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Post by 92220 on May 8, 2020 18:00:55 GMT
Paint, before WW2 was eggshell. They couldn't make gloss paint due to the natural materials being used to make it. During the war, synthetic paint was developed and the synthetics provided a gloss finish for the first time. Prior to that, anything that that needed to be gloss, had to have at least one coat of varnish. ALL paint on locos was varnished to help extend it's life. However, frames did tend to get fewer coats than the main body of the locos so did become dull very quickly. When I was matching the Swindon colours, I was able to borrow the original Swindon colour panels, and these had the painting specs written on the reverse sides. Frames were given one coat of varnish and the main colour (boiler, tender and cab) got 6 coats.
Bob.
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Post by 92220 on May 7, 2020 8:19:23 GMT
Don't use liquid/gel strippers on any riveted assemblies. You run serious risk of it getting into the joints by capillary action and then when you apply the new coat of paint, it can creep back out and ruin the paint finish. If using a solvent that can evaporate fully, any rivetted assembly should be heated up so that it is just touchable, to drive off any solvents trapped by capillary action. Keep at that temp for around 20/30 minutes.
Bob.
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Post by 92220 on May 7, 2020 8:05:56 GMT
Thanks guys. I forgot to say about the sections of the backhead plate. The individual plates are actually all one plate. It is made of 0.6mm nickel silver and the individual plates are done by cutting with a Stanley knife and a straight edge. The idea of using the Stanley knife instead of, say, a scriber, is that it doesn't remove any metal as in a scribed line. The Stanley blade microscopically shapes the 'cut' and makes it look like the edge of a guillotined plate...slightly rounded. I am sure this would also work with brass sheet, but I don't think with steel. The hex head screws are M0.8mm screws from Knupfer.
Another handy trick I found....I wanted slots in the door lever handles that are 1.8mm wide. Try getting a 1.8mm end mill or slot dril. No chance!! I machined a 1.5mm wide slot first, then using the end readings on the DRO to ensure a brand new 1.8mm carbide PCB drill, was in exactly the right places, I gently used that as a slot drill, right at the top of the flutes for minimum overhang, to open out the slot to 1.8mm wide. Worked a treat!
Bob.
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Post by 92220 on May 6, 2020 15:43:28 GMT
Thanks Pete. I will try that next time.
Bob.
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Post by 92220 on May 6, 2020 10:22:24 GMT
Thanks Steve. Just found it.
Bob.
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Post by 92220 on May 6, 2020 8:38:43 GMT
Help!! The photos have come out too big on here. Can anyone tell me how to reduce the photo size in Imgur? Flickr has a facility to limit the final photo size.
Bob.
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Post by 92220 on May 6, 2020 8:33:31 GMT
Hi folks. Before I start I should tell you I have been having problems again, with Photobucket! I then tried to use my Flickr account and had all sorts of trouble with that. I also realised they had changed how uploads are done and I couldn’t work it out, so I decided to try my Imgur account. I set these up ages ago, when Photobucket stopped hosting for free. Anyway, Imgur has been the easiest to get back in to and so HOPEFULLY, the photos will come out on here. I haven’t added anything to the build diary for some time because what I am doing is a very slow job, and I have been adding to the scrap bin quite extensively!!! Since last posting, I have been making the backhead and a scale firedoor sliding frame. I have the backhead plate fitted to the rear firebox clothing molded corners. I will then have to work out how to join up with the firebox clothing wrapper, but before I do that I have to complete the firebox sliding frame and fit it to the backhead. This is how the sliding frame was made: Machining the slideways: The frame jigged for silversoldering: Machining the door-sliding linkage: Machining the tray above the firehole: The finished tray: The tray jigged to the frame for silversoldering: Making up the glare shield: The glare shield bolted to the tray: The sliding frame with glare shield, mounted on the backhead plate: Mike Jack is going to cast scale doors with the raised text on them but I have made up some dummy doors to get it all assembled correctly. The made-up doors are nearly right but the cast ones will really finish it off. Machining the dummy doors out of 0.25” mild steel flat: The fire hole liner and front screen: This is it fitted to the door sliding frame: Here it all is fitted to the backhead: The next job was the ‘Flap plate’ that hinges up and down to also act as a glare screen. This was made of 0.6mm thick mild steel sheet. The shape is such that it is impossible to machine conventionally. Luckily, with CAD it is easy. The tool path was drawn in and then divided into 20 sections. Each of these sections were then dimensioned. A piece of 0.6mm steel was clamped to a piece of sacrificial aluminium and the milling cutter zeroed. The machining was done with a 2mm carbide slot drill, and used like a normal twist drill….I just positioned the cutter at each dimensioned position and carefully pulled the quill handle down as if I was drilling a hole. This left a scalloped edge but it was very easy to clean it up with a swiss file.This is the drawing used for the slot drill positions: This is the finish machined flap plate. The tail is over long because I’m not exactly sure how it will all fit in because everything is so close. As it turned out, the flap plate ended up very close to the BR drawing: This is setting it up to silversolder the hinge in place: This is the ‘press tool’ made up to produce the embossed cross, in the centre, that acts as a stiffening in fullsize: The flap plate has a chain fitted that eventually gets clipped to the back of the pedestal, but that will have to wait. Finding chain of the right size, was quite difficult. I did eventually find one on Ebay with 2mm x 1mm links – perfect size!! This is the finished slide frame with dummy doors fitted: You can see how close fitting the flap plate is, in the firehole. That is why I was concerned and left the tail longer than scale, before bending and finally cutting to size. Bob
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Post by 92220 on May 5, 2020 9:19:03 GMT
Hi Roger.
Thanks for the explanation. JB Tools, that John mentioned, do the polished carbide bits, so I will get on to them for a selection. Maybe I will be hooked on carbide turning tips. You certainly changed my mind on carbide milling cutters. I hardly ever use my HSS cutters now!!
Bob.
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Post by 92220 on May 5, 2020 8:27:11 GMT
Those injectors look brilliant!! Please put me down for one!!!
Bob.
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Post by 92220 on May 5, 2020 8:20:55 GMT
Hi John.
Thanks for that info. I'll follow that up.
Bob.
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Post by 92220 on May 5, 2020 8:11:57 GMT
Hi Roger.
I fully agree with you about machining printed stainless. I wasn't referring to machining that. It was the fact that the article was saying that stainless, in general, couldn't be machined on a 'hobby' lathe, which, frankly, was just not true. The article wasn't referring to printed stainless. it was referring to generally machining stainless steels. It also says, quite correctly, that HSS can be used on stainless. It was just the fact that they said 'hobby' lathes couldn't be used, that I had issues with. They also say that deep cuts are necessary when machining stainless. That is also not true. With a newly sharpened HSS tool, you CAN take a 0.001" deep cut on a 316 stainless bar. I've done it many times when I worked at Wynstruments. As I said, 90% of our machining was in EN58B (316 stainless), done on Myford S7 lathes.
About the polished carbide inserts you mention....can you point me towards a supplier, and what should I look for? I can find tips advertised, that are polished, but they are noted to be for machining aluminium, so I'm guessing the have a much greater top rake than for steels.
Bob.
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Post by 92220 on May 4, 2020 8:24:08 GMT
t ciao MArtyn General principles of machining stainless steels www.bssa.org.uk/topics.php?article=192Machine and tooling rigidityWhen machining stainless steels it important to ensure that there is no dwell or rubbing caused by machine vibration or tool chatter. Machines must be 'substantial' and capable of making the deep cuts needed in machining austenitic stainless steel without slowing down the set feed or surface speeds. Small training or 'hobbies' lathes and milling machines intended for machining mild steel, brasses etc. are unlikely to be substantial enough for the successful machining of stainless steels. Hi Martyn That is a very interesting statement in that text you got off that website. However, I would have to strongly disagree with their statement that "Small training and 'hobbies' lathes and milling machines ...... are unlikely to be substantial enough. When I was an apprentice draughtsman at Wynstruments Ltd., 90% of our work was in EN58B stainless steel, which equates to today's 316 stainless. The only machines we had were Myford Super 7s and one ML7. The milling machines were Senior M1 and a Senior Major......typical hobbies machines(!). We had absolutely no trouble machining stainless. It's just a case of having a VERY sharp tool. When I machined my loco wheel castings, which were investment cast in 316J stainless steel because I needed the strength for the scale section spokes, I tried using carbide tools but couldn't get them sharp enough at home, so I reverted to HSS. It machined the wheels perfectly, and very easily. My lathe is a Myford S7, so I would take what they print with a very big pinch of salt!! I must admit that if I had read that before I had machined my wheels, I would have been very worried though!! With properly sharpened HSS tools, it is perfectly possible to machine 316J stainless steel to tolerances of +/- 0.0005". I've done it, quite easily. Printed stainless would almost certainly be a totally different matter though. Carbide tools can be extremely sharp, these days, so as Roger suggests, they should be able to be used. By the way....VERY interesting thread. Keep it coming!!! Some lovely draughting to. Bob.
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Post by 92220 on May 3, 2020 8:29:50 GMT
Hi Wilf.
Thanks for that link. I've just been onto their site. They do an amazing range of models in wood!! The other surprise is that it's a UK company. I was also surprised that, considering the complexity of the models, how relatively inexpensive they are.
Bob.
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Post by 92220 on May 2, 2020 12:42:46 GMT
Just a point that might help...silver solder, once melted, becomes a higher melting point solder when next heated. I use that fact for all my complicated silversoldered assemblies and I only use one grade of 0.5mm wire and one grade of 1.5mm wire when needed. Previous joints have never re-melted, even with an oxy flame just over 1/4" away. I use CUP 0.5mm low melting point silversolder wire for most jobs, or Easyflo No.2 if I need to use 1.5mm wire.
Bob.
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Post by 92220 on May 2, 2020 9:26:26 GMT
Hi Roger, I think my paint sticks were just bits of mild steel, with 6, 8 or 10 ba holes in the end for screws, or turned down for nuts. depending on the parts to hold. There are some pictures in my book of scores of parts all on sticks waiting to be painted. For the turnover stand, most of it was turned by hand. IE for boiler, cab, tender, chassis etc. For smaller parts with a high gloss, I used a redundant cordless drill on a very low speed. Equally you could use the lathe, protected with plastic sheets etc. There's problem with gloss paint,and I think models should be gloss, at least on the "coachwork" parts. There is an awful lot of pseudoscience around about letting down the surface to a matt/eggshell finish, but I don't really buy that. I think most of this stems from tinplate and old hornby style models where the gloss made them look toylike because the detail shapes were poor. The gloss highlights this. In your model, the shapes will be wonderful and the gloss will just make it look like the original. Others will disagree.... But for gloss paint to work it has to be applied quickly enough (and thick enough) to be runny so that it flows out and pulls out flat. Otherwise you get an orangepeel effect which looks awful. You don't see the ripple/orange peel if the surface is even slightly dull. So it is the full gloss which is just so difficult to achieve well. This is when the turnover stand pays for itself 10 times over. The extra time to make it and turn the part is nothing compared to failure and having to strip back to bare metal! (funnily enough, nitromors, etc, doesn't seem to touch the 2 part etch primer that I found so good from Trimite. You would have to experiment with my other favourite etch primer from Upol. Acid #8) All good fun! Chris. Hi Chris. With many etch primers available to model engineers, generally the base solvent is isopropyl alcohol, mixed with other solvents. However, IPA, being the base solvent, will absorb most etch primers if they haven't had too long to harden off. Just wiping with an IPA soaked cloth should remove most etch primers, except the more exotic commercial 2-pack polyurethane or epoxy etch primers. Bob.
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Post by 92220 on May 2, 2020 8:35:29 GMT
It could be a piece of steel that was put into a bath of copper sulphate solution to check if it was mild or stainless steel. That was a standard test at the company I served my apprenticeship at. The mild steel takes on a very thin coating of copper but stainless stays self coloured.
Bob.
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Post by 92220 on Apr 29, 2020 12:59:29 GMT
Hi Adam.
I see you have a nice new guard dog for all those lovely fittings......and the wagon! Has he learned the ropes yet? Hope he's not TOO ferocious (but maybe playful)!!!
Bob.
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Post by 92220 on Apr 29, 2020 8:25:23 GMT
Gary is right. 2-pack etch primer is not any more harmful than other paints. It is not like other 2-pack paints such as epoxys and polyurethanes. The acid will also attack the tinplate on the inside of a paint tin and quickly be neutralised. It then won't etch. The etch primer is only 2-pack because the acid also starts the chemical reaction to harden the primer, so they supply it in a separate container.This means that the 2-pack etch primer has a very long shelf life, unlike single pack etch primer which loses it's etching properties after about 6 months after manufacture. That is why you should only buy single pack etch primer just before you need to use it. Gary is also right about the hazerdous nature of 2-pack polyurethanes and epoxys. For spraying these you MUST use an air fed breathing face mask. Ordinary paint spray masks are no protection against the 2-pack polyurethanes and epoxys. Basically, don't use these at home!!
Bob.
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Post by 92220 on Apr 27, 2020 12:57:19 GMT
Hi Keith.
You should never cover a newly painted item with a box, especially a plastic box. You trap the solvent vapours, and that stops the paint from drying. As long as the box is stood up off the worksurface, solvent vapours, which are heavier than air, can escape, though far slower than if the item is uncovered, because the vapours in the top of the box are slow to be replaced with clean air. So bear in mind that the paint will take longer to dry to a state that allows handling, than if allowed to dry naturally.
Bob.
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Post by 92220 on Apr 27, 2020 12:47:43 GMT
Hi Roger.
As long as you don't build up a paint spray mist in the room, you should be OK. It's just a good idea to bear in mind that if the air smells of solvent, the newly painted surfaces will take longer to dry than might be expected.
Bob.
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