What constitutes a "sharp edge"?

[70olds]

Good morning. I was having a discussion with a quality guy the other day because I had a part that was turned with a conical feature leading to a straight diameter. The conical feature was 120 degrees included. The print said "break all sharp edges" so he told me I needed to chamfer it. is there an angle that is the point at which an edge is or is not considered to be broken by default, or do I automatically need to break the edge at some angle to split the difference of whatever is left at my intersection? Please excuse the
poor artwork.

 

[Booze Daily]

Usually anything steeper than 45 I roll a .005 radius on it.

 

[FamilyTradition]

I would say it entirely depends on the customer and/or end use of the part. Customer may have a specification that will tell you which edges need broken, when a "sharp" edge is acceptable, etc.

IMO, if there is no burr or raised material on the edge that is 120deg, I would not consider that a "sharp edge" that needs broken. Again, your best bet would be to ask the customer and see what they expect.

 

[Conrad Hoffman]

For something like that I run my fingernail over it. There should be no "catch" which indicates a burr. Other than that, I'd hit it with Scotchbrite on a manual machine, but that's not a CNC process. As a customer I'd probably be unhappy if I saw a distinct flat where the edge was broken. And yes, I'd easily see 0.005" on a small part. Rolling does sound interesting.

 

[EmGo]

Usually anything steeper than 45 I roll a .005 radius on it.

Old fart

 

[70olds]

Usually anything steeper than 45 I roll a .005 radius on it.

I had a .010" radius I believe that terminated .005 over major on the part since I was going to raw stock. The part in question was not critical to anything and we were just using material we had to make a tool. It was not sharp but since they didn't see a chamfer they called it "not broken".

I was asking more if there was any official definition/standard that anyone knew of that specifically called this out. Obviously we wouldn't release parts that are going to have burrs on them.

 

[guythatbrews]

I had a .010" radius I believe that terminated .005 over major on the part since I was going to raw stock. The part in question was not critical to anything and we were just using material we had to make a tool. It was not sharp but since they didn't see a chamfer they called it "not broken".

I was asking more if there was any official definition/standard that anyone knew of that specifically called this out. Obviously we wouldn't release parts that are going to have burrs on them.

I've never heard of any official limiting angle.

I'd consider what you did fine. If the note is only break sharp edges, a partial radius will work.

If there is an official angle I'd like to hear about it.

 

[Kingbob]

We make a fair amount of "sharp edge" or "clean edge" parts. The finger nail catch is one way to detect a burr. I like to say that a burr "will" cut you and a sharp edge "may" cut you. A sharp edge will have no bur but still be able to take a shaving off the back of the finger nail a clean edge is a sharp edge that has seen scotch bright.

 

[guythatbrews]

I really think this falls into the common sense area. More of a company culture thing than a hard and fast rule. A real example of "Know thy customer."

I'll bet some companies do have published requirements.

 

[706jim]

I used to teach manual machine shop. We made woodworking vises for the term project. I told the students that all parts should be deburred. When marking them at semester end there were a few cases where my hands ended up bleeding. I would define those as sharp edges!

 

[Mtndew]

When programming lathes, I always put a .005/.010" rad on all corners unless they specify a sharp edge or "do not break edge".
To me, a sharp edge is one that doesn't have a radius rolled on to it, and your fingernail won't catch a burr.
Almost as if you stoned both faces of that edge being careful to not hit the corner.