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Draft call out

Draft call out

(OP)
I have a part that is 1" ± .005 with plus draft accompaning it, what does this mean?

 

RE: Draft call out

Is there a draft angle speficied somewhere on the print?  

Typical on castings, forgings and moldings.

What if any drawing standard is the print to?

I'd think it means that the dimension at the 'base' of the draft is 1"+-.005.  Elsewhere it's (1" +- change due to draft angle)+-.005.

Or something like that.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Draft call out

If this is what you are talking about:

"+ Draft" = This lets the manufacuturer know that the draft gets larger as it gets farther from the point where the dim it specified.  The draft angles outward from the dim.

"- Draft" is the the large side, where the draft gets smaller from the dimensioned point.  The draft angles inward from the dim.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

&

RE: Draft call out

I agree with kenat and FCsuper if yo have + draft I have always considered it as adding material and - draft is removing material.  I use this because of internal cores can get confusing on the addition or subtraction of the draft callout on the print.

Can you manufacture the part with draft within the noted tolerance?  This means having 1 inch at the say bottom and have .995 at the top of the part?
 

RE: Draft call out

I'm not sure that link helps. :)  That's the same sort of confusing description I encountered years ago before I finally found the more simple description.  Yeah, when there is a discussion about cores, the question does get confusing.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

&

RE: Draft call out

I always take the plus draft to mean that the tolerance applies to the smallest end of the feature and it is allowed to increase by the amount of draft allowed.  Minus draft is the opposite.  The dimension applies to the largest end of the feature and it is allowed to get smaller by the amount of draft allowed.   

RE: Draft call out

We encountered the same problems three years ago when we launched a new tooling in China, the attached figure help me to explain "what is a +draft" and "what is a –draft".

A. For +draft application
The draft is added to the dimension for external dimensions
The draft is removed from the internal dimensions

B. For –draft application
The draft is removed from the dimension for external dimensions
The draft is added to the internal dimensions

C. Application with both +draft and –draft

You may find out the similar result from the book : Chapter 7 figure 7-76 Print reading for engineering technology by David A. Madsen

SeasonLee
 

RE: Draft call out

Seasonlee That is not what I think of when I see negative and postive draft callout.  Now I am confused.  For example in option B.  I would have the 120 at the top then draft reducing material.  It looks like you moved the dimension describing the part to the bottom instead of keeping the dimesnion at the top in your example.

Please see how I would interpert option B in the PDF.  I know that this part can not be made due to the center undercut.  Please tell me what I am missing.   

RE: Draft call out

For application of -draft

The draft is added to the internal dimension but you are removing from the dimension, so the part can't be released from the tool.

SeasonLee

RE: Draft call out

Ok that is what I was thinking but I did not know for sure.  I now understand your explaination in your attachment clearly now. Thanks

RE: Draft call out

(a) is wrong, from what I understand.  The +DRAFT should be taken from the basin only, not a mix of the basin and peak.

On my models, I put in the draft to start with, so it is clear what I'm talking about when I use those terms on the drawing.

Matt Lorono
Lorono's SolidWorks Resources & SolidWorks Legion

&

RE: Draft call out

You are right, Matt.
This will be exactly same as (C) + draft.

SeasonLee

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