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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: Converting fractions to decimals
16/08/2021 14:51:04
Posted by Ramon Wilson on 16/08/2021 14:15:01:

Sorry, but I'm afraid I can't quite understand why using a simple basic hand held calulator is so challenging ...

Bad memory, finger trouble, distractions and error checking.

Spreadsheet is my preferred method. The numbers are typed in, remembered, and can be printed if required. The calculation is applied once to the whole column, and the result posted next to it. If necessary a third column can convert to millimetres or inches, and a fourth used to back convert to the original as a cross-check. Best of all, three weeks later, when a mistake is suspected, it's all there ready to be diagnosed. Good for up to about a thousand entries, beyond that consider a database, but I rarely tackle big projects.

Many CAD packages support spreadsheets too, which saves a lot of time when a drawing error affects several dimensions.

End of the day though, whatever technique best solves the individual problem. No point wheeling out a computer for a few conversions. Pre-tabulated answers save typing, but look-up errors are more likely, and it's down to the operator to manage them. Calculators suffer finger trouble and have no memory. Redrawing is most time-consuming except I find it helps me understand the design and the conversions are almost a side benefit. Slide rules and Nomographs are remarkably effective - faster than pre-tabulated, but less accurate.

Proper record keeping is an engineering skill in itself. In theory, I take careful notes. In practice, I don't. Shameful.

blush

Dave

Thread: Tinkering with Gary Liming's Stepper Motor control sketch
16/08/2021 13:43:52

The answer is probably a lemon because my copy of Gary's code (version 2.3) already defaults to Fast.

The gear ratio settings don't effect motor speed; Gary just allows for common rotary table ratios like 90:1 and 40:1. The two main parameters that do are:

  • Line 45: #define DefaultMotorSpeed 0 // zero here means fast, as in no delay
  • Line 73: #define pulsewidth 2 // length of time for one step pulse

The main thing slowing the motor down is the number of microsteps per revolution, probably set to 8. Setting the motor to 4 microsteps would double the speed and halve the accuracy. Probably don't want to mess with microsteps because the accuracy of your rotary table depends on them. It's at

Line 27: #define Microsteps 8

A few things you might try:

Gary updates the display after every step in moveangle and movesteps modes, which slows the motor down. Try disabling the display by altering the movemotor() function at about line 546, to cut out a section of code with an #if defined(DO_UPDATE) and #endif block thus:

limingupdate.jpg

The code between #if and #endif will be ignored when the sketch is recompiled, and not having to wait while the display is altered should speed the motor up. Noticeable improvement rather than gee whizz, and of course the display is disabled.

And/or try setting Line 73 to #define pulsewidth 1

The latter might not be satisfactory because how fast the motor can spin is limited by your power supply. 48V or more if the controller can cope please. Unfortunately the motor will skip steps If the power supply can't react fast with enough amps, so there's a limit to how quickly the software can issue pulses and have the motor keep up.

Ask again if #define pulsewidth 1 performs OK with the table carrying a load because delay() can be replaced by delayMicros() to give sub-millisecond stepping, which might be worth trying. I doubt it because stepping quickly takes the motor into unreliable 'here be dragons' territory.

Dave

Thread: choices of material to turn
16/08/2021 10:05:50
Posted by Circlip on 16/08/2021 08:11:20:

If you're just "Practicing" ie. just making swarf , doesn't really matter what you use.

Regards Ian.

With respect, I disagree!

Early on I nearly abandoned the hobby because, by chance, my collection of scrap supplemented by DIY store metal was all rubbish. A nasty mix of stainless, squishy aluminium, hardened steel, dead-mild steel, odd bits of welded pipe and special purpose alloys. Nothing worked as expected. I wrongly assumed it was my equipment, only later twigging the need to develop operator skills and that my materials were awkward b*ggers.

Depends where you live maybe: my part of England does very little manufacturing, so most of my scrap is domestic. These days makers prefer stamping, extrusion, rolling, and grinding to traditionally machined metal, so the machinability of domestic scrap is random. All the ground rods I've taken out of printers and scanners machine well, except for one. Identical except carbide and files won't touch it; I've no idea what it's made of.

With experience most metals can be machined more-or-less successfully, but learning on random scrap is asking for trouble. When things go wrong, it's either the tooling, the operator, or the material. To me it makes sense for beginners to eliminate material problems so they can concentrate on their own shortcomings and learning to drive the machine. Practising on weird scrap is highly educational too, but I feel is best saved for later.

Dave

Thread: Milling machine
16/08/2021 09:13:41

Is it this one, as advertised on lathes.co.uk at the moment?

jonesandshipman.jpg

Not a tool for removing lots of metal quickly I suspect. Looks like a mill-drill currently fitted with a Jacobs Chuck (no good for milling). I guess from its layout the machine was designed for delicate work and note the seller wants to upgrade to a Tom Senior or Centec.

Condition is everything. Are you able to travel to Newton Abbot to see it in action? Watching it cut metal will reveal if if suits your needs or not.

Anyone familiar with this machine or similar in action?

Dave

Thread: Dividing this would have been an interesting exercise !!
15/08/2021 17:54:13
Posted by Michael Gilligan on 15/08/2021 17:10:17:
Posted by Pete Rimmer on 15/08/2021 15:24:47:

I don't see it as a circular dividing problem at all […]

.

I think that’s pretty-much where we came in, Pete

MichaelG.

I've just tried drawing it and confirm the small pins aren't spaced by equal angles. On my metric version, the angle between the top two pins in a quarter is 1.01069° stretching out to 1.63147° apart at the bottom. So as Pete says, not a dividing problem. The same applies to the adjusting pins, which are offset as Michael said, and staggered on opposite sides to allow space for the screwdriver.

Looking closely, each pair of adjusting pins controls three spans between two small pins. If I were making it, I'd have two adjusters, one length of wire and more small spacing pins. I guess that layout was found wanting because the wires sag. Breaking the grating wires into spans of three allows a lot scope for equalising the tension.

Also, as Michael suggested, seems considerable trouble has been taken to put the pins neatly on circles. As only the height spacing matters, perhaps it's been done to emphasise the staggered adjusting pairs. Must have been annoying to accidentally twiddle adjusters on different spans.

Another mystery is the detector originally used with the grating? The spacing suggests infra-red or lower, which is invisible to the human eye. Sensitive semiconductor IR detectors make the job easy today, but weren't available when the grating was made. Considering the technical limitations of a hundred years ago, a lot of very clever experimental science was being done.

Dave.

Thread: Editing classified ads
15/08/2021 16:25:03

Doesn't seem my Junior Moderator Powers allow me to fix it for you Ritchie, sorry. Send a Personal Message to Jason Ballamy and/or Neil Wyatt asking them to mend it.

PMs are sent from the forum's Inbox, top left green banner.

Dave

Thread: Knurling tool
15/08/2021 16:13:21
Posted by Emgee on 15/08/2021 14:24:15:
Posted by Vic on 15/08/2021 12:06:06:

...

The clamp type knurling tool I use was made by a now passed toolmaker, although there is a fair amount of sideways movement (slop) of the arms in the yoke it doesn't affect knurling...

...

Emgee

Emgee's post and my experience suggest sideways slop doesn't matter much, and why should it? Correctly adjusted knurl wheels follow their own grooves and the forces keeping them on track are considerable. The tool doesn't depend on being well made. Clamp knurlers are an inexpensive solution to an ordinary problem, not high-end production tools. Are chaps assuming clamp knurlers are precision instruments?

The acid test is for a few dozen members to each knurl several samples of EN1A rod and submit them anonymously with no clue as to how they were made to an independent panel. Only if the panel score statistically better than guesswork how the knurls were made is the case proved. Believers in 'quality' should be aware few sacred cows survive this test, whether it be fine wines*, violins, or Hifi systems. The problem is personal opinion and experience are both deeply unreliable. In the absence of objective testing, whatever you and I think constitutes 'quality' is probably unsound.

On a large sample I don't think a panel would be able to separate out well-made from ordinary clamp knurls. They would be able to tell the difference between cut knurls and clamp knurls, because cut knurls are almost immaculate. If you need reliably perfect knurls, don't mess with clamps - they're all mildly faulty. Cough up for a Cut Knurler and do the job properly!

Dave

* One test showed professional Wine Judges forced to rely on taste alone were unable to tell the difference between Red and White Wine...

Thread: choices of material to turn
15/08/2021 13:14:33

Lots to learn about about materials, lesson one being they don't all machine well. In fact some are obnoxious! Beware unknown scrap, some of it is very nasty indeed!

Best thing is to check specifications for what's its says about 'machinability'. Look for at least 'good machinability', or 'free-cutting' in the blurb.

Are you in North America? 12L14 is equivalent to Leaded EN1A, which is a mild-steel alloy specifically formulated to machine well. EN1A-Pb is excellent - much better than ordinary mild-steel, which is 'OK' rather than 'good', because it tends to tear causing poor finish . Black mild-steel machines slightly better than Bright Mild Steel in my experience, and although bright comes with good surfaces, the way it's made can cause it to warp badly when cut. Don't let that put you off!

Cutting fluid is generally a good thing apart from Brass and Cast Iron, which both cut dry. Steels prefer a heavier oil or emulsion, but try without first, especially if using Carbide cutters. Aluminium and alloys benefit from a light oil like paraffin.

Most Brasses machine well. Cast iron often has a hard difficult outer skin that has to be penetrated, but is good once that's been done. Be warned though - cast-iron is filthy and the mess goes everywhere. Brasses produce sharp swarf that can't be removed from flesh with a magnet. Don't get it in your eyes!!!

Pure Aluminium and many of the alloys made to be extruded into window frames etc are nasty soft sticky stuff. They don't machine well. However, many Aluminium Alloys are 'good' - check the specification. Most online metal vendors describe what they're selling well enough. If buying from a local shop, tell them you will be machining the metal.

Some metals work harden, that is start soft and go hard and tough under pressure. Stainless steels are notorious, but Bronzes and other metals do it too. The trick is to cut and keep cutting, well lubricated, never allowing the tool to rub. If the cut fails, the metal hardens, perhaps harder than HSS, blunts the tool, causing more rubbing, and then complete failure. The metal can be hard enough to defeat resharpened HSS. I avoid stainless - too many bad experiences.

Most metals can be machined once a certain level of skill is achieved, but I didn't make progress until I'd practised on friendly metals. Once you know what to expect, trouble is more obvious, as it what to do about it. Balancing feed rate, depth of cut, rpm, cutter type and lubrication to suit awkward metals is the answer, but not easy to describe how to do it in words.

Dave

Edited By SillyOldDuffer on 15/08/2021 13:16:55

Thread: Dividing this would have been an interesting exercise !!
15/08/2021 10:38:37

Posted by Michael Gilligan on 15/08/2021 08:26:35:

...

The description is brief; but of course the fundamental requirement would be to have the wires parallel and equispaced. … So, I wonder how much effort must have gone into placing the holes neatly on three concentric circles ?

Unfortunately, the photo is not at high resolution; but it looks to be a fine piece of Scientific Instrument Making !

How would you have done it, with the tools of the day ?

... for comparison, here is a description of some ‘rectangular’ versions:

**LINK**

Dave's method would work, and is the only way I can think of producing a round diffraction grating to fit in the end of a telescope. (Rectangular gratings are rather easier to make once the kenyon paper has been read.)

The hard part is the accuracy required. Not difficult to make a rough grating if the purpose is only to demonstrate diffraction. Much harder to make a good grating for accurate measurements. Fine results demand the wires be accurately equidistant and accurately parallel, and I don't think an ordinary mill and DRO would do the job particularly well. I think the wires need to be much the same diameter too - accurarely made, and not stretched randomly when the grating is strung.

Really annoying, I can't give it a go. My workshop is full of boxes at the moment pending daughter leaving home, and I can't get at my tools or bench.

This paper has more on the theory. Went clean over my head at school! Don't bother reading it unless diffraction gratings are your thing.

Dave

Thread: Silver solder? ....... or what?
15/08/2021 09:57:49
Posted by Brian John on 15/08/2021 04:18:26:

Can you not buy silver solder with cadmium in the UK ? Doesn't that cause problems when soldering boilers and pipework ?

NOTE : I am in Australia. Model engineer suppliers still sell silver solder with cadmium.

Not easily; available in the UK for industrial purposes only, which is pretty much the case everywhere in the world. I'm surprised Australia is more relaxed than other administrations, yet it seems so. Nonetheless, read what Safe Work Australia says about Cadmium, it's not safe. I hope Australians aren't using Cadmium-Silver solder in blissful ignorance!

I'm reminded of another wonderful manufacturing substance. It's non-toxic, fire-proof, and a first class sound, electrical and thermal insulator. It can be woven into cloth or rope, made into cement, sprayed, and made into superb brake blocks. Dirt cheap too. Though suspected early on, it took 50 years for the problem to cause enough trouble for it to be banned. Asbestos...

Dave

Thread: Buying
14/08/2021 16:54:45

Welcome to the forum David.

It's to prove you're a human being rather than an automated spam-bot. Websites are bedevilled by programs creating accounts for the purpose of publishing adverts and other nonsense. They scan, and are usually tripped up by having to make more than one post to get started.

You don't need to type anything clever.

Dave

Thread: Which is better Thompson or er collets
14/08/2021 10:09:56

Ways to abuse an ER Collet!

  • Fail to insert the collet correctly into the holder. (ArcEuro's description is good)
  • Don't tighten the collet enough (the professionals apply a lot of torque.)
  • Force oversize items into the collet. (Causes permanent damage.)
  • Don't use the full length of the collet to grip the item (Collapses the far end)
  • Consistently use the collet clamped fully down at the minimum end. (encourages failure to tighten enough)
  • Fail to understand ER Collets are replaceable. (Industry chuck them out ruthlessly so beware second-hand 'bargains'.)

Dave

Edited By SillyOldDuffer on 14/08/2021 11:25:54

Thread: Unusual Go-No Go Tool?
14/08/2021 09:47:34

The non-linear scale implies the gauge is for measuring intensity rather than a physical dimension, and the peep hole and squared top suggest a simple optical assembly is missing.

As the instrument is a pocket tool, it's used by someone walking about. The peep hole suggests she eyeballs the target. Sound and light, hence heat, are perceived by humans on a logarithmic scale. I think it's for judging the temperature of a furnace or flame for making glass, normalising steel, welding, or melting without boiling etc. Possibly confirming a lighting system is performing to specification.

Any sign of anything mechanical missing at the top? If it's a visual intensity gauge I'd expect the control wheel to adjust an aperture between the peep hole and the lens carrier, now lost.

Dave

Thread: Which is better Thompson or er collets
13/08/2021 18:52:52

Can't comment on Clarkson holders from experience, but one advantage to us of the ER system is it can be used for both work holding and tool holding. The same ER32 collet set is used on my mill, lathe, and rotary table (with a Stephenson Block.)

For what it's worth, not much in my workshop, ER collets seem to rule on CNC systems, I guess this is because ER suits automatic tool changers: no need for the mechanism to faff about with a screw thread. They also have wide gripping range, plus the lighter weight/smaller diameter supports high speed Carbide, 30,000rpm woof, woof!

Dave

Thread: er25 collet
13/08/2021 11:58:51

I agree with Ian. The ER series are a tool-holding collet normally expecting a shank to go all the way through. I think work should be long enough to do the same. When the holder is tightened, the collet is pulled into a taper which compresses it equally on to the shank. If the shank is too short, the collet collapses unequally, losing grip and tipping the work in the collet, causing poor run-out. Might even damage the collet.

I sometimes use a stub-mandrel to save metal, supergluing the blank to it, and detaching the job later with a blow-lamp. Superglued joints are remarkably strong apart from a sharp sideways blow.

Dave

Thread: Centec 2B - New arrival and Q&A
13/08/2021 10:20:09
Posted by JasonB on 13/08/2021 07:10:04:
Posted by William Ayerst on 12/08/2021 21:56:15:

Looks like either someone has tried to enlarge the keyway or it has become seriously worn where the pulley has been moving about on the shaft. Worth sorting out so it does not allow the pully to start moving again.

Worth making a new one I think. Considerable damage can be done once worn components start flopping about. And not just to the worn part itself - shock forces hammer through the drive train, taking years off the life of bearings etc and causing poor cutting finish.

Decent challenge for a keen beginner too!

Dave

Thread: Hole diameters for single point threading
13/08/2021 10:00:11

Fools go where angels fear to tread, but it's never stopped me before!

The form of a metric thread, and relative dimensions, are defined whether or not the diameter is a preferred size or not. Details in Machinery's Handbook, and similar tomes. I pinched this chart off the web:

basic-thread-form-for-iso-metric-and-unified-threads.jpg

Internal Thread at top, external thread below. For all metric threads H = 0.866 × pitch. It's usual for metric threads to be cut or rolled rounded at top and bottom rather than sharp as shown in the diagram.

Thread tolerances are somewhat complicated, ranging from very tight to downright slack, such as threads that are going to be plated. More info on Tolerance Positions and Tolerance Grades here, but I don't think Joe need read it!

A thread made as shown in the diagram would be an uncomfortably tight fit, hard to assemble, and any error in it's manufacture would cause it to jamb. Force fits aren't acceptable if the joint is meant to be unscrewed, so practical threads are cut with slightly oversized 'V's, in effect broadening the bold line. The difference can be seen by comparing DIY store zinc-plated studding with the same sized thread on an Allen Bolt. Studding is crudely made and slack; the Allan Bolt should be much cleaner, well formed and tight fitting in it's socket.

I think Joe can control how tight his thread fit is simply by cutting less deeply than normal. Cutting less than 0.866 × pitch will create an over tight thread, exactly 0.866 × pitch will fit with difficulty, and cutting deeper than 0.866 × pitch will create an increasingly slack fit. I'd make the internal thread first getting as close to 0.866 × pitch as I can measure (not sure how I would do that!), and then use the internal thread as a gauge to make the external thread a tight fit. Could be very tight, needing a strap wrench, or hand tight, as required.

EN8 may not be a good choice because a smooth surface finish is vital for a tight thread fit intended to be screwed and unscrewed, and EN8 often tears roughly when cut.

A precision collar preventing slop might be an alternative to hard to make precision threads.

Dave

Thread: Vise/Vice advise
12/08/2021 10:37:05

I have two vices, both supplied by Warco:

dsc06486.jpg

I don't require them to 'last a lifetime'; I'm past my 'Before Date', and the hobby doesn't require me to thrash my tools. I'm sure they will last longer than I do!

The vice on the right is an ordinary 100mm machine vice. That in the centre is a DH1, with 80mm jaws. Note both vices are removed from their turntable bases. Swivelling is rarely required, and the bases take up space and reduce rigidity. Turntables are almost unnecessary in my workshop, and many others agree. For the same reason I'm suspicious of Angle/Swivel vices - bendy!!!

Although the DH1 is only 80mm wide, it's holding capacity is greater than the 100mm vice. Its jaws can be unbolted and moved, providing much wider jaw opening. I mostly use it in the plain 80mm configuration, but every so often the wider grip is handy.

The 100mm vice has a couple of vices, ho ho! There's a slight tendency for the jaws to lift on tightening, which is so common that it's respectable in professional workshops to tap jaws and work down with a mallet to correct the problem. More serious is a design compromise. The rear jaw has a stress-relieving gutter, also serving to collet swarf. Unfortunately spacing parallels tend to fall into the gutter and making sure they haven't is a time-waster. Not a problem with thicker work, but I mill lots of stuff under 10mm thick, which is spaced carefully to height.

There's no doubt the DH1 is a better vice, but 80% of what I do can be done just as well with an ordinary one!

I think both vices are about the right size physically for a WM18. Wider jaws come with a disproportionate increase in size and weight. A 100mm vice weighs about 10kg, 125mm about 15kg, worse as they get bigger!

Dave

Edited By SillyOldDuffer on 12/08/2021 10:39:03

Thread: Knurling tool
11/08/2021 10:00:15
Posted by Steviegtr on 11/08/2021 03:07:27:

Posted by JasonB on 07/08/2021 07:11:48:

...

Maybe it's not the tool that is "not fit to use" wink 2

...

...

I do not know why you support some not so well made imported, far eastern tools & continually belittle me for trying to point out the shortfalls of such pieces of equipment.

I will be doing a complete build video of the Hemingway to the best of my poor ability, I just hope some will like what i am going to do. Sure you can slag my work,.

But you must remember i am an Electrician by trade . With knowledge of many things & a master of none.

...

With respect Steve, perhaps the problem is you! No shame in that, because everyone has to start somewhere, but in engineering it's never good to rush to judgement before understanding the problem.

Poor results in the workshop are due to Tools, Material, or the Operator, usually in some new situation. Of these the biggest problem is the operator, because he is responsible for planning the job, choosing materials and tools, setting machines up, and optimising feed-rate, depth of cut, cutting speed and much else. It's not easy, requiring a steady hand and applied judgement. Learners cannot assume tools 'just work', they have to be used appropriately, which comes by reading, training, and practice. Learning has to be approached with a degree of caution. Perhaps the worst training material available to the home machinist are the Internet videos made by amateurs who don't properly understand machining yet. Lots of good machining advice on the internet, but also far too much third-rate junk: videos just as flawed as the cheapest, nastiest, Chinese tool. Over-confidence is no substitute for skill.

I'm on the forum to learn and to share what I've learned. Happy to be told whenever I get the wrong end of the stick because everyone on the Forum benefits from the correction. It's not about my ego and fantastic* work! For me the forum is about improving what Model Engineers know and do. Better for posts to be politely honest, rather than agree with SillyOldDuffer's latest faux pas in hope of sparing my delicate feelings!

Doesn't help when bad workmen blame their tools. Leads to beginners fretting about 'quality' and flapping around the second-hand market when they would be better off learning for themselves by cutting metal.

Anyone who thinks I'm wrong about anything I say on the forum is free to say so, Please do, if the explanation is good, I should change my foolish ways! If it's any consolation, I've lost count of the number of times Jason has put me right. And he's not the only one, blush. Done me the world of good.

Dave

*Fantastic can mean 'extremely good', or 'absurd, crazy'. Readers choose which applies to my efforts, not me.

Thread: Colchester Bantam Lathe
10/08/2021 11:34:10

One way of getting it across a lawn, or other rough surface, is to lay temporary track of hefty boards (1" thick plywood).

Difficult to advise on moving heavy unbalanced equipment because there's a certain amount of skill in it, and skills are best learned bu doing easy moves first. Worst case is a bunch of over-confident enthusiastic amateurs crushing someone under the machine. If it topples, it's natural to try and stop it: bad move - wrong! Top priority is to get out of the way! That said plenty of big machines are moved successfully, with simple equipment: rollers, levers, ropes, and a small team of fit blokes.

As they are taught in the Army 'Prior Preparation Prevents Piss-poor Performance'. Assemble a team and choose a leader; this shouldn't be the most gung-ho person available; be suspicious of anyone who wants the job. Drum into everyone they do what the leader says, when he says it. This is because teamwork is essential: lift together put down together. Plan the route, and rehearse it, paying special attention to awkward bits: doorways, steps, slopes, tight corners, and obstacles. How much planning depends on the geography. My workshop has a concrete garage door, accessed from a flat tarmac drive with a short ramp over the public pavement down to the road. The main danger is the tarmac, because it's surprisingly soft, otherwise rolling a big lathe would be 'easy'. My garden shed is far more difficult: steps to garden from road. Sunken path with steps to shed, or lift lathe 300mm from patio to soft lawn and then manoeuvrer machine across grass past goldfish pond and somehow swing past a tree surrounded by a low stone wall, and through a narrow shed door. Lathe in shed needs a lot more thought than lathe in garage.

Be good if you could take photos of the move and share your experiences. Interesting problem, but if it went in it can come out!

Dave

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