# Plywood Thickness and Blum Tandem Drawer Slides



## mculik5 (Nov 13, 2013)

I'm working on a design for a desk that will use Blum Tandem drawer slides. The desk will be built using 3/4" plywood and edgebanding. The Blum specs for the Tandem drawer slides indicate that the interior width of the drawer box must be the cabinet opening width minus 49 mm.

If I want my cabinet to be 18" wide overall, and I'm using 3/4" plywood for the sides, the top of the cabinet box needs to be 16 9/16" wide. This is 420.688 mm. The width of my drawer box then, based on the Blum specs, needs to be 371.688 mm wide. Obviously, it's not feasible to work at such a high level of accuracy.

My question is this:

If I round the drawer box width to 372 mm, will that cause any kind of binding or poor operation of the drawer slides? I would think Blum would build in (whether intentionally or unintentionally) 0.3 mm of "slop," but I've never used these drawer slides before. Is it perhaps better to round down to 371 mm? How much "slop" do I have with the Tandem drawer slides?

Basically, I want to make sure I can measure things to the millimeter (using a metric tape measure) and achieve a good result, vs. making a 49 mm spacer block and scribing cut lines off of that.

Any input is appreciated. Thanks.


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## AlaskaGuy (Jan 29, 2012)

What is the thickness of the drawer material? Which slide?


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## mculik5 (Nov 13, 2013)

The drawer box material is 3/4" plywood, so approximately 23/32", or 18.26 mm.

That said, based on the Blum specs, I can't figure out how drawer box material thickness matters, other than not exceeding the maximum. Meaning if the drawer slides are for 19mm (3/4") drawer box material, I can use any material up to 19mm thick. Thinner material is OK.

Based on the Blum specs, I think the goal of 19mm max material thickness is to maintain at least 5.5 mm of clearance between the drawer box side and cabinet side (which is where the 49 mm comes from, BTW….19 mm side thickness + 5.5 mm clearance = 24.5 mm per side X 2 sides).

Using 18.XX mm plywood with a 372 mm drawer back would provide a bit over 6 mm of side clearance, which is OK, I think.


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## 111 (Sep 2, 2013)

I don't think I have ever seen Tandum guides for 3/4" thick drawer material. 5/8" max.
What guide # are you talking about?


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## mculik5 (Nov 13, 2013)

The slides I'm referring to are 563F.


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## AlaskaGuy (Jan 29, 2012)

Drawer material will make a difference.

Look here:


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## MT_Stringer (Jul 21, 2009)

All of that foreign math confused me.  What I do is subtract 1/2 inch for the thickness of each side plus 1/32 inch per side.

So that results in drawer width = the width of the opening minus 1 1/16 inch.

Note: The mfg of my slides suggest subtracting 1/2 inch for each side. Yours may vary.

It is easier to add a thin shim or two if the drawer fits a little loosely vs remaking the drawer if it is too tight.

Good luck.
Mike


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## 111 (Sep 2, 2013)

Yea, your right. the 563F is for 3/4 material. Learned something new, thanks.
Thinner is OK, But I wouldn't round anything up or down, just make it as close to what the requirements are.
It says if your using 3/4" material you can subtract 7/16" from your opening to get the overall drawer width.


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## 111 (Sep 2, 2013)

Just looking at your comments, I don't think going with 372 would hurt anything. The wider drawer will change the holes in the back a little bit and when you put the clips on, they will be a little wider, but I don't think it will cause a problem. Just check those tolerances.


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## Loren (May 30, 2008)

Generally there's a couple of millimeters of play in the way
the slides are designed. Worst case you can make the 
drawer a little narrow if you're not sure and insert veneer
or paper shims under the screws to get it perfect.

I think rounding up by half a millimeter is probably fine. Look
at the manufacturers spec sheet for the product and it
should indicate the installation tolerances.


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## mculik5 (Nov 13, 2013)

Thanks for all the replies. I figured Blum was aware of all the variances in material thickness and build tolerance into their hardware. Also, the reason for using the metric measurements is because the cabinets will be made using the 32 mm system. The 32 mm system got me started combining imperial and metric measurements, and I find the whole metric thing easier, so I use it where I can.

Thanks again.


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