intruder tolerance on design

[cliff23]

Bye to all,

how should I interpret such a quota: 8.9.

in particular is it in accordance with the rules of mechanical design?

according to logic I should accept the particular if I measured 9.1.

Thank you.

 

[Preparation-H]

Bye to all,

how should I interpret such a quota: 8.9.

in particular is it in accordance with the rules of mechanical design?

according to logic I should accept the particular if I measured 9.1.

Thank you.

Yes, the base diameter is 8.9 (minimum), the tolerance field is .2mm and therefore the maximum admissible diameter will be 9.1

Bye!
p-h

 

[sampom]

Bye to all,

how should I interpret such a quota: 8.9.

so it is a little misleading; We should know what particular reference is and what processing is subject to.
to me generally the decimal quotas and with even decimal tolerance do not like, I seem to be a joke:smile:
I repeat, you have to see the real needs of the piece, but I could put a 9 ±0.1, it seems "more beautiful":biggrin:. the result does not change, field and limits of tolerance are the same and I seem to give more freedom to the performer/measurer. It was a hole, it would be like to say: <Don't go crazy, take the 9-point that everyone has in the drawer. If it is "consumed" or sharp not perfectly, or it turns a little dizzy, good or bad you can stand in.. Take it easy.>>

in particular is it in accordance with the rules of mechanical design?
according to logic I should accept the particular if I measured 9.1.

in "point of law" yes (... should.. but for me I repeat that it is bad).
and yes, at 9.1 is acceptable. But why wouldn't it be? if you are the one who projects only you can know; If you don't like to change and put appropriate tolerance.

greetings
Marco:smile:

 

[meccanicamg]

Bye to all,

how should I interpret such a quota: 8.9.

in particular is it in accordance with the rules of mechanical design?

according to logic I should accept the particular if I measured 9.1.

Thank you.

Hello cliff,
8.9 +0.2 is the short form that is used especially in catalogues in text-only mode and is to indicate:

       +0.2
8.9
       0

therefore the lower limit is zero (thinky) and the upper limit is 0.2 above the nominal.
9.1 falls into tolerance.

Remember that however the field of acceptance of a component governed by tolerance is lower than the indicated tolerance indication. i.e. in certified quality systems the central part of the gauss curve is good, so the extremes do not exist just (restricted field).

 

[PaoloColombani]

I repeat, you have to see the real needs of the piece, but I could put a 9 ±0.1, it seems "more beautiful":biggrin:.

I agree. it seems that the designer wanted to indicate a reference quota with a field of tolerance for some reason all "right" of the reference quota, although for practical purposes the notation "9 ±0.1" provides the same results as being more explicit. in "8.9 +0.2" the field is implicit and could give rise to ambiguity; the "+0.2" could in fact be understood as a supermental for the purpose of a successful resumption of the particular, for example rectification, although there is a specific notation for this purpose.

 

[MBT]

I repeat, you have to see the real needs of the piece, but I could put a 9 ±0.1, it seems "more beautiful":biggrin:. the result does not change, field and limits of tolerance are the same and I seem to give more freedom to the performer/measurer.

I'm sorry, but I disagree.
tolerances must be placed compared to the nominal quota
I imagine, being tolerated, that at that quota you associate another on another piece
I hope it is from trade (8.9 is not exactly a measure from Italians, it seems to me to be 0.35 ") but the nominal share is that and on that must move tolerance
If I checked the drawings tomorrow, I would check the nominal odds and expect to find 8.9 on both designs. if instead on one I find 8.9 and on the other 9 .... I send the first alarm signals!:angry:

 

[Focus]

If I am not mistaken, the din system does not provide 0 in the indications of the scaffolding.

Hi.

 

[innocente]

hi pleasure luca, the quota you indicated for logic rigor has as tolerance the marked measure of departure and then +0.2, here a range between 8.9 and 9.1 included.
Hi.

 

[Meccbell]

Remember that however the field of acceptance of a component governed by tolerance is lower than the indicated tolerance indication. i.e. in certified quality systems the central part of the gauss curve is good, so the extremes do not exist just (restricted field).

or beautiful... This is the first time I've heard her.
Are you sure? :tongue:
no, because then yesterday they went away 5 pieces that had a hole quoted to drawing like d.20 0/+0,02 and that they came practically all to 20,00equalcosa (tooth passes of the zero that enters right, almost forced). :finger:
according to your reasoning (client with certified quality system) should send them back all to lappa to recover at least a half cent.

maybe you're a little confused, in the sense that you exchange the execution tolerances (justly narrower) with those functional or design.

then there would be a speech about uncertainty of measurement and the fact that if you do not use the appropriate tools and conditions can happen that 2 or more people measure the same piece with different class tools or under different conditions and have 2 or more different results between them and also much.
However, this history of measurement uncertainty is also overcome with the system of having constructive tolerances lower than those functional.

Finally, the Gaussian speech is good if you have to make statistical processing for sample controls or to keep the production process under control, especially for series and/or continuous productions.
so that you do not have to wait for one of the limits, simply because when you arrive it means that the process has already gone out of control.
However, in the case of very small pieces or even single pieces, statistics are good only to make all those beautiful colored diagrams that now go so much fashion on the walls of the offices of the responsible quality.
:smile:

 

[PaoloColombani]

tolerances must be placed compared to the nominal quota
I imagine, being tolerated, that at that quota you associate another on another piece

Yes, rightly, just in case the quota was nominal and common reference to one or other details ...

no, because then yesterday they went away 5 pieces that had a hole quoted to drawing like d.20 0/+0,02 and that they came practically all to 20,00equalcosa (tooth passes of the zero that enters right, almost forced). :finger:
according to your reasoning (client with certified quality system) should send them back all to lappa to recover at least a half cent.

and you should turn them back to the drawingtre, perhaps arming him with a nice little scraper, a little blue of prussia and a lot of patience. ...and maybe he will try to download them to the certifying institution or to the standardization institution.
I don't know how many still realize the plan boards first and then move to the executive boards, but your example reminds us that doing academy is not always like doing practice.

 

[Er Presidente]

Finally, the Gaussian speech is good if you have to make statistical processing for sample controls or to keep the production process under control, especially for series and/or continuous productions.
:smile:

quoto, concordo, subscrivo, in short, yes!
:smile:

 

[Er Presidente]

I repeat, you have to see the real needs of the piece, but I could put a 9 ±0.1, it seems "more beautiful":biggrin:.

often the ugly fruit and the beautiful makes it soavi!

to those who put certain tolerances should first give him a hard prison year to dig holes "in tolerance" and then a couple of years on a bp platform so he would clearly have the substantial difference between the ugly and the beautiful.

Hi.

 

[Blackbird]

Hello everyone,

interesting this discussion, I will try to provide a small contribution indicating some normative reference.

I would point out that I fully agree with what has been said by samprom and meccbell.

I disagree with what mbt said.
if I have well understood you mean the nominal quota as a “objective” value. Although it is a statement I have already heard from other sources has no support from any technical norm (iso; cen; asme; uni). the definition of nominal quota is reported in iso 286-1 (= uni en 20286-1): “dimensions from which the limit dimensions are derived by applying the upper and lower deviations”.
therefore the standard uni en iso 14253-1:2001 geometric specifications of products (gps) - general concepts - part 1: model for the specification and geometric verification establishes that the limits of acceptability are those between the upper and lower deviation.
Although, as pointed out by meccbell, the same rule provides that measurement uncertainty and processing tolerances should be estimated (the norm defines them as “limits for declaration of conformity”) should be reduced by a value equal to “2u” (u = extended uncertainty). always the same iso/ts 14253 provides that the declaration of non-compliance (accounting of the customer) must be made by adding to the higher and lower limit values the value of the extended uncertainty.

Finally, as regards mechanicsmg, I confirm that some quality standards in productive areas such as automotive or aerospace provide that the tolerance of the process, in order to ensure good control, must have a cpk>1,33 but this is great series productions.

 

[Blackbird]

I add an annex

 

[MBT]

I disagree with what mbt said.

well... otherwise what taste is there?:tongue:

if I have well understood you mean the nominal quota as a “objective” value. Although it is a statement I have already heard from other sources has no support from any technical norm (iso; cen; asme; uni). the definition of nominal quota is reported in iso 286-1 (= uni en 20286-1): “dimensions from which the limit dimensions are derived by applying the upper and lower deviations”.

I don't care if you have support in technical standards!
you plow a pack of 150 designs and start to beat the odds.... That is my technical norm!
If you find a hole of 90 and you have to put a mouth of 89 on it, you will see that you throw unclean blasphemies if you have to start making the calculation of tolerances to know if actually the bushing enters or not!
In that phase of control, you have to check the nominal quotas. tolerances come later, with those you can play with and you can discuss it.
with the nominal quotas you have little to deal with... .

 

[FlatSix]

I allow myself to intervene even if I'm new to the forum and I can't define myself as a 'designer', but with the tolerances of this kind I compare myself every day.
I do not know the rules in detail, but if in theory I agree that writing 8,9+0,2 is equivalent to writing 8±0,1 or 9,1-0,2, the practical effect is sometimes completely different.
I produce special vines and tolerances I have seen things that you humans... :biggrin:
First of all if in production comes a drawing with writing 8,9+0,2, be sure that from 17-year-old apprentice to technical director with cubic attributes and 40 years of experience, the measure 'percepita' changes.
Who knows how it is, if on the drawing there is written 9.1-0.2 the average of the surveys of the statistical process control is above 9 if the quota is 8.9+0.2 the average is below 9.
if I have to give a commission to the tool that by character is pessimist or that by habit uses the caliber to course in the same way as a demolition bat, I have to put 9,1-0,2: If the tool on the contrary is an extrovert and optimistic, on the design I have to put 8,9+0,2 otherwise the screws will all have a plentiful diameter:smile:
to the precise, I have to write 9±0,1, otherwise the asymmetry of tolerance disturbs him, puts him in anxiety, his need for normality is not satisfied, is agitated and the vine is produced perhaps in tolerance but surely will be stunned:

now risk being banned to life by cad3d.it... :tongue:
and what about the great technical offices, where the super mega designers can not waste time behind the management of the vice and then delegate to the first-hand stage the design of the special screw?
These obviously do not know how to use the cad (or do not let it be used to draw a low-tech object like the screw...) and then make the drawing with paint where the '±' symbol does not exist and therefore the 9±01, must 'necessarily' become 9,1-0,2 or 8,9+0,2.
except then return to the hands of a technician who passes it in the cad, corrects to the flight in 9,1±0,2 or 8,9±2 giving a pyrla to the intern and combining of the disasters of biblical proportions
now bannatemi as well, but I swear on the gloepiere of the bellucci that really happened to me. . .

 

[Er Presidente]

I allow myself to intervene even if I'm new to the forum and I can't define myself as a 'designer', but with the tolerances of this kind I compare myself every day.
I do not know the rules in detail, but if in theory I agree that writing 8,9+0,2 is equivalent to writing 8±0,1 or 9,1-0,2, the practical effect is sometimes completely different.
I produce special vines and tolerances I have seen things that you humans...
First of all if in production comes a drawing with writing 8,9+0,2, be sure that from 17-year-old apprentice to technical director with cubic attributes and 40 years of experience, the measure 'percepita' changes.
Who knows how it is, if on the drawing there is written 9.1-0.2 the average of the surveys of the statistical process control is above 9 if the quota is 8.9+0.2 the average is below 9.
if I have to give a commission to the tool that by character is pessimist or that by habit uses the caliber to course in the same way as a demolition bat, I have to put 9,1-0,2: If the tool on the contrary is an extrovert and optimistic, on the design I have to put 8,9+0,2 otherwise the screws will all have a plentiful diameter:smile:
to the precise, I have to write 9±0,1, otherwise the asymmetry of tolerance disturbs him, puts him in anxiety, his need for normality is not satisfied, is agitated and the vine is produced perhaps in tolerance but surely will be stunned:

now risk being banned to life by cad3d.it... :tongue:
and what about the great technical offices, where the super mega designers can not waste time behind the management of the vice and then delegate to the first-hand stage the design of the special screw?
These obviously do not know how to use the cad (or do not let it be used to draw a low-tech object like the screw...) and then make the drawing with paint where the '±' symbol does not exist and therefore the 9±01, must 'necessarily' become 9,1-0,2 or 8,9+0,2.
except then return to the hands of a technician who passes it in the cad, corrects to the flight in 9,1±0,2 or 8,9±2 giving a pyrla to the intern and combining of the disasters of biblical proportions
now bannatemi as well, but I swear on the gloepiere of the bellucci that really happened to me. . .

admirable!

I was almost tempted to identify myself with the "precise", which I am not, because even to me the asymmetries put anxiety :smile:.

p.s.: from how you write I think we could go very well!

 

[cacciatorino]

admirable!

I was almost tempted to identify myself with the "precise", which I am not, because to me too the asymmetries put anxiety.

You should get through this piscological block, you'd get a lot more chances. :biggrin:

Anyway, all the time I've been presenting car projects, they've looked at me wrong...

 

[meccanicamg]

You should get through this piscological block, you'd get a lot more chances. :biggrin:

Anyway, all the time I've been presenting car projects, they've looked at me wrong...

Of course.

According to me the nominal values must be well defined, that is if it is 8 is 8 and if it is 10 is 10, then it is a h7, a 0/+0.1 or +- 0.5 that is another pair of sleeves but nominally the components must have the same indications.

someone argues that it is uncomplicated on the work centers to find a nominal value with its tolerance rather than a decimal share. they take the number and put it in the car without reasoning. sin that in the end if there are more tolerances and the piece must be relayed several times the result is an abortion

 

[cliff23]

Hi.
thank you all for the answers.
However the quota in question is relative to a crushing on a tube that acts as a decommissioned bow
guides of a seat. the crushing coupled with a fork solidarity with the guide. the problem arises from the fact that the first design indicated the quota without tolerance. was therefore part of the general tolerances indicated by cartiglio ±0.2. Subsequently due to noise problems in the coupling right in this area was issued
an additional design with the addition of tolerance +0.2. So my question was if it was no longer correct at the regulatory level to indicate in the toll both the sup and the inf.
clearly the piece would be functional, that would go to eliminate the noise, if
in practice measured 9.1. that therefore 8.9 would conform to the point that indicated in drawing but not functional.
So could I argue with the author of the drawing? ?
as soon as I can place the drawing in object.