How to draw a 90 degree break in 1/4" Steel

the plugin also changes the segment lengths of the arc making it cumbersome to revert.

Yeah. Fortunately it sometimes doesn’t matter.

Draw a box the size you want.

Delete the sides you don’t want, in this case the top, front and bottom as viewed.

Using Fredo’s Joint PushPull Tool, offset the three surfaces by the thickness of the chosen steel, call it .125"

This will give you an object which has the proper wall thickness.

Then using Fredo’s Round Corner Tool, set the radius to .020 for the two inside radii which is the bend allowance, set the number of sides to 24, click on the two inside vertical corners and click the check mark. You will now have the correct bend radius on the inside edges.

Now using the same tool, click on the two outside vertical corners, set the radius of the tool to .145" which is the inside bend radius plus the thickness of the material, click the check mark and you now have something which looks correct.

To make the blank to cut the part using a laser or a plasma cutter, duplicate your part, delete the outside faces so you have a single face from the inside of the part. Next, use the show Hidden command and all the vertical lines in the radii of the inside rounded corners are made the visible, select all the vertical lines that make up the corners so they stay visible. Next, use the Unwrap and Flatten Faces ruby to flatten the inside set of surfaces of the box. You always use the inside surfaces as this will give you the correct blank. You may need to make an additional allowance of .020" to the length of the middle segment depending on how the break you use works.

Take the now flat surfaces, delete the unneeded lines where the radii were which will give you a single flat planar object. Now make your view normal to that face and export that as a DXF to give to a laser, water jet or plasma cutter to make your blank.

Ruby’s can make your life far easier. The power of Pro :slight_smile:

You’re referring to the K-factor.

You can design with k-factor in mind if it’s something you do a lot, the form is complex, and/or you work with the same material and manufacturer often. For something like a squared shape that is a one-off it’s not worth the effort, just talk to the sheet metal shop about what the final shape you want it.

Reality is never depicted on screen, even if you have the k-factor right, the particular run of sheet metal might vary in thickness (within it’s tolerance), the shop’s tools have their own idiosyncracies, etc.

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