Standard draft angles for sand cast iron parts?

[sprintcar]

Does anyone have a good resource for this? I'm rewriting a spec and would like something more substantial than "tribal knowledge" or "between one and five degrees, depending on the mood of the pattern maker". Most foundries have their own guidelines but I'm looking for any industry standards.

Thanks folks!

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

 

[DAVIDSTECKER]

Unfortunitly thats about how the "industry standard" seems to be.
There are so many variables when it comes to "Sand" castings.
Things like green sand vs no-bake and some of the other chemical bound sands.
Foundry practices play a big roll in how well the mold is made from the pattern.
Type of pattern material also plays a part. Wood vs urethane or metal.
If you are out sourcing the work then put the monkey on the vendors back and let them decide. If your doing it play it safe and take as much as you can to CYA.

 

[arunmrao]

There are too many variables and factors affecting draft angle being provided on the pattern. Normally the practice is to have 1-2 degrees. 5 degrees draft angle suggests that either you are very generous in increasing the weight of the casting and the add on cost in bringing it to size or there are deep pockets in the castings ,hence the need for large draft angle.

It would be best advised that you decide on a case to case basis rather than having a common standard. Also the quality of pattern ,molding methods,machining allowances,etc will decide the draft angle needed. However as a thumbrule using 1-2 degrees should be a safe practice.

 

[thundair]

Sprintcar
I imagine you could generate a formula but it would be complicated. It would start with 0 degrees at .5" pull and increase 1/2 degree for every .5" addition but if you had multiple bosses stacked to 5" the last one wouldn't be 5 degrees.
So the next statement would be degree addition applies to continious (unbroken) surface of pull.But then a 5" pan with 5 dgrees pull is excessive.

Give up?.....I do

When I make a casting pattern it is something that goes through my mind. To add to that is the cores and all the problems they add to your cavity in the drag/cope

Cheers