Box width
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Shop estimate. Measure your stock and cut a test on scrap.
How to use it
- Measure the opening width and height, and decide the box depth. Depth is usually the nominal length of the slide.
- Type the side clearance per side. Many side-mount ball-bearing slides want about 12.7 mm (½ inch) each side. Undermount slides use a figure from that maker. Do not guess a brand from memory.
- Type any top and bottom clearance. Inset drawers often need a little air at the top.
- Enter the thickness of the sides, front, back, and bottom, and how deep the groove is cut.
- Cut the list. The bottom’s length and width include the two groove depths.
The formula
Box width = opening − 2 × side clearance. Front length = box width − 2 × side thickness. Bottom width = front length + 2 × groove depth.
- Between the sides. The sides are the full depth. Front and back are trapped between them.
- Groove. Cut into all four pieces. The bottom is larger than the opening inside the box by one groove depth on each edge.
- Slide. Not chosen for you. The clearance field is the whole of the slide’s requirement.
Worked example
A 450 by 120 mm opening, with 12.5 mm of clearance on each side and 3 mm at the top, leaves a box 425 mm wide and 117 mm high. The depth is the 400 mm you typed, which should be the slide length you are actually using.
Sides are 12 mm stock, full depth. Front and back sit between them, so each is 401 mm long. A 6 mm groove in every piece makes a bottom 388 by 413 mm. The 12.5 mm side clearance is a common side-mount starting point. If the slide sheet in your hand says something else, type that instead.
What it will not decide
- It does not pick a slide, a brand, or a load rating.
- It is one construction: a captured bottom and butt-between sides. A bottom that slides in under a shorter back is a different part list.
- A groove as deep as the stock is rejected, because it would cut the piece in two.
Questions
Is 12.7 mm always right for side-mount slides?
It is the usual half inch per side for a large family of North American side-mount slides. It is wrong for plenty of others, including most undermounts. The number on the sheet that came with the slide wins.
Does the bottom thickness change the panel size?
Not the length or width. It has to match the groove, with whatever hair of clearance you plane. The page checks that the groove does not pierce the side. It does not invent a groove width.
Where is the drawer front that you see?
This is the box. A false front or an inset face is extra, and it depends on the reveal you want around it. Size that after the box fits the opening.