Forum sponsored by:

Drawing projection, first or third?

Search for: in Thread Title in

Stub Mandrel	24/02/2010 22:06:45
4318 forum posts 291 photos 1 articles	Hi Dave I vote 1st angle, But the best thing is to make sure every drawing has the little truncated cone in a corner - no doubt that way! I was amused that one of Dave Parkes drawings in the issue before last had first and third angle mixed in the G/A. Poor Dave had obvioudsly gone to pains to get it right from his text, but it looks like someone else re-arranged it! Neil (B at O-level in GED - Geometric Engineering Drawing, despite my blunt pencils!)
Ramon Wilson	24/02/2010 22:57:04
1655 forum posts 617 photos	Lots of good comments here. First or third ? both are acceptable but I have to agree most with the concept of whatever system is chosen stick to it. I dont want to steal the thread but as we are on drawing style possibly this is the time and place to air the one thing on drawings that really gets to me and one that I simply don't understand why it continually happens. That is - the use of mixed (and sometimes several) datums. I find it most irritating when something has been dimensioned from a surface that has no exact reference to the main datum when it actually needs to be. Other than reading a drawing I have no training in draughtmanship as such but what is so difficult about dimensioning from two fixed points. Is there a really good reason for this practice that so far is not apparent to my old grey cells. Am I alone in this or does this bother anyone else? Ramon
Steve Garnett	25/02/2010 00:06:40
837 forum posts 27 photos	I don't mind which is used - as long as whoever does the drafting puts the appropriate BS projection symbol on the drawings, because then it's clear to anybody (or at least it should be) as to what you can see in the relative positions - rather better than just sticking arrows on, or whatever... Inevitably I had to create a pair of these for SolidEdge, because I couldn't find any that came with it. I have these as library parts drawn to the recommended proportions, and if anybody wants a copy of these they are welcome to them - send me a private message and I'll email them.
Ian S C	25/02/2010 00:10:12
7468 forum posts 230 photos	Could be that some drawings are submitted by Model Engineers who in their other life have no engineering experience at all, including no drawing at school. They proberbly can't understand what all the fuss is, they just scratch there heads and muddle on. Ian S C
Steve Garnett	25/02/2010 00:30:42
837 forum posts 27 photos	Posted by Ramon Wilson on 24/02/2010 22:57:04: Other than reading a drawing I have no training in draughtmanship as such but what is so difficult about dimensioning from two fixed points. Is there a really good reason for this practice that so far is not apparent to my old grey cells. Am I alone in this or does this bother anyone else? It's generally sloppy drawing practice, although there are allowable exceptions for drawings where it gets crowded. The exception that's mentioned in the BS is called 'superimposed running dimensioning', but even that is based on parallel dimensioning, which always starts from a fixed datum. The stuff that is a bit of a pain is chain dimensioning (presumably what you are complaining about) and that can be made even worse by combining this with the other sort, because then you get dimensions all over the place, and probably some redundancy as well. The system I use mostly is superimposed running dimensioning from a fixed datum, running in two directions, if it's for parts that are generally square-ish, and a slight modification of this for turned ones. This effectively gives you dimensioning by co-ordinates, which is what most people with access to a DRO seem to prefer, anyway... But as you've already said, really the important bit is that the result is unambiguous, and as easy to understand as possible, whatever system is used.
Circlip	25/02/2010 07:34:00
1723 forum posts	Dimension from two datum planes only. Yep I was taught this at school, but in the REAL world of imparting numerical information for manufacturing, logic takes over. OK Ramon, consider the frame plates for a loco. When you start marking out from one end, which is more important? Having the cut outs for the wheel centres in an exact position to the frame end or to EACH OTHER and additionally should the hornplate holes be dimensioned from the frame end or the hole they are dispersed around?? I remember on one forum that a Drafty working for BR mentioned that if he dimensioned using sub datums he would get a "Talking to" by his superiors. Believe me, I have been responsible in the past for having items made as a sub contractor and supplied to BR and the worst part at the start of the chain was to have to translate some ( quite a lot) of the said renderings supplied by the Ivory tower into PRACTICAL manufacturing information. It's no good that some, who are activey engaged in the generation of drawings in a manufacturing area to state BS (Bu S*) whatever to the attendant masses, but in trying to give instructions to someone who hasn't had the luxury of beng taught how to do it "Properly" the simplest non ambiguous drawing should take precedence. You want to "Play" with the various "Instant Draughtsman" programmes?? Fine, but leave the pins and eggs in the drawer when trying to teach some of us teeshirt/video makers the ropes. And before someone states the old nugget "A drawing saves a thousand words" Get real. A couple of lines of notes on a drawing saves any confusion if notated correctly, -- Oh heck, I am ASSUMING (yes, I've heard that one too) that the subject can actually read. Regards Ian. Edited By Circlip on 25/02/2010 07:34:42
David Clark 1	25/02/2010 09:10:47
3357 forum posts 112 photos 10 articles	Hi There I have emailed the illustrator. Where possible we will do drawings as third angle. Won't be possible to redraw everything bu it is a start. regards David
Ramon Wilson	25/02/2010 09:36:12
1655 forum posts 617 photos	Hi, thanks all for the response - helpful as always to see others thoughts but Ian, lets get this in perspective. I don't have a problem when its chain dimensioning providing it relates from or to the same source eg as you quote, the horn slots on mainframes - dimensioned from one end, then to each other or indeed the horn plate holes dimensioned to the edge of the slots or from the centre line. Straightforward stuff. No it's when for example one of those slots is 'suddenly' dimensioned from the other end of the original datum. There may be good reason for this 'transfer' but I'm b-----d if I can see it particularly when other parts have to fit. I accept that the average guy with no training, offering drawings for our pleasure all done at home with pen and paper or computer is going to make the odd error. Let's face it, like machinists don't all draughtsman from time to time? But the habit of transfering seemingly for the sake of it helps no one especially the unwary and no, don't assume anything - I can read a drawing annotated or not but maybe others less able may have difficulty realising the significance of the position of something a bit to late to rectify an uneccessarily made mistake. This was certainly not about teaching anyone, grannies or otherwise, quite the reverse actually. The implied question was simple enough - Is there a reason for it ? - and the specific one quite clear - Does this bother any one else? . Obviously not in your case. Kind Regards - Ramon
Steve Garnett	25/02/2010 11:48:23
837 forum posts 27 photos	Posted by Ramon Wilson on 25/02/2010 09:36:12: I accept that the average guy with no training, offering drawings for our pleasure all done at home with pen and paper or computer is going to make the odd error. Let's face it, like machinists don't all draughtsman from time to time? But the habit of transfering seemingly for the sake of it helps no one especially the unwary and no, don't assume anything - I can read a drawing annotated or not but maybe others less able may have difficulty realising the significance of the position of something a bit to late to rectify an uneccessarily made mistake. I have no problem with annotations, and absolutely no problem with providing notes either. Do draughtsmen make mistakes? Is the Pope a Catholic? For me, the acid test of whether I've made a drawing sensible, unambiguous and usable is when, several months later I have to re-manufacture what's drawn. The rest is obvious... And Circlip, I do them pretty much to BS. It may not be perfect, but what the heck, it's a standard. And without it I can absolutely guarantee that there would be a good deal more confusion than there already is. I started out with this whole drafting business at school where I was fortunate enough to be taught by an ex-draftsman rather than just an academic, and everything we were taught was based on it being practical to use, not just straight out of a book. So that's 35 years doing them the hard way on paper and about 8 doing them with a variety of CAD packages, none of which I'm entirely happy with. But when you have somebody leaning over your shoulder saying "what if...?"(this happened several times yesterday), then I'll accept the limitations, I think. And as for your loco frame plates, I'd probably use detail drawings for holes relative to axles with the datum taken from the axle centre - simply because in the absence of any other information, I'd assume that this was how you'd reference them when you cut them. And put accurate axle centre information on the main frame drawing. That would be until somebody told me that it was impractical. Then, for heaven's sake, I'd change the bloody drawing...!
Circlip	25/02/2010 12:17:21
1723 forum posts	At least we all seem to be working on the common sense page,sadly due to pressures from the "Lets all go Metric" brigade, things went awry when some tried to "Double dimension" drawings A La Opus Approximus and others. Yes qualified Drafties DO make mistakes, and the economics of test building and checking is a luxury that the toy comic trade can ill afford although to hear SOME of the complaints, you would think that it was intentional. Some of the day jobs of some muddlers must show perfection at all times?? Regards Ian.
Ramon Wilson	25/02/2010 13:11:53
1655 forum posts 617 photos	Well I think you've hit the nail on the head there Ian, I have had four machining jobs over some thirty years. Three were in small jobbing workshops serving local industry the other in a larger but by most standards a small factory - 'machine shop' support of the main business of producing electrical terminals.. In the jobbing workshop, 'mistakes' - whether you happened to be concientious or not - were not exactly met with favourable comments. Whereas they can be overlooked in the larger environments in the small shop 'time is very definitely money'. You get nowhere making mistakes!! The work, as varied as you can imagine, always 'took too long'. Perfection then, or the attempt to be, came from contientiousness and a certain degree of self esteem. I make no apologies for having tried in that direction. The factory on the other hand saw a different approach, much more laid back attitude to mistakes but the work, virtually most of which would fit in the palm of your hand, was of ery high tolerance that had to fit and work all carried out on basic kit so again an attitude toward perfection was required. Is this a crime? Well if it is it's not in my book. To consider anyone I feel - no matter what their background - who expresses a desire to participate in this vast arena of ours as a 'muddler' seems not a little disparaging toward the hobby and it's participants in general. Not my idea of encouragement of those with desire to improve I have to say. My apololgies to all for taking this off topic. Regards - Ramon
Steve Garnett	25/02/2010 18:38:27
837 forum posts 27 photos	What I do tends very much towards your 'small factory' approach, and a lot of it's developmental - hence the 'what ifs' and me having to make some of the stuff too. But if we need larger quantities of anything, it's straight off to CAM, hence the need for an acceptable standard of machine drawing. But I don't think that your comments are really off-topic at all. Even hobbyists place some value on their time, and attempting to construct anything from less than stellar drawings invariably takes longer than it would from ones laid out and dimensioned with at least some thought given to construction. Inevitably this is going to lead to an increased sense of frustration, especially for beginners. So I'd say that providing sensible drawings to an agreed format, and with serious thought given to dimensioning (the now out-of-date publication I mentioned earlier gives over about a quarter of itself just to this) is definitely the way to go. Just because people are hobbyists doesn't mean that they should be treated in any way differently to anybody else machining at a distance from the designer, does it? Since the editor employs a draughtsman, then I don't see why this requirement should even discourage people whose engineering skills are in excess of their drawing ones from submitting stuff for publication, either. So having this as a timely reminder on a thread about the way drawings are presented seems entirely relevant to me.
David Clark 1	25/02/2010 19:49:45
3357 forum posts 112 photos 10 articles	Hi There We employ an illustrator, not a draughtsman and he has 5 or 6 magazines at least per month to do. regards David
Steve Garnett	25/02/2010 20:20:21
837 forum posts 27 photos	Oh... are there any implications to this?
Circlip	26/02/2010 10:47:14
1723 forum posts	Firstly Ramon, despite having a lifelong career in "Full size" engineering starting in the toolroom and through my own efforts traversing via the D/O to works management, I would ALWAYS describe myself as a "Muddle Ingineer", so I would never try to insult anyone who has a more normal type day job and then chooses to impregnate their fingers with sharp bits of metal. One for Steve, ever worked with "Contract Draughtsmen"???? One of the problems in working in any "new" firm is finding the different working standards and manufacturing capabilities. My own training "Spoiled" me by dropping me in with "Old Ingineers" (Thank heavens) but the range of equipment for cleaving bits of metal was second to none, so having the grounding of HOW to cleave and WHAT to cleave with stood me in good stead to enable me to progress to "Design" tools, tooling and later components for both mechanical and electro/electronic product manufacture.I doubt that any of todays "Kids" could emulate that route in manufacturing cos the BASIC grounding is not there anymore. The problems I found with ALL the C/Ds I worked with was that they were shipped in to relieve an order "Glut" at the time, and then six months later when the jobs hit the shop floor, the land mines would start exploding. Their drawing skills were not the problem, but an alien (to their training) working enviroment didn't help when "Dropped in" for a few weeks contract. I'm also sure that Steve will have been "Involved" with "Designers" whose best use for a piece of pointed graphite would be cleaning their ears out with it. The use of an "Illustrator" for the Mag. is not a problem PROVIDING the information given to them is correct from the outset. We had a superb "Tracer" in my first drawing office whose pictures were like works of art, (SHE was pretty fit too) BUT had she been asked to design a press tool would have had no idea despite working in that enviroment for many more years than I had. A basic rule I worked to when designing bits to be assembled on "The Line" was ( and don't get your knickers in a twist over THIS one Ramon) make sure it can be assembled by monkies, and if you have a trained monkey, regard that as abnormal. Now I'm NOT insulting ALL shop floor workers, but many are motivated by ONLY the brown envelope at the end of the week, so making "Mindless tasks" had to be the norm and you NEVER stopped "the line" on pain of death, alarm bells and a Mexican wave of inactivity along the assembly benches is VERY frightening. So rounding back to the drawing representation, and given that you have to cater for all levels of mechanical knowledge from a road sweeper to a brain surgeon and all points in between, although some "Authors" might have delusions of becoming ace Drafties at some future point and work to BS/ISO or whatever current standard, I find it far more important to have an unambiguous and DIMENTIONALY CORRECT representation that ANYONE can understand without having to think 1st 3rd or whatever (Where's the truncated cone drawing). Summat else to chew and digest, Regards Ian.
Steve Garnett	26/02/2010 11:32:06
837 forum posts 27 photos	Hehe... Because we ship stuff out, at least some of the time I reckon that I qualify as the contract draughtsman some of the time as far as the firms on the receiving end are concerned! The last time we employed any outside contract help with a design was somebody to do a two-part plastic moulded case that's pretty damn complex. And I have to say that the guy that did it was seriously good - the manufactured result was excellent, even though we had to send it to China to get them manufactured at an affordable cost. We'd definitely use him again. But as far as the rest of it's concerned, I think we've all agreed that overall clarity in drawings is what's really of paramount importance, regardless of anything else at all.
Peter G. Shaw	26/02/2010 12:08:21
1531 forum posts 44 photos	So, given that I am neither a trained draftsman nor a trained engineer, where does that leave me? I have already said that I find 3rd angle rather more "natural" than 1st angle. I have also read, and try to understand and apply Tubal Cain's writings in Workshop Drawing, WSP no 13. I also have Brown's CAD for Model Engineers, WSP no. 29, which frankly isn't that much help because my CAD isn't the same as his. I know, for example, that partly due to the constraints of the CAD program, and the VDU, I do not do things as TC would wish, a good example being the use of heavier lines for the outline. I actually draw at minimum width because using the VDU, a heavy black line varies (and gets larger) if I zoom into expand a part of the drawing whereas a minimum thickness line remains the same no matter what the zoom. Also, I show dimensions, again due to the vagaries of the CAD, in different places to avoid clutter. Does this mean that anything I submit to the magazine will have to be completely redrawn? I think the answer has to be that for "our" purposes, we have to understand that "our" people will have the ability to be able to make sense of what is drawn, and whilst it may be "wrong" to the trained draftsman/engineer as long as it is clear and unambiguous then surely that is the most important factor. Let's face it, whilst on the shop floor, drawings will have to be, as Circlip says, suitable for untrained monkeys whose only interest is the brown envelope at the weekend, "we", as amateurs, are doing it for our own interest, and thus will be prepared to invest our time in understanding the drawings, even if they are not to the relevant BS/ISO. Regards, Peter G. Shaw
Ramon Wilson	26/02/2010 12:22:50
1655 forum posts 617 photos	Steve, Thank you for bringing such a commonsense approach to this matter. For myself, I have been fortunate never to have worked with monkeys, nor for that matter to be in charge of them, just good people who have held a pride in their work and what they do. (Don't wear knickers either - preventative measure you know- if you don't wear 'em you can't twist 'em) On the matter of self deprecation then by all means go ahead, be my guest - I certainly won't lose any sleep over it but please leave me out of the equation. I learnt at an early age that deriding your troops is a negative and fruitless exercise. As I said before the questions are simple enough - is there a good reason for the practice of transfering datums and does it bother any one else. Steve has gone some way to try and answer the actual question - thank you. Ramon
David Clark 1	26/02/2010 12:23:55
3357 forum posts 112 photos 10 articles	Hi There Most things are redrawn anyway because of line weights and text sizes. regards David
Steve Garnett	26/02/2010 13:01:40
837 forum posts 27 photos	Posted by Peter G. Shaw on 26/02/2010 12:08:21: "we", as amateurs, are doing it for our own interest, and thus will be prepared to invest our time in understanding the drawings, even if they are not to the relevant BS/ISO. Couple of points, Peter. The standards allow quite considerable latitude in what's drawn, primarily because it's realised that you invariably have different drawings for different purposes. And I still think that there's a distinct limit to the amount of time that anybody would be prepared to spend trying to decipher less than helpful ones. Okay, it might make you increase your appreciation of the clearer ones, but does it really have to be like that? I would hope not... There are a few snags though. Whilst I really don't think that it's that difficult to create basic drawings to an acceptable standard when it comes down to it, some of the more helpful drawings, certainly in terms of an overall understanding of what you are making, aren't so easy. I have heard it said several times that most complex engineering drawings make far more initial sense if, for instance, some sort of axonometric projected view (typically an isometric one) is included, and I'm sure that's correct within reason. But generally that doesn't happen these days, and there is one very good reason for that - the now much more common inclusion of photographs with drawings. So really, you have to regard photographs in that sense as a part of the drawing set. And in many ways, that's the saving grace of a lot of submitted projects - a decent set of photographs is a very important part of them, and, let's face it, rather easier to do. So as Circlip was saying earlier, you can't just regard the drawings in isolation - annotations, notes, photographs and clarity in the text is just as important. A major skill for an author to have under these circumstances is to be able to put themselves into the position of somebody else having to recreate their work - and I think that's really the key to the whole thing.

<< First < Prev 1 2 3 4 Next > Last >>

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts

*Oct 2023: FORUM MIGRATION TIMELINE*
05/10/2023 07:57:11
Making ER11 collet chuck
05/10/2023 07:56:24
What did you do today? 2023
05/10/2023 07:25:01
Orrery
05/10/2023 06:00:41
Wera hand-tools
05/10/2023 05:47:07
New member
05/10/2023 04:40:11
Problems with external pot on at1 vfd
05/10/2023 00:06:32
Drain plug
04/10/2023 23:36:17
digi phase converter for 10 machines.....
04/10/2023 23:13:48
Winter Storage Of Locomotives
04/10/2023 21:02:11
More Latest Posts...
View All Topics

Support Our Partners

Shopping Partners

Subscription Offer

Latest "For Sale" Ads

Reeves** - Rebuilt Royal Scot by Martin Evans
by John Broughton
£300.00
BRITANNIA 5" GAUGE James Perrier
by Jon Seabright 1
£2,500.00
Drill Grinder - for restoration
by Nigel Graham 2
£0.00
WARCO WM18 MILLING MACHINE
by Alex Chudley
£1,200.00
MYFORD SUPER 7 LATHE
by Alex Chudley
£2,000.00
More "For Sale" Ads...

Latest "Wanted" Ads

D1-3 backplate
by Michael Horley
Price Not Specified
fixed steady for a Colchester bantam mark1 800
by George Jervis
Price Not Specified
lbsc pansy
by JACK SIDEBOTHAM
Price Not Specified
Pratt Burnerd multifit chuck key.
by Tim Riome
Price Not Specified
BANDSAW BLADE WELDER
by HUGH
Price Not Specified
More "Wanted" Ads...

Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues