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Drawers

Drawer layout is dependent on panel design. Panel top and bottom reveals, slide offset, minimum slide clearances and face indexing all affect layout.

Drawer faces are always a multiple of 32mm tall, less gap/reveal. Drawer faces can be indexed with their top and bottom edges (before reveal is subtracted) centered on ("System"), or between ("Shifted"), system holes.

Drawer Terms and Acronyms - basics
Full Overlay
   Bottom Clearance - basics
   Undermount - examples
Half Overlay/Flush Inset
   Indexing Wood Drawer Boxes - basics
   Center Indexed - examples

Indexing Wood Drawer Boxes

Balanced drawer boxes, like balanced panels, keep things simple. The following is a simplified version of the old How Wood Drawers Utilize System Holes article. Note: While the basic principles apply to all drawers, this is a fairly half-overlay/inset-flush centric article... Feb '10: added undermount slides... more
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Half Overlay Center Indexed

Half Overlay Center IndexedHalf-overlay and flush-inset drawers work quite well with true center registration. All drawers have the same top and bottom drawer box to face reveal. The one potential issue is that undermount (37 BC ... and Tandembox, 33 BC) drawer layouts work much better with shifted system holes and bottom mount (typ. < 22 BC) layouts work much better when face edges fall on system holes. Note that center indexing bottom mount boxes only works with applied bottom drawer boxes. Side mount slides work either way.

Half Overlay Center IndexedThe only difference between the half-overlay and inset flush layouts are that the system rows are moved back the thickness of the faces (or a tad less) and the drawer faces are 22mm shorter (and narrower, -11 all edges).

All system registered half-overlay/railed inset cabinets have slide bottom clearances of 32mm - 1/2 panel thickness (e.g. 32 - 9.5 = 22.5 BC). For shifted registration its 48mm (32+16) - 1/2 panel thickness (e.g. 48 - 9.5 = 38.5 BC).

See also: Indexing Wood Drawer Boxes and Drawer Terms and Acronyms
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Bottom Clearance

Cabinet bottom clearance is the distance from the system hole that a slide will mount to, to the top of a horizontal cabinet member. Drawer slide bottom clearance is the distance from a slide system mounting hole, to the bottom of the slide (lowest point). The required drawer slide bottom clearance cannot exceed the available cabinet bottom clearance.

Working with 19mm material and 3mm gaps, all drawer faces overlay all drawer rails/stretchers 8mm and the bottom clearance is 22.5 for system registered faces and 38.5 when using shifted face registration. With all shared panel cabinets, the bottom of the cabinet has a reveal of at least 11 (i.e. <= 8mm overlay) and the rail BC numbers work well - 22.5 for bottom mount/Metabox/Zargon (typ. 16-19 BC) and 38.5 for Blum style undermounts (typ. 37 BC) - for all drawers. The problem with full-overlay is that the bottom drawer face has significantly less reveal/more overlay on the cabinet bottom (VS at the rails). What compounds the issue is that the available BC is not close to standard slide BC's. This is why there is a full page covering full-overlay bottom clearance

The table uses a 19mm panel thickness (PT) and a 3mm gap (g). Bottom Clearance (BC) = start hole (+/-32) - PT.
revealoverlay sys startsys BCshift startshift BCtype
r PT - r 32 - 1/2 g + rstart - PT48 - 1/2 g + rstart - PT
22 -3 52.5 33.568.5 49.5 full inset
11 (22) 8 (-3) 41.522.557.538.5ALL rails, half-overlay/System32, (railed-inset)
9.59.5 40215637custom
4.5 14.535165132 KISS
316 33.514.5 49.530.5 custom
1.517.5 3213 4829modular, Proulx
01930.511.5 46.527.5 modular/True32, Process32

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Full Overlay Bottom Clearance

Traditionally, 32mm drawer and door faces are indexed so that their top and bottom edges center on "System" holes. With half-overlay and inset cabinets (where most box components center on system holes), drawer layouts are relatively easy because all drawer openings are the same size (when drawer rails are used).

With full-overlay cabinets, the bottom drawer faces look best when they are flush with the box bottom (0mm reveal). What this means is that the bottom edge of the bottom drawer opening is 9.5-19mm higher than the rest of the drawer openings, i.e. is 9.5-19mm closer to a system hole. Because drawer slides are mounted to system holes, the bottom drawer clearance (BC) for all slides is determined by the bottom drawer. The reduced clearances caused by full overlay faces can complicate drawer layout... more
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Full Overlay Undermount

There are two drawings, one with layouts based on system hole registration and the other with layouts based on shifted registration. Both are based on fairly standard undermount slide specifications. The examples all work with standard full overlay box sides (n x 32mm)... Both BC (bottom clearance) numbers are wrong, they should be 43.5 system/27.5 shifted (62.5 system/46.5 shifted mount holes minus a 19mm box bottom)

Full Overlay UndermountShifted (face edges between system holes) registration layouts. The first is straight 32mm system (better drawing) and requires that the slides be mounted using the lower (by 12mm) row of mounting holes, but not all undermounts have 2 rows of mounting holes. The second layout is Plus 32 which wastes less space and uses the standard mounting holes (as do the rest of the layouts). Both were drawn with drawer boxes sized in multiples of 32mm. The Plus 32 boxes could be up to 14mm taller (which may allow drawer front adjusters in the top rail). Using 32 x N + 5 would result in an easy to remember/use 32mm top B2FR (adjuster holes +/- 32mm in face/box). The third layout is as close as I can get center registration to work (the true center registration of HO/FI doesn't work). The fourth layout is Blum's Process 32 and is pretty worthless because there is no consistent relationship between the drawer boxes and faces.

Full Overlay UndermountSystem (face edges on system holes) registration layouts. The straight 32mm system layout (better drawing) wastes a bit more space (...not much, the mounting holes are only 4mm higher). The Plus 32 and first center indexing layout are better, but there's no room for drawer rails. The second center indexing option requires drilling mounting holes centered between system holes for all but the bottom drawers (opposite of the center indexed shifted layout).

See also: Full Overlay Bottom Clearance and Drawer Terms and Acronyms
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Drawer Terms and Acronyms

I've used so many acronyms in my drawings that I'm starting to confuse myself. Hopefully the following will help me to standardize them and help you to decipher my drawings. I'll try to come up with images of each, Indexing Wood Drawer Boxes has a couple.

Slide Offset (SO) - the distance from the slide system mounting hole, to the ledge that the drawer box side or bottom sits on. Applies to all bottom and under mount slides. This is a primary variable when designing a drawer layout, or in determining whether or not a manufacturers slide will work with a given layout.

Box Offset (BO) - the distance from the slide system mounting hole, to the bottom of the drawer box (lowest point, typically the sides). Applies to all slides. With under-mounts, this is slide offset (SO) + lip (how much the drawer sides overhang the bottom of the box). With bottom mounts, box offset (BO) is the same as slide offset (SO). Since side mounts have no slide offset (SO), this is the number that matters when designing side mount drawer layouts.

Face Offset - the distance from the slide system mounting hole, to the bottom of the drawer face. For system registered faces its 32 (x n) - 1/2 face gap/reveal (typ. 30.5). For shifted registration its 32 (x n) + 16 - 1/2 gap/reveal (typ. 46.5). Used for calculating B2FR (below).

Box to Face Reveal (B2FR) - the distance between the drawer box top/bottom and drawer face top/bottom. To be able to consistently register drawer boxes to faces, the top and/or bottom B2FR needs to be the same for every drawer in every drawer stack. While it is possible to center register faces without having consistent top or bottom B2FR's, true center registered faces have equal top and bottom B2FR's. B2FR's can be calculated as follows:

   Bottom B2FR = face offset - box offset
   Top B2FR = face height - box height - bottom B2FR

Slide Bottom Clearance (BC/SBC) - the distance from the system hole that a slide will mount to, to the top of a horizontal cabinet member. Minimum required BC is the distance from a slide system mounting hole, to the bottom of the slide (lowest point). Used for determining slide to cabinet box bottom, and/or rail/stretcher, clearance. Will the slide work with the layout, will it be reasonably close to horizontal cabinet members. While slide specifications are usually fairly similar, some manufacturers slides won't work with some layouts. One example is Salice under-mounts which require a minimum BC of 42.5/30.5 (top/bottom mounting holes) VS the more standard 37/25 (e.g. Blum)... Note: At least one drawing uses SBO (slide bottom offset) instead of BC (bottom clearance).

Top Clearance (TC) - how much space is needed to install/remove the drawer box. While most slides specify at least a bit of top clearance, this is most important when designing bottom mount drawer layouts - because 3/4 extension bottom mount slides need a relatively large amount of TC.

Bottom mount specifications for top clearance typically assume the drawer box depth is roughly the same as drawer slide length and that the drawer will be pulled straight out. Slide specifications less ~3.5mm will work but require tipping the drawer downward so that the back of the box can clear the carcase when the drawer box wheels go over the carcase wheels. Reducing box top clearance more requires making the drawer boxes shallower than the slides or using full extension slides, i.e. have it so that the back of the drawer box comes past the front edge of the counter-top before the box is removed.

Box Side (BS) - the height of the box sides. Typically presented as some multiple of 32mm (plus a constant).
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