Hole Punch at 90 Degree Corners?

[Gosut]

I didn't know for sure where else to ask this, so moderators, please move if necessary:

My knife sheath project has become a checkbook cover project courtesy of ordering the wrong weight leather. The design I've come up with has a one-piece interior instead of separate top and bottom pieces. The idea is to reinforce the outside edge of the middle of the cover, as I've noticed considerable wear on this part of my current checkbook cover. This one piece interior simply requires a rectangular cut-out. But this brings the issue of the inside corners and tearing.

I've noticed on a few other leather pieces here that there's a tiny hole terminating the end of a cut. My guess is that it's to prevent the cut from tearing further. With that in mind, I'm thinking of chaffering the interior corners by laying out the 90 degree corners, then using a small punch to make the chaffer, then making the cuts. I'm hoping the chaffer will make the leather less subject to tearing than a 90 degree interior corner.

Anyone have any thoughts on this? Would a chaffer make it less likely to tear than a 90 degree interior corner?

Thanks in advance.

[tsunkasapa]

What is a 'chaffer'?

[Dwight]

Pictures and drawings do a lot to explain the chatter I read above . . . and could not decipher . . . 

May God bless,

Dwight

[Gosut]

Sorry. I misspelled chamfer. I meant a rounded corner instead of two sides meeting at 90 degrees. Below is my pattern. I did it in LibreCAD, printed them as a PDF, copied the pattern itself, then used GIMP to export it as a jpeg. All measurements are in millimeters. I plan to cut out the rectangle marked Remove on the inside plans to form the two pockets typically found in checkbook covers. Where I'm thinking about punching a chamfer is at the corners of the portion marked Remove.

You may notice that on the outside of both patterns, I have a chamfer but also drew out the corners. That's to help in cutting out the leather, since I'll cut out the rectangle first, then cutting the outside rounded corner.

[fredk]

I think your use of the word chamfer is wrong

But, simply cut a curve round the corner to join the vertical and horizontal cut lines. Just as you have for the outside corners

[Dwight]

In answer to your "hole" question . . . yes . . . kinda sorta.

What a lot of us do when making a "cut out" in a piece of leather . . . is first punch a hole . . . in this case I would use about a 1/4 inch hole.

Those holes are punched in the corners of he cut out you want to make.

Then starting at the top edge of the two holes at the top of this cut out . . . make straight cuts to the edges of each.

Same for the two holes on the bottom . . . then cut the edges.  

You then wind up with a box that has 4 rounded corners for your cut out.

Yes . . . that does definitely keep the corners from tearing better . . . makes for a cleaner look . . . 

I copied your drawing . . . stripped it down to the affected area . . . and here is what the finished product should resemble.

May God bless,

Dwight

[Gosut]

Thanks, all.

[TomE]

11 hours ago, Gosut said:

I've noticed on a few other leather pieces here that there's a tiny hole terminating the end of a cut. My guess is that it's to prevent the cut from tearing further.

This idea of a hole at the end of a cut is used in bridle headpieces.  The "split" separates 2 points for attaching a noseband and bit to the bridle.  It is common practice to punch a hole at the end of the split to prevent tearing of the leather.  What usually happens instead is the point is torn at one of the buckle holes used to adjust the length of the noseband (cavesson) or the bit billet.

[Gosut]

Important Note to Beginners Like Myself:

The dimensions in my pattern might not work in reality. This is only a pattern I've drawn, and I don't know what I'm doing. I did a pattern before this one that didn't work, and this one might not, either. In particular, the dimensions for the cut-out is measured to a tight tolerance, and I'm going to remeasure to see if rounding the corners is going to result in the checks and check records being supported only by the corners and not the straight part between them. Ideally, I think the rounded corners should be beyond the checks and check records, which means the length of the cut-out should be the length of the checks plus the twice the radius of the curved part. So if I use a hole that's 6mm in diameter for corners (1/4 inch = 6.35mm), then I think the length of the cut-out should be the length of the checks + 6mm. I might even go to a 4mm radius like the outside corners, which would make it check length + 8mm. Either way, I may have to make the entire pattern slightly bigger. But I don't know what I'm doing, which is why I'll cut it out in paper first and see if it fits to my liking, and if not, back to the drawing board. 

[Tugadude]

1 hour ago, Gosut said:

Important Note to Beginners Like Myself:

The dimensions in my pattern might not work in reality. This is only a pattern I've drawn, and I don't know what I'm doing. I did a pattern before this one that didn't work, and this one might not, either. In particular, the dimensions for the cut-out is measured to a tight tolerance, and I'm going to remeasure to see if rounding the corners is going to result in the checks and check records being supported only by the corners and not the straight part between them. Ideally, I think the rounded corners should be beyond the checks and check records, which means the length of the cut-out should be the length of the checks plus the twice the radius of the curved part. So if I use a hole that's 6mm in diameter for corners (1/4 inch = 6.35mm), then I think the length of the cut-out should be the length of the checks + 6mm. I might even go to a 4mm radius like the outside corners, which would make it check length + 8mm. Either way, I may have to make the entire pattern slightly bigger. But I don't know what I'm doing, which is why I'll cut it out in paper first and see if it fits to my liking, and if not, back to the drawing board. 

The main thing I noticed is that the inner and outer pieces are the exact same length from what I can tell.  That isn't ever going to work if you wish to fold it.  And obviously you do.  The outer shell in my opinion, and this varies according to thickness of leather, needs to be at least 3/8" to 1/2" longer than the inner piece.  So in mm, about 9.5mm to 13mm or thereabouts.

You seem to be very cautious and wanting to draw a perfect template.  Nothing wrong with that but don't let it become paralysis by analysis.  I'm one of those who is pretty lucky in that I can look at something and pretty much recreate it without resorting to detailed templates such as yours.  Not everyone can do that I realize.  But my advice is to buy some cheap "practice leather" and just begin creating.  You might be surprised how simple it can be.  And still get great results.  

I have bought sides from Springfield Leather Co. from their discount table that have been perfect for this.  I think on their website they call them $35.00 sides or something like that.  They used to be even cheaper.  But you get an entire side of usable leather that is good enough for actual projects and definitely good enough for practice.  Some that I've gotten was extremely impressive but they were one-offs I guess and they just wanted to move them.  I'm sure a leather company in your area might have similar hides.

Good luck and have fun!