Nominal material thickness?

[bcammack]

I need to CAD up some shelving to fit a specific space and I just realized I don't know the actual thickness of 2-sided melamine-coated particle board.

How thick is 5/8" thick material such as I described? How about 3/4"?

Peripheral question: I plan on using biscuits and screws to assemble this. Is particle board going to be able to handle the swelling of the biscuit without deforming? Should I use 2-sided melamine-coated plywood instead? If so, what are the nominal thickness compared to particle board?

Thanks!

[jamesgilliam]

Brett, The best thing to do at this point would be to take a dial caliper and go to your supplier. That is probably the only way to get true dimensions for the materials. I have bought birch plywood from two different suppliers in my area and the thickness has varied by as much as 0.040". Even from the same supplier out of the same bundle I have found differences between sheets of as much as 0.020". That may not seem like alot, but the fit for dados in cabinet work it matters. Sorry I can't be more help. James

[richards]

Brett,

Thicknesses vary.

I use several digital calipers to measure the thickness of the actual material. Just last week, I got lazy and didn't measure a batch of 3/4-inch ultra-light MDF. My cut file supposedly left a 0.030-inch 'skin' on the bottom for vacuum hold-down. As the perimeter cut progressed, a part started to shift, and I knew that I was in trouble. When I got things stopped, I measured the ultra-light MDF's thickness - 18mm or 0.7086 inches. So, my cut depth of -0.720 inches was actually cutting about 0.010 inch deeper than the thickness of the material instead of leaving a 0.030 inch skin.

I have had no problems with biscuits in 0.750-inch thick particle board, both plain and melamine covered. When I use screws (most of the time), I use a V-cutter to counter-sink the screw holes and then manually drill the holes for the screws using a 5/32-inch bit in an air-drill. The Shotbot drills the counter-sinks perfectly and manually air drilling the screw holes free-hand saves a cutter change. In fact, most of the time when I'm drilling holes (except shelf-pin holes), I just use a 1/8-inch cutter on the Shopbot and drill a shallow spotting hole. Then I manually drill the hole free-hand or on the drill press depending on the size of the material and the size of the hole. Part of the problem of drilling holes with the Shopbot is the fact that I use a spindle and I don't want to put an axial load on the bearings. The other problem is that I don't have collets to handle anything other than 1/4-inch, 3/8-inch and 1/2-inch shanks.

[dray]

Same here. My supplier gets trupan 1/4 of the time then he gets some UL MDF from chile and canada and they are all slightly different

[jay_p]

Brett,

Get yourself a pair of digital calipers and measure everything. Very few building materials actually measure the same as they are named, and they can change depending upon storage, moisture, etc.
Shouldn't be any problem with biscuits.

Jay

[bcammack]

Thanks, folks. I get myself in this predicament frequently. I am not effective in communicating.

I know that there is variance. I was just looking for a generalization like "0.750 inch thick stuff is usually closer to 0.650 most of the time" Like how a 2x4 is more like 1.5x3.5 these days (if not even smaller)

You all are, in the final analysis, correct, though. I need to have precise information if I want the piece to fit precisely together in the intended space. Why waste the precision intrinsic to the CAD/CAM/CNC process, let alone my time?

I'll just buy a sheet and measure it before I finalize the CAD drawing.

Thanks everyone.