Legacy/Retro-Fit Information Page
Retrofit: Exposed Hinges → 35 mm Concealed Hinges
Thinking about upgrading visible (“exposed”) hinges to modern soft-close concealed hinges? Read this first. Your existing doors must be drill-compatible for a 35 mm cup.
What “compatible” means
Concealed hinges require a round 35 mm (≈ 1-3/8″) “cup” hole bored on the back of each door. Most standard cups are ~12–13 mm deep (≈ 1/2″). To retrofit your existing doors:
- Door thickness: typically 5/8″–3/4″ (16–19 mm) works best. Thinner doors may need a shallow-cup hinge.
- Room for the cup: there must be enough wood behind the panel—no glass/inset panel where the cup lands.
- Setback room: cup center is usually ~21–22.5 mm from the door edge (varies by hinge/overlay). That edge area must be solid.
These are typical industry ranges. Final dimensions depend on the specific hinge + plate you choose. We’ll guide you to a safe setup.
Quick self-check (5 minutes)
-
1
Measure door thickness
- ≥ 5/8″ (16 mm): generally OK for standard cups.
- ~1/2″ (12–13 mm): may require shallow-cup hinges (reduced depth).
-
2
Check the panel behind the hinge
- Where the cup goes, confirm it’s solid wood/MDF—not glass, metal trim, or a thin raised panel.
- Avoid drilling into stile joints or panel grooves.
-
3
Check the cup position
- Standard cup center is ~21–22.5 mm from door edge.*
- Leave ≥ 3–5 mm of material between the cup edge and door edge after drilling.
*Exact spec varies by hinge/overlay; we’ll match it for you.
-
4
Run a test
- If possible, drill a test door (or use an offcut).
- Use a 35 mm Forstner bit and a simple jig; drill ~12 mm deep, adjust if spec calls for 13 mm.
Common outcomes
- Doors 5/8″–3/4″ thick, solid in the hinge area.
- Flat panel or shaker with solid stile where the cup goes.
- No glass or thin aluminum trims at the hinge location.
- Very thin doors (~1/2″) without a shallow-cup option.
- Glass-insert doors or raised-panel doors with very narrow stiles.
- Metal/stone/composite faces that cannot be drilled.
Face Frame vs. Frameless (Euro)
| Cabinet Type | Retrofit Notes | Mounting Plate |
|---|---|---|
| Face Frame (FF) | Use a concealed hinge + a face-frame plate (often “wing” style). Recommended overlay for simple retrofits: Half Overlay. | (0/3/6 mm options fine-tune reveal) |
| Frameless / Euro (FR) | Concealed hinge mounts to the case side via a Euro (often “wing” style) plate. Reveals set by plate height and drilling pattern. | (0/3/6 mm options fine-tune reveal) |
Plate height (0/3/6 mm) + hinge cams give you the last bit of reveal/gap control.
Considering Drawer Upgrades? (Undermount Retrofit)
Minimum requirements (most brands)
- Drawer box hole & rear notch: undermount runners need a small hole and a notch at the back underside of the box for the hooks/rollers to seat.
- Bottom setback & clearance: the drawer bottom usually sets up from the underside and sits above the runner hardware. Follow the runner’s notch/hole diagram.
- Side thickness: many systems assume 5/8″ (~16 mm) drawer sides. 1/2″ or 3/4″ can work if the runner supports it.
- Runner length vs inside depth: choose 18″ or 21″ undermount length that doesn’t exceed your inside cabinet depth.
- Locking devices: most undermounts require clip/locking devices at the front underside—plan for those.
Face Frame vs Frameless (undermount)
- Usually the easiest retrofit if your drawer boxes meet notch/hole and thickness specs.
- Often requires new drawer boxes sized for undermount geometry, or additional blocking/adapter brackets. Expect extra work.
- Converting existing side-mount boxes is frequently not plug-and-play due to width and bottom position.
Quick measuring checklist
- Inside cabinet depth (to choose 18″ vs 21″ undermount).
- Drawer box outside width & opening width (confirm clearances).
- Drawer side thickness (1/2″, 5/8″, 3/4″).
- Box construction: bottom position, rear panel area clear for notch/hole.
What if I can’t notch my drawers?
- Use side-mount soft-close slides (simpler retrofit, no notching).
- Or order new undermount-ready boxes sized for your cabinet and runner choice.
If your current box doesn’t have the rear notch & hole—and you don’t want to modify boxes—stick with side-mount upgrades (we stock 18″ and 20″ lengths) or plan for new boxes.
Tools & prep
- For hinges: 35 mm Forstner bit, cup-boring jig, depth stop (~12 mm), square & layout template.
- For undermount slides: manufacturer’s notch/hole template, drill bits, jigsaw/trim router for back notch, clips/locking devices.
- Safety: eye protection, backing board to prevent door blowout, hearing protection when routing.
FAQ
Can I retrofit any exposed hinge door?
Not always. The door must have enough thickness and a solid area to accept a 35 mm cup without breaking through. If in doubt, do a single-door test.
Do I need new mounting plates?
Yes. Concealed hinges pair with specific mounting plates (Face Frame or Euro). Plate height helps fine-tune overlay.
Can I switch side-mount drawers to undermount without new boxes?
Sometimes, but often no. Undermounts need a rear notch & hole and specific bottom/side geometry. Many existing boxes won’t meet those specs without modification.
What slide lengths do you stock for simple retrofits?
Side-mount: 18″ & 20″ (even-inch increments). Undermount: 18″ & 21″ (choose the longest that fits your inside depth).
Next steps
Tip: Send photos of your doors/drawers (front & back), box thickness, opening width, and inside depth—we’ll confirm the cleanest path (concealed hinge + slide choice) before you order.