Single Cap vs Double Cap Rivets: How to Choose the Right Rivet Press Machine Set

Rivets are what turn a home-made bag into something that looks professionally finished. They hold straps to bodies, reinforce belt buckles, secure dog collar hardware and stop stress points from tearing — permanently, without a single stitch. But if you have never bought rivets before, two questions stop you dead: single cap or double cap? And which size?

This guide answers both in plain language, then shows you which rivet press machine and die set matches the work you actually want to do.

Single cap vs double cap rivets: the simple rule

Forget the jargon. The choice comes down to one thing: will anyone see the back?

• Double cap rivets have a polished, domed cap on both sides. The finished join looks identical front and back. Use these when both surfaces are visible or handled — bag straps, belts, tote handles, dog collars, wristbands, decorative studs.
• Single cap rivets have a decorative dome on one side and a flat, plain back. Use these when the reverse side is hidden — inside a bag lining, the underside of a belt keeper, or where a flat back sits more comfortably against the body.

Most makers reach for double cap rivets the majority of the time, simply because they look finished from every angle. If you are unsure which to start with, double cap is the safer default.

How to choose the right rivet size (the part nobody explains)

A rivet has two measurements: the cap diameter (how big the dome looks) and the post length (the shaft that passes through your material). Getting the post length wrong is the single most common beginner mistake.

The rule of thumb: measure the total thickness of everything you are joining, then add about 3 mm (1/8 inch). That is your post length.

• Post too short → the cap will not seat properly and the join stays loose.
• Post too long → the shaft buckles sideways as it is pressed, leaving a crooked, ruined rivet.

As a rough starting point: 5–6 mm rivets suit thin work like wallets, card holders and light straps; 7 mm suits general leatherwork and bag straps; 9 mm handles heavier belts, thick straps and denim. This is exactly why owning a range of sizes matters — your project decides the size, not the other way around.

Why use a rivet press instead of a hammer?

You can set rivets with a hammer and a setter, but a press gives you three things a hammer cannot: consistent pressure, no glancing blows that dent the cap, and a straight set every time. Crooked or crushed rivets are frustrating — once set, a rivet cannot be removed without damaging the material. A hand press machine makes clean, repeatable results the norm rather than the exception, and it is quiet enough for an apartment or shared workspace.

Which rivet press set should you buy?

For double cap rivets: the most popular choice

The Double Cap Rivet Press Machine & Die Set is our focused kit for makers who work mainly with double cap rivets. It includes the hand press machine plus dies for all four common sizes — 5 mm, 6 mm, 7 mm and 9 mm — along with a 2 mm hole punch die and brass base. Because you get the full size range, you are never stuck mid-project with the wrong die.

Already own a press? The die-only Double Cap Rivet Die Set (5–9 mm) gives you the same four sizes without paying for a second machine.

For single cap rivets

If your work calls for a flat back, the Hand Press Machine & Single Cap Rivet Die Set (5–9 mm) covers the same four sizes with single cap dies and a hole puncher. There is also a die-only version: the Single Cap Rivet Die Set with Hole Puncher.

Want rivets, eyelets and snaps together?

Many projects need more than rivets — a bag might want rivets on the straps, eyelets for a drawstring and a snap for the flap. In that case a mixed kit is far better value:

• The Leather Hand Press Machine Kit for Rivets, Eyelets & Snaps — built around leathercraft, with both single and double cap rivet dies.
• The Hand Press Rivet, Eyelet, Grommet & Snap Machine — includes 7 mm and 9 mm rivet dies in both single and double cap, plus eyelet and snap dies.
• The All-in-One Snap, Rivet, Eyelet & Grommet Set — our broadest starter kit with five double cap rivet die sizes.

All dies use a 6.3 mm (1/4 inch) top screw thread and an 11.9 mm (1/2 inch) bottom diameter, so they fit our hand press machine. If you have another brand of press, check those measurements first.

How to set a rivet, step by step

1. Measure your material stack and pick a rivet whose post is about 3 mm longer.
2. Punch a clean hole using the included punch die over the brass base. The hole should fit the post snugly — not loose.
3. Insert the post from the back and place the cap on top.
4. Fit the matching die (a 9 mm rivet needs the 9 mm die) and pull the lever in one firm motion.
5. Test on scrap first and adjust the depth screw until the rivet seats tightly without crushing the cap.

Frequently asked questions

Are the rivets included with the set?
No — the kits include the press machine and the setting dies. Rivets themselves are bought separately so you can choose your size, colour and finish.

Which rivet size should I buy first?
If you are working with typical leather bags and straps, 7 mm and 9 mm cover most jobs. Our sets include 5, 6, 7 and 9 mm so you can match the rivet to the project rather than guessing.

Can I remove a rivet if I set it wrong?
Only by drilling it out, which risks damaging the material. This is why practising on a scrap piece first is worth the two minutes it takes.

Can the same machine set snaps and eyelets?
Yes. The hand press is universal — swap the die and it sets snaps, eyelets, grommets and jeans buttons too.

Start riveting properly

Once you know the two rules — double cap for visible backs, and post length equals material thickness plus 3 mm — rivets stop being intimidating. Pick up the Double Cap Rivet Press Machine & Die Set for the most popular setup, and give your bags, belts and straps the finish they deserve.