Member postings for SillyOldDuffer

This morning's graph is looking much better:

To test the code I ran the clock with compensation switched off. In this state the graph should show straight-line drift with deviations due to changing temperature. The graph is consistent: it show rate of drift falling overnight as the temperature drops. (The pendulum should speed up when the rod shortens due to cooling.)

Too soon to break out the Champagne, so I'll leave it running for another day to make sure. If all good tomorrow, I'll switch the compensation on.

Meanwhile, a couple of bugs to sort out in the logging program. It crashes when sent an illegal empty command, and there's something not quite right with the way it calculates synchronisation times.

One of the two missing components needed to build the vacuum system turned up this morning. The vacuum gauge was accidentally missed off the order by guess who, so I had to start again.

Still dithering about sealing details, which reminds me, I'm nearly out of 1" Brass Rod.

Dave

Does Dell need to worry about thread profiles?

I often single-point threads on my lathe with a 60° V HSS cutter for metric, creating sharp peaks and valleys. Although the threads have the correct pitch and angle, metric form calls for a flat top and rounded bottom. The rounded bottom is for strength rather than fit, and isn't essential. The flat top is easily produced with a file, again the dimensions aren't critical.

Whitworth and BA call for rounded tops and bottoms, but again not strictly necessary. In the US, Sellers decided Whitworth's round form was OTT, and defined an easier to make 60° thread with flat tops and bottoms. Sellers thread morphed into UN, which has flat tops and round bottoms.

If I thought a round-bottom was important on one of my sharp threads, I'd round off the point of a V tool for a finishing cut with a stone. For strength, the round bottom doesn't have to be particularly accurate - the main point is to remove the sharp stress-raiser. Lathe cut threads are weaker than rolled, making commercial fasteners a better bet when safety matters, but safety isn't a concern in clocks.

I suspect traditional threads made with thread-plates were crude by modern standards, like as not with plates producing sharp threads when new, gradually rounding off as the plate wore out.

Bearing in mind I'm a bodger, I'd make the odd thread as close as I could with a sharp cutter (concentrating on angle and pitch, not the form) , flatten the top, perhaps with a pot scourer rather than a file, and ignore the bottom. Then fettle to fit. When a thread screws in and holds tight, 'good enough', I'm happy,

Dave

I had a senior moment! ER32 collets are 1mm, not 2mm range.

Apologies for the confusion.

Dave

Thanks Martin, I wish I had the skills to build a W5.

Just checked my own clock and it still wasn't keeping time. However, I reckon I've found the bug,so maybe the next run will make sense, fingers crossed.

Nothing wrong with the code, except 6 lines were run late, opening a window during which period could be mangled, basically because the pendulum was working before the clock was ready. Bug introduced after I changed the way the clock starts to allow for a heavier bob.

Dave

Alas the model isn't sticky because my pivots don't fit! Only one joint has an actual pin, the others are all axial aligns with rotation allowed. More likely the problem is in the head.

To answer my own question, FreeCAD doesn't have this type of Assembly. Fusion does, and I found it easier to learn than SE.

Been waiting in for a package, just got a message it's coming tomorrow when I'm out, sigh...

Dave

Edited By SillyOldDuffer on 22/05/2023 17:57:55

In another thread we got to discuss what constitutes an Assembly in 3D-CAD. One form consists of parts positioned statically in space. Another allows parts to be jointed as well, so they can move dynamically, realistically modelling entire mechanisms.

This type of Assembly often allows parts to be developed from other parts already in an assembly, making it easy to see interferences. Moving joints can be animated, making it easy to detect collisions between parts as they alter position when the mechanism is working.

This is my go at a lazy tong riveter: it has more joints than parts! A real example:

In developing my version the only measurement is of my fingers to determine the handle size. All the others are derived from the model, and maybe rounded to the nearest millimetre.

First step:

Then refined to this:

Same model, except the joints have been operated:

Nothing is ever easy! The crank-arm geometry doesn't move the pull-rod as far as I want, the cam action should operate along a curve, shape not known, and something is wrong with the head, where the blue crank has popped away from the head and it's driving tong arm:

This is a symptom that a joint or part isn't quite right. Another is that although the tong model works, the movement is sticky.

A possible cause is jointing 'this' to 'that' instead of 'that to this' : makes a difference, and I've not found an easy way of finding where I went wrong! No joy from Solid Edge's diagnostic tools, but I may not be using them properly.

Equally likely is Solid Edge dislikes my cam puller design. It's certainly flawed because the round arms pinch together as the cranks rotate, when a straight pull is needed. I don't know how a real one pulls the rod and guessed.

Any suggestions.

Also, how easy is it to develop a lazy tong riveter with your software?

Dave

Carbide inserts have two big advantages over HSS lathe tools, both of which make cutting metal cheaper.

Carbide is harder and more heat resistant than HSS. Cutting edges last longer and at the same time can safely generate a lot of heat during the cut that softens the metal so more metal is removed per kilowatt. This alone justifies carbide.

Secondly, carbide inserts are accurately moulded to shapes race-tuned for peak cutting efficiency; this saving big money in a production environment. And because inserts of a given type are identical they can be swapped in the tool-holder without resetting it, reducing downtime and labour costs. Further, as each insert comes with 2, 3 or 4 cutting points and edges, 'n' failed edges are quickly fixed by simply reindexing the insert. No skill is involved.

In comparison using HSS is liable to bankrupt the company! Or would if it weren't for the dreaded Account-Ant. He or she makes short shrift of HSS fans by taking into all the costs into account. True HSS blanks are cheap but then:

• A skilled man has to sharpen HSS, and he costs £££ per hour in training, pay, rates, tax, pension contributions, holidays, overtime, heat, light, and toilet facilities, plus management and admin overheads.
• A decent grinder is needed, not a cheapo hobby job, plus consumables, The grinder takes up space, uses electricity, and has to be checked periodically. Maybe the operator has to be trained to use it, because grinding tools wrongly wastes power and might spoil the finish. More £.
• Once an HSS tool has been ground, it has to be set correctly on the lathe. This takes time, because hand grinding always disturbs the centre height. Unlike an insert, the whole tool is removed, so resetting it involves fiddling with shims etc. This wastes so much time that most HSS shops fit a QCTP and buy several cartridges for it. More £.
• In action, HSS pushed hard doesn't last long, and it has to be touched up frequently. The machine has to stop work whilst the cutter is sorted out. For a business this money down the drain, worse if the operator grinds his own cutters!

Time and money are much less critical in a home workshop, where the general purpose nature of HSS pays off, especially for form tools. I find HSS tolerates mistakes better than carbide too, generally getting a decent finish no matter what. However, the indexability of inserts is very convenient. I think an ordinary 4-way tool-post with a set of pre-shimmed carbide insert tool holders is nearly as quick as a QCTP, and wins in the long run because carbide edges lasts a lot longer than HSS, and can be rotated.

As always much depends on what the workshop is doing and why. I prefer carbide inserts most of the time, but not when HSS is better suited. Agood reason for staying loyal to HSS is owning a classic lathe - they're often too slow to get the best out of carbide. Although not as rigid or powerful as they should be, Far Eastern hobby lathes usually have high enough RPM to get results. Without stopping to do any grinding.

Dave

I'm with Nealeb too. In theory my metric collet set covers all the Imperial sizes, and it does. However, in practice imperial diameters often require metric collets to be clamped most of the way down. (1/2" is 12.7mm, requiring a 12-14mm collet to be squeezed by 1.3mm) As far as I can tell big squeezes don't affect accuracy, but tightening takes a lot longer and feels wrong especially in small diameters. After a while I decided it was worth buying some common Imperial collets.

That ER32 have a 2mm clamp range is highly convenient on unusual occasions, but using the full range is extra work, annoying if it has to be done a lot.

Dave

Keeping different types of work separate is always a good idea if you can. Woodwork and metalwork don't mix because sawdust soaks up oil and makes an abrasive mix with swarf on machine tools. And metalwork generates oily black mess that spoils clean woodwork. Painting demands cleanliness, and so does electronics. Apart from fumes, and corrosive flux fumes, flames in the workshop produce a lot of water - the condensation caused by hot work is nastier than ordinary wet.

My ideal workshop would about 10x10 metres and air-conditioned. No chance, I have to make the best of what I've got...

Dave

Poor choice of words on my part, but at least no-one would break anything as a result of the advice! By side cutting I meant slotting, which levers the cutter.

Rules of Thumb are just that. Mine get safely near the right answer in most circumstances - a starting point, unlikely to be optimum. Always necessary to experiment a bit because machines, tooling, work-holding and materials all vary with circumstances.

Productivity is interesting. Anyone else noticed Jason works much faster than me, even though we happen to have similar equipment?

I estimate about 20x faster, and it's not exaggerated false modesty! Many reasons for that, and one of them might be my preference for lower metal removal rates. Not the major reason though; I'm inexperienced and self-taught, and my skills are part-developed because other interests steal time from metal-working. More, I mostly do development work, rather than production, which coupled with inexperience pushes me into spending far more time planning and setting-up than cutting.

Not so bad now, but early on I wasted a lot of time due to mistakes, misunderstandings and sub-optimal cutting sequences. Experienced workers minimise these. They're far more likely to find the best route for making several different types of cut whilst minimising work-holding adjustments, tool changes, moving the table farther than necessary, and re-referencing to maintain accuracy.

I also have a messy workshop, which wastes time when stuff needed by the workflow gets lost in the clutter. My tools and materials are semi-organised, so tap drills might be in the tap drawer, or in the drill drawer. Or in the machine, left on the bench, dropped on the floor etc. I know it's inefficient, it makes about 1 in 5 sessions frustratingly slow, but on balance I enjoy muddling through. My productivity would be zero if I was a perfectionist as well! My other faults mean how fast cutting removes metal is the least of my time issues.

And when cutting my main goals are accuracy and finish, not making swarf quickly. Cut, don't rub, and don't flog bendy hobby machines.

Dave

Edited By SillyOldDuffer on 22/05/2023 09:47:56

Duffer's Patent Rules of thumb:

• For HSS cutting mild-steel, RPM = 10000 / cutter diameter in mm. So a 10mm cutter would spin at 1000rpm. For smaller diameters as fast as the mill will go: 1mm wants about 10000rpm, and my mill can only do 2500.
• Side contact area, up to 15% of cutter diameter. Opinion varies, some say 20%. More than 20% is likely to cause loss of accuracy due to flexing the cutter.
• Feed rate, adjusted by ear. Make sure swarf isn't being minced , and increase the feed until the motor is heard to be working, but not stressed.

These should get the cut into the the right ball-park, but be prepared to experiment. Reduce speed for Cast -Iron. Most other metals prefer faster than steel, and least x2 RPM if the cutter is carbide and the machine can do it.

Dave

Presumably the shock hazard is from the Class X and Y capacitors used to filter RFI? If so, electrocution is unlikely, in the strict sense that the word means receiving a fatal shock.

Filter capacitors don't hold much charge, so although they can leave as much 350Vdc on the pins of a 13A plug after disconnection, there's not enough energy in them to kill a fit human.

Well worth protecting against though in the workplace, because they deliver a painful shock, causing folk to jerk into live wires, fall off ladders, and get entangled in moving machinery etc.

Last time I had a shock was tidying the cable after unplugging a laptop. I touched the plug pins, still here, expletive deleted...

Dave

Yes, I wasn't pleased to find that my cylindrical bob is worst aerodynamic shape!

I toyed with the idea chamfering it in this build, but didn't because I hope my vacuum plan will work. If if does, not removing metal is an advantage because the weight is helpful.

Bob design is more complicated than I realised, so at this stage I've kept it simple. There's a lot I don't understand. Just for starters, mild-steel isn't the ideal material either. In the event the vacuum idea fails, there are a lot of bob ideas to try. Tungsten, for example!

I did improve the bob over a simple cylinder in this version though. It's now suspended from the rod at its centre point, not at the bottom, and the rod is unconstrained at the top. If the rod lengthens due to warming, the top half of bob expands in the opposite direction, providing partial temperature compensation. Seems OK, I feared it would wobble.

Dave

Ho hum, another lack of progress report.

Although the pendulum is running well, Q a little under 14000 with low deviation, I've been bedevilled by a series of small software bugs, all due to 'improvements' made by me. They take an age to discover because it's necessary to let the pendulum swing undisturbed for at least 12 hours, ideally longer, to get meaningful statistics.

Each time I check the stats the pendulum is good, but the clock is wrong! The symptom is faulty drift correction, which is annoying because constant drift is the easiest compensation in the book. Trouble started when I switched from compensating in microseconds to compensating in 62.5nS ticks for more resolution (0.0625uS is 16x 1uS). Then I got plus and minus the wrong way round, and today's result shows drift compensation is ignored.

I blame distractions! I was rung up, tired, or rushing to go out every time I tweaked the code. So restarted the clock with compensation OFF to get a clean baseline, whilst I look for software bugs AGAIN.

Meanwhile, the parts needed to plumb the vacuum have all arrived apart from the vacuum gauge and its adaptor. next job is to check what's happened to the order. UK supplier, so I hope it's not stuck on a slow boat from China.

Dave

Until recently, I used a Logitech M185, and still do when I remote access Solid Edge from laptop whilst half-watching TV. It's fine.

More recently I switched to a Cherry MW3000 high precision mouse, which is ergonomically shaped and heavy. It has 6 buttons but I only use 3 (Right, Left, and Scroll/Middle). It also has a DPI button allowing the sensitivity of the mouse to be varied: I almost always run SLOW. Bit dearer than the Logitech but not top of the range. The extra weight makes it a notch easier to control compared with basic mice.

Chief problem I have is the surface mice run on. Their sensors struggle with too shiny, too white, too coarse, and dislike dirt. I'm using a commercial black foam mouse mat at the moment, which is much better than the vinyl tablecloth underneath. A4 printer paper, poor. Reversed wall-paper is almost as good as the commercial mat when new, but picks up dirt and goes off. Finding the perfect mouse-mat seems harder than finding a decent mouse!

For 3D-CAD, I also have a Space Mouse, driven left-handed to supplement my ordinary right-handed mouse. The ordinary mouse does most of the work. So the space mouse isn't essential, but it accelerates functions like Zoom and Rotate. It's brilliant for exploring and moving around a 3D model quickly. Quite expensive, need practice to get the best out of them and probably not worth buying for occasional modelling. They pay off once a model gets above a certain size and complexity. Mine is unjustified about 80% of the time because my models are mostly simple. Much appreciated when I do a big one though. I think a full-time CAD modeller would be unwise not to have a Space Mouse or similar; there are even smarter CAD devices about, £££.

Dave

Threads are complicated subject, and pre-standard threads are a complete muddle! I don't see any alternative to measuring their pitch and form.

I highly recommend Tubal Cain's "Model Engineer's Handbook" because it contains most of the technical data needed in a small workshop in digestible form. Section 4 covers standard threads: Whitworth, BSC, BA, Unified, Holtzapffel and Metric. Near the end there's a table summarising lathe infeed data for Metric, UNF, Whitworth and BA, note that internal and external threads are slightly different, and that threads can be sharp or rounded.

The infeed is related to Pitch, so step one with a TPI thread is to calculate it. If the ELS is programmed in inches, the pitch is simply 1/TPI. Otherwise, convert inch pitch to metric 1/TPI*25.4

The infeed varies by system, exact values in the book, but for an external thread the infeed is about:

• 0.6 x pitch for rounded, or
• 0.8 x pitch for sharp

I rarely cut big threads to exact specification, and - so far - they have all been metric. So I infeed by about 0.6p or a little more. Most fasteners are a loose fit; more care would be needed if I was targetting a tightly specified thread.

My approach to medium threads is to lathe cut them to about 0.5p and then finish off with a die. The lathe does most of the work and guarantees a straight helix; the die finishes the thread to correct form.

Not my thing, but I've successfully made the equivalent of a thread-plate for a non-standard thread:

• Determine the pitch and diameter of the wanted thread, usually by measuring it
• Set the lathe up to cut that pitch, or as close as the banjo & available gears allow.  (With luck it will be 'good enough' for a short thread
• Cut a sharp thread into a length of silver steel of the correct diameter.
• File or mill the silver-steel lengthways to make a tap and harden
• Tap drill a larger diameter disc of silver steel, countersink one side slightly, drill or file 2, 3 or 4 lengthways notches and use the home made tap to thread it. The disc, (or strip of gauge plate if a thread-plate is wanted), need not be as thick as a commercial die. Then heat harden.

Don't expect the result to be long-lasting or tip-top, but the tap and die will both cut provided the lengthways notches provide a sharp edge with some relief.

Dave

Edited By SillyOldDuffer on 21/05/2023 09:40:26

Another breakfast treat from Michael, thanks. I've often wondered how mine works.

Knowing how they come apart is pure gold. I've broken several things that could have been repaired by forcing their mysterious casings at the wrong point.

Dave

One thing that can be done with a metal ball that Nitrile can't do, is to whack one with a hammer into the seat so it deforms to fit the ball accurately. Replace the whacked ball with a new one because it probably squished out of shape and is no longer a sphere.

Beware - I've never tried it!

Dave

Edited By SillyOldDuffer on 20/05/2023 19:18:24

Three advantages of Nitrile:

• the ball wears out rather than the valve seat.
• the material squishes slightly into the bed and makes a better seal than a metal ball, especially if the valve seat is a bit manky
• there's no risk of electrolytic corrosion damaging the seat

Replacing a nitrile ball with metal increases the chance of a weeping leak in the short term, and maybe much worse trouble later due to physical and corrosion damage.

I'd replace the ball with new Nitrile. The designer probably selected Nitrile rather than metal for sensible reasons. All design is a compromise. In this example the ball doesn't last forever and has to be replaced, but that's less painful than having to replace the whole valve.

Dave

That misunderstands Vevor. They're a reseller, not a tool-shop or manufacturer. They deal in anything they think they can sell at a profit. I doubt they know anything about milling tables!

Unlike Rolex, there's no connection between the Vevor name and the quality of the products they sell. Their stock comes from many different sources and can be anything between wonderful and poor. The business model is based on price-point, not quality. The good thing about buying from Vevor is the financial risk is low, because your money is refunded If the item isn't fit for purpose. That's the protection, not that everything has been expensively quality assured.

This type of trading is more common than not these days, and no one who's been in a Pound Shop should be surprised! It is what it is. Not impossible that Vevor really are selling industrial-grade milling tables at a rock-bottom prices, but unlikely. For that reason machine shops usually de-risk by paying big money to get their tooling from industrial suppliers: they don't expect a consumer-grade retailer like Vevor to meet high-end needs.

Be great if brand-names really did guarantee well-made tools at bargain basement prices, but that's not how the world works. Maybe when we've died and gone to heaven! Until then, buyer beware. It has always been so. Buying cheap risks low performance, buying expensive risks overpaying for a label, or a fake.

Dave

Edited By SillyOldDuffer on 20/05/2023 11:05:03