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Drawing projection, first or third?

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Circlip	26/02/2010 14:50:32
1723 forum posts	Yes Steve, and I'll bet the designer had done one or two mould designs before?? How was he at laying out a Printed circuit board from the electronic circuit?? You have to compare apples with apples, so you are agreeing with my earlier statement on understanding the product. My PCB designs were manufactured in the UK, but my moldings were sourced from Taiwan, and although I had left mold design behind, only one of my moldings ever need a "sliding core" and that was for a product security feature only. Where it leaves you Peter is covered in the last three lines of my previous text. Draw it how you like, as long as the target can understand it. Another variable you have drawn into the discussion is which drawing Programme (Program for the collonials) you use. Although ALL the systems are derivatives from AutoCAD, to make them more user friendly, they all have their little quirks and have been generated to allow the non professional user a method of putting straight and square pitched lines on a "Paper" space. Pity the originators didn't all use an interchangable compatible system of generating the drawings. One thing the electronic generation method HAS changed is the need not to have to draw to "Scale" IE. 2 :1 or 1 : 500 or the likes. Full size is Full size no matter how big or small the finished item is, so Davids point on lines and text smooths this out. Ramon, you REALLY should chill out. Regards Ian.
Gordon W	26/02/2010 17:27:32
2011 forum posts	As mentioned earlier I was a draughtsman most of my working life, I've drawn on everything from linen and ink (and pounce) to autocad. I worked a lot as a contract draffy, on everything from lawnmower engines to oil production jackets (rigs). Always the main consideration is to draw , clearly and unambiguously, what has to be made. Part outlines thicker than the rest, center distances dimensioned, etc. etc..The tool operative should not have to calculate anything. I could go on. But this is a hobbey to most of us, and not worth all the hassle.
mgj	26/02/2010 18:29:06
1017 forum posts 14 photos	Personally I'm less worried about projections or conventions. I agree that getting it right does make for a lot of convenience, (Especially if one is used to working with the conventions in the past) However, we are different from many production workers. Mostly we are making the whole thing, and we know what it should look like and what should fit. Unlike the man who is making 500 off of x and x is simply an object with a set of dimensions, a part of a whole which he may never see. Nor does it worry me frankly that someone dimensions from one line, or in steps of 1/2" for example. I'm quite capable of measuring from a single edge or not, or even of letting my DRO do it for me, and of knowing when one might be critical and one not. My concern is with accuracy - that the dimension you get off the drawing is actually the one that is needed to get a fit on the metal. We seem to have fallen a bit foul of that one just recently.
Steve Garnett	26/02/2010 19:37:32
837 forum posts 27 photos	Posted by Circlip on 26/02/2010 14:50:32: Yes Steve, and I'll bet the designer had done one or two mould designs before?? How was he at laying out a Printed circuit board from the electronic circuit?? You have to compare apples with apples, so you are agreeing with my earlier statement on understanding the product. Oh yes, of course he'd done them before - he came recommended, and that's all we wanted him to do. We do our own PCBs - have done for ages for loads of different products and that's not a problem. So yes, understanding what you are producing is clearly important - possibly more important than anything else when it comes to drawing it in a meaningful manner. I'm not quite sure where that leaves us with ME/MEW drawings. I mean, they all relate to different products, and they're all originated by different people. Somehow one person has to reconcile these into a house style, not necessarily understanding what the significance of some aspects of the drawings are. With the best will in the world, this is surely not going to be an error-free process, is it? Incidentally, in an idle moment this afternoon I had a careful look at the Edgar T. Westbury tailstock turret drawing (Jan 2010), and I don't think that I would have dimensioned this in the way he did (assuming that it was him that did it) - it's not entirely consistent either. And I'd say that it was short of a few centre lines, too. But could you make one from it as it is? Well I'd say yes, except that if you were creating the toolholder from scratch, you'd be scratching your head for a while!
Peter Tucker	26/02/2010 20:57:15
185 forum posts	My preference is for 1st angle. As our drawing teacher explained you place your object on the page, its in plan, roll it up, side elevation, roll it right, end elevation. Perfect logic. Peter.
Stub Mandrel	26/02/2010 21:15:35
4318 forum posts 291 photos 1 articles	I have a 1947 volume of ME here. The standard and clarity of the drawings is excellent, though sized for a much smaller page. Plenty of chain dimensions on the drawings for E.T.W.'s Seal, and only the essential ones given - but I defy any model engineer to struggle to 'read' the drawings correctly. Somehow the drawings from those days look less stark, yet they work even at reduced size - this week's free plan is another example - look at the tiny drawing of the sump! I also have some two engraved views of an 19th century engine - you could build the full size thing just from these two drawings and a basic knowledge of steam engines. In truth technical drawing is (or can be) an art, and needs to be done with an understanding and sympathy for the work to be done. I think Steve's earlier post that explained how loco frame dimensioning needs to reflect the process of making them got it right. I'm not sure someone in 2070 will get the same pleasure looking at today's drawings that I get from those of 60 years ago. One reason is the manual drafting uses a lot more line weights, computer drawings with just 1 or 2 line weights are dull and sterile. Another reason is that cross hatched sectioning, now disparaged, really enhances readability. Not sure that takes the discussion forwards! Neil W.
Steve Garnett	26/02/2010 23:08:05
837 forum posts 27 photos	Posted by Neil on 26/02/2010 21:15:35: I'm not sure someone in 2070 will get the same pleasure looking at today's drawings that I get from those of 60 years ago. One reason is the manual drafting uses a lot more line weights, computer drawings with just 1 or 2 line weights are dull and sterile. Another reason is that cross hatched sectioning, now disparaged, really enhances readability. Dunno what CAD package you've got, but Solid Edge uses 11 line types, all the colours of the rainbow if you want, and 9 different line widths. And if that's not enough line types, you can create your own custom ones. Any limitations are with the user, not the software! Do I use coloured lines? Yes I do sometimes - because we do stuff with weird cross-drillings, and it often makes the intersection points easier to see, certainly at the draughting stage. Sometimes I even print them out like this, although usually by the time we've got to a final drawing I leave them black. Hatching. Hmm... we haven't touched on that. I'd agree that we don't see so much of it these days, but maybe that's because we don't see so many sectioned drawings? In fact hatching is a lot easier to do effectively on a CAD system than it ever was by hand, and if it significantly enhances something, then I'll use it anyway, because I don't care about being disparaged that much! What I prefer though is that the hatching should have a relatively light line weight - I don't want it looking like the rest of the construction lines. As for the loco thing - all I did was apply what I thought was common sense, based on manufacturing lots of small things with holes in (not locos!) from drawings. And in a way, I think that's important; you only really appreciate what it is you need from a drawing when you have to put one into practice. On that basis, I'd say that most successful engineers are a lot closer to being able to produce good drawings than they might perhaps realise, even though they don't think they have the skills. What's important is to make notes during the manufacturing process regarding what's not so easy, and modify your drawings accordingly. After a while, you intuitively sense what's more likely to work, and generally make less mistakes - and clearer drawings! And as a footnote to what I said above about Edgar T. Westbury's tailstock turret, I've now discovered that the drawing as presented in January is incomplete in some rather important ways, mainly concerning the aforementioned toolholder and details of its construction. I don't have the original article it was based on, but I very much get the impression that the version of the plan that myhobbystore sell contains the missing information. Perhaps somebody who has the original article could confirm this?
Stub Mandrel	27/02/2010 21:06:16
4318 forum posts 291 photos 1 articles	See what I mean only 9 widths Seriously though, look at the drawings in ME today and you will rarely see more than one or two weights being used, however manty are available. I make do with corel draw, and that's got almost unlimited line widths and styles - I can even fill with tesselated escher lizards if I want. It's far from a CAD program, but I really hate using things like Autocad with their incredibly steep learning curves. Perhaps its about time that someone with a good understanding of these things did a review of the competing CAD programs out there, from freeware to the top end stuff. Not a ten-part series, but a good overview with a feature comparison matrix. Neil
Steve Garnett	28/02/2010 02:25:04
837 forum posts 27 photos	Posted by Neil on 27/02/2010 21:06:16: See what I mean only 9 widths Seriously though, look at the drawings in ME today and you will rarely see more than one or two weights being used, however many are available. I had a look in my old PD7308, which pretty much predates the CAD revolution (although not completely) and it strongly suggests that only two thicknesses of lines are recommended to be used, the thicker one being twice the thickness of the thin one. For other differentiation, it promotes different line types, rather than weights. What it says is that thick lines are for visible outlines and edges, and thin lines, in various forms, are for almost everything else. The only exception stated (although there may be others I'm not aware of) is that chain line used on cutting planes should be thick where they change direction, and at the ends. And I think that this is pretty much what you are seeing. Now, I don't have a more up to date version of this (although I'm looking into getting one), so I don't know yet whether any of this advice has been superseded. Personally, I hope that it has - for instance, I mentioned hatching weight above, and that's one area where at least an extra thin line wouldn't go amiss, IMHO. As for tesselated escher lizards - I suppose that somewhere, there must be a suitable mechanical device where it would be appropriate to use these as cutaway hatching, at the very least. I don't think that I'm going to lose any sleep over it though! I remember using Corel Draw in the past for the odd thing, and I also recall that I never really got on with it that well. In comparison with a few of the older CAD packages, like Autosketch, I suppose it didn't do that badly, although it never had anything like the scaling possibilities of the latter, or quite a few of its other useful features. But in comparison with something relatively modern, like Solid Edge 2D, which is a free download and way more than adequate for the vast majority of normal home machining purposes, I'm afraid that Corel Draw is nowhere in it at all. Once you've got to grips with the relationship manager, and a few more of its neat dimensioning tricks, you'll never use Corel for anything like machine drawing again, believe me. There's a good chance that anybody into 3D CAM on a mill would ideally want a little more, but for them there's always Alibre, and a few other apps. That's not something I've ever really got into; at a bare minimum, it would have to wait for my complete retirement when I could concentrate on it rather more, I think.
Circlip	28/02/2010 11:32:02
1723 forum posts	Although it sounds like the "Proffesionals" ganging up Neil, Corel draw really is a POS when it comes to drawing anything else other than Graphics. Before the howls, I used to have severe arguments with SWTSMBO who regarded Lotus123 as a do anything programme from accounts to letter writing etc. A BIT like "Works". NO, it's an accountancy based programme which does extra bits, but NOT a sectively dedicated "Fits all" suite. Go back to post No. (Oh sorry, we still haven't got that one sorted yet David) re A/Cad being the generic tool, and yes it was and probably still is a b***h to master, but is STILL the industry standard, but like everything else, if Proffesionals need to talk to each other and interchange technical info without fear of data conflict, their employers will pay whatever to get the latest "Release" or issue or whatever AutoDesk now call it and CHARGE for it. All the spinoffs have had the "Edges" softened to try to make their own versions more user friendly and each have their own band of loyal followers who claim whichever is the best. OK. to put this in easy terms, which CAR is the best??????? While I have "Slagged off" Corel Draw, if you're happy using it, why not?? There is no "One size fits all", so one of the problems with generating a league table is who do you ellect to generate it?? Although I was taught how to use A/C and having both Release and Year issues of it, an extended lapse of use would create a long blip in picking it up again ALTHOUGH after downloading a free (Has to be) issue of DoubleCad (successors to TurboCad), it became obvious "who" the daddy programme was. To illustrate the way various programmes suit different users, a mate who is a non professional in engineering terms was quite happy to use Corel and had difficulty using A/Cad changed over to "Alibre" recently and found it a "Dream" to use as opposed to A/Cad and wondered why he's been fooling with Corel for so long? A free trial version was the decider but he has gone on to buy the official version. I tried Alibre and can't be bothered fooling with the 3D INITIAL layout proceedure. Get whatever you can as a free trial and see how the water suits you, BUT make sure, as we've already said, Make sure ANYONE can read and understand what you've drawn. Regards Ian.
Peter G. Shaw	28/02/2010 12:01:37
1531 forum posts 44 photos	A bit tongue in cheek here. Why, oh why, does everyone have to bow down to AutoCad. Is it because it was the first program that really worked? Or was because some big firm with an interest pushed it? By all accounts not only is Autocad expensive, but it is difficult to understand, as is, in my opinion, TurboCad. And yet, the program I use, Design Cad 3D Max is reasonably cheap, dead easy to use and understand and it is capable of exporting data in a variety of formats, including Autocad dwg formats. Circlip mentioned Lotus 1-2-3. This leads me on to another hobby horse of mine. Until recently I used the Lotus suite of programs in preference to the expensive Microsoft Works or Office programs. Unfortunately, for a variety of reasons, the majority of people use the Microsoft offerings, and when exporting data almost always do so in Microsoft's proprietery format, eg .xls or .doc etc. Which means that I have now had to switch over to Open Office as these programs are compatible with the Microsoft formats as otherwise I cannot exchange data. If people were to realise that there are alternative universal formats which any program can use, then the likes of Microsoft would lose their stranglehold on the market which can only be a good thing. Similarly, when I sent a drawing into the Editor, I have to use one of a small number of specific formats, at least one of which was an Autocad format. Now I have to say that I don't know what, or even if, there is a universal drawing format, but it seems wrong to me to enforce formats which are proprietary. It also seems wrong to me to hold up one very expensive program as the ultimate standard to aim for. One final point about line thicknesses. Although I usually only use the one, my program is capable of producing many thicknesses although I have never tried it. Regards, Peter G. Shaw
Steve Garnett	28/02/2010 13:06:12
837 forum posts 27 photos	I used to use AutoCad, but for the use we made of the 'advanced' features, it simply wasn't worth the effort. And if we wanted more than one seat of it, that cost even more still. As it is, we have quite a bit of mission-critical software on a support basis, so anything that can be removed from that list goes down quite well. We tried a number of the free ones, including AutoSketch for a while - and so far the also DXF-exporting Solid Edge is winning, but as Ian says, that's just a personal preference (well, two of us think it's fine so far...). There has been some muttering about modelling some of the stuff we do in 3D, so if I get a couple of spare days (!!!) I will at least try Alibre, I think. And if we ended up buying it, at least it's on the affordable side - but there again, compared to AutoCad, just about everything is. Even if a league table of different offerings was to be prepared, then the only thing one could do without prejudice would be a feature comparison list, and even that would need extensive notes. Everything else is problematic, although a basic benchmark test might at least remove a few from any real contention. The sort of thing I have in mind is a standardised drawing - how long does it take to create it from scratch on each program, and what were the difficulties involved for a new user? Trouble is, you'd almost want to give the task to several people per package, in order to arrive at any sort of consensus at all, I suspect. This is beginning to look like a serious effort would be required - is it worth it? Absolutely the worst thing I ever tried, years ago, was a couple of DOS-based draughting programs. It was those that persuaded me to stay with pen and ink for quite a bit longer than I might have done otherwise. AFAIK, these pre-dated AutoCAD, although didn't this start out the same way?
Steve Garnett	28/02/2010 14:07:31
837 forum posts 27 photos	One of the more useful CAD links, in terms of what's available for free and with a few useful comments too is Peter Eland's CAD page.
Circlip	28/02/2010 15:40:35
1723 forum posts	One thing to watch if anyone does go down the Alibre road is that the first upgrade from free allows you to use a 3D and auto 2D converter that was previously free for a "Limited" (30 day) trial period. After that, an "Offer" price is introduced. When I first tried it, the Dollar rate was nearly 2 to the pound so as the American site was offering $99 for the intro price, the British arm offered at £99. When I challenged this, I was given the robbing out of the vendors kids mouths tale but they would reduce it to a lower figure although it still didn't meet the American figure and mumbled about VAT charges. Sadly (For the British arm) many purchased via paypal and the American site and got a good deal. So be warned. Where this, and many others, profit is from the extras and tutorial packages that cost whatever more. Regards Ian
Gone Away	28/02/2010 17:49:45
829 forum posts 1 photos	Posted by Peter G. Shaw on 28/02/2010 12:01:37: A bit tongue in cheek here. Why, oh why, does everyone have to bow down to AutoCad. Is it because it was the first program that really worked? Or was because some big firm with an interest pushed it? Historically, Autocad was not only one of the first CAD programs but was also pirated a fair bit in the early days. Autodesk put on a good show of jumping up and down about the pirating but it did create a good few people who were experienced with Autocad at a time when CAD was just being taken up by the companies ... encouraged by the people who were able to use it. So naturally they went for Autocad and established it as the de facto leader (not that it had much competition then anyway). Although Autodesk's market share was eroded a little when alternatives like Pro/Engineer, Unigraphics, CATIA, Solid-Edge, Solid-Works etc came along, they have still managed to maintain that mystique of being "The" CAD program ... despite the fact that some of their development history has been abysmal. They had so many false starts at 3D before they got it right.
Stub Mandrel	28/02/2010 21:59:43
4318 forum posts 291 photos 1 articles	I'm not defending Corel for tech drawings; I just use it because I was used to it for what it's intended DTP, and inherited a V10 cd when it was upgraded. There will be howls when you discover I've used it to lay out double sided PCBs... I looked at Peter Elands site, and what with the chorus of voices championing different solutions it emphasises the need for a simple overview! Neil
Steve Garnett	28/02/2010 22:47:01
837 forum posts 27 photos	Posted by Neil on 28/02/2010 21:59:43: There will be howls when you discover I've used it to lay out double sided PCBs... I looked at Peter Elands site, and what with the chorus of voices championing different solutions it emphasises the need for a simple overview! Corel Draw for PCBs? Hehe! I bet it does really good design rule checking! Seriously though, anybody who's learned to do drawing the hard way should be able to produce perfectly competent drawings with it. When there were only very expensive CAD alternatives, it looked like quite an attractive proposition if you were in that position. Nowadays though, it, er, does not... Whilst I agree that a simple overview of what's available in basic CAD terms would be an excellent utopian ideal, the one message that I get from Peter Eland's site is that this ideal gets further and further from being realisable... Edited By Steve Garnett on 28/02/2010 23:03:36
RILEY COMBS	02/09/2011 17:26:12
1 forum posts	To anyone who has an opinion: I am an Engineering Standards writer for a large US furniture company . Our product drawigs created in North America are drawn in 3rd angle projection. Our product drawings created in parts of Europe are drawn in 1st angle projection. We are having problems with getting each part of the world to understand both systems. We would like to choose one system (I prefer 3rd angle). Do you know of companies that have this problem and how are they dealing with it? Thank you. Riley Combs
Bill Dawes	05/09/2011 18:37:00
605 forum posts	I woked in a DO in the 60's and we allways used 1st angle. It seemed logical at the time, eg. if you looked down at a physical object, turned it 90 deg. to the right and the new view you saw is what you put on the drawing. However can also see the logic of 3rd angle in that the view appeared next to the face in question. Bill D.
Roderick Jenkins	05/09/2011 19:33:17
2376 forum posts 800 photos	As a self-taught amateur with no formal training in engineering or technical drawing, I found 3rd angle to be much easier to understand than 1st angle, using the concept of the object in a box, like a Dinky toy. The projections are then as if the box is opened out with, assuming the car is facing from right to left, the plan view in the middle, the rear view to the right, front view to the left etc. Exactly as if you are looking at it on the table in front of you. To my relief, all the drawings I look at in my industry are in 3rd angle. Rod

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