About Bend Radius
You can dimension bends in the following ways:
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Inside Radius—Dimensions the bend using the inside of the bend radius. Sheet metal parts typically dimension to the inside radius.
Inside Radius—Dimensions the bend using the inside of the bend radius. Sheet metal parts typically dimension to the inside radius.• 
Outside Radius—Dimensions the bend using the outside of the bend radius.
Outside Radius—Dimensions the bend using the outside of the bend radius. | You can also select the By Parameter option to dimension the bend according to the location set by the SMT_DFLT_RADIUS_SIDE parameter. |
You can define the dimension location of bends during feature creation, or you can predefine the location using the SMT_DFLT_RADIUS_SIDE sheet metal parameter or in the Bends area of the Sheetmetal Preferences dialog box.
Make sure you add material thickness to the desired radius. If you create the bend when adding an extruded wall, you can thicken the sketch section and redimension to the inside of the bend. For extruded or swept walls, you can specify no radius and manually sketch the radius in the section.
Zero-radius Bends
You can use zero-radius bends using the Bend and Attached Flat Wall tools. The resulting geometry shows a sharp edge on the side to which the bend is dimensioned. You can unbend zero-radius bends.
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Zero-radius Bend (Outside Radius) | Zero-radius bend (Inside Radius) |