A decorative snap is a piece of jewelry with a job. The whole point is the face of it — so the one thing you must not do is flatten that face while you set it. Here is the order of work for setting a decorative snap that protects the cap.
What ruins a cap when setting a decorative snap
Three things, in this order of frequency: setting the cap on a flat anvil instead of a dished one, hitting it once as hard as you can, and using a setter that does not match the snap. All three are avoidable, and none of them can be undone afterwards. A crushed dome does not come back.
1. Mark both halves with the piece closed
Close the strap, fold the tab, do up the collar — whatever the finished thing does — and mark through from the top. Do not measure each half separately from an edge. Edges are rarely as parallel as they look, and a two-millimeter error is enough to make the snap feel stiff and then pop open by itself.
Misalignment is the most common first-timer’s mistake and the least forgiving, because the only remedy is a second set of holes somewhere else.
2. Punch the hole, do not cut it
Use a round punch, and use the smallest one the post will pass through. The leather should grip the post slightly. A hole one size too big lets the post tilt, and every open and close works it a little wider until the whole snap pulls out through the face.
Err small. You can always ease a hole open with the tip of an awl. You cannot make one smaller.
3. Seat the cap in the cup — this is the one
Snap setters come with an anvil that has a dished, domed recess in it. That recess exists for exactly one reason: to support the whole curved back of the decorative cap while force goes through it. Put the cap face-down into that cup and it is cradled. Put it face-down on a flat bench block and the only thing touching is the very crown of the dome, so that is where all the force lands — and the design flattens.
If your anvil has several recesses, use the one the cap sits in snugly, not the one it rattles around in. If the cup is shallower than your cap, stop and get the right anvil. It costs less than the caps you will spoil.
4. Strike straight, two or three times
Hold the setter vertical — square to the leather, not leaning — and give it two or three firm, controlled blows rather than one heavy one. Light taps leave the post half-formed and the snap loose. A single hard swing deforms the cap, splits plated finishes and can crack an epoxy-filled face.
Use a mallet or a rawhide hammer if you have one. A steel claw hammer transmits a sharper shock and is harder to keep square.
How to tell setting a decorative snap went well
- The dome is still full and even, with no bright flat spot on the crown.
- No tool marks on the cap face.
- The two halves close with a definite click and hold when you tug the piece.
- The back of the post has spread into a neat round head, not a folded-over lip.
Practice setting a decorative snap on offcuts first
Set two or three snaps into scrap of the same thickness before you touch the real piece. It costs a few pennies of hardware and it tells you exactly how many blows your hammer, your anvil and your leather want. That number does not change once you know it. Still choosing hardware? Which decorative snap fits your leather covers sizing, and the full range is in our decorative snaps collection. For how the two halves lock together, see the snap fastener entry on Wikipedia.
