Metric Drawing?

[smwdrum]

Looking for some help with reading this print? I have not had to much experience with metric prints, and mostly wondering about the toleranceing? Obviously you can convert the dimm. to inches but what about that tolerances? For instance it has .003 R/O on the cone, is that .003MM or what is that? same with on the Dia 16, -.001/-.005 is that +.001/-.005MM and if you convert that to inches that is really tight? Also in the title block it is in a different language but what is the mean there with +/-.1, +/-.2 etc?

 

[cowski]

Unless you find a note on the drawing that specified a different unit system, then yes, all the dimensions shown are in mm. Some of the tolerances are tight, but consider the source: Mitutoyo, a company that makes measuring equipment (gages, micrometers, calipers, CMM's, etc); I'd expect them to deal with precision parts.

 

[smwdrum]

I would agree so then for instance the .003 R/O is actually .0001" approx? if you convert it over....

 

[ctopher]

this is how I read it:

0-4 = +/- 0.1
4-16 = +/- 0.2
etc

So, dim 13.8 would be +/-0.2, 90 would be +/-0.5, etc

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[CheckerHater]

Yes, the tolerances are that tight. You are looking at the part of precision measuring instrument.

0.1, 0.2, 0.3 are for dimensions without tolerances, sorted by the size of the feature:

less than 4 mm - 0.1

4 to 16 mm - 0.2

16 to 63 mm - 0.3

So the length of 900 mm on the drawing will have tolerance of +/-0.5

Also 3 triangles mean surface texture of 1.6 micrometers (somebody correct mi if I am wrong)

Good luck!

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[CheckerHater]

Sorry, it's 90 mm

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[juergenwt]

The 16 -.001/-.005 is a lapping tolerance. All dim's incl. tolerance are in metric.

 

[BiPolarMoment]

I wonder which datum A the inspector is going to use...

 

[CheckerHater]

I wonder which datum A the inspector is going to use...

As you probably noticed, the drawing goes back to 1981. Back then (now outdated) version of ISO 1101 allowed application of datum symbol to the common axis of suitable features providing that there aren't too many reasonable interpretations. The inspector with common sense then could chose sharp point and center drill as basis for establishing the axis.

As you can see from enclosed picture, 10 years ago it was already considered "former practice"

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[smwdrum]

So would Datumn -A- in today standards be the OD of the part?

 

[dgallup]

I'm pretty sure most inspectors would use the ground 16 mm OD as Datum A. However, CheckerHater chose a different Datum A which is why this type of datum indication is no longer allowed.

If you can still buy one of these for $32.70 go for it, you won't be able to make one for that price!

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[smwdrum]

The problem is I have this bench center from Mitotoyo and I need some other centers of different sizes (bigger) for some larger parts and from what I have been hearing from there customer service is they don't make multiple sizes which to me doesn't make any scence so i was going to get some larger ones made.

 

[CheckerHater]

Well, that was my fault, didn't take another look at the drawing.

I would agree that TWO 16 dia ground surfaces will make better datum.

And, smwdrum, by today standards you have to explicitly specify what are you going to use as datum feature(s)

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[robertib]

One thing that I would note, is that the drawing is in metric. If I send a drawing to a supplier in metric, it is reasonable to assume that it will be machined in metric. After all, the drawing is a contract between the customer & the supplier, so if the drawing is metric...

 

[JNieman]

@robertib

Parts are not made "in metric" or "in inches" - the metal and machines have no idea what units are used to measure it. The part exists in its own state and is only measured using a certain system. Parts are made by gear, belt, screw, cutter movements. There's also nothing stopping a shop from taking your metric numbers, converting them to inches, and using those measurements to create the part.

If I'm measuring a part with a digital caliper, a metric-part is only a button-push away from being an inch-part.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[ctopher]

A lot of machines are programmed using inches for movement, at least here in the US. Parts have to be converted first. Usually it's the decimal rounding that can mess up a part.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[drawoh]

JNieman,

Button push?

I just look on the opposite side of my vernier calipers.

--
JHG

 

[engiNERD77]

Did I miss something? How exactly is a minus minus tolerance read?

 

[looslib]

Easy...0.16 -0.001 to -0.005 means that 0.16 is the nominal size but the actual dimensions must fall between 0.155 and 0.159.
Normally this dimensioning is done with fit classes. It is common with sliding fits.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[juergenwt]

16 -.001/-.005 = 15.999/15.995