Rounding corners on a briefcase

[esantoro]

I like the look of this Mullholland Brothers Briefcase. Does anyone have ideas for how to go about rounding the corners in such a way as to get a curve that is not circular? Is there a formula to follow, or a tool I can use?

My next step is to graph out the curve and a lot of trial and error.

Thanks,

Ed

Edited June 4, 2007 by esantoro

[Clay]

I like the look of this Mullholland Brothers Briefcase. Does anyone have ideas for how to go about rounding the corners in such a way as to get a curve that is not circular? Is there a formula to follow, or a tool I can use?

My next step is to graph out the curve and a lot of trial and error.

Thanks,

Ed

Ed,

Here is what I would do, it is not by formula or sientific but it works for me. Take a piece of heavy paper and cut it to the same dimensions of the full piece that you are making. Fold it in half and then take a large circular item (around two inches across)and place it in the outside corner (where the two sides come together not where the fold is) be sure that the edges of the circular item and the edges of the paper are lined up. Draw this curve on the paper. Cut this off and then (still folded) mark a point about one half inch up from the bottom of where the flap edge will be. Freehand an arch fron the marked curved corner to the other corner (where the fold is) of the paper. It might take a couple of tries to get the arch just right. Cut and unfold and you should have a similar pattern to the flap on the briefcase you showed.

ClayM.

Edited June 4, 2007 by Clay

[Dale]

Circles are just a variation on an ellipse. Try this:

http://www.benchnotes.com/Laying%20out%20a...out_an_oval.htm

[Art]

Hi Ed,

Take a piece pf paper for a pattern and fold it in half. Place the crease on the right or the left (the center of the bottom of the flap will be at the crease) and then mark the bottom edge using a French Curve. The French Curve allows you to vary the radius of the curve to suit the job. I freehand draw what I want something to look like in pencil and then go back and make the curves with the French Curve to make the final pattern. Hold the pencil on one point of the hand drawing and slide the curve around till you find the radius that fits (or nearly fits) one part of the freehand and then draw that; then proceed on until you complete the line the way you want it. You may refine your drawing quite a bit before you get what you really want, but it doesn't take long and that is why they make erasers so big. Cut your pattern along the line and unfold it and you are done.

Art

I like the look of this Mullholland Brothers Briefcase. Does anyone have ideas for how to go about rounding the corners in such a way as to get a curve that is not circular? Is there a formula to follow, or a tool I can use?

My next step is to graph out the curve and a lot of trial and error.

Thanks,

Ed

[esantoro]

Circles are just a variation on an ellipse. Try this:

http://www.benchnotes.com/Laying%20out%20a...out_an_oval.htm

thanks, Dale. This is a great link. I've got to study it awhile to figure out what to do, but it seems like just the bit of learning I need to take on right now.

Ed

[esantoro]

Hi Ed,

Take a piece pf paper for a pattern and fold it in half. Place the crease on the right or the left (the center of the bottom of the flap will be at the crease) and then mark the bottom edge using a French Curve. The French Curve allows you to vary the radius of the curve to suit the job. I freehand draw what I want something to look like in pencil and then go back and make the curves with the French Curve to make the final pattern. Hold the pencil on one point of the hand drawing and slide the curve around till you find the radius that fits (or nearly fits) one part of the freehand and then draw that; then proceed on until you complete the line the way you want it. You may refine your drawing quite a bit before you get what you really want, but it doesn't take long and that is why they make erasers so big. Cut your pattern along the line and unfold it and you are done.

Art

Art and Clay,

Thanks for the ideas for the pattern. They're just what I need.

Ed

[leatherkind]

I am having a similar problem.

I need to cut round corners on brief case and i would like to get it done as accurate as possible.

Attempts to use a thick paper pattern and exacto knife or a metal pattern do not produce professionally looking cuts.

They do not match very well and... look like someone just cut them with exacto knife

There are corner cutting machines and i am curious if anyone used them and what is important to know about them to make a good choice?

Thank you very much.

[AndyL1]

Step 1. Go to the hardware store.

Step 2. Locate a large fender washer, close to 2 or 3 inches in diameter.

Step 3. Cut your leather out with square corners.

Step 4. Lay the washer on the leather so the edges meet up side and bottom.

Step 5. Cut the leather off using the washer as a guide.

Step 6. Sit back and smile at your perfect radius results.

For Step 7 I usually go have a beer.

If you hit up a specialty hardware store they usually have washers in a lot of diameters.

Cheers,

Andy

P.S.

I also do as Art suggested with french curves and drawing it out on paper. I then transfer my drawing to stiffer illustration board and use that as a rigid template to transfer the pattern to the leather. The washer method I use on the bottom corners of the bag.

Edited October 3, 2011 by AndyL1

[leatherkind]

Thank you AndyL1, I like your advise and especially the step # 7

I like simple solutions and what can be easier then a washer?

I however was looking for something that would produce a very repeatable quality result.

After searching leatherworker.net some more i found this suggestion http://leatherworker.net/forum/index.php?showtopic=25656&view=findpost&p=161712

$13 bucks later and three hours of work in my shop i arrived to the following solution.

The monster punch!

it is a 3 inch (75mm) large round corner leather punch made out of steel pipe.

I got it in plumbng supply store. One whack does it all. Notice that just like it was suggested in the link above i have bent the sticking out parts outwards to form 90 degree corner.

Works great.

Thank you for your time.

Round punch for leather. Corner cutter punch. Cutting leather corners. Semicircle punch. 90 degree punch.