I may have posted this before but it's such an interesting technique...and I've refined it a little...and it just works so well.
I'm currently making a pair of Balmoral shoes for a customer. He ordered alligator facings and a calf vamp/golosh with a folded edge.
So, after I had made the fitter's models and gotten them approved, I designed the standard and the patterns. I cut the vamp pattern out of manila folder stock making notations for folding and seam allowances. Cut this pattern accurately.
Then I made an exact copy of that pattern out of
heavy duty manila folder. Next, using a pair of dividers, with a sharp pencil mounted in one leg, I marked a line one millimeter in from the top edge (the folding edge) of the golosh. This distance is roughly equal to the thickness of the calf I needed to fold. Then, carefully, carefully, I trimmed that one millimeter margin away.
Now I have a folding pattern.
Next, I ran some 3M Book tape along the edges on both sides of the folding pattern. The tape is thick enough to protect the manila folder long enough to fold the edges of both the left and right vamp. Hammer or rub the tape...esp. close to the edge of the pattern...to make sure it is firmly adhered and then, using some fine sandpaper (220) lightly scratch/rough the surface of the tape.
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When I cut the leather I added a 1/4" folding allowance. I skived this margin wider than the allowance, say 3/8" wide.
Place a swath of rubber cement on the tape on both sides of the folding pattern. Allow it to dry. Place a swath of rubber cement along the skived side of the vamp/golosh.
While the rubber cement on the leather is still wet, position the folding pattern on the leather aligning the pattern so that it matches the outline of the leather perfectly. This should result in the folding edge of the pattern being perfectly place--one mm shy of where the leather will fold.
When the cement has had time to dry, make relief cuts along inside curves. Do not cut all the way to the edge of the folding pattern--allow at least two millimeters clearance. Then brush more cement on the edge of the pattern and on the leather. Allow to dry.
I like to fold leather while it is damp or even wet. Turn the vamp over and apply stretching fluid or a mix of alcohol and water to the folding margins. Let that soak in for a minute or two and then, with a paper towel, pat it dry on both the grain side and the pattern side.
With the grain side of the vamp down, use a modeling tool to lift the folding margin upright so that it is at right angles to the workspace surface. Because some of the rubber cement stuck to the very edge of the folding pattern the leather should remain upright.
All that remains is to gently pull/push the leather over and down to stick to the folding pattern. Hammer gently and allow to dry.
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When dry, the leather may be gently released and the folding pattern removed. The leather can then be easily re-folded to the exact same position it was in when it was stuck to the folding pattern. Hammer gently and it's done. The pattern can then be flipped and the same procedure done with the other vamp.
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Why do it this way? It's an easy way to fold leather edges precisely and cleanly. Complex curves and reverse curves are done easily and quickly. No unsightly flat spots, no wobbles, and both vamps will be exactly the same size and shape.
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