Member postings for Andrew Johnston

In my experience 303 machines beautifully. For standard threads I use full form inserts, and they work very well on 303. The threads on the piston rods are 3/8" 32tpi Whitworth. I also find that 316 machines well, but 304 is a pig for some reason. According to a recent thread on Practical Machinist even the professionals hate it.

Andrew

I have just been invited to apply for my UK state pension.

When I log into HMRC I get an estimated value, which is almost, but not quite, the full basic pension. However there is a note to say I was contracted out (which I was) and it gives an estimated COPS equivalent value. It clearly states that the estimated COPS value does not affect the quoted pension estimate. As I understand it means that I am not entitled to any additional state pension. It used to be called SERPS, I think?

I have talked to a government pension service and they tell me that the headline estimated pension is what I will get. But my brother, and neighbour, are convinced that the value is reduced by the COPS estimate.

Does anyone know for definite, and ideally by experience, if the headline estimated basic state pension is what you get, having been contracted out?

Andrew

Edited By Andrew Johnston on 26/09/2022 08:16:26

Not prototypical, but I am using 303 stainless steel for piston and valve rods, and associated nuts, on my 4" scale Burrells. Piston rods and nuts on the right, external threads are screwcut to ensure proper alignment:

Andrew

+1, bought my copy in the 1970s from (I think) the TI factory just up the road from my parents house in Bedford. One problem now with pinouts is the myriad of packages, all with different pinouts. Back in the 70s it was plastic DIL or ceramic DIL.

Andrew

I make no secret of the fact that I am a professional engineer, and that I don't regard myself as a modeller, although I am building a couple of traction engines. For me machining is interesting if it's something I haven't done before. Although there is satisfaction to be gained from making a part to the right tolerances and with a good finish machining is mainly a means to an end. I tend to have a different approach to making a part; if it looks difficult I'll try and change the design while retaining functionality. Of course, on my engines I tend to stay with what is prototypical.

What really interests me is understanding how things work and hence being able to create designs that perform as expected. For example the governor on my traction engine could never have worked as drawn. So I am in the process of redesigning the governor, and the steam passages in the cylinder, so there is at least a chance that it will work. To do this it helps to have an understanding of how the governor works and the mathematics behind it. Not many people seem interested in this aspect, as opposed to the making of parts.

A long time ago I started a thread here on injectors, as it is one of the items I need to design for my engines. Unfortunately the thread attracted some derogatory responses to the effect that I was wasting my time as the experts already had designs that worked and there was no need to change them. The recent articles in ME on injectors has confirmed my view that there are better ways of making injectors rather than the traditional arrangement of the cones, and that some of the features of the traditional design are not needed.

For a number of (non-engineering) reasons 2022 is turning out to be a bit of watershed year for me, so over the autumn/winter I will be considering what I want to do over the next few years, which may include writing articles again. It was a shock yesterday to get a letter from the DWP saying I could now apply to get the (UK) state pension.

Andrew

Edited By Andrew Johnston on 25/09/2022 10:55:34

Given that the thickness is said to be more or less than a number then any number satisfies that criteria, unless it is the number that exactly represents the thickness of the folded paper.

Andrew

I looked up the spec for my Tektronix digital scope; the AC cutoff frequency is about 10Hz, equivalent to 600rpm. I suspect that AC coupling may well give a false picture of the waveform.

Andrew

Neither am I, in at least two senses.

Andrew

Probably not a good idea for the input to be AC coupled. I'd go for an external box specifically designed as an oscilloscope. Or take Robert up on his offer.

Andrew

To answer the original question I don't think my fixtures, tooling and setups would merit being a readers tip. And the voucher would be of no interest as there is nothing I need from the supplier.

In general I don't make tools. Which brings me on to the point made above about criticism of Far Eastern machine tools. I have the opposite, snide remarks about those who run ex-industrial machines. One attribute of ex-industrial machine tools is that they are designed to take accessories that are not available for Far Eastern machines, so there is less need to upgrade.

I have had a cover picture on MEW and have published articles about some of my machine tools and a tour of my workshop; article written and I think it was published. I have also written some technical articles for ME and MEW in the past and had discussed a number of other topics that would be suitable for articles. But I never got around to finishing the articles, partly due to work pressures and partly because I felt they were too technical.

No doubt a few people are put off by the forum and stop posting. Each forum has it's own ethos and sometimes it just doesn't gel. I've stopped posting on another ME forum as the ethos and subject matter didn't really fit. I also suspect that quite a few people appear simply because they want the answer to a specific question, or want to look at an advert, and have no intention of continuing to participate.

Andrew

That's not a straightforward measurement, and not something an ordinary oscilloscope can easily do. Way back in the mists of time one could use an oscilloscope to produce Lissajous figures using two (sinsoidal) signals to produce a pattern from which frequency, phase and amplitude of a signal relative to a known signal could be deduced. But the scope needs two inputs, the normal Y input, and one for X which replaces the internal time base. I haven't seen an X input on a scope for decades.

I assume that a voltage proportional to polar position is not available? However the voltage signal from the sensor should be periodic and any reasonable scope ought to have cursors, or automated measurements, that can be used to determine period and hence rpm.

I'd forget about an X-Y display and look for a simple single channel USB scope board. I can't help with specifics as I'm only familiar with the offerings from Pico Technology, and they are probably outside of the budget. They are good, but can have some issues, although they wouldn't be a problem in the proposed project.

Andrew

I'd just grip on the thread with a 3-jaw chuck and turn down the end. As long as the workshop gorilla doesn't tighten the chuck the thread will be fine.

Andrew

Good grief, I had to sit down after looking! Interesting that it is a collection of articles by different authors. Seems quite common with professional level books. The book certainly covers a wide range of topics. I expect that many topics will be a summary of the subject matter; useful, but probably not what the OP is looking for. I won't be buying the book!

Andrew

Me neither, although I have a sensitive level; 0.0005" in 10" per division. If I want a top surface to be "level" I set it to zero with a cheapo digital level zero'd on the table, and then use a DTI to get zero movement as the table is moved. Using the DTI references the work surface to the ways, not the table, which I think is better.

Andrew

I've never even thought about it let alone measured it, so for me it's of zero importance. The CNC mill sits on a welded steel tube stand. The base is shimmed to the stand so that mill is trammed. The manual vertical mill (Bridgeport) sits on the concrete floor but isn't bolted down. The head is trammed. The horizontal mill (A&S 2E) just sits on the concrete floor; at nearly 2 tons it's not going anywhere.

Andrew

There are a myriad of circuit books at the amateur level, but no good ones. Professional level books tend to be highly mathematical and not very practical. i would agree with RA that H&H is about the only book at a professional reference level. It is biased towards analogue electronics and is weak on digital and power. There is a supplement - The X Chapters - which goes into significantly more detail on a range of (mostly analogue) topics.

There are also a range of books published by Butterworth and Heinemann, some in association with EDN, on analogue design, troubleshooting and design philosophy. I have no idea if they are still in print. I'm not going to type out all the information unless someone is specifically interested. Datasheets and apps notes can be useful and in the past design companions were published by some semiconductor manufacturers. But they have long been superceded by the internet.

To an extent I think John is looking for the Holy Grail; there isn't one book that can cover all topics. In my experience electronics design is partly a mix of ideas gleaned from multiple sources but mostly the designer being clear in his own mind as to what he wants and creating his own design, not copying another. Each designer has his own signature style and method of designing.

Andrew

I've never machined carbon filled, but I would expect it to machine similarly to glass filled. I normally buy plastics from EDPlastics as they are local and will deliver for a nominal fee. I assume they will ship, but never tried it.

Andrew

EDPlastics

I don't know about piston valves, but have machined a lot of PTFE. It's horrible stuff to machine; deflects away from the cutting tool and creeps badly. It is also poor at resisting loads. It is difficult to hold any sort of tolerance.

I have also machined a lot of glass filled PTFE. This is much easier to machine, much less deflection and creep so easy to hold tolerances. I made the wing valves for my traction engine water pumps from glass filled PTFE, the white objects towards bottom left:

Andrew

I'd be surprised if the VFD didn't have a display that could be used to display frequency or rpm. For constant power from the motor the output frequency should be 50Hz or higher. I assume that the VFD was set up by Newton Tesla so that the motor parameters and values are correct for the motor? It would be much better to leave the VFD on 50Hz and change the belt drive to change speed.

Unfortunately a 1/2hp motor probably doesn't really have the grunt to make proper use of a 5-insert face mill. I'd stick with ordinary endmills.

Andrew

It's always good to start at the beginning. So the first thing to assess is the motor. What type of motor is it, and what nominal horsepower? How is the motor driven - VFD, static converter or something else?

Andrew