….. back on the workpiece!
Powerandpassion :
Yes with wire EDM you can cut flat plate,
the cost is approx. 1 cent/euro X 1 sqare millimeter !

Dko, thank you for the price, let’s us compare apples with apples.
I suspect most EDM folk in the antipodes will look confused if I talk about flat plate cutting, can you give me direction on what brand/type/year of machine & settings will accomplish this, so I can walk in and ask the right stupid questions.
Qldspitty, had to put plastic over the keyboard, tears were squirting out !

Things I have learnt so far :

1) No body really knows, across a range of fora. Waterjet seems to be accepted in the same way that everybody accepts the earth orbits the sun and quantitive easing means someone is actually in control of the global economy. The whole thing is a grey area. I think in 1992 there were problems with effective laser cutting of material like aluminium that rapidly absorbed heat, perhaps resulting in rough, melting edges with the lasers of the time. So it may have been written off by chaps who played croquet with Geoffrey De Havilland.

There is a side story to this, which is the rising tide of engineers who came with the war effort, and carried through to the 90’s. To anyone younger than 60, these were Gods. Now that the tide has receded, we are still playing their LP records in the form of The Knowledge (most worthwhile) while youth struts its stuff with iphones, no doubt in a few years with direct brain implants of wireless devices on 24 month payment plans. I reckon there is something to be got from both tables. Anyway :

2) Laser cutting creates the anecdotal phenomena of edge hardening. Perhaps this can be utilised to make rapid, low cost press tools, strip forming tools for low runs of antique metal work. Eg, create 3D model (3D scan?), slice into 3mm slices (like that frozen crim in the US sliced for science), laser cut slices with common locating holes, bolt assembly together to make press tool/froming wheel with intrinsic hardfacing. You could also make quick, ‘hardfaced’ custom tools like spanners for disassembling Japanese engines copied from British and made in metric etc

3) I didn’t know that you could program into laser a cutting run followed by a defocused beam ‘heat treating’ run while the work was still in position. This might help in ‘single process’ making up of things like high tensile springs in the contact breaker assembly of a magneto, maybe the intricates in a turn and bank indicator, CC interrupter gears, crankshaft shims etc. I think the precise control over the laser beam offers possibilities.

4) I know lots of laser cutters and can reach one as easily as opening a fridge. I have to search for waterjet cutters and they say things like, ‘ join the queue.’ Therefore I think the competitive pressures on the laser industry will drive costs down and innovation up more readily than waterjet. Waterjet is a Japanese tea ceremony and laser is Coca Cola. Maybe it is more appropriate to use the geisha, I would like to discover some things about it and other processes.

At the moment I am trying to get an origianal part, a laser/water/EDM cut equivalent from original equivalent material, then convince the uni down the road to put them under their microscope, upload the photos and ask you to indentify which is which for phase one of the beer competition. It will be a trick question, so beware !

Thank you

Vega ECM, I have absolutely filled my nappy ! I feel like Dorothy, or more like the lion without courage in front of the Wizard of Oz ! I am grateful for your considered reply, which has peeled many layers off the onion. You have provided the first logical framework to allow me to explore this. I feel 100% wrong to be pursuing laser cutting, but I guess in being wrong, or proving myself wrong, I will more fully understand what is right.

I still will not give up my beer without a fight ! If there is an approval from the sheriff to use waterjet cutting, then it is a no brainer that this is the process to use, let alone stop upsetting folk who are comfortable with it. My hunch is that there is no direct approval, just a considered consensus within the intellectual ameoba that is aircraft restoration. Now I will fight : Were lasers last looked at in 1992 ? Are the affects of water pH in waterjet cutting considered ? Does a damp, acidic process setup micro oxidation in a shattered boundary layer ? Does process water recirculated from the previous run on water cutting a brass object inject micro particles into a subsequent run on aluminium that set up electrolytic corrosion ?

My thin odds are based on probably the dearth of knowledge about high tensile steel materials used in old aircraft, as the world moved on from this when Glen Miller was swinging it, and its interaction with a tool like laser cutting. Secondly the astonishing progress of the tool, from the scene in that James Bond movie where Sean Connery is set to lose his goolies to the modern combination of micro lasers/gases etc, which has changed dramatically in the decade or two that I became sentient to it. Mostly I love the competitive pressures that have reduced its cost per cut mm. I see waterjet at its Mt Everest already, but laser still drinking tea in Kathmandu, plenty of potential for progress.

The issues about inclusions/porosity etc make me see my beer slipping away. Trying to demonstrate to the sheriff a Mod is beyond my capabilities, but I guess if I can show evidence of yeti in the form of an OK part, then it will all feed in to a greater understanding of the tools available.

I think what I will do is get an original DTD 166 fish plate part, an identical water jet cut part and an identical laser cut part from contemporary equivalent material and see what results under magnification. I will tell the laser man that the honour of the laser world is at stake, to give me the best combo of power/gas/speed/axes of cut to create a safe edge.

In the new spirit of collectivism if I can crudely demonstrate an outcome that indicates a safe process that reduces cut cost per mm by a %, then this will feedback to more old, restored, safe aircraft in the sky. Then I will ask you to help me get the Mod approved !

Stress cracking

I appreciate your responses to this.

The question relates to fish plates, not tubular members. Fish plates feature in composite steel timber structures post WW1 and particularly in what floats my boat which is 1930’s biplanes. With a fish plate being die cut sheetmetal I guess riveted laminations of die cut metals takes us all the way through to the 1980’s. Fish plates are really a sleeper for another drumbeat, and, as a forum, indulge me to bang my drum.

Mostly this is driven by wonder at the amazing manufacturing productivity tools that I see applied in modern engineering with a reflection on the artisinal approach of modern historical aircraft restoration. I see old planes as a product of an immense historical collectivism : the power of a state to harness immense resources to create complex mechanical devices. To expect an individaul artisan to reproduce such a phenomena in a shed is to pass an eye glass over the consequent phenomena of the historical aviation movement : (a) lots of great people, too old to fly, with 75% completed projects (b) volunteer collectives, that sway in and out of productivity under the influence of immensely patient politicians (c) rich folk converting cash to aluminium, that like the Florentines of old, sponsor artisans to create works of art. It’s all pretty good, but I wonder if some of the modern productivity tools will allow something else to develop. Making it cheap to actually recreate historical aircraft may actually open it up. To be less argumentative, I will say recreate historical replicas, even though we seem able to now create originals out of furnace slag.

I am ******** to know where consumables like crankshaft bearings, bakelite distributor caps, platimum breaker points, (non asbestos?) brake pads, slick tyres for biplanes etc are going to come from unless a rebirth of some form of collectivism takes place – eg, somebody aggregates the global demand for Merlin engine magneto bakelite distributor caps and casts 1,000 units to support the movement for the next 50 years. (BTH or Bendix?) As nobody does bakelite I think you could sucessfully piggyback modern electrical transmission insulator manufacture, which uses modern materials, but has the science to demonstrate that this is a safe replacement for bakelite. Too hard?

There are really no more old boxes of auction stuff left to support the future, and I wonder if 70 year old bakelite even performs, or could have been conceptualized as safe to use 70 years later back in 1942. (Mind you, the Rolling Stones are still banging it out). Probably we need to start a conversation about what sort of will, in terms of intellectual property, the first generation of restorers will be leaving to the next. Handcuffs or possibilities ? The first generation could jump a fence at Hughes and flog a part, sift through the parts detritus of the wartime collectivism and tap someone on the shoulder who knew all about the backlash of reduction gears. What do subsequent generations have to carry on their legacy?

In respect of die cut parts, no individual has the wherewithal to recreate tooling, thus laser cutting, water jet, CNC routing. But you rub against the rules of old, or, terrified to face authorizing powers, who are terrified of you, a compromise evolves which says stick with the ‘tried and true’. The reason I so admire historical aviation is for its dynamism, experimentation and incredible progress. The carryover from analysing gun interrupter mechanisms, palmer brakes, spar metallurgy etc into the daily cornflakes of a prosiac, modern engineering task is to be carried into it on a wave of passion, wonder and enthusiasm.

I guess I find it incompatible with the spirit of those times to be told to ‘stay within the old rules’. As those who made the rules die out, we are left in a trap, where commonsense is secondary to an archaic engineering form. We can make a religion of it, but I can’t see that as exciting or sustainable or even safe.

I use the word ‘gut feel’ as shorthand for hypothesis, but I think that water jet cutting or CNC routing is a shearing operation, that with the benefit of high speed video, would show a brutalization of material crystalline boundaries, with subsequent systems of edge filing/treatment varying between different artisinal workshops. As the original aircraft may have been designed or survived in practice for 500 hours, similar shear stresses caused by original die cutting with blunt forms and indifferent employees did not matter. As we are now restoring for 100 years, perhaps it now will. My gut feel is that people troubled by laser cutting have started with annealed material that would have better been subsequently heat treated to relieve stresses. I think the Boeings of the world are comfortable with modern productivity tools like laser, know how to treat materials, get low cost production and a result. This needs to trickle down to historical aviation.

I am a mug on this stuff. The more I ask folk about these things, I realize I am on a well filled bus. There was always an old gent around that could answer tricky things, but they’re now gone. In the end my gut feel is that it does not matter. An old engineer once told me to ‘trust in the strength of materials’ despite what we might do to them. Enough Sturmoviks assembled by peasant women and enough ME 262s by slave labour accountants and enough Spitfires by grandmothers probably demonstrated that. I guess we need to address our fears to progress.

The scientists seemed to have put a great effort into finding the first bloke who touched a chimp many years ago and gave us AIDS. In this spirit of scientific enquiry I think I have found the first bloke who instructed timber carriage builders in Bristol on how to make die cut parts from high tensile steel, and give us poetry like the Bristol Bulldog. I think his name was Hatfield from Vickers Steel and he has given us the HCl test for revealing stress cracking in sheared parts. I still have a six pack of Coopers stout on the line. I reckon my laser cut, post annealed part will have less stress cracking than your waterjet/CNC routed/hand cut/filed part. If you win the beer, please share it with me in a new spirit of collectivism, comrade.

Thank you Anne, I appreciate it. You have driven me back to the bookshelf where I have rediscovered my 1937 A Licence Inspection of Aircraft by Pitman where I have now fossiked and read about air driven generators while drinking Coopers stout, antipodean bliss.

I have found out that the proper material was “B.12 Brass sheets, annealed, max stress 18 -24 tons/sq/inch, very soft for small intricate pressings” Materials Of Aircraft Production FT Hill 1934.

I don’t know if these are the materials used on the oil cooler but the B grade solder you quoted is listed in Isaac Pitman’s 1935 Inspection of Aircraft After Overhaul (Category “B” Licence) as:-

Grade B Solder, 50/50 Tin/Lead, 205°C Melting point.

Grade A Solder, 65/45 Tin/Lead, 180°C Melting point. Is recommended for repairs as it’s lower melting point would not affect the grade B soldered joints

It doesn’t list the brass sheet but it gives the composition of the brass tube used in radiators (2.T.47) as.

68% to 74% Copper with the remainder being Zinc.
With impurities as not more than
0.1% Nickel
0.5% Lead
0.5% Iron
0.006% Bismuth
0.005% Any other metal excluding silver.

Anne.