Undermount & Side-Mount Drawer Slide Clearance & Deduction Chart
Undermount drawer slides require deducting 42mm (1-21/32") to 49mm (1-15/16") from the cabinet opening width depending on drawer side thickness (1/2" vs 5/8"), plus a 12.7mm (1/2") bottom recess and a 14mm minimum top/bottom vertical clearance. Standard side-mount ball-bearing slides require a flat 1.00" (25.4mm) total width deduction (1/2" per side).
Master Reference Lookup Table
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| Action | |||||||
|---|---|---|---|---|---|---|---|
| Accuride 3832 Classic Full Extension | Accuride | Side Mount | 25.4mm (1") | 19mm (5/8") | 0mm (0") | Top: 12.7mm / Bot: 12.7mm | Cut-Sheet Tool → |
| Blum Movento 760H (High Capacity) | Blum | Undermount | 42.5mm (1.673") | 16mm (5/8") | 13mm (0.5118") | Top: 16mm / Bot: 14mm | Cut-Sheet Tool → |
| Blum Tandem 563F (3/4" Material) | Blum | Undermount | 42.5mm (1.673") | 19mm (5/8") | 13mm (0.5118") | Top: 19mm / Bot: 16mm | Cut-Sheet Tool → |
| Blum Tandem 563H / 563F (5/8" Material) | Blum | Undermount | 49mm (1.9375") | 16mm (5/8") | 13mm (0.5118") | Top: 19mm / Bot: 16mm | Cut-Sheet Tool → |
| Grass Dynapro Soft-Close (5/8" Sides) | Grass | Undermount | 43mm (1.693") | 16mm (5/8") | 13mm (0.5118") | Top: 20mm / Bot: 15mm | Cut-Sheet Tool → |
| Heavy Duty 250lb Cargo Side-Mount | Knape & Vogt / VEVOR | Side Mount | 38.1mm (1.5") | 25mm (5/8") | 0mm (0") | Top: 25.4mm / Bot: 25.4mm | Cut-Sheet Tool → |
| Hettich Quadro 4D V6 (Silent System) | Hettich | Undermount | 42mm (1.654") | 16mm (5/8") | 13mm (0.5118") | Top: 19mm / Bot: 15mm | Cut-Sheet Tool → |
| King Slide 4DPF Push-to-Open | King Slide | Undermount | 42mm (1.654") | 16mm (5/8") | 12.5mm (0.4921") | Top: 18mm / Bot: 15mm | Cut-Sheet Tool → |
| Salice Futura F70 / F7ONG | Salice | Undermount | 42mm (1.654") | 16mm (5/8") | 12.5mm (0.4921") | Top: 18mm / Bot: 15mm | Cut-Sheet Tool → |
| Standard Side-Mount Ball Bearing (1/2" Clearance) | Generic / Knape & Vogt | Side Mount | 25.4mm (1") | 19mm (5/8") | 0mm (0") | Top: 12.7mm / Bot: 12.7mm | Cut-Sheet Tool → |
Core Mathematical & Engineering Breakdown
Datasheet equations, derivations, and step-by-step worked shop math.
Why Undermount Deductions Change Based on Wood Thickness
Unlike side-mount runners that screw to the outer face of the drawer box, undermount runners (Blum Tandem, Salice Futura, Hettich Quadro) nest beneath the drawer and engage with the inner face of the drawer side. For Blum 563H runners, internal drawer width must always equal Opening Width minus 42mm. If you build with 15mm (5/8") sides, total external box deduction is 42mm. If you use 12.7mm (1/2") sides, external deduction increases to 49mm so the internal guide span remains exact.
Butt-Joint vs. Dado vs. Dovetail Sub-Front Cut Math
In modern cabinetry, drawer sub-fronts and backs fit between the two outer drawer sides. For butt joints and pocket-hole construction: SubFront Length = Overall Outside Box Width - (2 × Actual Side Thickness). For 1/4" housed dado joints: SubFront Length = Overall Outside Box Width - (2 × Actual Side Thickness) + (2 × Dado Depth). Dovetail joints use full box width for all four sides because pins and tails interlock flush at the corners.
Rear Notch & Locking Device Drilling Coordinates
Undermount runners require a clear rectangular cutout at the rear of the drawer box to clear the slide runner: 35mm wide by 12mm to 15mm high above the bottom recess. In addition, an upward hook hole (6mm or 7mm diameter, 10mm deep) must be drilled into the rear back panel at the manufacturer's specified offset (typically 7mm up from the bottom edge and 11mm inward from the outer box wall).
Interactive Micro-Tool: Real-Time Calculation
Adjust sliders and inputs below to calculate custom dimensions instantly.
Cabinet Opening & Slide Hardware
Pre-loads exact manufacturer deduction (1.9375") and bottom recess.
Exact clear opening measured between cabinet face-frame or sidewalls.
Selects a 21" nominal runner length while preserving cabinet rear clearance.
Opening 24" minus 1.9375" hardware clearance
Saw cut between 2 sides
Clearance top & bottom
Workshop Saw Cut-List (Dadoed Bottom)
- 2x Drawer Sides:21" × 4 5/8"
- 2x Front / Back Sub:20 13/16" × 4 5/8"
- 1x Bottom Panel:21 5/16" × 20 1/4"
- Bottom Recess / Dado:1/2" recess; 6.35mm dado depth
Order Blum Tandem 563H / 563F (5/8" Material) Runners
Genuine full-extension runners with integrated soft-close dampers and locking device clips.
Failure Modes & Workshop Troubleshooting Matrix
Common fabrication failures, caliper inspection methods, and prevention rules.
| Failure Mode | Root Cause | Caliper / Scale Check | Shop Prevention |
|---|---|---|---|
| Drawer box jams or refuses to close completely on undermount runners | Bottom recess height is less than 12.7mm (1/2"), causing slide mechanism to drag against drawer bottom panel | Caliper measurement shows 9.5mm (3/8") recess from bottom lip to plywood underside | Rout bottom panel groove exactly 12.7mm to 13.5mm above the bottom edge of side stock |
| Locking clip catches on front edge but rear hook does not engage | Rear notch height too shallow or 6mm rear hook hole drilled at incorrect vertical height | Slide arm strikes bottom of rear panel instead of slipping smoothly into notch | Cut rear notch to full 35mm width and 15mm height; use manufacturer drill jig for rear hole |
| Side-mount drawer box binds halfway through stroke | Cabinet opening is out of square or box width exceeds Opening minus 1.00" (25.4mm) | Opening width is 450mm at front face frame but pinches to 447mm at cabinet back | Check diagonal squareness of face frame and shim rear slide mounting brackets to match front |
Frequently Asked Engineering Questions
High-intent technical fabrication inquiries verified against lab standards.
Q1What is the standard opening deduction for Blum Tandem 563H slides?
Q2Why does drawer side thickness change undermount drawer box dimensions?
Q3What is the required bottom recess depth for undermount drawer slides?
Q4How much side clearance do standard ball-bearing slides require?
Related Programmatic Calculators in this Silo
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