Sharp edge tolerance?

[trickysheep]

Just started a new job and they don't have any asme / ansi specs here! Anyone tell me what tolerance I have on a sharp corner callout per ANSI Y14.5M-1982?

 

[aardvarkdw]

The tolerance is whatever you call out on the print. The ASME specs don't tell you what the tolerances are, they just tell you how to interpret them.

David

 

[KENAT]

If I understand your question correctly I agree with aardvarkdw answer.

I don't have ANSI Y14.5M-1982, only ASME Y14.5M-1994 which replaced it but I dont think it says anything.

We put the following note on our drawings to address this:

REMOVE ALL BURRS AND SHARP EDGES ____ MAX RADIUS OR CHAMFER.

We select the value based on function of the part.

KENAT, probably the least qualified checker you'll ever meet...

 

[trickysheep]

Actually the issue is I am measuring a part with a callout of " sharp corner, do not deburr". I always used a .002 max edge break for a default on a sharp corner and thought there might be an actual tolerance listed in a spec.

 

[KENAT]

If it says

sharp corner, do not deburr

I'd think the max edge break would be less than .002. I'm thinking knife edge, but I'm no inspection guy.

KENAT, probably the least qualified checker you'll ever meet...

 

[aardvarkdw]

I would talk to the designer and ask them what they mean by "sharp". Without an edge break or corner round callout you have nothing to measure.

Technically "sharp corner" should mean that the point is exactly a molecule wide, anything less than that and you no longer have a theoretically perfect corner. That however, is ridiculous, so I would ask the designer what is acceptable.

David

 

[ctopher]

It is very vague. If you call out a sharp corner, you will get different corners based on various machine shops. It can have a small radius or a razor sharp edge. a R.002 is common. As they others wrote, there is not a spec for a simple corner ... only threads, o-ring grooves, etc.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

 

[MintJulep]

"Do not deburr" is a process (or lack thereof), and does not belong on the engineering drawing.

The existence of such a statement on the drawing suggests that the designer had a specific manufacturing process in mind for the part as a whole. The size and "sharpness" of an edge or burr is very much process dependent. Consider a shear, a band saw, a wire EDM, an end mill or a disk grinder. All could be used to make a similar feature, but the edge would be very different.

 

[meintsi]

In order to get the 'sharp' edge I think you're really after, we add the note: NO NICKS OR BURRS ALLOWED.

It's not so much a defining "how sharp is sharp" or another one we have come across here. "how clean is clean", it's more of a case of uniformity of the edge.

ie. PROFILE OF A LINE ......(even if circular ..)

Remember...
[navy]"If you don't use your head,[/navy]
[navy]your going to have to use your feet."[/navy]

 

[dingy2]

The statements such as "no burrs" or "no sharp edges" shown on drawings is fuzzy to say the least and it is difficult to get a usable or measurable definition out of Engineering. It is usually sluffed off to Quality to come up with some sort of standard which, I think, is wrong.

Product standards should come from the Design Engineering group and not Quality. Quality would then come up with the best way of measuring the standard as long as the standard is measurable.

What do you think? Am I wrong here?



Dave D.

http://www.qmsi.ca

 

[KENAT]

dingy, I think I agree. Hence the standard note we have specifying a max value for burrs or sharp edges.

Of course we dont specify a min value but I'd hope in our notes case it was fairly clear.

If I wanted a sharp edge I'd probably reword our note and put a very low maximum.

KENAT, probably the least qualified checker you'll ever meet...

 

[fcsuper]

I partially agree. My definition of burr is that it is an irregular proturding piece of material that is by design not supposed to be on the finished product.

I've seen notes such as "Break all sharp edges..." but I don't like this term because break size does come into question. I use "Deburr all sharp edges, corners and threads" (i.e., remove the burrs without changing the design of the part). If a vendor gets into the question of how big or small a burr can be, they are already aware that they are talking something that they've been instructed to remove without question. By using this note, I say "I don't really care how you do it, just get rid of the burrs" yet at the same time, avoiding a specification that's going to be rejected against unnecessarily.

Where necessary for extensive handling, I specify a toleranced radii, chamfers or controlled radii.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[dingy2]

fcsuper:

I love to see someone on the shop floor figure out a quantitative value of "an irregular protruding piece of material that is by design not supposed to be on the finished product.

It does appear a bit vague.

The requirements should come from Engineering and should be clear. One does not see on a drawing that the dimension is, as an example, 100 mm +/- a little bit.

Burrs are a sore point on the shop floor and usually, Engineering are not enthusiastic about defining what a burr really is.



Dave D.

http://www.qmsi.ca

 

[MikeHalloran]

To me, " sharp corner, do not deburr" is perfectly clear. It means that you shouldn't _touch_ the edge, even with a measuring tool.

I have on occasion used a similar note ... with imperfect results. I still had to speak personally to the fabricators and explain that I wanted a sharp edge (on an orifice), and I specifically did _not_ want the edge 'broken', especially 'just a little bit', in my case because edge radius has a very strong effect on orifice predictability. I had to explain that I did _not_ want the orifice to flow 'better', I wanted it to flow 'predictably'.

If you really _are_ going to insist on a number, I think it is possible to measure the radius of a sharp edge with micron resolution, and that it's done on cutting tools routinely. No, I don't know how, or how much it costs to get tooled up for it.


Mike Halloran
Pembroke Pines, FL, USA

 

[dingy2]

Mike:

I have seen burrs on large stampings that were .030 in height and one could shave with it. That is certainly sharp.

I guess that would be OK with your "sharp corner, do not deburr".

When it comes to attribute characteristics such as burr or no rust, etc., maybe a company standard should be developed with personnel from Engineering, Quality and Production having input. Right now, it usually someone in Quality only if a company has standards at all. If there are no standards, then each person would have their own standard and you are in a mess.





Dave D.

http://www.qmsi.ca

 

[trickysheep]

Thanks to all for the response. This is an Air Force print so the Design Engineer would not be readily available! I still thought that there was a spec out there that called it out...

 

[ctopher]

For the Air Force, or any military, all specs are called out in the contract.

Chris
SolidWorks 07 4.0/PDMWorks 07
AutoCAD 06
ctopher's home (updated 04-21-07)

 

[fcsuper]

"I love to see someone on the shop floor figure out a quantitative value of "an irregular protruding piece of material that is by design not supposed to be on the finished product. It does appear a bit vague."

Are burrs spec’d as a feature on the part on the drawing? Normally no. So why would there be a quantitative spec for something that isn't supposed to be there. Something that is irregular and protruding is not part of the spec. Essentially, it's a feature on the part that is not on the drawing. This is about as black and white as one can get. If the drawing says burrs should/could be on the part, then a spec IS required. However, when the drawing says nothing or says burrs should be removed, then the feature (burrs) shouldn't be there at all. To have a spec, one presumes measurement. How do you measure something that isn't supposed to be there?

"The requirements should come from Engineering and should be clear. One does not see on a drawing that the dimension is, as an example, 100 mm +/- a little bit."

Respectfully, you are making my point for me. Having this discussion about burrs means the person questioning the spec is already aware they don't belong there at all.


No measureable spec should be called out unless there is some requirement for an edge to meet, such as a radius or chamfer, or unless burrs are allowed or required. Otherwise, one would be spec'ing out something that isn't part of the design or design intent.

Matt
CAD Engineer/ECN Analyst
Silicon Valley, CA
sw.fcsuper.com
Co-moderator of Solidworks Yahoo! Group

 

[dingy2]

Matt:

I could go out on the shop floor and reject any part I want - "been there and done that".

I feel something on the edge. Oh, a burr or what I deem is a burr. All the product in that lot is now red tagged for disposition. Sure does upset Production.

Someone from Production comes out and checks the same spot edge. No burr here. Now comes the discussion. Is it a burr or isn't it a burr?? Talk to to the Designer and see what happens. They, usually, don't want to get into the discussion of what a burr is. Let them fight it out on the shop floor.

This happens all the time. If Design people cannot come up with a maximum parameter then standards should be developed in each company. The drawing would then refer to the standard in notes.

Guess I beat this thing to death but it is a sore point on the shop floor and in the Quality department.



Dave D.

http://www.qmsi.ca

 

[MikeHalloran]

Okay, large stampings often do have large burrs ... but there's rarely a design reason to want a sharp edge on a stamping, and there are a lot of liability reasons not to want one.

I've seen hole edges with no _easily_detectable_ burr, e.g. at the intersection of a ground flat surface and a lapped hole, and at the edge of laser- cut holes and waterjet- cut holes in sheet metal blanks.








Mike Halloran
Pembroke Pines, FL, USA