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Member postings for Robin Graham

Here is a list of all the postings Robin Graham has made in our forums. Click on a thread name to jump to the thread.

Thread: Buying metal - caveat emptor.
20/01/2020 23:02:26

Thanks for replies/discussion.

Mick B1 - the Holmes quote was tongue-in-cheek of course. Being relatively inexperienced I have a tendency to blame my technique and/or inappropriate tooling when things go wrong - I really didn't expect the metal to be the problem, hence 'whatever remains, however improbable, must be the truth'. And so it turned out.

Although the immediate problem was solved by using another bar I tried cutting the thread on the other end of the original piece, about 500mm in from the factory end, to test Hopper's suggestion that it might be an 'end effect'. No better. So it's just a crap piece of steel, for this purpose anyway.

This has all been quite enlightening for me. In retrospect I should have smelled a rat when I skimmed the bar to take off rust/mill marks. It didn't go well, but I put it down to my inexperience - I hadn't tried turning such a relatively slender 500mm piece before. But it went fine with the other piece using the same procedure.

In future I shall make some test cuts to get an idea of how the metal behaves before beating myself up.

Both pieces came from a local family-run ME business, not random eBay stuff.

It seems that global production of 'crude steel' (whatever that means!) is about 1.8 billion tonnes annually, so perhaps not surprising that not every bit is top-notch.

Thanks again, Robin

20/01/2020 01:19:15
Posted by Hopper on 20/01/2020 00:23:46:

Was it the very end of the bar? Sometimes the end bit is not much good. Something to do with the production process.

Yes it was - I just turned off the wonky end of the rolled bar, perhaps about 3/16". Maybe that's it.

Thanks, Robin.

19/01/2020 23:32:29

More a beginner's observation than a question perhaps.

A while back I started a topic on thread cutting with carbide inserts - thanks to advice from here and experimentation I thought I'd cracked it. Imagine my horror when I needed to make an M16x2 thread on the end of a bit of 3/4" EN1A bar and found I was back to square one, or worse.

After much faffing about with all the variables I sent a street urchin round to my mate Sherlock - he came came back with the response "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth. It is the metal". I didn't really believe him, but chucked up a bit from another bar anyway.

m16threaden1a.jpg

Annoyingly he was was right yet again! Both (supposedly) EN1A from the same supplier, green blob on the end of the bar, but behaved quite differently. How can this happen?!

Watson.

 

 

 

Edited By Robin Graham on 19/01/2020 23:45:57

Edited By Robin Graham on 19/01/2020 23:59:42

Thread: PSU for anodising.
16/01/2020 22:41:28

Thanks. Encouraged by Neil's excellent results with his telescope I made some preliminary experiments with the battery charger using brine as an electrolyte - I just wanted to see how it coped with differences in electrolyte concentration, electrode areas, separation &c and didn't want to splash acid about at this point. It claims to be 'intelligent' but obviously that's for its intended purpose - I don't suppose an anodising tank looks like a car battery from the charger's point of view. But it seems I can fool the thing, and that this is going to work.

As an aside, the ammeter on the charger has two scales - 'effective' RMS amps and 'Arithm' amps:

psu_ammeter.jpg

I suppose this means that the output is unsmoothed, but I don't understand the ratio A_rms/A_arith =1.5 . Any elucidation would be welcome!

Robin.

14/01/2020 23:14:47

OK, thanks. I guess I just need to suck it and see.

Dave's suggestion that 2V might be enough is surprising and seems to go against the tide of opinion and experience. I thought about trying to make calculations based on the conductivity of dilute sulphuric acid solutions, but it seems that the surface resistivity of the electrodes is dominant. Maybe that's why it's all a bit up in the air.

Making the cathode will be fun, melting old lead pipes in a saucepan on the sitting room fire might raise a wifely eyebrow.

Robin.

 

 

 

Edited By Robin Graham on 14/01/2020 23:16:58

14/01/2020 20:19:08

I'd like to have a go at anodising aluminium and have the chemicals and other stuff, except for a power supply. I have got a 12V car battery charger which claims to be capable of 6A - that should be enough for the part I want to anodise (about 30 square inches), but there is contradictory advice out there on the internet. Some say 12V is fine, others say results are 'likely to be variable', but don't go into more detail.

I'm wondering if anyone on here has experience of trying this with a battery charger?

Robin.

Thread: The cultural status of engineers in the UK
12/01/2020 00:55:41
Posted by John Haine on 10/01/2020 10:52:52:

Please PLEASE don't lets get started on this hoary old chestnut yet again! This has been discussed to death here I'm sure and in publications from the engineering institutions for at least 50 years. And it's not just an issue in the UK. We all know that without engineers society would be nowhere, just suck it up and get on with life.

I'm sorry that I distressed you by my question John - I didn't know that this had been discussed before on this forum. Links to previous discussions would be more useful than 'suck up and get on on with life' which doesn't really help me.

Thanks for other replies though. The story behind my question goes back to a telephone call I had from my sister. "What is heat" she asked "Has it anything to do with motion?" That lead, by a very tangled route, to wondering about about the status of engineers.

Robin.

 

Edited By Robin Graham on 12/01/2020 01:03:22

Edited By Robin Graham on 12/01/2020 01:03:45

Edited By Robin Graham on 12/01/2020 01:20:00

09/01/2020 23:11:01

Just some tea room musing.

I sometimes watch old WW2 propaganda films - mostly from the British point of view, as that's what comes up most often, but once I saw a German subtitled version. Sadly I can't remember what it was called but it involved a submarine in distress.

What struck me was that hero of the German film was the Chief Engineer who got the thing going again against all odds, whilst the hero in the British boats is usually the Captain. The strength of the British Captain is that by virtue of his cut glass accent, Oxbridge education and commanding manner he brings the crew together and they save the day, against all odds of course.

I am not an engineer myself but in my time as an acadaemic scientist I have often worked with (as it seems to me) very talented engineers and machinists. To give an example, I have the dubious distinction of being the first (and quite possibly the last) person to make a direct observation of the hyperfine splitting in Holmium by NMR. To do that it was necessary to make a microwave cavity which would work at 1.7K. I gave my design to the workshop guy - to his credit he didn't suck his teeth, he just gave me a sorrowful look, shook his head and two days later came back with a somewhat different cavity - which worked perfectly.

The point of the anecdote is that when the work went for publication 'workshop guy' was relegated from the byline to 'Acknowledgements'. Head of Department overruled me. I didn't like that. It wouldn't have worked without his skills, But you can't argue with HoD...

To come back to the thread title - I'd be interested to know how those of you who work or have worked in engineering or thereabouts view the status of the craft/art/discipline or whatever in the UK today.

Robin

Thread: Colour matching.
03/01/2020 00:32:03

Thanks. I do indeed have only a digital image to work from, and MichaelG's suggestion of EasyRGB seems a good place to start. I can't be blamed if I'm doing the best with the info I've got!

The 'customer' actually said "some degree of colour matching would be required" so maybe it doesn't need to be exact. Anyhow, a learning opportunity for me, I'll follow it up. I suspect that the customer might not understand that for hand made work aesthetic finishing can take longer than making the functional parts.

Robin

01/01/2020 23:43:25

I make things mostly for my own use, but occasionally take on 'beer token' jobs for others when I think I can learn something. The latest is a simple enough engineering project, but needs to be colour matched. I've never tried that (my stuff is either shiny or black) - so I'm wondering how people go about it.

All I have is a photograph, which isn't much to go on I know. But GIMP will give me RGB values. Would that be that enough to identify a RAL colour?

I suspect that I'm dipping my toe into deep water here, and might not want go further, but I'd be interested in any advice.

Robin.

Edited By Robin Graham on 01/01/2020 23:51:37

Thread: Making a miniature leaf spring.
31/12/2019 23:26:29

Thanks for further replies. I have a copy of the 'Tubal Cain' book somewhere but can't lay my hand on it the moment. My problem isn't so much to do with annealing, but initial hardening. It's not easy to get such small parts from the flame or furnace to the quench before they have cooled too much. I think TC touches on this, but doesn't give advice beyond 'you've got to be quick'. That's from possibly faulty recollection though. I do remember his discussion of the 'blazing off' method for annealing though, now I'm reminded - thanks John.

I wondered if horologists (who presumably do this kind of thing routinely) had some cunning method for initial hardening unknown to TC....

I've made some experiments with hacksaw blades, they're a bit too thick for what I want, but I'm getting there.

Thanks for advice, Robin.

28/12/2019 23:26:32

Thanks for suggestions. I had thought of clockwork, but not having anything suitable from which I could scavenge a bit of spring I discounted the idea. However following MichaelG's mention of clock spring material I Googled and found Meadows & Passmore . Good Lord, they've got everything!

I like the suggestions for 'repurposing' blades from retractable rules and knackered junior hacksaws.I tried with the latter, but unsurprisingly it snapped before I could bend it tight enough. Which leads to my next question...

Meadows and Passmore supply the right stuff in annealed form, which they say has to be heat treated after forming, but they don't give details. Likewise I would have to anneal the hacksaw blade to form it, then re-harden. How does one go about that with such thin material? In my experiment with shim steel I heated the metal over the gas hob in the kitchen then chucked some water over it which simultaneously cooled the metal and extinguished the flame. But there must be another way less annoying to the wife!

Thanks also for other scavenging suggestions which I shall bear in mind.

Robin.

27/12/2019 22:52:58

I want to make a small leaf spring for a catch of my own devising. It needs to be in the form of a U about 1/4" high with maybe 3/16 between the arms and around 1/8 'front to back'. None of those dimensions are set in stone - they're just to give an idea of scale.

I tried a bit of 10 thou shim steel, which seemed springy, but not springy enough. Sadly when I tried to stiffen further it by heating/quenching it ended up softer.

Maybe bits from defunct electrical sockets? Cheapo feeler gauges?

Any suggestions would be welcome.

Robin

Thread: Bandsaw woes.
21/12/2019 01:44:52
Posted by JasonB on 20/12/2019 07:07:58:

I think the vice is an integral part of the base casting. Though the blade is pulling in the cut so would do the same whatever angle the work were held at eg blade not inline with plane that the arm moves in.

You are right Jason. The vice is indeed integral with the base casting. I'm now pretty sure that there are several problems with this machine. I think the pics of a square in the vice show that the axis on which the arm swings is not parallel to the vice base. Maybe I could fix this by making a 'sub base' with an arrangement of fixing/jacking screws to allow adjustment. The blade pulling might also a be problem, but perhaps secondary. This is becoming a challenge! I'll get a better saw when finances are better, but I don't like chucking stuff without having a go at fixing it.

Postie delivered a package with the Zoro logo on it today - my wife confiscated it immediately. What can it be I wonder? Do they sell socks?

Merry Xmas, and thanks to all who have helped me out with advice and entertaining engineering chat over the years I've been on this forum.

Robin

19/12/2019 23:21:31

Thanks for replies.

Bill - (Cornish Jack) maybe you got the first one I bought from them and sent back! It was even worse on vertical alignment than the replacement, and as you know there is no provision for adjustment.

I'll fit a new blade and see if that helps. When I bought the machine I also ordered a small stock of replacement blades from Axminster. They are 1470mm x 1/2" 14tpi carbon steel - I think I might still have one left, However it may be better to fit a third party blade. My Record woodworking BS certainly works better with Tuffsaw blades than the Record offerings.

I'll go for bimetal with M42 teeth. Ian at Tuffsaws stocks these with various pitches - from what's been said here it seems 8/12 or 10/14 Vari-Tooth might be a reasonable choice.

Having said that there is a fundamental problem with the machine which I'll have to address at some point if I want to get it to cut true:

bs_squareness1.jpg

bs_squareness2.jpg

 

Apologies for it being sideways - I forgot that if I want things to come out the right way up on this forum I have to turn my camera 90 degrees.

Robin.

 

 

 

Edited By Robin Graham on 19/12/2019 23:22:25

Edited By JasonB on 20/12/2019 07:03:16

19/12/2019 01:48:17

Yes, solid - why is that relevant?

Robin.

19/12/2019 00:19:09

I may have posted about this before in a 'which bandsaw should I buy' context. A Femi would be nice, but it's not going to happen for a while. So I have to live with what I've got.

Here is a cut in 1.5" aluminium square:

axibandsawbadness.jpg

At this point the blade jumped off the wheels (I was hoping to get all the way though, hence the redundant 'top' reminder). So two problems, which I think are linked: (a) the cut is way out of square and (b) the blade jumps from the wheels. Probably relevant is that the cut starts smoothly, but the machine makes a clunking noise and the arm 'hops' a little in time with the clunk before the blade jumps the wheels. I've watched the weld and it isn't catching in the workpiece, it happens when the weld is somewhere inside the machine.

Here's a pic of the machine:

axibandsaw.jpg

and another with the arm set at an angle to make it clearer how the castings fit together:

axibandsaw2.jpg

Obviously there are many variables here. What I'm after is advice on systematic diagnosis of the problem(s). Everything is fixable with a lathe and a mill!

Robin.

 

Edited By Robin Graham on 19/12/2019 00:37:00

Thread: Silver steel - bizarre Zoro pricing.
15/12/2019 00:29:03
Posted by jimmy b on 14/12/2019 04:49:17:

Robin, 333mm is a pack of 5.

Some smaller sizes are for packs of 25.

Jim

Thanks - I just looked at the 'headline' prices and missed that embarrassed .

Robin.

13/12/2019 22:51:42

I was ordering a couple of things from Zoro, came just shy of the £20 break for free delivery so I thought I'd bung in a length of 6mm silver steel.

333mm £6.20, 1000mm £3.89, 2000mm £15.19 all inc VAT. Think I know which length I'll go for...

Similar anomalies for other diameters.

Just thought it was worth mention in case anyone else is looking for silver steel.

Robin.

Edited By Robin Graham on 13/12/2019 22:52:58

Thread: Lathe lighting
07/12/2019 02:07:16

Thanks for further replies. I'll get rid the light and fix something to the splash guard. I've got a couple or three IKEA Janso flexible neck lights, but the clip on versions are pretty much useless for this type of thing - they don't stay put, and I read in another place that current offerings have a shorter neck than the old ones. I'll look around.

I've been investigating the Noah situation and it seems that he had a Hardinge for the prop shaft and cut an exclusive deal with Lie-Nielsen for hand tools. I might be wrong of course.

Robin.

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