conversion inches to millimeter

[Mauriziol]

Good morning, everyone. .
I would like to ask you for help!!
I received a drawing from an American customer in inches and I have to redesign it for colleagues in production for feasibility analysis.
in the conversion phase come out of the dimensions to 3 decimals and I would like to know if there are reference rules (to be mentioned to the customer) that allow to round these values.
it is a stainless steel fitting.
Thank you.

 

[TETRASTORE]

you can find references to the topic you propose on various network documents more or less updated.
one of the first, a little dated, obviously dating back to the period of introduction of the system to which, inevitably, even the countries that use the vetusto and anachronistic anglosassone system have had to adapt is themetric asthma design (see page 5 with a little practical example).
subsequently, the same institution issued theastm si 10-2002 (see annex b - p. 47).
I have found international standards as regards eu iso 370-1975 - conversion from inches into millimetres and viceversa.a more complete document is of in: (metric) handbook where the part you are interested is: 8.3.2 interfaces of different measurement units on page 95 where you can also see examples of drawings quoted with the dimensions and roundings in the two systems.

 

[Mauriziol]

Thank you very much

 

[Mauriziol]

Thank you.

 

[ragnol]

@terastore It is not exactly the same thing, but using two measuring systems (international and imperial) cost to the nose the mars climate orbiter...two spikes.. .

question from naive: considering that in practice "only" (it is done to say) canada, united kingdom, united states, birmania and free use the imperial system, how is it possible that they have not yet passed to the metric?

demand from naive and also a little tonto. maximum, "only" the countries of the commonwealth have the guide to the left. I often wondered: what cost (€, €%) has, for all automotive homes (car, truck etc) having to produce the "specchiati" models? of course the mirror parts are only a few, but...cruscots, weed and steering box with relative steps/looms, etc...

 

[Fabietto]

@ragnol on the speech cars with right driving, I believe that the automotive houses pay additional costs in part on the driving cars dx, and in part on those left driving.
So, in my opinion, we pay all of us buyers (guide sx and dx) those costs.
However quiet, the automotive houses are the last to put us back. . .

 

[TETRASTORE]

@tetrastore is not exactly the same thing, but using two measuring systems (international and imperial) cost to the nasa the mars climate orbiter...two ears.. .

is true and 'only' for a failure to convert data from the base (in n) and those managed by the module (in lbf); There was no effective communication between companies that participated in the project.

question from naive: considering that in practice "only" (it is done to say) canada, united kingdom, united states, birmania and free use the imperial system, how is it possible that they have not yet passed to the metric?

changing habits involving both the productive and economic world requires a lot of time, as an example, it is enough to think that since the introduction of the international system in 1961 the various industrial companies have employed more than 20 years only to change the symbolism in the catalogs (e.g. kgm > nm, hp > kw and rpm > min > min-1) maintaining also for a certain period the double symbolism not to confuse customers.
The British are conservative, for which, even if they had adopted the system paralleled their Anglo-Saxon, a condition necessary to be admitted in the ue, after the brexit, boris johnson took a step back taking away his fellow citizens the obligation to use the double system.
This is still possible because the British economy still suffers little from the influence of the EU market and other countries being still very linked to the United States, Canada and some smaller countries.
It will take a few decades but the process of change has already begun in the United States and Canada as, using imported products, machines and plants and wanting to increase their economic presence in other countries, they are forced to adapt.
I quote as an example the export of transmission organs and other mechanical organs towards the uses for which, up to twenty years ago, it was necessary to build trees and interfaces with measurements in in inches and now, often, are accepted with metric measures instead, now they are forced, to sell in eu, to manage double production.
There remains a speech apart from the voltage and frequency of electric motors as well as some products (type televisions (inch screens), types of threads, etc. and nautical and aviation measuring units that I doubt can change in the near future.
the same applies to countries with a left-wing direction for which change would be very challenging for high costs and, due to the high traffic intensity, the risk of accidents.

 

[ragnol]

thanks for the answer @terastore

 

[Marco F inox]

Whereas an inch is 25.4 mm. (indicated by everyone with only one decimal), I would multiply all inch quotas for 25,4 and save only two decimal digits, considering also that in carpentry it is already very much to respect the tenths. if we add the fact that all quotas are under tolerance, in any drawing or piece, I would add to every quota, algebraically, the shocks, but never more than two decimals.

 

[ragnol]

I'm afraid it's not that simple in mechanics. If you multiply and roll to the second decimal number all quotas (excel sheet mode), you will have roundings for excess and others for defect. It is probable that many of the tolerances between, for example, the seat of a tree/key/cuscinet etc and such elements go to be blessed.
I am not of the field, but in my opinion it cannot be avoided to reevaluate measure by measure so that they are "compatible compatible compatible compatible compatible".

 

[Marco F inox]

I'm afraid it's not that simple in mechanics. If you multiply and roll to the second decimal number all quotas (excel sheet mode), you will have roundings for excess and others for defect. It is probable that many of the tolerances between, for example, the seat of a tree/key/cuscinet etc and such elements go to be blessed.
I am not of the field, but in my opinion it cannot be avoided to reevaluate measure by measure so that they are "compatible compatible compatible compatible compatible".

To remove the thousandths at a quota, it does not mean to change its nature, as it does not mean to change its mark to the shocks of tolerances. the types of couplings required by the designer, remain such and are respected, does not distort anything, are only eliminated the thousandths of mm. when you have respected the mm, the tenths and the cents, believe me, you are already at good point.

 

[ragnol]

I don't know. if the seat has as its share x (+/-)y (his tolerance), and the tree has quota z (+/-)w (his tolerance), which of these multiply and round values "automatically" to ensure that the coupling tolerance is still respected? If you do it with everyone, the fact that some will be rounded by defect and others by excess will change you in fact the values of tolerances.
Let's see if someone "cuts the bull's head"

 

[Fabietto]

this happens if you apply the scaffolding on the quota and work with symmetric tolerances.
less problems you have if:
the seat has as quota x (+/+)y (his tolerance)
the tree has quota x (-/-)w (his tolerance)
then the scaffolding applies it with tolerance.
But I don't know if it's correct. .

 

[Vittorio]

years ago I worked for an American company
we make molds and the precision of the cent is already a luxury.
as already said by someone.. multiplied by 25.4
3 decimal odds.. If you don't make watches, it seems exaggerated.
then the hole shaft tolerances (h7/g6 to make an example) are identical for both the metric system and the Anglo-Saxon one.
therefore 1" 3/4 quoted 44.45 h7(0+0.025)

 

[Marco F inox]

years ago I worked for an American company
we make molds and the precision of the cent is already a luxury.
as already said by someone.. multiplied by 25.4
3 decimal odds.. If you don't make watches, it seems exaggerated.
then the hole shaft tolerances (h7/g6 to make an example) are identical for both the metric system and the Anglo-Saxon one.
therefore 1" 3/4 quoted 44.45 h7(0+0.025)

bravo.