Draft dimensioning
Draft dimensioning
(OP)
Are there any hard rules concerning the dimensioning of draft angles on castings and forgings. We (QC) find our engineers seem to have their own rules on how to apply draft. They have a dimension that will say
+dft. and one that will say -dft. They will have in the notes; Dft. angle 1 degree max. or Dft. to be within tolerance, usually meaning the box tolerance. Although they do not specify they usually mean per side but not always.
Thanks
+dft. and one that will say -dft. They will have in the notes; Dft. angle 1 degree max. or Dft. to be within tolerance, usually meaning the box tolerance. Although they do not specify they usually mean per side but not always.
Thanks





RE: Draft dimensioning
RE: Draft dimensioning
RE: Draft dimensioning
According to the standard dimensions affected by draft are specified using the following technique:
Specifying “DRAFT ADDS MATERIAL” or “DRAFT REDUCES MATERIAL” in general notes.
Specifying “+DFT” when the dimensions may increase due to the draft.
Specifying “-DFT” when the dimensions may decrease due to the draft.
Specifying “DFTINCL” when the draft must be contained within the given tolerance.
The standard also suggests using such technique preferably for non-critical dimensions
For more detailed explanations you still need to refer to actual standard. It has a lot of good stuff besides draft.
RE: Draft dimensioning
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Draft dimensioning
thread1103-275160: Draft call out
Chris, CSWA
SolidWorks 14
ctopher's home
SolidWorks Legion
RE: Draft dimensioning
We are dealing with a .065 wide slot in a casting. My immediate concern was the Note "Draft included in tolerances". The box tolerance is +/-.005.
Since Dft. is per side we (QC) interpreted this as adding a max. of .0025 per side to the dim. (ID Dim). We rejected it because it was + .004
per side. Engineer says we got it wrong and the draft, as called out, is max. .005 per side.
RE: Draft dimensioning
I'm thinking that all the way through the slot the width has to be .065+-.005.
There is no implication that the draft has to be equally divided between the sides. The effect of the draft on slot overal width needs to be within the +-.005 boundary.
I'm not sure why you're even directly measuring the draft.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Draft dimensioning
We do not start by measuring the draft angle we measure the feature.In this case we rejected the part because the slot went out of tolerance
because of the draft. We then had to accept the engineers view even though we did not agree with his interpretation of the draft callout.
Since we are getting different call-outs and interpretations I wanted to see if there was a rule within GD&T for the dimensioning of Draft.
RE: Draft dimensioning
RE: Draft dimensioning
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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.
RE: Draft dimensioning
RE: Draft dimensioning
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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.
RE: Draft dimensioning
RE: Draft dimensioning
I think you're bloody lucky to be in a position where you CAN argue about 0.001 difference in a cast part! More often, it is a 1/16 or more.
RE: Draft dimensioning
Our job is to inspect the part to the relevant prints and report what we find. While we are not into arguing with the engineers we will question ambiguous call-outs. The
biggest problem we have of course is that the engineers start their 'Notes' with "Interpret Drawing Per ASME Y14.5-1994" and then go on to prove that that they don't have
a clue what GD&T involves and they don't want to hear it because they are the 'Engineers'.