geometric tolerances

[MATT2091]

Good morning, everyone.
I would like to expose my doubts, with the hope that some more experienced users of me can help me.
I have no clear ideas between the tolerance of parallelism and that of flatness. One is a form tolerance while the other of orientation.
nothing to laugh at. question.
when should I go to use the tolerance of flatness and when that of parallelism?
flatness, does it have to do with roughness?
I hope I've been quite clear.

 

[MassiVonWeizen]

flatness refers to a single entity
parallelism refers to multiple entities
neither has anything to do with roughness

 

[TECNOMODEL]

tolerances, shape or size, must be inserted depending on the function of the particular.
An example, trivial, of parallelism tolerance is that for a particular one that should be housed within one seat obtained in another (e.g. a tab). In that case if the faces were not parallel the piece would not rise.
an example of tolerance of flatness can be that of a face on which a particular should be supported, perhaps with an o-ring for a seal.
in that case a tolerance of flatness should be inserted.
planarity has to do with roughness in the sense that it can limit the maximum value of the same.
if the tolerance of flatness is narrow you will not have a high roughness on that plane.

 

[MATT2091]

tolerances, shape or size, must be inserted depending on the function of the particular.
An example, trivial, of parallelism tolerance is that for a particular one that should be housed within one seat obtained in another (e.g. a tab). In that case if the faces were not parallel the piece would not rise.
an example of tolerance of flatness can be that of a face on which a particular should be supported, perhaps with an o-ring for a seal.
in that case a tolerance of flatness should be inserted.
planarity has to do with roughness in the sense that it can limit the maximum value of the same.
if the tolerance of flatness is narrow you will not have a high roughness on that plane.

You were very kind and thank you. But I have a question. if as roughness put 1.6, what value can I do as flatness?

 

[MassiVonWeizen]

as said by technomoof roughness has relatively to do with geometric tolerance.
a tight tolerance almost always implies a processing; the closer the more precise the processing and the machine must be to perform it and consequently the roughness.
So you have to ask yourself the reverse question: for this tolerance that work I have to do?

 

[TECNOMODEL]

the reasoning is reversed, that plan I need has a flatness x for functional reasons, what is the max degree of wrinkle acceptable?

 

[cacciatorino]

the reasoning is reversed, that plan I need has a flatness x for functional reasons, what is the max degree of wrinkle acceptable?

There is no specific relationship. you may have a low wrinkle (for example, a very small tool) but a roller coaster surface because of the tool machine that has the twisted guides or because the piece is badly stirred or because the extension was not done, etc. etc.
The only relationship could be the indication of a wrinkle that can only be achieved with certain types of machines that are by precise definition: If, for example, you indicate ra0.8 you want the surface to be rectified, and in general the grinding machines are very precise.

 

[TECNOMODEL]

There is no specific relationship. you may have a low wrinkle (for example, a very small tool) but a roller coaster surface because of the tool machine that has the twisted guides or because the piece is badly stirred or because the extension was not done, etc. etc.
The only relationship could be the indication of a wrinkle that can only be achieved with certain types of machines that are by precise definition: If, for example, you indicate ra0.8 you want the surface to be rectified, and in general the grinding machines are very precise.

right, but if I have a flatness tolerance of 0.01 I will not be able to indicate a roughness ra 12.5, for example.

if I remember there was a rather animated discussion about it long ago, only that it had ended in flames because of a propensity to the same of one of the participants.
there were, however, if not mistaken, some interesting ideas.

 

[MATT2091]

right, but if I have a flatness tolerance of 0.01 I will not be able to indicate a roughness ra 12.5, for example.

if I remember there was a rather animated discussion about it long ago, only that it had ended in flames because of a propensity to the same of one of the participants.
there were, however, if not mistaken, some interesting ideas.

I meant that. If I insert a flatness I can do without inserting roughness?

 

[TECNOMODEL]

I meant that. If I insert a flatness I can do without inserting roughness?

if you do not insert the face will take the value of general roughness, then at all effects a roughness indicate it.

 

[MassiVonWeizen]

right, but if I have a flatness tolerance of 0.01 I will not be able to indicate a roughness ra 12.5, for example.

precisely, it is the tolerance that determines roughness. or better tolerance determines the process to obtain it and therefore roughness.

to obtain a flatness of 0.01 I must pass to the rectification that does not make high wrinkles /(unless to voluntarily put harassment from blacksmith), but it can be indicated both a roughness from 0.8 and 0.2. both allow fdi to get the result, but the cost is definitely different

I meant that. If I insert a flatness I can do without inserting roughness?

depends on the value of tolerance. a 1mm flatness is obtained in trivial drawn and does not need it, one from 0.1 requires a mechanical processing and can suffice 6.3, one from 0.01 another type of mechanical processing and serves a 0.8 or less.
also a concrete wall has its own flatness which however is in the order of the centimeters.

 

[cacciatorino]

right, but if I have a flatness tolerance of 0.01 I will not be able to indicate a roughness ra 12.5, for example.

.

Yes, we are clearly talking about realistic cases.

 

[TECNOMODEL]

precisely, it is the tolerance that determines roughness. or better tolerance determines the process to obtain it and therefore roughness.to obtain a flatness of 0.01 I must pass to the rectification that does not make high wrinkles /(unless to voluntarily put harassment from blacksmith), but it can be indicated both a roughness from 0.8 and 0.2. both allow fdi to get the result, but the cost is definitely different


depends on the value of tolerance. a 1mm flatness is obtained in trivial drawn and does not need it, one from 0.1 requires a mechanical processing and can suffice 6.3, one from 0.01 another type of mechanical processing and serves a 0.8 or less.
also a concrete wall has its own flatness which however is in the order of the centimeters.

Just what I meant.

 

[MATT2091]

Okay, thank you very much.