Blum Tandem Drawer Slides: Question on Drawer Box Measurements
I would appreciate any insight you guys have on drawer box measurements...especially if you have experience installing Blum TANDEM slides. I recently purchased Blum Full Extension TANDEM Drawer Slides for my bathroom vanity. These are undermount slides. I'm getting ready to start cutting boards for the boxes, but I've run into a dilemma/question with the measurements. The instructions are very explicit about determining the Outside Drawer Width and also for ensuring proper Inside Drawer Width. Below, I'm referring to these measurements as Step #1 and Step #2. Here it goes:
Step #1: How to Calculate Outside Drawer Width
Per the Blum instructions, to determine the Outside Drawer Width, you should deduct 5/8" from the Interior Cabinet Width when your Drawer Thickness is 1/2". The interior width of my cabinet frame is 11". If I deduct the required 5/8", my Outside Drawer Width should be 10 3/8". This seems pretty straightforward.
Step #2: How to Calculate Inside Drawer Width
Per the Blum instructions, the "Inside drawer width must equal opening width minus 1 21/32 for TANDEM to align and function optimally." In my case, that would be 11" minus 1 21/32", which equals 9 11/32". Again, this seems like a pretty straightforward calculation.
However, if I take the inside drawer width of 9 11/32" and add 1" to that for the total width of my two outside drawer members (1/2" x 2 = 1"), that would equal an Outside Drawer Width of 10 11/32". I don't know if you're still with me here, but I'm trying to compare that figure with the 10 3/8" I calculated under Step #1. I am off by 1/32nd of an inch when comparing the two figures. I've read that drawer box measurements need to be exact to work with Blum TANDEM slides. I'm concerned that my calculations are inaccurate in some way leading to the 1/32 difference.
I have one more question that might contribute to or compound my dilemma. The plywood for the boxes is labeled as 1/2" material, but I suspect the actual thickness is less than 1/2" (I will double-check). Does anybody know if the Blum instructions really mean a precise 1/2" when determining Outside Drawer Width? Or do they take the "nominal" effect of dimensional lumber into account already?
Thanks in advance for any guidance you can offer.