Masking and spotface - difference?

[magic612]

I know, there's no dumb questions, but this feels like a dumb question, so here goes: What's the difference between masking and spotface?

I was reading this thread:

http://www.eng-tips.com/viewthread.cfm?qid=242333&page=1

...and the discussion at one point was "masking vs. spotface." Having heard of tape masking disks called "spotface masks" by several different customers, I was trying to figure out what "spotface" really should mean. In the context of that conversation, I got the impression that "spotface" didn't have much to do with the process of masking, yet that's the only way I've ever heard it used.

So that made me think, "Huh?" *Insert 'me-feeling-dumb' emoticon here*

Thanks in advance for helping me understand this.

 

[mcgyvr]

Masking is masking with tape. (done prior to finishing)

Spot facing is done with a tool that looks like an endmill (some with a pilot point for inserting into a hole to keep it centered) that mechanically removes the finish. (done after finishing). The spot face typically just removes the finish and a little from the actual material to provide a clean/unfinished surface

Spot facing is also done to cast parts,etc.. where you need a perfectly flat surface for washers,etc.. to sit on.

 

[KENAT]

Yeah, in context I was talking about a machined spot face.

Often used in castings as mcgyver says, or sometimes if you are putting fasteners onto a curved surface, you want a local 'flat' so might use it there.

It's essentially a counterbore but of 0 effective depth.

KENAT,

Have you reminded yourself of faq731-376 recently, or taken a look at posting policies:

http://eng-tips.com/market.cfm?

What is Engineering anyway: faq1088-1484

 

[magic612]

Got it - thanks for the clarification guys!

Much appreciated.