3/4" X 4' X 8' Birch Plywood!

[Gary Lange]

I am working on a Router Table so I buy some 3/4" X 4' X 8' Birch Plywood for the project. Now I don't check the thickness cause like a fool I think its 3/4" cause that is what Lowe's said it was. Well I get a bunch of the pieces cut out and start doing the dado work and set the dado at 3/4" and run my pieces. I got a scrap piece of MDF 3/4" check the dado's and we are cool. Then a little later I check the shelf that is going in the groove and it is like almost 1/8" to big. I check the Birch Plywood and find it is not really 3/4" but closer to 11/16". My dump mistake for not checking I know but was I that wrong in assuming that when I bought 3/4" plywood that I was getting 3/4" or does all birch plywood measure less then what it says at Lowe's. I bought a sheet of 1/2" X 4' X 8' at a Hardwood Supplier and it measured the 1/2" that it stated it was. I had to go and get more and remake the sides and then adjust my measurements for the smaller dimensions. It is going to work out just fine now that I know but really bugged me when I first found it. I guess next time it will be the Hardwood Supplier for me. Norm's Table sure has a lot of parts.

[Joe Chritz]

All plywood is like that. It is almost always a metric measurement and it always is very important to set the dadoes to match the existing sheet goods.

MDF and melamine are nearly always a true 1/2 or 3/4.

You may get better quality cores and veneers at a hardwood supplier but the thickness will be the same or at least very close.

Joe

[Steve Flavin001]

The undersize which Gary points out is standard for the last decade, or so, is really just 4 mm - nothing like 1/8"; e.g. about 1/32". Since this is "just" for a shop table, I am wondering what would justify the cost and labor to start all over.

In the future shim the dado set to exact size, or get a set of plywood router bits of for the respective plywood sizes, 1/4, 1/2, and 3/4"

[Harley Reasons]

Freud makes a set of plywood router bits, has 4 different sizes in it for about $69.00 + shipping. I either got mine from Rockler or Woodcraft. They work like a champ.

[Don Abele]

Most of the ply I work with is 23/32" and it's even listed that way. The Freud dado set I have has the shims necessary to create a dado this thickness. Like several others have mentioned, I also have the set of four router bits in the plywood thicknesses.

I always measure EVERY piece of ply in multiple spots with a set of calipers to get the REAL thickness before making any rabbits or dados. I've had two sequential pieces vary in thickness by 1/16.

Be well,

Doc

[Richard M. Wolfe]

I imagine that 3/4" plywood at some point was 3/4", but all I've ever gotten has been 23/32". Just about every company that sells router bits sells one that size made specifically for dados for plywood. I have one chucked into an old router that's dedicated to that.

[Frank Drew]

This may be the reality, and we have to live with it, but we don't have to like it. Does everything have to be cheapened and degraded???

[Ken Fitzgerald]

I got burned by that recently big time! I was building the 1st of my shop cabinets. I inset the dados for the 1/2" plywood back just under 3/4 from the back of the sides and tops so I could use a french cleat and the cabinet would be very close to flush with the wall.

I checked a SCRAP of 1/2 plywood for thickness as the full sheet I was going to use was under a pile of scrap.

After I got the sides, top and middle shelves glued and screwed, when I went to install the back in the dados....you got it! Luckily, with a little glue in the dados and my 8 lb. persuasion hammer and block of wood. And when the glue I used as a lubricant set up, I'm not worried about that back coming out.:D

[Gary Lange]

The undersize which Gary points out is standard for the last decade, or so, is really just 4 mm - nothing like 1/8"; e.g. about 1/32". Since this is "just" for a shop table, I am wondering what would justify the cost and labor to start all over.

In the future shim the dado set to exact size, or get a set of plywood router bits of for the respective plywood sizes, 1/4, 1/2, and 3/4"

Steve it was just a case of I wanted it to look good when I got it done. It only cost another $25.00 to make the new sides and I can use the left over plywood for another project down the line. Since I am just getting started in this wood working stuff I felt like doing it right was as important as anything else. Now that I know that the Lowe's Birch Plywood is less then 3/4" I won't be making that mistake again. We all started someplace and learned from the mistakes we made on the way. The 1/2" Birch plywood from the Hardwood Supplier was 1/2" as stated. Lowe's must get theres from China.

[Harley Reasons]

The Blue BORG's plywood comes over on the same boat as the Orange Borg's. If you don't have a good set of calibers to measure plywood thickness, then that should be your next investment. Even a cheap set of General Brand calibers are better than none at all. However, digital are very nice & precise. They are great also for measuring your dado depth of cuts allowing you to fine tune to exactly where you want it.

[Gary Lange]

That's a good idea Harley Thanks for the tip.

[Matt Ocel]

It only took me one time to get burned on the called out thickness size.
Then went and got a caliper. Problem solved, I check every sheet and set my dado accordingly.


As for "Does everything need to be cheapened and degraded" well yes and no.

Some things, yes, are just plain junk, where as some items through an engineering process become smaller, lighter, less expensive but actually are all around better.

[Basil Rathbone]

Just glue a sheet of formica to your -3/4 table top and it will bring the thickness to as close to 3/4 as can be measured. Plus your table top will look great.

[Curt Harms]

I was looking for some decent shop quality ply and found some 1/2" B/C ply at Lowes that was....1/2":eek: replete with APA and "made in USA" stamps. The thing that's weird about it is that it's 4 plies. I'm not sure how they worked the grain orientation. They did have some 4X4 sheets that were similar but were 5 plies.

[Jim King]

Here in South America what you would buy as 3/4 is actually 19 mm.

[Gary Lange]

We learn from our mistakes and reading about those of others such as myself. I am putting it together now and it looks pretty good if I do say so myself. It is just a shop table but it is good to practice on something like this rather then an oak table that needs to be perfect. Next trip to Lowe's I will get some calipers.

[Rich Engelhardt]

Hello,

Next trip to Lowe's I will get some calipers.
Harbor Freight sells a decent digital caliper for around $20.00. w/a resolution of 0.0005'' .
They also have a cheaper one - by about half - which has half the resolution.
I use the lower resolution one all the time.
The digital readout is easy to read.

[Paul Greathouse]

Gary

Another tip for you, if you use a router to mill your dado's. Use the next size smaller bit than the width you need and make two passes. IE 1/2" bit for 3/4" dados, that way if the ply is undersized then you can allow for the correct thickness on your second pass. Decent quality 1/2" straight bits are reasonably priced and pretty easy to find locally or on the internet.

[Rick Hubbard]

FWIW, the shrinking dimensions phenomena in plywood all come back to economics. More precisely, it is a result of plywood manufacturers (and their accountants) trying to increase the yield from raw timber. For example, reducing the thickness of a 3/4 inch panel to 23/32 resulted in a yield increase of almost 4 1/2 %. When you are operating a plywood mill that is using, say 100 million feet of raw material per year at a ready-to-use veneer cost of $225 per thousand, the cost savings would be more than $960,000, most of which would fall directly to the mill’s bottom line.

Similarly, the 4-ply plywood developed for essentially the same reason. This product became popular in the late 1960’s as a way of reducing labor costs. At this time, plywood was assembled one piece at a time by 4 man spreader crews. By reducing the number of plys in 1/2 plywood from 5 pieces of 1/10 inch thick veneer to 4 pieces of 1/8 inch thick veneer, the number of physical movements required by workers who were doing the assembly was reduced by a factor of 20% (although the actual time saved was something closer to 16% due to other factors). Hot press (cook times) for the 4 ply plywood was slightly longer, but the over-all gain in press through-put (on a cost per panel basis) was something in the vicinity of 8%.

[John Schreiber]

FWIW, the shrinking dimensions phenomena in plywood all come back to economics. More precisely, . . .
More precisely, we are sold less at a lower quality and we accept it. We are as much to blame as the manufactures. It's a demonstration of poor ethics as much as it is a demonstration of good economics.

[Rick Hubbard]

.....We are as much to blame as the manufactures. ....
Agreed.

My sense is that American consumers are so intent on "CONSUMING" that they will consume whatever is placed before them.

The examples of this bizzare behavior are too numerous to count, I'd guess. For as many years as I can remember (and it's quite a few) Americans have lined up to buy third-rate junk from US car companies. It looks like now, just maybe, consumers are beginning to dummy-up a little. I heard on the way to work this morning that for the first time Toyota will have sold more cars in a 3 month period than ANY of the domestic manufacturers! Further evidence that **perhaps** consumers are fed-up is the news item that GM stock is selling at the lowest price since 1954.

We'll see, I guess.

Rick

[Bruce Benjamin]

Now that I know that the Lowe's Birch Plywood is less then 3/4" I won't be making that mistake again. We all started someplace and learned from the mistakes we made on the way. The 1/2" Birch plywood from the Hardwood Supplier was 1/2" as stated. Lowe's must get theres from China.

Gary, I know it's been said in this thread several times but just to make sure you understand...Most but not quite all plywood is sold undersized now days. Not just that from Lowe's or that made in China. A while back I bought some inexpensive poplar plywood from my hardwood supplier and I was surprised to find that it actually measured 3/4" thick. But the 1/2" that I bought later was about 1/32" shy of 1/2". So don't just assume it was Lowe's fault. Expect if from anyone and be pleasantly surprised when it isn't.

Regarding those plywood router bits that everyone sells, I've never found a good use for them. The problem is that the bit manufacturers assume that all 3/4" ply is really 23/32" or all 1/2" ply is really 15/32". In my experience it's not. It will vary so how is the plywood bit set going to be any better than a regular straight bit set? It may work sometimes but not all the time.

Either shim your dado stack blade set to match the plywood or make multiple cuts with either an undersize dado stack or, (as I prefer) use a smaller router bit and make multiple passes.

Bruce

[Chris Padilla]

Just be happy that whatever the thickness your plywood, that it is at least CONSISTENT throughout the plywood. I have had some "cabinet grade A-1" plywood that meandered on me. Now that was FUN to deal with. :(

[Gary Lange]

I got the dado's done right on the second set of sides and have it together. I made a few bone headed mistakes but I am working around them and should have it done soon. Need to make the top and fence yet. It has been a good learning experience to say the least. I have been waiting for about 30+ years to have my own workshop so I am enjoying myself on rainy days and fishing when it is nice. God I love retirement!!!!!!:):):):):):):):):)