I built this cabinet the other day and needed to make some drawers for it, and drawers can be a pain on the width since some styles of rails are less than forgiving. A little too wide and you have to shave wood of the cabinet and too small and you may have to shim out the rails with something. Most types of rails need 1/2″ for each side and I’m making the sides of the drawer out of 1/2″ plywood so you would think the front and rear pieces of the drawer would need to be 2″ less than the width of the opening, however 1/2″ plywood is usually really 1/32 thinner than it’s name so two sheets makes it 1/16″ smaller. That little difference creates many opportunities to get the measurements wrong so it’s good to have a way to test if you got it right before you glue and nail everthing together.
So one way to do that is to put the sides in the opening on one side and place the front and rear pieces next to them and then measure the space that is left.
That lets you know with some level of certainty how wide the final box will be. It isn’t by any means the only problem drawers can have but it can eliminate one of them. It is still possible to have a drawer bulge out in the middle of the sides or get something out of alignment or any number of ways it can be wrong. The biggest thing is to know how it should work and look to see where a drawer is now working right and adjust accordingly. I’ve had to cut a notch down the length of a drawer to allow the rail to be partially recessed but that is very limited because other parts of the rail start colliding with the drawer, or sometimes the front stile on the cabinet can be notched for the same reason but that may throw the allignment of the drawer to one side. Many times a solution to one problem can create another. It is definitely something to watch out for.
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