1N4148 to the open collector device which forces the reset pin low. Not sure what Atmel recommends for the AVR types.

For these kind of add ons I prefer a simple monostable with a voltage comparator which gives a defined pulse duration. Something like a LM339 family works well and very low cost. I detest the 555 timer and all its problems! But YMMV?

Hi John.

Agreed. The diode mangles the waveform slightly on the rising edge and it's very unlikely that's causing Steve's symptoms. There's no substantial difference between a 1N4148 and a 1N4001. Here's the 4001 pictures:

Before Diode:

nodiode.jpg

After diode:

diode.jpg

POR. The Arduino family of boards all wrap the processor up with the components needed to manage Power on Reset and the other stuff needed to make the CPU user friendly. That's why Steve's circuit is so simple.

Arduino boards include a loader in firmware. As a result an Arduino reset isn't quite a simple CPU hardware reset. The process also checks the serial line to see if the IDE has a new image to download and installs it if necessary. Only after doing that does the CPU re-start the users program.

I know exactly what you mean about the 555: lots of us have a love-hate relationship with it!

Steve will have to look at his code to confirm that the reset pulse coming out of his Arduino lasts long enough to reset the 555. As Neil points out the pulse has to be at least 12mS long. On the output side the 555 also generates a 12mS pulse and that would explain why the relay doesn't work - not enough electrons can pass in 12mS to work the coil.

I can now confirm that the circuit reliably resets a Arduino Mega. As this afternoon's domestic task turned out to be much easier than expected so I might bunk off and write the code needed to generate a software heartbeat with it.

I paid about £270 for my Siglent and prices have dropped since then. The advantage of the CML models is that they have more memory to capture extra waveform detail, but they all pretty good. If money is no object Siglent have just released a new "go-faster" range that''s even more impressive. Bit pricey though.

Cheers,

Dave

22/04/2016 15:23:05
Posted by Andrew Johnston on 22/04/2016 13:42:36:
Posted by SillyOldDuffer on 22/04/2016 11:10:48:

A number of people have criticised the external circuit as being unnecessary. The technique was new to me but reading more widely about the quirks of resetting Arduinos revealed there are several valid use cases for it. I would ignore their advice.

Sadly it's that sort of attitude, and the diatribes by Simon Williams, that mean I no longer participate in electronics threads on this forum.

Andrew

Many apologies Andrew, no offence intended. I should perhaps have said something like " I would ignore their advice in this particular case". The criticism is certainly valid in other circumstances.

Sorry,

Dave

22/04/2016 12:28:39

Hi Andrew,

I nearly failed to do this interesting investigation because I'm down to my last 555: must buy some more. I would like to experiment with different models too. I have a Uno but it's tied up at the moment and will take some disentangling. I may be able to try it later. Likewise my Mega is in hiding and I don't have time to search for it today. So I still don't know if different models of Arduino are more or less fussy about reset pulses.

I hadn't spotted that the original circuit specified a 1N4148 so it's pure coincidence that I used one. You may be on to something there.

I believe the 1N4148 and 1N4001 both have the same forward voltage drop. In this sort of application the big difference between the two types is their junction capacity and what that capacitance does to the shape of a pulse. A 1N4148 will be less than 1pF and a 1N4001 could well be more than 20pF. I must have some rectifier diodes that could be tried in this circuit to see what happens.

My Siglent is an SDS1072CML and I'm very impressed with it. It almost makes debugging electronics fun! Over the years I've owned several "pre-loved" conventional oscilloscopes and despite being beautifully made they all developed horrible multiple faults as they aged. In the end I bought a new DSO. Although it felt like an expensive buy at the time I've never regretted it. It piddles all over kit that cost several thousands in my youth.

Cheers,

Dave

22/04/2016 11:10:48

Steve,

Fortunately I'm also in the midst of an Arduino based project and had the wherewithal to build and test your circuit all ready to go on my dining table this morning.

My set-up is a Duemilanove, a Siglent DSO, and a breadboard containing the NE555 circuitry.

I used a modern NE555. The original NE555 tends to crowbar the power supply when it switches and this can cause odd results. If you happen to have one of these you will also need to heavily decouple the power rail. Better to buy a modern 555.

I can confirm that the circuit works for me with the component values given.  It reliably resets the Duemilanove.

The NE555 is set up as an ocsillator with a long period and high duty rate. Fo me the output of the NE555 is high for 14 seconds and then goes low for 12mS. The waveform is repeated unless the Arduino breaks the cycle with a heartbeat pulse. Therefore the Arduino needs to send a heartbeat at least once every 14 seconds.

sds00002.jpg

Zooming in on the short pulse:

sds00001.jpg

 

I tested the heartbeat function by manually shorting the capacitor because I'm too lazy to write the code needed to produce the ticks! As it works with a manual heartbeat I don't see why the Arduino shouldn't do the job just as well, assuming that the low pulse is long enough to discharge 22uF through 560 ohms.

Like Simon Williams I'm suspicious of the component values used. This is because they are outside the normal range recommended for an NE555. Consequently the circuit might not work for everyone. It doesn't help that the maths that comes with the original circuit appears to be wonky, though that might be me! There's some ambiguity about whether the capacitor should be 220uF or 22uF.

If it's 220uF that's a bad idea because it's well outside the recommended range! Even if the circuit works with 220uF there's a two minute wait between reset pulses and it would be easy to miss them on an oscilloscope (unless you deliberately set it up to catch them.)

The diode is needed to stop the NE555 squirting volts into Arduino through the reset pin which is an output. I used a silicon small signal type rather than a 1N4001, mainly because I don't have any 4001s. I don't think the type of diode is a problem with the circuit values given but note the 4001 is a power rectifier that switches relatively slowly. Unlikely, but the type of diode might be part of the problem.

You had to reduce the value of the 1M resistor to 47k to get the circuit to work at all. I suspect this is because the 22 microfarad capacitor is leaking or is the wrong way round. All electrolytics leak and some are worse than others. I would try replacing it.

With 47k rather than 1M and a good 22uF, the 555 issues a 12mS reset pulse every 660mS.

You said you might have done something simple. When I first looked at the diagram I "saw" the reset and Vcc wiring the wrong way round. Shorting the power line rather than the reset would create the symptoms described. I also get confused by the cross-connections needed to wire 555's correctly and usually make at least one mistake whenever I breadboard one.  Well worth triple checking.

A number of people have criticised the external circuit as being unnecessary. The technique was new to me but reading more widely about the quirks of resetting Arduinos revealed there are several valid use cases for it. I would ignore their advice.

You mentioned trying an Op Amp and the awkward need to provide these beasts with a negative rail. I don't think an Op Amp would help in this particular application but an easy way to provide an op amp with a negative supply is to use a voltage conversion chip like an ICL7660.

And of course "Failsafe systems fail by failing to fail safely", ho ho.

Good luck,

Dave

PS Sorry to hear about your mum.  I lost my father to Dementia recently and it was Hell.

 

Edited By SillyOldDuffer on 22/04/2016 11:11:44

Edited By SillyOldDuffer on 22/04/2016 11:15:09

Edited By SillyOldDuffer on 22/04/2016 11:30:18

Thread: Steam engine - homemade
21/04/2016 19:48:02

Nice engines Juan. Welcome to the Forum and Viva Espana!

Cheers,

Dave

Thread: Jan Ridders Coffee Cup Stirling
19/04/2016 21:42:14
Posted by Ian S C on 19/04/2016 12:34:56:

How are you polishing the graphite? The correct way to make the piston is to turn it until it's just too big to enter the cylinder, then cut some strips of paper, and back it with your 6" steel rule, and use this as you would use carborundum strip on steel (graphite, paper, pencil, paper).

Ian S C

That's almost how I did it Ian, except I used a bit of wooden strip. Using a steel rule is a better idea though - if nothing else it would be easier to handle.

I've been out most of the day but I did find that the scraping noise was because the crankshaft was misaligned. In the coffee-cup design the crankshaft is supported by a single pillar that's held in place with a grub-screw. It's quite easy to mess things up by accidentally bumping the flywheel, and I am on the clumsy side of slap-dash.

Duty calls tomorrow so it will be Thursday before I get to play with the engine again.

Thanks again,

Dave

Thread: How are people finding Windows 10?
19/04/2016 21:18:07
Posted by Martin W on 19/04/2016 13:20:56:

....

So far I am quite happy that the upgrade happened and have not had any problems, it would appear to be as stable as W7 and faster on boot up not that W7 was particularly slow.

...

Martin

Hi Martin,

For many people the issue isn't that W10 is unstable, it is the privacy issues it introduces. There's plenty on the web about these concerns, this article for example.

It is not made obvious or easy during installation how to turn the privacy leaks off, or even that W10 is going to share some of your information and facilities unless you explicitly tell it not to.

After installing W10 I spent a lot of time wading through various settings undoing the damage. That's because I thought the default settings were unacceptable, particularly as the upgrade deliberately contravened some of my W7 security settings. You may not share my concerns, but if what I'm saying is news to you it might be advantageous to do more research before making your mind up.

This article seems to cover the ground if you want to know what to switch off.

Regards,

Dave

Edited By SillyOldDuffer on 19/04/2016 21:18:59

Edited By SillyOldDuffer on 19/04/2016 21:20:06

Thread: What Did You Do Today (2016)
19/04/2016 20:25:42

Ban campus motto, "Bottoms up MacNab"

Thread: Black 5 first steam up
19/04/2016 20:08:38

Well done Ron!

Like many others I've been following your trials and tribulations with considerable interest. When things got difficult you hung on in there and made a success of it. I've been inspired by your persistence.

Thanks,

Dave

Thread: Jan Ridders Coffee Cup Stirling
18/04/2016 18:18:31

Thanks again for the advice everyone.

I now have the engine running with a new graphite piston. This one is a little too tight and it makes a scraping noise. As I can't see any sign of any damage to piston or bore I hope it will sort itself out in due course.

I failed again to tap the piston. It doesn't matter much because the screw protrudes through the piston and I can bolt it together. But I like a challenge.

I drilled a 2.6mm hole for the M3 tap and took a lot more care. It went well until the very last moment when all the threads stripped. I wonder if the tap is blunt at the end of the taper and tears the graphite when it should be completing the cut. Next time I'll use a new one.

Now I've had so much practice it only me about 10 minutes to make the piston, with another 20 or so polishing it carefully to a tight fit in the cylinder. Then I spent 2 hours cleaning black muck off the lathe - nearly as messy as the time I used an angle grinder to cut a chunk off a cast-iron block. I wonder where I can get an apprentice to bully into doing the dirty work?

The Wright brothers were a clever and determined pair. It wasn't just that they designed and made the plane, they also designed and built a lightweight engine with the necessary power-to-weight ratio.

Cheers,

Dave

Thread: Are dogs clever or stupid?
18/04/2016 16:12:44

The best kind of dog is the hot dog. It feeds the hand that bites it.

18/04/2016 16:10:53
Posted by David Colwill on 18/04/2016 12:54:26:
Posted by SillyOldDuffer on 18/04/2016 12:34:43:

The cleverest animal is of course the horse. Mr Ed had his own show on TV.

This is wrong! White mice are the most intelligent species followed of course by dolphins then humans. smile p

Regards.

David.

Only 42 people believe that, and they all work for Megadodo Publications!

18/04/2016 12:34:43

After a short paws whilst decoding the meaning of Clive's " I am sure more tails will follow." : I read somewhere recently (New Scientist?) that whilst dogs had to be domesticated by people, cats chose to move in with us.

That would conclusively prove that cats are smarter than dogs except that dogs have somehow trained their "owners" to run after them cleaning up dog poo. It's true, I know some quite intelligent people who are avid collectors of dog excrement.

The cleverest animal is of course the horse. Mr Ed had his own show on TV.

Thread: Jan Ridders Coffee Cup Stirling
17/04/2016 22:31:40

I've always thought that if people were meant to fly we would have been born with feathers! I only know 4 flyers and they've all been in crashes, two of them bad ones. An uncle was in two "minor" incidents, no one hurt but the aircraft were written off both times. All of them due to pilot error, we humans can be very unreliable. Now I have to worry about the ground crew using the wrong oil as well!

Back to hot air engines, I tried flushing the first set of ball bearings used on the Coffee Cup engine with acetone and it initially helped. But only for a while. The bearings eventually failed, mainly due to sideways forces, but there was also a gummy residue in the race. I think this might have been the remains of the rubber seals.

Looking online later for replacements I found that these bearings come in a range of different types. Now I believe flushing may or may not work depending on the bearing you happen to have. There isn't a universal answer, you have to experiment.

I had a frustrating afternoon machining graphite for a new piston. It's the first time I have worked with graphite. Apart from being very messy it wasn't difficult to machine. Unfortunately the diameter of my first attempt was exactly 1mm too small. That's what I get for trusting my mental arithmetic.

My second attempt went very well until I broke it getting ready to part off. I bumped the cross-slide into the work when I meant to retract it and graphite's not very strong.

The third attempt is a near failure too. I took just a little too much off leaving the piston a tad loose in the cylinder. Although the engine works with an undersized piston I shall have to make another one. More mess.

The graphite piston seems to have solved my corrosion problem. Despite a strong smell of vinegar there is no sign of scratching or corrosion after a 40 minute run.

The engine spent the last couple of days sat on a radiator in the hope that the sealant would finally cure. It seems that completing the cure needs a higher temperature than my central heating system.

On the hot-plate at 40C there's still no trace of vinegar. But at 102C the engine reeks of it. I may try baking it in an oven.

I have, of course, got a new problem. How do you tap Graphite? Jan Ridder's design calls for an M3 tapped hole through the piston. I drilled a 2.5mm hole in the piston and tried to form the thread with an M3 tap in the usual way. At first the tap was reluctant to cut, then it started in squishy way, but most of the thread stripped just as the tap was about to finish. The flutes were clogged with powdered graphite.

Is there a preferred way to tap a soft material like graphite?

Thanks,

Dave

15/04/2016 21:07:56

I couldn't find much on the web to suggest that there's any kind of problem with Molybdenum: instead it seems to be a jolly good thing.

The lubricant is Molybdenum Disulphide rather than the element and it's a solid with properties akin to Graphite or PTFE. The only negative comment I found was "Thermal stability in non oxidizing environments is acceptable to 1100C (2012 °F), but in air it may be reduced to a range of 350 to 400 °C (662 to 752 °F)." That doesn't sound too bad.

Either I'm misremembering or maybe there was some sort of FUD campaign back in the day.

Does anyone know if small ultrasonic cleaners are any good for 'our' purposes? They seem to be aimed more at jewelry than the filth I have in mind.

No workshop progress today apart from keeping the engine toasty warm in the hope of getting rid of the vinegar.

Cheers,

Dave

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