Engineering Drawings and Tolerances
Engineering Drawings and Tolerances
(OP)
Does it required (as a rule) that every technical drawings (with dimension) should have specified condition for tolerancing? In other words can some dimension be left without tolerances?





RE: Engineering Drawings and Tolerances
RE: Engineering Drawings and Tolerances
How many percentage of drawings you've been engaged with were completely tolerance-specified?
RE: Engineering Drawings and Tolerances
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Engineering Drawings and Tolerances
As per ASME Y14.5-2009 1.4 A "Each dimension shall have a tolerance, except for those dimensions specifically identified as reference, maximum, minimum, or stock (commercial stock size)."
Dave D.
www.qmsi.ca
RE: Engineering Drawings and Tolerances
It is quite common in my view in the buisness since 1980 to see drawings without proper tolerances specially fabrications and for small production runs. I am not saying this is ideal or the way it should be. We do not live in a perfect world.
Required by who is the operative question. ASME,ISO and I say they should.
Frank
RE: Engineering Drawings and Tolerances
Mike Halloran
Pembroke Pines, FL, USA
RE: Engineering Drawings and Tolerances
Not the first time stuff was made from sketches, I would bet. I would say the majority of the fabrication drawings I have seen imply unrealistic tolerances by the tolerance block impication. Just a fact.
Frank
RE: Engineering Drawings and Tolerances
RE: Engineering Drawings and Tolerances
Frank
RE: Engineering Drawings and Tolerances
There is no such thing as a perfect dimension. Some tolerance is involved in every one, because perfection is only a concept. Deciding what that tolerance should be is a requirement for any "proper" drawing and it can be extremely tight or extremely loose. There is no such thing as a "perfect" dimension, only a range of acceptable dimensions which provide for final design function.
Have you read ZEN AND THE ART OF MOTORCYCLE MAINTAINANCE? This book explains the concept fairly well.
A skilled fabricator can work to a drawing without tolerances on every dimension because they can make allowances for resulting dimensions, but don't expect a large product run with interchangable parts from such practice.
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Engineering Drawings and Tolerances
When you send out drawings, you write up a purchase order telling the vendor to fabricate parts as per your drawing. Your drawing is part of a contract. When the vendor delivers something, you pay him.
If you leave out tolerances or otherwise send out a poorly done drawing, the vendor does not really know what you want. Your ass is not covered when he delivers something that does not work. The vendor probably cannnot take you seriously when you tell him you are expecting high quality work.
RE: Engineering Drawings and Tolerances
I don't disagree with that, such is the state of quaility in our buisness. I just don't see quality improving in many things in my day to day life.
jmas,
I have stated my guess on the amount of drawings out there here: thread1103-265286: pattern positioning, I would love to know what others see.
I have been in this buisness since 1980, I have 4 family members in the drafting/engineering field: My mother (many years befor me), wife and 2 brothers in-law.
The fields are hydraulic power units, specialty machine tools, water treatment machines, aerospace, motors and Oshkosh Truck (the one brother-in law I have the least experiance with as he is new to the buisness).
Frank
RE: Engineering Drawings and Tolerances
Your response is drifting a little off topic. I have started a new thread.
thread1103-265799: Drawing Quality
RE: Engineering Drawings and Tolerances
If you accept the fundamental fact parts will almost never be exact(statistically infinitessimly small chance), then yes.
I see a lot of spec sheets or drawings that are really spec sheets without tolerances.
I've seen a few sketches without tolerances but these were mostly one off 'hammer to fit, paint to match' type situations, often for some kind of test rig or something.
There are a number of ways to do the tolerance, +- on each dim, GD&T, title block tolerance or referencing some other tolerance standard such as ISO2768 or a workmanship standard or something or it can even be a min or max dimension where appropriate.
If you are relying on a separate tolerance standard make sure it is somehow explicitly referenced.
A reference dimension doesn't have tolerances.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Engineering Drawings and Tolerances
That's engineering: determining the window of allowable imperfection. Otherwise, it's just bad art.
RE: Engineering Drawings and Tolerances
For actual formal drawings, I'd say close to 100%. Although, much of this was achieved by reliance on block tols.
If you ask ""How many percentage of drawings you've been engaged with were [s]completely[s] correctly tolerance-specified? "
Then it drops considerably.
Even for my own drawings mistakes happen, especially now we don't have any real checking process, but mine are probably better than anyone else here.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Engineering Drawings and Tolerances
That said, 100% of all specifications need a tolerance zone of acceptability. This doesn't just apply to dimensions, but also performance specifications
Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion
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