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Spot Face dia, and depth. 3

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Jarquafelmu

Jarquafelmu

Mechanical
Feb 4, 2009
4
Hey guys. I had a question about a spot-face that I need to put on a part in NX5.

The diameter of the hole is 5/16". Its on a flat surface. I can't find any mention of it in my drafting book and all I can find online is definitions what what a spot-face is and not how to determine the correct values. I read that as a rule of thumb you should have a depth of 1/16" for your spot-face. But it made no mention of any dia.

Is there a formula that would give this information? or is it just "what looks good"? Thanks for any help you guys can give me.

I read the thread: thread1103-152443 It dealed with the GD&T call out of the spot-face but it also didn't describe what you might need for a dia. Thanks again guys.
 
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The diameter would depend on function. What is the purpose of the spotface? What is the purpose of the hole?

"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]
 
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There is no specification on what the hole is used for. Or what the spot-face is used for. Just to find the proper depth and dia. to go with the hole dia. of 5/16" +/- .005".
 
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The spotface diameter depends on using a washer(what size) or not. Depends on the type and size of the fastener head. If the fastener uses internal wrenching, then no wrench clearance. If the fastener uss external wrenching, then spotface diameter depends on required wrench clearance.

There is no standard for spotface diameter for a hole size. It depends on the intent of what goes in the hole.

Ted
 
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For instance, when spotfacing a casting, sometimes the designer's intent is just to remove enough material to clean up 100% of the cast surface, so as to ensure a flat wrenching surface. Other times, it might need to be deep enough to accomodate the length of a bolt or cap screw head (although then it might properly be called a counterbore).

And there is everything in between.

Software For Metalworking
 
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Thank you Ted, this helps alot. And thank you everyone for your answers.
 
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You mentioned that the spotface is on a flat surface. I'm a 27 year veteran of the shop with extensive machining and Tool & Die experience before getting into management, and I can tell you that the chief purpose of a spotface is to clean up the surface of a cast or forged article to provide proper seating for a bolt head or other shouldered item. If your surface is already truly flat, skip this operation, unless it is a casting or forging. To use a spotface as a washer seat is unnecessary and just adds cost.
 
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