yang686526

decimal dimensioning/fractional equivalents
once upon a a time,
i believe there existed a standard/spec which recommended the appliication of decimal/inch dimensioning for designs where allowed, verses fractional/inch dimensioning as much as possible.
that is to say for example, use 6.20 x 4.80 for the sheet size instead of 6.25 x 4.875.
does anyone on this forum have a handle or recall?
i have seen such examples in company drm's, for machined parts but not any published standard.
there was a push for such round offs when decimal inch measurement began replacing fractions for programming and nc machining purposes. often it was metric based people who didn't know or like fractions anyway. don't know or any industry spec like that, however.

what bugs me is not dimensions like 4.312 or 4.413 for
4-5/16", but cad generated dimensions like 4.179. why not 4.800?
ringman,
i do not worry about the standards here. i worry about what my fabricator understands. if they have to take a pencil and a calculator and convert all your dimensions into units they understand, you are driving up costs and errors.
i don't think machine tools work in fractional inches. the displays all are in decimals. if it were welding, i would call the shop and ask.
jhg
i don't fully understand your example. are you asking why don't people round to the nearest 10th of an inch? why do they carry out to the thousandths place? we have applications that are machined to within tolerances that require 3 decimal place accuracy so that they line up with the adjacent part, which is often in another country.
or are you asking why 0.25" instead of 1/4"? that, i think, has much more to do with qa measuring device read-out and cnc-driven machines.
as for a "standard"...doubt you will find one because the construction industry would probably go nuts if you didn't use architectural dimensioning of 0'-1/4" in the us, while the aerospace industry likes decimal or metric units.
let me try again.
i am not suggesting that the dimensions need not be controlled to 3 or more decimal places....
i am looking for old information that i thought directed us away from decimal equivalents to fractions as much as possible. such as .3125 when most likely .3 would do the job.
does that clarify my position? and question?.
try telling the mechanical installation contractor to use a eight-tenths bolt sometime instead of a 3/4"... let me know how that goes...
seriously though, i think that unless a part for form/fit/function requires decimal, i would much prefer fractional.decimal places and ordinate dims if nothing else, the decision to use a 5/16" hole for a 1/4" bolt is simple. if i were using decimal and not driven by some standard/code would i put a 0.31" or 0.32" hole? maybe 0.30" or 0.35" because i like multiples of 5...
-- mecheng2005 decimal places and ordinate dims
hello,
im in a bit of a pickle. any help would be appreciated.is it standard practice to hold all decimal places in a dwg the same? if there are 4 views, for example, should all 4 have the same amount of decimal places or can they vary depending on the importance of the feature?
i know that if the dimension on a part is held at, lets say 3 places, the tolerance for that dim is held at 3 places.
i could be wrong.
one more, is it practical to call out dims on lets say a round part, such as a pulley, to be ordinate dimensions? do machinists and toolers read these easier rather than non-ordinate dims.
any insight would be appreciated.
the number of decimal places used in a dimension normally refers back to the drawing's title sheet where there is often a note (either in the note block or imbedded in the format) saying something like:
unless otherwise specified:
dimensions are in inches.
tolerances:
.x±.1
.xx±.01 (could be .xx±.015 too!)
.xxx±.005
.xxxx±.0005
angles±1o
once you understand the functionality of the part then you'll know which dimensions have to be held tightly and which ones can be held loosely. to keep costs down you want to keep tolerances as coarse as possible.
in any given view you may have any combination of four-place, three-place, two-place, or one-place dimensions depending on the tolerance you wish to impart on a particular feature. these tolerances are often called the "block tolerances" and apply throughout the drawing regardless of the sheet, dimensioning method, or view. if a feature's tolerance has a geometric control (per asme y14.5-1994) then those rules say that the dimension be identified as a basic (theoretically exact) dimension by placing a box around it. in this case the number of decimal places has no significance. i think that if the size of the feature is presented with a three-place dimension then the convention is to write the basic dims with three places.
you could apply a set of block tolerances to a particular view by placing them in the view's caption (unusual but ok) and these would override the tolerances appearing on the title sheet.
as for ordinate dimensioning, this method may be used alone or in combination with any other method (chain, basic, baseline) and the type of part has nothing to do with it. this is very useful by increasing the number of dimensions you can place in one view.
after a while you learn to draw views that look "clean." in such a view there aren't so many dimensions as to make it look cluttered. add a second identical view elsewhere in the drawing if you need to provide more dims.
believe me i've seen drawings where every dimension was held to a three-place decimal. this makes for an unecessarily expensive part while the "draftsman" just didn't care enought to give any thought to tolerances. don't ever make statements such as "this part will be machined. they can hold every dimension this tightly." do not let the manufacturing process dictate how the part is drawn. this practice tends to generate designs that are intolerant of changes in mfg process. for example, a part that is machined in the product's early production may end up being die-cast later on as the demand greatly increases. who wants to be stuck with dozens of drawings of parts that can only be machined? you would be cursing the people who drew those drawings!
tunalover
it is a requirement of asme y14.5 that any basic dimensions and releated feature control blocks be the same number of decimal places. other than that, what tunalover says.
youve been a great help. thgank you. hat tipped.

decimal places required for angles

asme y14.5m-1994 directs the use of decimals and does not address fractional dimensions.
however it doesn't as far as i know say anything about using 'true decimal' rather than the decimal equivalent of fradecimal places required for angles
using y14.5 and decimal inch on drawing, how should an angle of say 25.000 (basic) degrees be expressed. how many decimal places are required?
the standard seems to be a little vague or again i am overlooking.

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2.3.3 angle tolerances. where angle dimensions
are used, both the plus and minus values and
the angle have the same number of decimal places.
example:
25.0° ±.2° not 25° ±.2°
when used in conjunction with positional tolerance, does the positional tolerance have any influence on the number of decimal places?
supposing 6 holes at 60 degrees, with a positional tol of .005 dia. is the angle required to have 3 trailing zeroes? again by the standard?
from a recent thread
while a positional tolerance does determine the number of decimal places in inch dimensioning, i have found no references to it affecting angular dimensions. i have always used only as many decimal places as required to define the requirements, be it none or three.
when the people fear their government, there is tyranny; when the government fears the people, there is liberty.fff"> - thomas jefferson

take a look at 2.3.2 (d) on pg. 25
as far as i know the number odecimal places required with basic anglesf trailing digits dictate the measuring equipment. for example: a dimension such as 10+/-0.1 need to be measured with a caliper having 0.01 accuracy. a dimension such as 10+/-0.10 has to be measured by a caliper or micrometer having 0.001 accuracy.
ctional sizes. decimal places required with basic angles
how is it determined as to the number of decimal places when using basic angles and decimal parts of degree?
(are trailing zeroes necessary?)
by the application.
use as many places as necessary. (rarely more than 2)
do not use trailing zeros.
if you have 7 features equally spaced you can just show the quotient in the box [360°/7] to specify the basic angle.
paul

i always match the basic dim decimal places to its tolerance decimal places, regardless of trailing zeros.
chris
solidworks/pdmworks 08 3.1
autocad 06/08
ringman,
i would rather the trailing zeros were not displayed, but solidworks does not have a setting for that. usually, i set it to one decimal place, just in case the decimal is something other than zero.
jhg
i would use only as many decimal places as necessary. while y14.5 specifies that basic inch dimensions contain the same number as the fcb, it does not address basic angle dimensions.
believe it if you need it or leave it if you dare.fff"> - robert hunter

sw does have a setting to remove trailing zeroes.
since basic dimesnsions have no tolerance, one only needs as many decimal places as necessary to get the precision one needs. trailing zeroes have no effect on tolerances in feature control frames.
on most drawings it does not matter because the angle tol is driven by the title block, i normily keep it set to one place. the only time that i might see it mattering if there is a ± to the angle. if it does matter i would use a slop of some other way of dim the part.
chris
"in this house, we obey the laws of thermodynamics." homer simpson
motorvib, the op is talking about 'basic' dimensions so the title block tol isn't relevant, it's also not +-.
kenat, probably the least qualified checker you'll ever meet...
thetick,
on sw2007, i can remove trdeep drilling gdailing zeros from metric dimensions, which allows me to conform to asme y14.5m-1994. it does not seem to allow the removal of trailing zeros from angles.
jhg
deep drilling gd&t
question regarding gd&t for deep drilling / boring drawing. what is the common practice for tying down an internal bore, taking into account straightness, cylindricity, and 'wander' from start to finish of the bore?
00viggen
eng-tips forums is member supported.
assuming for a metal machined part. how deep and do you need to hold the tol the whole depth, or part of it?
chris
solidworks 06 4.1/pdmworks 06
autocad 06
yes, it is a metal part. the bore is through the entire part. about 12 feet long total.
as the od of the initial stock bar will be turned to a finished diameter, i have usually specified a drift of 0.001" per 1.0" depth. as the od is sufficiently oversized, the total 'wander' of say 0.144" is not outlandish.
my feeling is to define cylindricity on the bore itself, and then perpendicularity to one of the ends.
the finished diameter (after turning the od) would then be controlled by way of concentricity to the original internal bore (difficult to check though)...
what are your processes? are you boring the hole then honing or burnishing to finished diameter? what diameter and depth? i've seen really precise deep bore holes but they have been multiple processes to achieve the critical tolerances.
best regards,
heckler
sr. mechanical engineer
sw2005 sp 5.0 & pro/e 2001
dell precision 370
p4 3.6 ghz, 1gb ram
xp pro sp2.0
nvidia quadro fx 1400
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never argue with an idiot. they'll bring you down to their level and beat you with experience every time.
the od of the stock material is 3.5"
the id of the bore (though entire length) is 2.125"
depth of bore (thru' all) is 12 feet.
hole will be bored, stock od will be turned down to finished diameter 2.875".
as there is sufficient stock od to work with, it should be relatively straight forward to bore the hole, then use the bore's axis as the datum to turn the od. as long as the bore does not wander excessively, and remains straight (or cylindrical) relative to itself along all 12 feet.
depending how the part is used.
you can use projected tol or total runout.
if the part is assembled to mating parts only on the ends you can call out a tighter tol on the ends.
you can use the i.d. as the datum, that is will it will be chucked for turning the o.d.?
chris
solidworks 06 4.1/pdmworks 06
autocad 06
almost sounds like you might want to just control the mininum wall thickness of the tube.
what is the function of the tube?
never did get a definite answer on this one... any further thoughts or comments?
all i am really after is the tolerancing required for the first step in the deep boring operation, which is to drill the hole straight though the bar. all the finishing is handled by another drawing. i just want to have a drawing that is easily understood and can be inspected with minimal difficulty for the first boring op.
my thoughts have been somewhat mixed, including: perpendicularity of a cylindrical tolerance zone (specifying an allowable deviation of the axis per unit length) to the entry or exit plane. also cylindricity appeared to be somewhat sensible, but prohibitive to inspect.
i can see runout being useful on the finishing drawing, but not necessarily of any use on the initial operation as adeficiencies in y14.38 - abbreviations means of putting a bound on the allowable drift.
someone out there must do deep hole borings for a living and have this done to a fine art!
the tolerancing should normaldeficiencies in y14.38 - abbreviations
anyone else get annoyed by some of the obvious words and abbreviations omitted in y14.38. especially those that were in y14.1 before it was replaced.
for example container isn't in 14.38. in y14.1 it was apparantly cntnr.
make that y1.1 not 14.1.
haven't noticed. my employer's too cheap to provide either y1.1 or y14.38. instead i use mil-std-12 which is dowloadable free from the internet.
tunalover
mil-std-12 is pretty out of date, but i guess better than nothing. what asme y14.38 has done is remove all the slashes and dashes from abbreviations and acronyms, as well as delete several of my favorite and most useful abbreviations. why??? that is why, as long as i'm doing commercial and not military anyway, i still use the good ones that are in asme y1.1.
ultimately, i've seen companies develop a colloquial system of abbreviations which are meaningful internally, regardless to what standards exist.
matt
cad engineer/ecn analyst
silicon valley, ca
then there are acronyns, of which many industries (especially mine, the semiconductor and metrology industry) are full of.
abbreviations, if not in an industry standard or a disseminated company standard, should be initially defined on the drawing or document, then used after that.


ly be driven by the function of the finished part not the process to be used to make it. obviously you need to make sure the tolerances you ask for can be met but hopefully you get the point.
as such without knowing the effect on the finished part & assy it can be difficult to answer a question like this.
if all you really want to do defining tangency with gdis maintain a minimum wall thickness for later machining why not consider positional?
if minimum thickness is all that is required, which appears to be the case, specify that and forget all the other 'stuff'.
defining tangency with gd&t?
i have a solid cylindrical part with a diameter of .375" and a sr.275" at one end with a blend radius of sr.050" between the dia. and spherical radius. the sr.275 and sr.050 blend radius must be tangent, but we cannot figure out how to specify this with gd&t without having an unreasonable profile tolerance. the boss wants a profile tolerance of .0001, but the .275r and .050r can vary +/-.002 each. any ideas?
can you show a pic to be more clear? from your description, i think i would call out the sr .275, but leave the .050 as a fillet or radius callout r .050. then add a note on the dwg that all radii/fillets to be tangent and free of burrs. (or something like that).
hard for me to tell without a pic.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
first, you can't have a sr to blend a cylinder and a spherical dia. that is just a regular old fillet radius. call the radius out to blend--in other words, don't define a center point for it, just the radius. a fillet radius by definition has no steps. it starts tangent to one surface and ends tangent to the other. to nail it down (if it is critical that there be no steps) do as chris suggested and put in a note that there can be no steps, or that there must be a smooth transition.
actually, a fillet radius isn't specifically identified in gd&t and is called out with a standard r symbol. as of y14.5m-1994, a radius can have a step unless it is a controlled radius (cr). y14.5m-1994, section 2.15, fig. 2-19 shows that the controlled radius cannot have any flats or reversals, and must be tangent at the ends of the radius. a radius marked with just an r symbol can have flats and reversals, and therefore does not need to be tangent at the ends (fig. 2-18).
the difference is not typically a concern until finer toleraces are needed, then use a cr along with a suitable sizedefinition of north elevation tolerance. i love surface profile, but this isn't a good use for it as it sets up a symmetrical tolerance zone which conflicts with the cr tolerance zone.
this was not the case in '82, when cr did not exist and r had the meaning that cr now has. (fig. d-2)definition of north elevation
can someone tell me where i might find the exact definition of an elevation? such as "facing the side that faces south you are at the north elevation".
i could use a document stating this.
thanks
a north elevation is the one facing north. ie. as seen from the north.
i thought that was it but i need to quote a spec or document - do you know of one?

hope that helps.
jim sykes, p.eng, gdtp-s
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cad-documentation-gd&t-producdegradation of drawing standardst development
good update, jim!


degradation of drawing standards
ok i am not old old school because i didn't start on the board but has anyone else noticed the degradation of drawing standards? i think this really boils down to the use of cad. now that most packages have become easier to use (unlike the early versions of pro e & mdt) i think more people are creating drawings. things i see a lot of are missing hidden lines (i understand clarity reasons), lack of centerlines, dimensioning with disregard to intent (like not coming from datums), lack of tolerance consideration (like 3place decimals throughout), dimensioning to hidden lines, poor overall dimensioning & view layout, over crowding, etc. and god forbid they try to use gd & t.
i must just be getting older and grumpier...

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chancey:
i am in agreement with you totally.
i do a lot of training in gd&t and also blue print reading. i re
every drawing i see from every vendor i deal with is crap.
some are less crappy and some are more crappy - but all are crap.
chancey, i agree (well maybe not on the hidden line thing) and i too don't date back to using a drawing board in anger.
i was brought to this company as part of a team trying to improve this. it's been a long hard struggle and now it appears we may have finally lost.
despite proving the benefit of higher quality drawings/checking by reduced eco count on programs that were checked it appears we may have lost the fight.
we've been suffering in the current economy as well as some questionable management decisions and now managements big idea seems to be to give our vendors any old crap drawing and expect them to fill the voids because 'they're hungry'. how the #@$%#$%!#$% they're meant to know the design intent, required tolerances is beyond me & it's all tied in with wanting to outsource/offshore more and more work.
i think our ceo's wet dream would be him as the only us employee just having to phone the relevant subcontractor in whatever country he can find the cheapest sweat shop.3
rant over..... for now.
kenat,
drawing standards are not taught in school and managers that are not experienced in engineering or drafting don't care or don't know about them.
therefore, a don't care or lazy attitude take precedence.
with jobs being global now, standards are mixed and some become overwhelmed or confused, sometimes raising costs for various reasons.
i don't see it getting better in the near future.
chris
solidworks/pdmworks 08 3.1
autocad 08
the standards are the same. compliance is dwindling.
i agree with everyone else on this. not sure how to enforce it though as many don't see the problem.
amen, amen and amen. a mend is virtually imposssible.
this subject has been visited many times before on these fora, and it's true. with the advent of cad, management figured that the engineers could now do their own drawings, as the required skilss for board work were no longer necessary. the only areas that this is true are maybe line work, lettering and descriptive geometry. they neglected to factor in the ability to put a lot of information in a small area, keeping it easy to understand and not open to varying interpretations.
i am currently checking a mold drawing and design created by a contract engineer. it is obvious he does not understand gd&t basics. he used first angle projection, odd scales, lower case lettering, included unnecessary fabrication instructions, used vertical text, unassociative dimensions, poor tolerancing, etc... and i have found this to be quite common.
the basic design, however, was good. the only thing i found that i would change is a #10-32 threaded hole he made 1" deep for a shear application.
i spent enough time on the board and had enough blood spilled on my drawings to have an appreciation of a good drawing and you're right, they are becoming rarer than hens teeth.

the ambassador and the general were briefing me on the - the vast majority of iraqis want to live in a peaceful, free world. and we will find these people and we will bring them to justice."fff"> - george bush, washington dc, 27 october, 2003

was drafting ever rigorously taught in college? i recall being taught the basics. my present knowledge comes from reading all the literature i can get my hands on, including the standard itself, and taking extra courses.
how many companies and organizations have mechanical design and drafting as their primary expertise?
i suspect that many if not most companies were started by product experts or salespeople. mechanical design got added later. a major problem with mechanical design is that it looks easy. everybody understands what plates, gear and screws do. there is no need to start off your mecdepth of a cb hole on a inclinehanical group by hiring someone experienced and competent. by the time someone experienced and competent gets into the office, standards have become low.
about twelve years ago, i was sent out for unix system administration training, so that i could manage the cad sdepth of a cb hole on a incline
hello all,
i am looking for standard definition of depth of a cb hole on a inclined surface.
for e.g., i have a triangular gusset. i have a cb hole on the inclined surface parallel to the base. so the depth of the cb hole varies from a min. value to a max. value. so when i do a hole callout annonation in a drawing for a cb hole what should the depth be? min. value, max. value or value at the center? what is the standard manufacturing practice?
and is there any standard that defines this and what is it? any help would be really appreciated.
regards,
i dimension this type of hole in a section view so that i can reference a surface from which to measure.
i agree with ewh. you can dim from a surface or a defined point. the min, max, etc is up to you.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
ewh and chris,
thanks for the quick replies. section view makes sense.
so a regular cb hole callout using a cad software would be ambiguous and incomplete?
if not how is the machinist going to interpret it?
regards,
ps: i have used "a" instead of "an" before an vowel in my previous post. sorry, it was a typo
quote (gunt):
so a regular cb hole callout using a cad software would be ambiguous and incomplete?
if not how is the machinist going to interpret it?
can you clarify? how can it be ambiguous and incomplete using cad?
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
as explained in my above example, i have created a cb hole using solidworks hole wizard and made the drawing of the part. and called out the cb hole using "hole callout" annotation of the software.
the callout is as follows:
<dia sym>hole thru
<cb sym>cb hole <depth sym> depth of cb head.
the depth you obtain is the max depth by default(if no subsequent operation is performed on hw hole).
but some machinists i talked to say that the depth should have been "value @ center of cb" not min or max.
hope this clarifies.
it should be a nom depth by default. then dim it on the dwg with tol.
but, depending on your design, it could be called out as min or max. i don't know what the cb is used for.
create your holes, make a sect view, then dim dia and depth.
your callout looks good to me. draw a centerline thru the center of the hole on the dwg. the machinist should never have a problem with it.
i hope i understood you correctly and i made sense.
chris
systems analyst, i.s.
solidworks/pdmworks 05
autocad 06
the problem with measuring from the center is that the center point no longer exists when inspecting. the machinist may want to machine it that way, but i would get the opinion of an inspector as to how it should be called out on the drawing.
this is one of those situations that are not always covered by today's cad packages.
look at your application to determine how to best dim the cb... for example
1. the cb is for a socket head cap screw, and you do not want the head exposed, well then, a min depth will be your guide.
2. you are using the cb to fit a bushing. you don't require an amt lenght of bushing, but you must maintain a minimum wall thickness on the machined part... then you should specify a max depth, and trim the bushing.
there are numerous examples where only experience will tell you which way to go... but hey, that why we get paid the big bucks right?
wes c.
------------------------------
when they broke open molecules, they found they were only stuffed with atoms. but when they broke open atoms, they found them stuffed with explosions...
i am sorry if i created any confusion by calling min. and max. depth. i am not talking about "tolerances". and i definitely understand " design intent" and know how to accomplish it.
my question relates to a depth callout of a "variable depth cb hole" and how does one interpret it.
i have obtained 3 different answers and unable to find a standard definition of depth in case of a variable depth hole.
here are the three answers:
1. depth is measured from the point where a full cylinder of the feature is defined aka min value of the depth ( not tolerance).
2. depth is measured from the center of the cb hole cause it is to where the location of the hole is measured.descriptive geometry
3. depth is measured from the point the probe makes initial contact aka max value of the depth.
so my questions are "if i specify the cb depth (of a variable depth hole)o n my print how is the machinist/inspectodescriptive geometry
does the cad systems do descriptive geometry as we had to do manually years ago?
eng-tips forums is member supported.
which cad system?
by "descriptive geometry" i assume you mean the construction or witness lines used to create alternative views of an object?
if so, then i don't know of any cad system that does that automatically. why would they need to? are you looking for the artistic effect? any cad system would be able to easily create the construction lines manually.

i agree with cbl.
are you currently using cad?
also, you may want to red-flag your other thread. you entered it twice.
chris
solidworks/pdmworks 08 3.1
autocad 08; catia v5
with 3d modeling, there is no reason for a cad system to do descriptive geometry. it is my understanding that the purpose of descriptive geometry is to manually develop various projected views. if you need to show examples of how views are developed using descriptve geometry, you will have to place your desired views and manually add the witness or construction lines.
the ambassador and the general were briefing me on the - the vast majority of iraqis want to live in a peaceful, free world. and we will find these people and we will bring them to justice."fff"> - george bush, washington dc, 27 october, 2003

i used descriptive geometry back in 1955 to determine if the tubing around a rocket motor would run into other tubing. i'm just wondering if there is a need for drafters and designer to take a class on this subject these days.
maybe a fairly brief explanation but any cad which incorporates 3d modelling to generate the drawing views probably removes the need for a detailed class.
on the other hand, if they're stuck doing 2d then maybe it's of use.
kenat,
i don't know if classes exist on the subject anymore, but if there is it wouldn't hurt to take it. it's not needed though for cad.
chris
solidworks/pdmworks 08 3.1
autocad 08; catia v5
while it is an essential skill to have for manual or 2d drafting, drafting boards seem to be going the way of the buggy whip. personally, think it is a worthwhile subject of study, but i don't think that there is much demand for it in today's design environment. though if we wake up one day and everyones computers don't work, it will be a valuable skill to have.
the ambassador and the general were briefing me on the - the vast majority of iraqis want to live in a peaceful, free world. and we will find these people and we will bring them to justice."fff"> - george bush, washington dc, 27 october, 2003

ewh,
that has happened to me a lot. i wake up and the stupid computer doesn't work!
...then it's back to the drawing board!

chris
solidworks/pdmworks 08 3.1
autocad 08; catia v5
whitmiregt,
most cad systems offer an option to use a grid when sketching in the 3d model and the 2d drawing. the grid lines could effectively be used to do what you are asking.

descriptive geometry was the graphical method of developing a "true shape" view--i.e. a view perpendicular to the surface--that is not an orthogonal view. with solid modeling it is about as useful as using trigonometry to find an angle or a length. the computer does it faster.
r going to interpret it? min value, max value or the mean value. or the callout incomplete without a section view? and what standard defines it and where can i find it?"
i appreciate the discussion guys. thanks a lot.
if you use a section detail of the hole as ewhfff"> stated there is no room for misinterpretation.
i think there is a world market for maybe five computers.
thomas watson, chairman of ibm, 1943.
tations. once i got into the administration stuff, i was amazed at the complete lack of supervision. everyone tried to micromanage my mechanical stuff, at which i had more than ten years of practical experience. my system administration was two weeks of training plus a month's experience, and i could not get supervised even if i wanted to. design basics
jhg
nothing like opening pandoras box. it takes the sting off a bit knowing that others share in the pain!
design basics
i posted this in another forum earlier and realize this was probably the more appropriate location. if you come across it twice, i am sorry for the confusion.
i have a designer who is self-taught autocad. in that respect, he is not bad, but he was never taught the basics of design. simple rules like eliminating doglegs, text size, hidden lines, scaling, and the like, are beyond his comprehension. my attempts to teach him these concepts have not been embraced. i have a dozen textbooks that describe these concepts, but this man is not going to read a book. he also will not simply comply because i say it is so; he insists upon seeing why it is correct and necessary. this has proven a difficult challenge since, as i mentioned, he will not read a book.
can anyone recommend some smaller texts where these guidelines might be complied with explanations of why this is proper practice?
thanks
sc
find a job or post a job opening
asme y14.5m 1994 is a good place to start. if he does not want to follow it, it is a good time to find someone else. imo.
chris
sr. mechanical designer, cad
solidworks 05 sp3.1 / pdmworks 05
first off, we are talking about the basics of drafting, not design.
if you are in a position of leadership over him, and your engineering department has standard drafting practices established, he should follow. if your engineering department does not have drafting practices established, it's well beyond the time to start to identify them. train your department to follow what has been established and agreed upon. this would include standardized templates and settings for all software (auotcad) being used in the department.
sounds like he needs to learn to step-off his high horse, remove his "designer" cap and put on his "drafter" cap if he wants to produce his own drawings. if he can't understand the value of following industry standards as they are related to drafting practices, he has no business working with production drawings.
i think there is a world market for maybe five computers.
thomas watson, chairman of ibm, 1943.
"blueprint reading basics", by warren hammer.
one of my most frequently turned to references for drafting questions. my first edition has a friendly orange cover, but i see on amazon that the second edition has a nice sky blue cover.
i agree with the other responders, if he can't or won't follow industry or internal standards he is a liability, not an asset.
document your attempts to teach him; when, what, how and the results to protect yourself when the time comes....
madmango a for your reply
best regards,
heckler
sr. mechanical engineer
sw2005 sp 4.0 & pro/e 2001
dell precision 370
p4 3.6 ghz, 1gb ram
xp pro sp2.0
nivida quadro fx 1400
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"there is no trouble so great or grave that cannot be much diminished by a nice cup of tea" bernard-paul heroux

sounds like a very difficult situation. with any program like autocad, solidworks, or any kind of simulation program, one has to have a strong desire to learn it. otherwise they will fight you till they wear you down, and any difficulty or anything that goes wrong they will make sure you know it. i was there when cad came in and some of the guys on the board had to be told to use it or hit the gate. you never get full productivity out of them.
like others are saying, if he won't open a book his mind is closed. good luck.
i have that problem. there are approx 10 users here that went to the same training i did several years ago and still can't cope with the basics. i am done with baby sitting them. i am now 95% finished with writing a sw/pdmw procedure to give them and wash my hands with daily training. i know if we were to ever have a layoff, i know who will most likely be staying and who is going.
chris
sr. mechanical designer, cad
solidworks 05 sp3.1 / pdmworks 05
my solution would be to dismiss him and hire a greenhorn with drafting skills but no design or electrical knowledge. if i could have someone who understood the basics of drafting and could operate autocad, i can teach them everything they need to know about electricity.
however, this is not the challenge i have been given. perhaps i am asking the wrong question. i have references for the standards that he needs to be practicing. i can summarize them for him. how do i get him to embrace them though? until now, every attempt at such has been met with resistance. i have been told that those are antiquated rules that were only important before the computer age. do you have any suggestions on how i can explain why these are not just arbitrary rules intended to make the job more tedious. thus far, my best explanation has been to show him how much better the drawing looks if you follow these rules and how it is easier to read. he is not getting it.
thanks
sc
i would simply keep bleeding on his prints until they met the standards. don't sign off on them until they are correct. sooner or later he is going to get tired of working on the same drawing. that is how i and many others learned proper drafting. it may make the checker unpopular, but i owe my skills to those red marked prints and still think of those checkers with much appreciation. it is unfortunate that in todays engineering environment drawing checkers are becoming a thing of the past.
i agree with ewh. also, after you have a correct drawing to your standards, make a copy of it and have him use it as a template.
you can also explain to him ydesigningengineering directly in cad softwareou are the boss and you have to follow company standards. if he doesn't like it, write him up, give him a warning.
chris
sr. mechanical designer, caddesigning/engineering directly in cad software?
hello,
i'm interested in the way people look up to designing issues in a cad environment (especially mechanical design but i think the issues are always the same - also in other disciplines).
i hear a lot of managers complaining that the engineer spends to much time in putting his ideas en calculation results into the cad software. it would be more interesting to do a lot of the designing and engineering in 鈥渁n other way鈥? this then should give the advantage that in a late state of the design process the proper cad/cae/cam tool could be chosen. another advantage that we are looking for is that a senior engineer could do the real design/engineer work a pass this on to a junior engineer who could do the detailing of the engineering. the problem in this context is the transfer of the knowledge between the senior en the junior engineer. this sometimes costs so much time (and is a source for errors) that in practical terms the senior engineer very often also does the detailed work鈥?br>
my question to you is now:
do you have experience in this matter? or does may be somebody know some kind of study cases that cover this issue?
i would also find it very interesting to hear your opinion in this matter.
please feel free to react!
find a job or post a job opening
in my experience, usually the senior engineers are the ones with masters or phd's. they have the original ideas, pass them down to the engineers who do the design/testing. then passed down to the designers for details design, then do the drafting themselves or pass on to drafters. some engineers do the prelim cad work then pass to the designers to complete it and draft them. it all depends on the size of the company and the type of work. with solidworks/cosmos it works well.
cadtrainer,
at the mechanical level, i do everything from design concept to fabrication drawings and specification controls.
back in the days of drafting boards, i concluded that the way to be efficient was to at least try to generate final, official documentation from the very start. i would plan would plan to convert my design layouts into assembly drawings or arrangements. one of the big failures with mechanical design from what i see is that people fail to generate assemblies and parts lists. for design layout, there is no substitute for scale drawings and models.
if you are doing to do all your design outside of cad, you might as well buy the cheapest edition of autocad. your drafter can read the napkins the engineer has been scribbling on, and transfer the information to a pretty drawing.
for the $5k(us) it costs to bring in medium level 3d parametric cad, you should anticipate that design gets done.
jhg
from my point of view - the engineer aquires the work and provides the concept, the designer makes the concept physical (develops a 3d model which includes routing pipe and fitting choices, etc) and the drafter takes care of document production (editing, refinement and revisions).
hello,
thank's for your replies.
what i would like to add to my question is how dou you setup a efficient way to share information/knowledge between for example the designer and the drafter?
in my environment a lot of work is done by the designer because in the time he has handed over the work to a drafter all the work allready could be done...
thank you for your reactions,
pw
quote (cadtrainer):
in my environment a lot of work is done by the designer because in the time he has handed over the work to a drafter all the work allready could be done...
for that matter, i have worked with too many drafters where it took more time to check and correct their work than to just do it myself.
such seems to be the case in many places. my theory is that competent drafters quickly become designers, while less-than-competent drafters...
customer satisfaction, while theoretically possible, is neither guaranteed nor statistically likely.--e.l. kersten
how many companies still have drafters? every company that i have worked for in the last 10 to 12 years, the engineers do the design and drafting of new products. if the company had any draftsmen they were usualy dedicated to document control and handling eco's. with the advent of cad and especially solid modeling the need for draftsmen has diminished.
i started out as a draftsman right out of high school in 1976. back the in the pencil and paper world, there was more of the traditional structure, engineer, designer, and drafter. in the early part of my career i did work for companies(commercial and military)that had this hierarchy.
most of the companies i have worked at within the last 12 years have tended to be smaller and the engineers did thier own detailing. actually, i worked at lucent for a time before the telecom bubble burst and i still did my own details.
i have been saying for the last 8 years that the concept of a drafting pool is a dead one. this was proved two years ago at my company where we had a new engineering director, one with a dod and general electric background. he proceded to restructure the department into something he was familiar with. he took a lot of good designers and bumped them down to "drafters" to create a drafting pool. he then took all engineers and made them design engineers, regardless of experience.
he wanted all design engineers to do the designs and the drafters to do all the detail drawings, with redlines being used as the means to correct problems. it did not work, but we suffered through it for several months. many of the newly created designers were not familiar with the cad system, some having no experience at all. many of the drafters were happy to correct redlines, considering that they were still being paid $20-25 an hour.
the director resinged a few months later (we think forced) and the department was reverted back to the was it was, sans a few good people that left during the turmoil. in this day and age of 3d design, engineers need to be cad operators and the traditional drafter needs to not only be a cad operator but be willing to do learn and apply a little engineering as well.
i'll agree with thetick, competent drafters often become good designers. the ones that fall short soon find themselves stuck behind a stack of eco changes to process.
i think there is a world market for maybe five computers.
thomas watson, chairman of ibm, 1943.
computer aided drafting?/design?/documentation?/development?
also what area of mechanical?
in construction of facilities, mechanical designs vary considerably.
older engineers tend to design on the back of a napkin then give to a secretary or draftsman to place into autocad/microstation.
younger engineers are probably more intuitive with pc based tools and fea software.
recent college graduates probably can communicate more efficiently via autocad if they comply with past drafting and filing standards.
a certain amount of professional wherewithal also dictates what elements are included in a biddable design and what's considered a shop drawing. depends on the client, owner, customer, situation.
aia/csi a/e/c cadd standards don't even comply with database normalization standards which a graduate it/compsci student from stanford might associate with donald gray's transaction processing. those standards, though, are detailed enough that a separate documentation/draftsman is probably required to keep the layers, groups, elements, and other information well organized per contractual requirements with government entities.
practically, the engineering professional must retain wherewithall in the design process. the final drawings and specifications are merely formal methods of communication publicly recognized as professional correspondence.
one problem with computerized designs is the same as architects had with 'cut & paste' for many years after the copier came out and before computer technology. each particular project needs a professional to devote due diligence in assessing the problem and communcating thew proposed and designed solutions.
today, there are many, many off-the-shelf solutions to problems which used to require professional problem solving.
many of the designs i see today in facilities are off-the-shelf designs which either require a seasoned engineer in multiple disciplines to troubleshoot or accept without question. the codes and regulatory issues tend to dovetail into one another, so there is little difference in suburban new england, suburban new mexico or hawaii. some have more micromanaged regulations or local codes, but it never substitutes for simple professional wherewithal.
ideally, today's engineer needs a $200/year cad program subscription to install on whatever machine he can access. he needs to be able to access a pricing/estimation database such as mean's or sweets, run schedules attached to his designs, compose details with attached lisp or macro based excel spreadsheets to run a standing cost estimate, a separate linkable calculation design space parallel to model space and paper/plot space.
at present, autocad still has the entire industry racked up on a constantly changing overpriced application inhibiting professional growth, which doesn't even normalize the elements of information and data management. it's a good package, but considering they've been around for over 20 yrs and have never charged less than about 10 times market rates, i have no doubt autodesk has done more to impede the professions than to promote professional wherewithal.
mean's is far more respectable imho. ms office has become a defacto standard, but if i did it,..i'd get autocad, office, access, mean's and tool up accordingly. use linux where possible and keep your eyes open for something that will generate a .dwg/.xls/.doc/ file format in odbc for your professional tooling-up at least cost with the most open design.
next big step i see is digital cameras and photogrammetrics coming into play. 2 shots and generate an autocad as-built in 3-d.
pes and architects still needed for the professional wherewithal to identify the actual problems and communicate appropriate solutions.
madmango, i agree with your last statement.
however... i believe that you just can't be a good drafter without some engineering knowledge. the several places i've been employed as a drafter, it was not only expected that we should create the drawings, but also that we should know how to do tolerance studies, how to decide what kind of geometric tolerances to put on a part or assembly, the whole eco riggamaroll, and we were also encouraged to check the designs for flaws!
i don't think the drafting position is going anywhere. i think that the expectations of drafters is changing.
i see the engineers doing the number crunching and much of the conceptual stuff (although not all of it) and the drafters doing the rest (solid modeling, fine tuning of the designs, drafting, etc.). designer... drafter... who know's which is which anymore.
i agree with you mechct, you must have missed a line in my 31dec04 (so long ago) post.
quote:
in this day and age of 3d desdesignmanufacturing notesign, engineers need to be cad operators and the traditional drafter needs to not only be a cad operator but be willing to do learn and apply a little engineering as well.
rereading this topic, i see that we never did answer one question:
quote (cadtrainer):design/manufacturing notes
after moving to a new state i found that i no longer have my files of designs and design notes.
can i have some samples of standard or suggested notes for my documentation for plastic parts and tooling? i work for a blow-molding company and i'm updating their drawings and need correct notes.
thanks
1. this drawing is prepared in accordance with asme y14.100-2000. all dim and tol per asme y14.5-1994 unless otherwise specified.
wes c.
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light travels faster than sound. that's why some people appear bright until you hear them speak.
they found them stuffed with explosions...
[/i]
your new company should already have notes. also, ask some of your vendors if they have any.
chris
systems analyst, i.s.
solidworks 06 4.1/pdmworks 06
autocad 06
we also put all that stuff plus asme screw thread specifications (so we don't have people checking threads with nuts and bolts), packaging, workmanship and other requirements into a quality manual that we provide to all our employees and suppliers who then must sign off that they read and understood it. then we cite the manual on our drawings just in case we left anything out. works well for us.
it was quite an eye-opener when we implemented this. we had vendors calling us saying things like "we don't have a copy of asme b1.1 or asme y14.5" and our answer would be "better go buy 'em, bub. here's the website."
very common. a lot of companies do not use the specs, or even care about them.
chris
systems analyst, i.s.
solidworks 06 4.1/pdmworks 06
autocad 06
either in the title block or in a note you'll want to specify what units you are using.
haven't done much molded plastic parts, don't know if global surface roughness, burr removal etc is really relevant.
i like what john says about screw threads, definitely reference the spec if you have threads, even though the standard only recomends it.



what i would like to add to my question is how dou you setup a efficient way to share information/knowledge between for example the designer and the drafter?
we handle this transfer of knowledge by using a project notebook that contains all design notes, sketches, communications and other data, but nothing beats good 'ol verbal communication and comprehension.
i think there is a world market for maybe five computers.
thomas watson, chairman of ibm, 1943.

solidworks 05 sp3.1 / pdmworks 05
if the guy cannot do the job and does not want to learn show him the door, i am sure many others would jump at the opportunity.
if this is not an option and he insists on drawing without hidden lines and with dimensions crossing all over the show, let him take one of his drawings on the shop floor and be with the guy who is trying to build it.
i have always found those guys are more than happy to point out the error of my ways and what a fool i am

i've seen similar somewhere ringman but i don't think it was in a standard.
kenat, probably the least qualified checker you'll ever meet...
thank you kenat.
im with you and your answer assures that i am not totally bonkers perhaps but still looking for the lost spec. i do believe it existed at one time. thanks again.
it sounds like you're looking for guidelines with regard to "preferred numbers" (
the previous post should read "ansi z17.1", not "asme b17.1"....