Chamfer square hole

[cmarinelli]

The problem I'm about to describe sounds like it should be easy to resolve, but has me dumbfounded.

I have a rectangular hole in a plate with a radius (not full) forming one side of the rectangular hole. There is a .025 chamfer on three edges of the hole. The intersecting chamfers have a .040 radius, and the two ends of the chamfer also have a .040 radius. When you chamfer the edges, you get a sharp corner where the chamfers intersect. This of course, does not reflect what actually occurs when you use a conical form tool to machine the chamfers. Additionally, when you chamfer the edge intersecting the unchamfered edge, you get a sharp end to the chamfer, whereas in reality you obtain a conical surface at the end of the chamfer.

I've tried doing a cut-sweep which does fine on the right angle edges to be chamfered, but leaves a vestigial post or boss at the center of the .040 R at the end of the chamfer. The sweep cut command fails if I enlarge the profile to try to eliminate the post because the sweep profile interferes with itself.

Is a sweep cut the best way to do this?

Is it possible to create a 'form tool' with a 90 degree tip and conical ends? This form tool could then cut this shape out of the part.

Does anyone have a better idea?

Thanks in advance,
Chris Marinelli
Dynatech Engineering

 

[cmarinelli]

Sorry, meant to post this to SolidWorks forum

Chris

 

[pohbah]

spark erode the form

 

[CAEman]

Hello cmarinelli, can i ask you what is the function of that chamfer ?

 

[cmarinelli]

Hi CAEman,

The edge break is for clearance on a turbine engine variable vane trunnion. We are reverse engineering the part, so we must duplicate what is present. I know it's an odd example, but I think the general idea of removing material with a solid moving along a path is something many would want or need.

 

[smcadman]

EDM it.
(electrical discharge machining)

Flores

 

[brengine]

cmarinelli,
In SolidWorks (or whateverCAD), when it won't giving me the chamfer I expect, I break the chamfer into sepatate "Cut" features. So for your model, I would Cut-Sweep along the *straight* edge, then to a Cut-Revolve (separate feature) in the corners.
Ken

 

[CAEman]

Hello cmarinelli, sorry for late reply because I'm very busy for the last two weeks. Since the chamfer is for part of turbine engine, I believed this part is very critical. The only way to do it (I agree with Flores) is to use Electrode Discharge Machine (EDM). Is it posssible for you to change the chamfer design because the sharp edges is the weakest point, it is a very bad design because i had faced this similar problem before. If this part is not critical, there is another way to do it which is very cheap, just file it.