Decoding Abbreviations on a Technical Drawing

[JasonBModerator @jasonb]

I have put a set of Stew's original drawings here which are a lot clearer

[MuzzerParticipant @muzzer]

Posted by SillyOldDuffer on 17/08/2016 19:02:46:

Looking for answers on the web led me to several different drawing standards. What's preferred by Model Engineers?

Doesn't really make much difference as long as you are consistent. But no matter where you come from you should be following BS8888 or the ISO equivalents.

No real need for tolerances in model engineering unless you are doing interference fits, precision threads etc, as it's all basically hand fitted.

In terms of projections, first angle is normal in most of the world but naturally the US / Can / Aus / Japan use third angle. So in practice you have to work with whatever is in front of you. In the UK we are ambidextrous, being sort of piggy in the middle.

[AjohnwParticipant @ajohnw51620]

I don't suppose it makes much difference using cad but with paper and pencil plus a drawing board one makes far more sense than the other as it saves drawing projection lines through a view. As far as I am aware it's been the standard in the UK for a long long time now. A very long time.

John

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[MWParticipant @mw27036]

Posted by Steven Vine on 17/08/2016 18:54:41:

So, bearing in mind this is a hobby drawing, and apart for the unconventionality of JDWs drawings, what is so bad about them? Why is the drawing in question so disgusting and only fit for bog paper?

Steve

 

 

 

I guess it would be annoying if something that was supposed to be quite straightforward was presented to you in the most confusing and laborious way to understand. In that way i think the discussion on drawing "quality" is a bit of a red herring. It isn't really about how good the drawing looks, it's a question of how clearly the information is presented.

For e.g a drawing done on the underside of a beer mat or on a sticky note could provide me with all the information needed to make something, if the information is clear. A very nicely presented set of drawings in a glossy hard back book, if the information is confusing it's useless as a tool.

But other than that, it's probably a case of hyperbolic language. Besides which, i'm pretty sure you'd get fed up of needing to make a drawing every time you needed the loo!

Michael W

Edited By Michael Walters on 17/08/2016 21:07:49

[HOWARDTParticipant @howardt]

When I started draughting some drawings were still drawn on elephants in first angle with waterproof pencils. CAD certainly made things a lot easier if you stuck to the standards that the system imposed on you. I also redraw most parts detailed enough for me to understand the part, at the moment making 3 1/2" Eveving Star and even with the book a 3D model helps.

Howard

[SillyOldDufferModerator @sillyoldduffer]

Seems you have to spend money to get a copy of BS8888 but this overview looks useful.

Dave

[SillyOldDufferModerator @sillyoldduffer]

I like to provide feedback after asking a question. Firstly the people who offer advice deserve some recognition and secondly others may like to know if the advice helped.

In this case a triple thank you to Jason for providing:

• the link to http://www.modelenginemaker.com. This turned out to be an interesting site that I'd not seen before.
• the link to Stewart's build thread on http://www.modelenginemaker.com. I wish I'd read it before starting my own build.
• a copy of the original, clearer, drawings on dropbox

All of these were useful aids to progress,

Yesterday I assembled the engine to check the fit. I would love to report that it turned first time smooth as silk: in fact the engine has several all too obvious tight spots. The worst problem by far is that the crank assembly is slightly bent, a problem I would have avoided had I made the crank the Stewart Hart way, ho hum. I got away with the "Drill After Assembly" mistake; the crank is bent because an 8mm drill wandered, not because the pin holes are misaligned.

I've a few more bits to make before the engine might possibly run. If all goes well I shall be putting air in it later tomorrow. Fingers crossed…

Cheers,

Dave

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