Proofgrade Thickness

I currently often buy materials at Home Depot. If I buy their 1/4" thick sheets of MDF, and stack 8 of them on top of each other, I would expect something that is very close to 2" thick. But it’s not consistent. Sometimes it’s off by as much as 1/8 of an inch. So their 1/4" thick material is not always exactly 1/4", and it’s not consistently too thin or too thick.

Will the Proofgrade material be more consistent in this regards? If I sell a design on the GF store that stacks four 1/4" thick Proofgrade layers, can I count on it being very close to 1" thick? Or will I have to have a parameter in the design for users to enter the “actual” width of the material, measured with calipers?


I too hope that they pay attenchen to this. One of the first things I learned with my cnc router was to put calipers to any wood product bought at Lowes or Home Depot and adjust acordingly. Also to get everything out of the same sheet if possible.


It seems hardware stores like homedepot do not account for sanding or saw cuts so their measurements are always off.
On other materials like plexi that I get from estreetplastics, the thickness is pretty consistant but the 1/8" plexi is not .125"…its .110".
Best to buy a caliper for accuracy. Laser settings dont really change but your Z setting and focal length can be affected.


I’m seeing that more now with all sorts of materials. They list the “nominal” size but deliver something smaller. I (sort of) get it with regards to things that get a finishing treatment (e.g. wood that gets milled before it’s dried) but I think it’s b.s. when it’s a manufactured product like plastics. There it seems only to be a way to cut material costs (aka raise prices) without being too obvious. It might make sense if the actual size was a common metric size so they could claim global consistency but .110 in is 2.7 mm so they’re not doing it for supply chain consistency.

On the other hand if my old .125" sheet is now .110" and I charge the same I just got a 12% price increase with no one the wiser.

Don’t get me started on why all of the cans in the supermarket that used to hold 16oz are now anything from 12.5 - 15oz and there are no 1lb cans anymore even though they’re the exact same physical size they used to be. :disappointed:


And oddly enough the PVC sheet and rod products I used to buy were often oversized by quite a bit, whereas Delrin and polycarbonate rod are close to spot on. The aluminum bar stock I’ve been buying lately is also 10-12 thou oversize in height and width, which is almost enough to allow machining to size for a better finish.

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Sometimes the engineered materials are manufactured to metric units. Home Depot has to decide if they want to sell 6mm plywood as 1/4" plywood or 6mm plywood. Even if you’re an American familiar with metric units, you’re very unlikely to instinctively know 6mm is about 1/4". So I get why they do it. Also, Home Depot, so the materials are unlikely to be made to the strictest tolerances, although they are probably fairly consistent. And this brings us to tradition versus lasers. With highly accurate and precise CNC equipment becoming more and more common outside factory floors and easy-ish to use design software becoming ubiquitous will the ancient and honorable construction paradigm of “we’ll make it fit on the work site” survive? Or will more and more customers demand more precise materials until Home Depot, Lowes, Menards, etc… become approved NASA suppliers?

The grocery store thing of the missing ounces is a rant I don’t have time for :rage:.

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True enough and I’m okay with that. But 1/8" ply or plastic would be 3 mm (.118" or .120”) with that approach. Millimeter sizing is not why they’re selling as 1/8" something that the small print shows as .110" (which would be 2.7mm). It’s disguised price hikes through managed perception.

It’s why I was conflicted when my son was working at an ad agency in Manhattan - he was good at creating the perception the client wanted but his job well done was another person’s deception. Fortunately he’s gone straight now :grin:


No wonder my jeans seem to fit tighter and tighter at the waist every year! The dang clothing manufacturers must be using less material…



I like the way you think…


unfortunately, that’d be a “nope” :wink: The reverse is true - they’re upsizing the clothes but downsizing the label. A woman’s size 8 now used to be a 10 or 12. Men’s clothes which used to be logically associated with the actual measurement (e.g. 34" was 34 inches) are now expanded as well (that size 34 pant is likely 35 or 35 1/2"). Makes people feel better about the clothes they’re buying then smacking them in the face that they need a size or two larger :slight_smile:

Some things you’re better off letting Madison Ave get away with the perception management :smile:

omg, now I’m really depressed…lolol

btw, anyone see that “inventor” on Shark Tank who wanted to sell basically fun house mirrors to clothing stores and consumers, that made people look slimmer than they really are? Talk about deceptive and false advertising!

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I would guess that if proofgrade is going to guarantee (for some value of guarantee) that the automated settings retrieved by reading the barcodes will engrave and cut properly, they’re going to have to exercise pretty close control over thickness. Might not be the nominal number, but will be consistent.

The whole “nominal” vs real measurement thing is such a dog’s breakfast. When I was a kids I was actually shown (reverently) some 2x4" 2x4’s. And plywood is all 1/64 thin to allow for “sanding loss” except when it isn’t. And I bet the 1/8" nominal for acrylic is based on window class, which was probably based on a wire gauge… (Remember the story that claimed to link 19th-century railroad gauges directly to roman chariot wheels?)

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They already do that with lighting to a fair degree. I would think the mirror isn’t an issue since it is pretty hard to keep people from realizing what they are looking at (distorted image). This because the mirror hinges on viewing angle so heavily. But I didn’t see the pitch, so maybe they accounted for that one.

Heck, if humor was fairly universal, department stores could put amusing posters and stickers in the changing rooms to raise the chances you are smiling when you look at yourself in the mirror, which would naturally enhance your opinion of what you see.

I suppose cats are pretty much universally amusing… so maybe that is a Shark Tank worthy pitch. Cat Posters for Changing Rooms.


Not just materials, tools too, cheap endmills are great, you don’t worry about breaking them so much but until I worked out that my 6.35mm (¼") mill was actually 6.2mm stuff just would not fit. I guess it means they can sell them as 6mm, 6.35mm, or ¼" +/- a tolerance.

I measure everything now, even expensive mills.


All TBD, but great suggestions and stuff we’ve been thinking about a lot recently.