The dual dimension is giving a discrepancy when converting to mm. 5in is equal to 127mm but Solidworks is giving 124. What can be the issue.

The dual dimension is giving a discrepancy when converting to mm. 5in is equal to 127mm but Solidworks is giving 124. What can be the issue.

Best guess: rounding. The 5 isn't actually 5, it is something smaller and has been rounded up. Increase the number of decimal places for the 5 dimension and see what it says.

Thank you, that is correct.

Why is the 124 representing the true dimension and not 5? If the 5inches is rounded shouldn't 124 be too?

Matt Calzone wrote:

Thank you, that is correct.

Why is the 124 representing the true dimension and not 5? If the 5inches is rounded shouldn't 124 be too?

The computer use 20 decimal, all the time. It never round anything.

So stop cheating on your dimensions. Model it 5" if you want 5". Not 4.8 something.

Matt,

In addition to Jim's comments, generally SW let's you control your type of rounding to get the results you'd expect. In particular, SW is powerful in that it allows you to around dual dimension tolerances to remain within the specification of the primary units (so that you don't have conflicting information on your drawing). I realize that in your particular case, this wouldn't affect the outcome, but it's an often overlooked functionality that will allow users to get the results they may require.

First, you can set your document rounding method here:

"Round half to even" is the preference if you wish to avoid biases introduced by "Round half away from zero" (always round 5 up), and Round half towards zero (always round 5 down). "Round half to even" isn't a requirement of ASME, but other standards, such as those made by NASA, do require it. Even though "Round half away from zero" is common for computers, it isn't necessarily best for Mechanical Engineering Principles. We leave Round half away from zero as default only because it is what is most likely to be expected by a computer user.

For Dual Dimensions, goto the PropertyManager of the dimension and turn on Inward Rounding. This setting determines if the secondary unit tolerance range is currently being rounded to be outside the range established by the primary units. If one or both limits of the tolerance range for the secondary unit does fall outside the range established by the primary units, the secondary unit is rounded so that it will fall within the limits of the primary unit. That way, your secondary units will not create ambiguity.

Best guess: rounding. The 5 isn't actually 5, it is something smaller and has been rounded up. Increase the number of decimal places for the 5 dimension and see what it says.