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Stupid stupid me. China 3/4" plywood is thinner than TRUE 3/4" plywood!

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Forum topic by Holbs posted 12-02-2015 01:32 AM 1185 views 0 times favorited 16 replies Add to Favorites Watch
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Holbs

1654 posts in 1722 days


12-02-2015 01:32 AM

Topic tags/keywords: plywood 34 18 mil 0703 china plywood

I remember years ago, I read that box store 3/4” plywood was not actually 3/4” or 0.750”, but more 45/64th or 18mil 0.703”. I use SketchUp to create things just to see what the end result kinda looks like. For some mystical old man reason, I’ve been inputting 3/4” and not 45/64th and noticed some joints being loose or actually off, because I forgot there was a measurement difference. Arrggggh. I talked to my hardwood supplier and asked about his 3/4”. He said it is exactly that…3/4”, and it’s only $2 less than the box stores. So keep that in mind for those who buy plywood at the box stores vs hardwood supplier.
I am not sure what everyone else pays for red oak plywood, but here in northern NV it is a little more spendier than average since located in wasteland. $48 for 0.750” is better than paying $49 for 0.703”. Hardwood supplier says plywood gets cheaper as well, just right now it’s $48.

  • On a side note, my hardwood supplier is only open Mon-Fri 8am-5pm, closed weekends. I do not have time thru the week to get the 3/4” plywood due to daytime job of 8am-4:30pm (hence, relying on box stores often). I asked him about it and he said order it via phone during the day. They will set the order outside (no security, possible theft if sits outside too long) and I can rush home to grab my Dodge 1500 pickup and be there by 5:15pm’ish to grab it. Ok..maybe 5:30pm with rush hour traffic.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter


16 replies so far

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ChefHDAN

927 posts in 2542 days


#1 posted 12-02-2015 01:51 AM

Question or rant, I’m not sure, but I feel your pain (with my best Clinton accent)

I’ll pile on because I have 2 sets of “undersized” plywood bits that are a crap shoot to have fit the ply. Best lesson learned on my side is an exact width dado jig when applicable, shims on the dado, tape shims on the router guide fence for 2nd pass, AND ALWAYS remember to cut a Damn sample first… Don’t know why I frequently forget the small sample before the 3 foot dado…

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

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Holbs

1654 posts in 1722 days


#2 posted 12-02-2015 01:54 AM

there..added ”!” :)
My hardwood supplier said his 3/4” plywood is exactly 3/4”. I have not bought any as yet. Would this be true for most hardwood suppliers? Or is quality plywood still off a little here and there?

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View Daruc's profile

Daruc

460 posts in 825 days


#3 posted 12-02-2015 02:40 AM

I don’t think your going to get a full .750 in a plywood these days. China or American
(could be wrong though)

-- -

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woodbutcherbynight

3130 posts in 2101 days


#4 posted 12-02-2015 03:32 AM

Kinda like a 2×4 has not been a 2×4 for how long? Anyone?

-- Live to tell the stories, they sound better that way.

View rwe2156's profile

rwe2156

2572 posts in 1173 days


#5 posted 12-02-2015 01:02 PM

I agree with Wood dust. The premium ply I’ve bought from my supplier is 18 or 19mm, not 3/4”.

Don’t think they make it anymore.

In the end, it doesn’t matter you just build it into the design.
I’ve found it helps tremendously to simply convert everything to metric.

-- Everything is a prototype thats why its one of a kind!!

View bondogaposis's profile

bondogaposis

4305 posts in 2044 days


#6 posted 12-02-2015 01:32 PM

I haven’t seen any true to dimension plywood for many years, even the $120 a sheet stuff.

-- Bondo Gaposis

View johnstoneb's profile

johnstoneb

2488 posts in 1865 days


#7 posted 12-02-2015 01:51 PM

I think all plywood is metric. Even that made in the US because it is sold on an international basis and the rest of the world is metric.

I use Sketchup for my plans but in the shop once the outside dimensions are established everything is measured and cut to fit.

-- Bruce, Boise, ID

View Fred Hargis's profile

Fred Hargis

4482 posts in 2186 days


#8 posted 12-02-2015 01:53 PM

The only plywood I use for furniture projects anymore is cabinet grade ply from Columbia Forest Products. Even at that, none of it except the prefinished both sides is a true 3/4” thick (or 1/2”, or whatever). I guess the prefinished is because of the thickness of the coating…

-- Our village hasn't lost it's idiot, he was elected to congress.

View Nubsnstubs's profile

Nubsnstubs

1086 posts in 1423 days


#9 posted 12-02-2015 02:52 PM

I owned my own cabinet shop for 40+ years, and from day one, I have never seen a 3/4” sheet of furniture grade plywood measure out to 3/4”. Always about 1/32” smaller. Doesn’t matter the grade, A1, A2, or B grades to Shop grades. Always the same.

When they started using MDF as the core, the 3/4” sheets measure approximately .740”. I’ve noticed that 1/4” MDF core sheet is as close to 1/4” as you can get. ............... Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

View bonesbr549's profile

bonesbr549

1400 posts in 2760 days


#10 posted 12-02-2015 02:56 PM

Yep, never been 3/4 in my world. I even bought a plywood router bit that was undersized on purpose, but that even stopped working as they thin the veneers to squeeze out another few cents out of every sheet. Someone finally showed me a method of cutting grove to a standard width and cutting a slight rabbit(rebate whatever) on the edge of the ply and its never been a problem since. Fits snug and gives a bit of extra rigidity.

-- Sooner or later Liberals run out of other people's money.

View helluvawreck's profile

helluvawreck

26797 posts in 2559 days


#11 posted 12-02-2015 03:09 PM

I’m not sure when was the last time I had ‘3/4 plywood’ that was 3/4”, but it’s been quite a long while ago if ever. I always fit the dados to the actual thickness of the plywood either by using shims on dado sets and/or undersized router bits.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

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CaptainSkully

1470 posts in 3251 days


#12 posted 12-06-2015 04:39 PM

They sell 23/32” router bits to make 3/4” plywood fit perfectly. This comes in super handy for letting shelves into the sides of cabinets. There’s also a way to build a dado jig so that you adjust it up against your stock, regardless of the thickness and the jig allows you to make a dado that fits perfectly.

-- You can't control the wind, but you can trim your sails

View Ger21's profile

Ger21

1074 posts in 2824 days


#13 posted 12-06-2015 04:44 PM

Hardwood plywood is almost never 3/4”. It’s almost always thinner, and can and will vary in thickness form batch to batch.
We’ve done jobs where we’ve ordered 150 sheets, and ended up with 3 different thicknesses.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

View Richard H's profile

Richard H

489 posts in 1373 days


#14 posted 12-06-2015 06:31 PM

I also find it odd that you hardwood dealer said it was exactly 3/4” since I have not seen that in a long time either. Is the plywood they are selling a traditional veneer core or is it something like a MDF core?

It seems like you are going though a lot of trouble to make the measurements match your plan exactly. I don’t know how elaborate these projects are but does your cut list really need to be that exact? I know it’s how each person approaches this issue but I rarely use plan dimensions for more than a reference and fit to size most of my pieces. I suppose if I was making a bunch of the same thing and wanted to batch them out or if I was using a CNC machine exact would be more important but for a one off project it just seems like a lot of trouble for little gain to me.

View Holbs's profile

Holbs

1654 posts in 1722 days


#15 posted 12-06-2015 07:03 PM

Rich…
I have not made a return trip to this hardwood dealer, but when I do I will bring dial calipers :) From the replies here, I doubt to see true 3/4” sheet goods.
I really HATE seeing a sliver gap in any of my joints, even if it’s 1/16th”. It’s not critical but it does get under my skin. When I see the fine precision wood working projects, I see perfectly mated joints, no gaps, etc. I am making work shop organization projects this winter, so thought it best to keep the practice of precision. Example: if I cut a 4 ‘x 4’ square, I do not want a 4’ x 3’ 11 7/8” square. I’ve gotten really good lately :) With my Grizzly track saw, I am down to 1/32nd deviation.
But you are right, Richard about plans being used only as reference. I am just not 100% comfortable keeping track of the different measurements and picturing how it goes together in my head like lego’s. This, I assume, comes with experience. I have much more to go :)

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

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