Hide Cabinet Cup Mortises (Face Frame Spacers)
A concealed hinge cup is bored into the door, not the face frame. For a face-frame cabinet, use a hinge maker’s matched mounting plate or adapter to position the hinge on the frame. Confirm the hinge model, door thickness, overlay, and clearances before drilling. Follow its template for cup diameter, setback, and depth; there is no universal code dimension.
A neat hinge installation depends on two parts working together: the cup mortise in the door and the plate or spacer fixed to the cabinet frame. If those parts are mismatched, the door may sit proud, bind on the frame, or miss the reveal you planned. The spacer does not hide or correct a poorly placed cup bore; it changes the hinge’s mounting geometry.
I treat the first hinge as a test fit, not a production run. That small pause gives you a chance to check the door position and swing before you bore the rest of the doors.
Plan the hinge, overlay, and door geometry
The cup mortise is the round recess in the back of the door that holds a concealed hinge cup. Overlay is the amount the closed door covers the cabinet frame. Measure the cabinet and door first, then choose a hinge and face-frame plate that are designed to work together.
Start by identifying the hinge model and reading its installation sheet. Hinge families can use different plates, spacers, drilling templates, and adjustment ranges. Do not choose a plate based on appearance alone; confirm that the manufacturer lists it as compatible with your hinge.
Measure the door thickness, frame width, door size, and planned reveal. The reveal is the visible gap between the door and its neighboring parts. Check the door’s back for a panel profile, rail, stile, or existing fastener that could conflict with the cup or hinge screws.
Record these details before drilling:
- Hinge model and cup diameter
- Door thickness and door-edge profile
- Face-frame width and intended overlay
- Plate or adapter model and listed thickness
- Desired gaps at adjacent doors, drawers, and trim
- Hinge maker’s cup setback and bore-depth limits
There is no universal IRC or IBC measurement for a cabinet hinge cup mortise. Building codes do not set one standard cup position for every cabinet hinge. Use the hinge maker’s template and dimensions for the exact hardware you plan to install.
Check cup-bore and face-frame clearances
Cup-bore clearance means leaving enough wood around the hinge recess and keeping the bore clear of the door edge, panel detail, and screws. A 35 mm cup is common, but it is not universal. Confirm the cup size and every drilling dimension in the selected hinge instructions.
For many 35 mm hinges, the maker specifies a bore depth around 13 mm. Treat that as a common reference, not a target for every door. Follow the stated depth for your hinge and door, and keep enough material at the front face so the bit cannot break through.
The K-dimension is the distance from the door edge to the nearest edge of the cup bore. Some systems use a K range of about 3–7 mm. If the bore is 35 mm across, its center is 17.5 mm plus K from the door edge. That gives a possible center range of 20.5–24.5 mm, but only when the hinge template calls for that K value.
| Check | Common reference | What to confirm before drilling |
|---|---|---|
| Cup diameter | 35 mm is common | Exact hinge model and template |
| Bore depth | 13 mm is common | Maker’s depth and safe remaining door thickness |
| K-dimension | About 3–7 mm in some systems | Hinge-specific edge setback |
| Bore-center position | 17.5 mm + K for a 35 mm bore | Template dimensions, not an assumed standard |
| Frame spacer or plate | System-specific | Overlay, plate compatibility, and door position |
Mark the door from the hinge template, not from a generic online diagram. Check that the marked circle stays within the door and does not cut into a shaped edge or panel. If the door is too thin for the required cup depth, stop and ask the hinge maker or choose a hinge suited to the door.
Install the matched spacer, plate, and hinge
A face-frame spacer or adapter is a hinge-system part that helps place the mounting plate on a face frame. Its thickness and position affect where the door sits and how the hinge pivots. Use the plate, spacer, and hinge combination listed by the manufacturer; do not stack loose or unapproved spacers.
Dry-fit the system before boring every door
Set the door against the cabinet in its planned position. Use the manufacturer’s overlay chart, calculator, or template to select a plate and adapter. Temporarily hold the hardware in place, or make a simple test setup with scrap matching the frame and door thickness.
Check the proposed door position at the top, bottom, and hinge side. Open the door through its full travel and check nearby doors, drawer fronts, trim, and the face frame. A hinge can fit the cup and still be wrong for the cabinet if the pivot makes the door strike an adjacent part.
Bore and mount one hinge
Clamp the door flat and secure it so it cannot shift. Use a Forstner bit or the maker’s recommended cutter, and set a depth stop. Keep the drill square to the door back. Bore slowly, clear chips as needed, and stop at the specified depth.
Install the cup using the specified screws and holes. Then fasten the matched plate or spacer to the face frame with the hardware called for by the hinge maker. Confirm that the screws are long enough to hold securely in the frame, without breaking through or striking another fastener. Do not guess at screw length or substitute a short screw simply because it is on hand.
Hang the door on that one hinge and check the fit. If the door is off position, review the plate selection and measurements before changing the bore. A spacer alters hinge geometry; adding an extra spacer can shift the pivot, reduce screw engagement, or make the door hit the frame.
Verify reveals, swing, and fastener engagement
A successful test fit has an even planned reveal, a door that clears the frame, and a hinge plate that stays firm under adjustment. Check the full opening and closing path, then inspect the screws and hardware. Make corrections with the hinge’s intended adjustments, not by forcing the door or changing spacer thickness at random.
With the door closed, compare the gaps at the top, bottom, and sides. Open it fully and look for contact with the frame, nearby doors, drawers, or trim. Then close it slowly. Binding, rubbing, or a sudden change in reveal can point to a plate position, overlay, or hinge compatibility issue.
Most concealed hinges provide some adjustment, but the directions and range vary by model. Use the maker’s instructions to adjust overlay, side position, and depth. Avoid pushing an adjustment to its limit to compensate for a wrong plate or misplaced bore.
Check each mounting screw for firm engagement. If a screw spins, the plate shifts, or the frame is damaged, stop and repair the mounting point using a method suited to the material and manufacturer guidance. Do not hide a weak attachment with a thicker spacer.
If a cup mortise or hole is exposed after a change, use a compatible approved plug or replace the affected component. A cover may improve appearance, but it does not correct an unsafe hinge position or poor screw hold.
Two fit checks that prevent rework
These examples are shop-style diagnostic scenarios, not universal hinge specifications. They show how to use measurements and a dry fit to find the cause of a poor door position before repeating the setup across a cabinet.
Scenario 1: Door sits too far out. The cup and hinge are installed, but the door face projects beyond the planned position. I would first verify the hinge model, plate number, and overlay chart. If the plate or spacer is not the listed match, changing the cup setback may make the problem worse. Confirm compatibility and test the corrected plate setup on one door.
Scenario 2: Door edge hits the frame. The door closes partway, then rubs the face frame. I would inspect the hinge’s swing path and plate position, then compare the door thickness and overlay with the maker’s chart. A spacer added without approval can shift the pivot and increase the collision. Do not force the door through the tight spot; correct the matched hardware or door position first.
For either case, mark the door and frame measurements, then change one variable at a time. That makes it easier to see whether the cause is the cup location, plate choice, or cabinet geometry.
Frequently asked questions
These short answers cover the decisions that matter most when boring a concealed hinge cup and mounting its plate on a face frame. The hinge maker’s instructions remain the final reference because cup dimensions, setback, plate selection, and adjustment range vary by system.
Is a 35 mm cup bore standard?
It is common, but not universal. Check the selected hinge’s cup diameter before drilling.
How deep should I drill the cup?
Use the depth in the hinge instructions. About 13 mm is common for some doors, but door thickness and hinge design matter.
What is the K-dimension?
It is the distance from the door edge to the nearest edge of the cup bore. Use the value specified for your hinge.
Where should the center of a 35 mm bore go?
For a 35 mm bore, the center is 17.5 mm plus the K-dimension from the door edge. Confirm both values on the hinge template.
Can I use any face-frame spacer?
No. Select a spacer or adapter that the hinge maker lists as compatible with that hinge and plate.
Can I stack spacers to move the door?
Do not stack unapproved spacers. They can shift the pivot and reduce secure screw engagement.
Does a spacer hide a badly placed cup mortise?
No. It changes the hinge’s mounting geometry; it does not correct a misplaced bore. Recheck the hinge instructions and repair or replace the affected part if needed.
How do I choose the mounting plate?
Use the hinge maker’s overlay table or calculator with your frame, door, and desired door position measurements.
How do I check the fit before drilling all the doors?
Install one hinge and its matched plate or spacer first. Test the reveal, full swing, and clearance to nearby cabinet parts.
Is there a building-code measurement for hinge cup placement?
There is no universal IRC or IBC cup-mortise dimension. Follow the hinge maker’s template and installation instructions.
Final check before repeating the layout
The reliable sequence is simple: identify the hinge, measure the cabinet and door, select the matched plate or spacer, then bore and test one door. Keep to the template’s cup size, K-dimension, and depth. Once the door clears the frame and the screws hold firmly, transfer the verified layout to the remaining doors.
(This article was written by one of our staff writers, Nathaniel Pierce. Visit our Meet the Team page.)
