Standards Wednesday - Dimensioning Features Pt3
For the past couple of weeks for Standards Tuesday…ummm…Wednesday…No it was Standards Tuesday, now it’s Standards Wednesday. Anyway, for the past couple of weeks I have been covering the Dimensioning of Features per Section 1.8 of ASME Y14.5M-1994. Today we are going to continue this section and it looks like this section will take us until next week to finish, but it’s worth it. Almost every aspect of dimensioning drawings uses the rules described in this section.
Counterbored Holes
Counterbored holes can be dimensions as shown below. When using SolidWorks click the Hole Callout button in the Annotations bar.
Then click the outermost diameter and place the dimension. If created properly the dimension should not require any modification, although there may be times you will need to add or remove symbols. Some would argue that the depth symbol and the depth diameter should be on their own line but I feel it is easier to interpret when the depth is shown with the counterbore diameter. As with anything here, that is just my opinion and your welcome to explain to me why I am wrong.
If it is more important that the thickness of the material is specified then it is acceptable to remove the depth callout and add another dimension.
When dimensioning holes with more the one counterbore you can dimenion them as show below; with the depths shown separately. I recommend this way since it is completely clear about the depths of each counterbore.
However if you do wish to include the depths with the couterbore diamters, I would recommend showing the depths as reference dimension on the profile view. Of course, if you wish you do not need to show the dimensions in the profile view.
Countersunk Holes
When dimensioning Countersunk holes the diameter and the included angle must be specified.
You can also dimension the counterbore as shown below.
Counterdrilled Holes
When dimensioning counterdrilled holes the diameter and depth of the counter drill must be specified but the included angle is optional.
When using a callout for the counterdrills, no symbol precedes the counterdrill dimension. As with before, the included angle is optional.
Spotfaces
To dimension a spotface, the diameter of the spotface is dimension and you can dimension either the depth or the material thickness. If you are so inclined, you may just describe the spotface in a general not and not even dimension it in the drawing. Also, If the depth or material thickness is not specified then the the spotface depth is to be the minimum depth necessary to clean up the surface to the indicated diameter.
Machining Centers
When it is necessary to leave the machining center in the finished part it must be indicated by a general note, local not or dimension on the drawing. Refer to ANSI B94.11M for more information. I would tell you about it…but I actually don’t have that one. 
Chamfers
Two common ways of displaying chamfers are shown below. On the left, .100 X 45.00°, is to be used only when the chamfer angle is 45° since the linear dimension can apply in both directions. This type of dimension cab be applied using the Chamfer tool in the dimension fly-out on the Annotation toolbar. On the right, the linear dimension and angle dimension could apply to any chamfer type.
To change the Chamfer Text Format, select the desired format in Options -> Document Properties -> Dimensions -> Leaders -> Chamfer Text Format
Click OK and dimensions created with the Chamfer Dimension will be updated to the new format. The new format shown on the right, .100 X .100 can apply to any chamfer dimension regardless of the angle.
Chamfering Round Holes
Chamfering round holes can be done using the procedures shown above except when it is necessary to control the chamfer diameter. When it is necessary to control the diameter dimensions of the chamfer, one of the practices illustrated below could be used.
Total Angle
One Side Angle
Well that just about does it for today. Like I mentioned earlier, next week will probably the last of Dimensioning Features per ASME Y14.5M-1994. After next week we can move on to even more ASME goodness. Until next week, keep those questions coming and I will answer them all to the best of my ability.
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