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Please explain why 1/4" plywood does not fit into a dado cut with a 1/4" router bit. I had to move the fence and rout twice to get the bottom to fit into the dado. Obviously the plywood is to thick, or the 1/4" dado is too narrow. The difference is too small for me to see. Which is more likely?

It's time consuming to have to cut the dado three times (shallow cut, full-depth cut, widening cut). The plywood came from Lowe's. There's nothing special about it.
 

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I think it has to do with different tolerances between sheet goods manufacturers and the finishing they go through? Sanded vs unsanded. Just a guess..

A set of calipers or a micrometre would allow you to determine the exact thickness and choose an appropriate size but I've only ever made multiple passes. More work but a custom fit each time. Good luck!

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What kind of plywood is it, Mike?
Sanded one side Fir sheathing?
Not being critical, just looking for more info. I have no problem using sanded sheathing for shop stuff myself.
Can't get decent Hardwood plywood up here on the Sunshine Coast, so if it isn't critical to me...
 

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Discussion Starter #4
What kind of plywood is it, Mike?
Sanded one side Fir sheathing?
Not being critical, just looking for more info. I have no problem using sanded sheathing for shop stuff myself.
Can't get decent Hardwood plywood up here on the Sunshine Coast, so if it isn't critical to me...
Home Depot Special
 

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Please explain why 1/4" plywood does not fit into a dado cut with a 1/4" router bit. I had to move the fence and rout twice to get the bottom to fit into the dado. Obviously the plywood is to thick, or the 1/4" dado is too narrow. The difference is too small for me to see. Which is more likely?

It's time consuming to have to cut the dado three times (shallow cut, full-depth cut, widening cut). The plywood came from Lowe's. There's nothing special about it.
WTB one (bit or ply) is metric and the other (ply or bit) is Imperial...
save work...
cut the dado on the TS...
 

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I'm a little confused, you are saying the dado you cut with a 1/4" bit is too small for 1/4" big box plywood? That is completely backwards from what I've seen. Usually the plywood less than 1/4" thick and the dadoes are loose. maybe you had 3/8" which is about 1/16" over 1/4".

Calipers would be a good idea anyway.
 

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Calipers will tell the tail, but in the link Mike posted the spec sez the 1/4" ply 'Actual Product Thickness' is 0.47" (just over 15/32).
 

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I guess great minds think a like Herb, not sure how I got included in that though.:no: I guess even a broken watch is right twice a day.
 

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Usually finish ply is smaller because of the sanding not bigger. I know metric comes in 3mm for drawer bottoms and backs but I thought much thicker came in even mm such as 6 or 8. 8mm would be quite a bit thicker, about 5/16.
 

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The same reason your toilet paper is much smaller than the holder, a candy bar is 2 inches, etc. MONEY, they keep making it a little smaller, then a little smaller thinking we do not notice. WELL YEAH we do, especially in wood working. I was noticing today the under size 1/4" router bit I use for my drawers is not working. I am getting a gap with the oak plywood now.
Before long we will have to use 1/2 to fill a 1/4 in dado.
 

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homedepot in the US doesn't sell metric. 1/4" will be be something 7/32". If it was thicker than 1/4", they'd be selling it for thicker (and more $$$).

Maybe it was mislabeled product but 1/4" nominal is never thicker than 1/4".
 

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HD here would be sellin that for 3/8", never seen 5/16".

What is the metric 2X4 size?

Herb
38mm x 89mm. That`s how it reads in the Canada Building Code. Because metric is the law up here the Code is written in metric. It`s not supposed to be nominal in metric, it`s supposed to be actual.

If that ply came from offshore, especially China, the chances are it`s metric. Just about everything I`ve seen out of China is a metric equivalent of the Imperial version.
 

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38mm x 89mm. That`s how it reads in the Canada Building Code. Because metric is the law up here the Code is written in metric. It`s not supposed to be nominal in metric, it`s supposed to be actual.

If that ply came from offshore, especially China, the chances are it`s metric. Just about everything I`ve seen out of China is a metric equivalent of the Imperial version.
So what is 38mmX89mm equivalent in inches (actual)
 

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It might be a metric thing.
If you have got hold of a 6mm bit, thats fractionally under 1/4".
some charts give you a straight conversion between 6mm and 1/4" but they have rounded things up and down. a true mathematical conversion of a 1/4" is 6.35mm. so if it is a 6mm bit, the board wont fit by 0.35mm which is just over 1/32"
 
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