Tolerance Talk
This term describes the acceptable range of variation in a part’s dimension.
tolerance
When two parts always have space between them when assembled, this type of fit exists.
Clearance
This statistical term represents the average value in a set of data.
Mean
These three tolerance formats are most common in CAD drawings.
Unilateral, bilateral, and limit tolerance
Name one permanent and one non-permanent joining method.
adhesive or welding; bolt or screw
A dimension of 5.000 ± 0.010 means the part can range between these two sizes.
4.99 and 5.01
When parts must be pressed together and friction holds them, this fit is called a(n) ____.
Interference
This measure describes how spread out data is around the mean.
Standard deviation
The total permissible variation between upper and lower limit dimensions.
Tolerance
This type of tolerance allows variation in only one direction from the nominal dimension.
Unilateral
A fit that can result in either a clearance or interference depending on actual sizes.
Transition
About what percent of data lies within three standard deviations of the mean in a normal distribution?
99.7%
This type of drawing shows how multiple parts fit and move together.
Assembly
Snap-fit joints are often used for these types of consumer products
Plastic housings or electronics enclosures
When no specific tolerance is shown, engineers rely on this type of default tolerance in the title block.
General tolerance
The minimum clearance or maximum interference between two parts is called this.
Allowance
What is another name for the curve that we use in the Normal distribution?
Bell curve
In an exploded view, these numbered circles point to parts and connect to the parts list.
Balloon annotations
Give one advantage of using adhesives instead of bolts or screws.
Reduces weight / avoids stress concentrations
A drawing shows a dimension as “2.500 +0.005 / -0.003.” What is the total tolerance?
.008
True or False: The tighter the tolerance, the cheaper the part is to produce
False
A sample of hole diameters has a mean of 8.00 mm and a standard deviation of 0.01 mm. What range covers roughly 99.7% of the data?
7.97 to 8.03
Why is it important to specify tolerance directly in CAD instead of leaving it to the manufacturer’s judgment?
Prevents miscommunication and ensures consistency
When designing assemblies, engineers must consider how many independent motions a part can make — known as its ____.
degrees of freedom