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I need to cut datos into 3/4" oak plywood and found that my router bit is too big.  I'd purchased the 3/4"  at Home Depot and it measures .695 thickness.  I thought my 23/32" bit would work, but there's slop in the fit.  Is there another bit out there that would make the fit better? 

 

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Thanks Phillip for your reply.

I bet what you're saying is true, It's probably in metric. This is the first time I had this happen to me and I was stumped for a minute for a solution. I have undersized bits for different size plywood and thought I was covered. Surprise, Surprise!!
It's a good thing I made a test cut & fit with scrap material. Anyway, I'm making a tall cabinet that will have seven shelves in it. So I figured I cut a 5/8" dado on the side of the cabinet and then notch shelf material on the table saw to make a tight fit. I thought this would be the easiest and quickest solution.

My other thought was to use the Kreg pocket hole jig I just purchased yesterday. I've always favored dadoes as my first choice and just have to decide which way to go. I wasn't sure which way would be stronger.

I must say, I love this sight and getting ideas from fellow woodworkers. Thanks again!

John
Hi Jens Jensen,

I have these bits, but the plywood is less than the 23/32" cut. Like Phillip said, the plywood is probably foreign and in metric thickness. There's about .023 less than the 23/32" plywood which converts to somewhere between 11/16" - 45/64". Therefore allowing the extra slop in the dado cut.

What's surprising is that the sell 23/32" plywood and list it as exactly the thickness it is, which I've purchases many of times and successfully made tight dados. But on the Oak plywood, they list it as 3/4" plywood and it's actually less than the 23/32" material. Go figure! They should list it exact.
Hi Phillip,

You're correct, I do have all the undersized bits and now have this new Kreg pocket hole jig. Being brand new to this concept, I have to learn to trust this type of equipment. I'm sure I'll like it once I try it and I plan to give it a whirl tomorrow. Thanks so much for your help.



Phillip said:
You may want to find a metric bit that fits. If I read your original post right you have the special nominal size plywood dado bits. Though I would encourage you to try the other solution below.

The fastest solution to your problem is to trust the Kreg. I got to the point where I only use the Kreg pocket screws on the top and bottom shelves then set the middle shelf with the Kreg. All the rest of the shelves (if I have them) I make adjustable with 5mm shelf pins. I just completed an 8' tall bookcase that way. Yes I know 8' is a dumb idea, and I won't do it again, but the shop is 9' 6" tall so it worked OK. I set the middle shelf with pocket screws to brace and control bowing or belly in the sides. I do glue every joint, with Titebond. I set the back in 3/8" ply, glued perimeter and 1" staples all around. It is holding an incredible amount of weight. I have maybe 8 wall hung bookcases, 4' x 4' with top, bottom, and middle shelf. I am using a face frame, and Kreg pocket screws. Each shelf is holding solid books and magazines. Not so much as a groan under the load.

The short point is this. Use the Kreg, butt joints with glue, and Kreg Pocket screws will hold. The reason most of us use the Kreg is speed. You will be done with the shelves before you could get the dados dialed in correctly, and cut. I do like the use of Titebond, and face frame with a nice solid back. Your shelf will last longer than some high priced furniture.

Phil
I second what Phillip said about the pocket hole joints. They are all you need... even with plywood. Try it and you will not be disappointed!
These are metric bits

John said:
Hi Jens Jensen,

I have these bits, but the plywood is less than the 23/32" cut. Like Phillip said, the plywood is probably foreign and in metric thickness. There's about .023 less than the 23/32" plywood which converts to somewhere between 11/16" - 45/64". Therefore allowing the extra slop in the dado cut.

What's surprising is that the sell 23/32" plywood and list it as exactly the thickness it is, which I've purchases many of times and successfully made tight dados. But on the Oak plywood, they list it as 3/4" plywood and it's actually less than the 23/32" material. Go figure! They should list it exact.
http://www.sommerfeldtools.com/Ply-Groove-Bit-23_32CD1CL2-5_8OL1_2S...

This is the 23/32 nds bit

John said:
Hi Jens Jensen,

I have these bits, but the plywood is less than the 23/32" cut. Like Phillip said, the plywood is probably foreign and in metric thickness. There's about .023 less than the 23/32" plywood which converts to somewhere between 11/16" - 45/64". Therefore allowing the extra slop in the dado cut.

What's surprising is that the sell 23/32" plywood and list it as exactly the thickness it is, which I've purchases many of times and successfully made tight dados. But on the Oak plywood, they list it as 3/4" plywood and it's actually less than the 23/32" material. Go figure! They should list it exact.
Where are you located cause out here in West end all our plywood is fractions and MDF is in inches I dont think i have seen metric plywood Sorry about confusion


Phillip said:
Jens:
I am not trying to stir things up. I am confused, and curious if there is something I am missing. I follow the links you give to Sommerfeld Tools and the bits end up in the USA measurement listings. The sizes you sent match the sizes of my Grizzly Dado bits for plywood (USA) sizes. I was understanding that the special bits are due to the nominal size of the American plywood, not being a true full step measurement. All due to shrinkage. At least that is the explaination that both Grizzly and Woodcraft give in their sales materials. My suspicion is that the metric sized plywood does the same thing and that is why John was having trouble.

My first trip to our new Home Depot Store, I bought some "Birch" face ply, in a paint grade. I was cutting the stock down and noticed that I was getting some different sizes (I was stepping off some shelving) and thought it was my bad measuring. A little later I saw a bar code sticker with a Millstead name and 12mm (if I remember correctly) printed on it. I looked at the 1 X 8 that I got at the same time with the same name on it. Metric again. I called the store and asked, the "associate" told me that I might get the exact thing in again and maybe not. Alluding to the idea that sometimes it is one way and sometimes another. He told me that resupply is not consistent and they were correct, I made the face frames from the 1 X 8 South American "pine" that I have never seen again. I have noticed that rabbets to join the plywood are by fit, since neither my Rockler, Woodriver, Frued, or Grizzly bits matches the metric sizes exactly. Which is why I was confused when I followed your link. Is there something I am missing? At my age I do that a lot! I was building a wood box yesterday, and upset that I could not find the right bit, only to realize I had my hand on it. I claim the old age explanation, not the IQ deficit. I also know that there is much I do not know, and I am always interested in knowing more.
Phillip
Gotta chime in here.There is NO standard.Datoes must be custom made every time. Period !! Here's acouple solutions:#1 Freud Dial a Width Dado Set,$250.00,when I bought em. #2 DADOWIZ { www.woodline.com } $139.00 set. Both work well for me. Lot's to say/poor typing skills Dado wiz,now called "DADOMAX " I need both for different applications. The DADOMAX is probably ,what Phil used the jig for. I use a down cut spiral with the DADOMAX,especially cross cutting oak and oak veneer: no chip out on cross grain. Note: Dont make the dado so perfect,you squeeze out the glue;I've done that before. Either one of these tools works great,first time,every time. More to say....gota go. Dave
Well, I'm sold and I have a new favorite tool now!! I finished the shelf installation phase of this project and I must say the Kreg K4 is my new friend for life. What a neat tool that is so simple and easy to use, so I'm hooked now.

I ended up using a 5/8" dado for the top and bottom of the cabinet and notching each end of the shelf to the right thickness on the router table. The shelves are only 18" wide and 6 inches deep, so it was quite easy to remedy the dado problem. I used the pocket hole jig on the other 5 shelves and it worked quite well. What a time saver!

As far as the plywood issue, well I now know that when I buy plywood, I need to double check the thickness every time. I probably never would of realize this if I didn't try to make dado cuts. As far as one of the earlier questions, this was purchased at Home Depot in Atlanta. I'm sure it's a matter of who gives them a good price as to where it comes from. Also, their oak 1x's are junk and very hard to get a decent piece of lumber. I'll have to ask around to find a better supplier.

Thanks for everyone's help, greatly appreciate it!
John
Try lacuer sold at Menards. I used it straight out of the can no thinning,did 8 doors,both sids and edges in 1 hour Interior,full size. Dave

Phillip said:
I was certain you would love it. I got so addicted to the speed, I really found more uses than I ever would have imagined. I have two outbuildings that I put together with regular framing lumber, and the Kreg. Both building withstood the 140 mph hurricane we had 3 years ago. That says something to me.

I use the Kreg and pocket screws and sometimes I do not even bother with the hole plugs. You will find that the more you use it, the less the pocket holes matter. I love finishing a project. If I could get the finish coats to dry as fast as the pocket screw goes in, I would be in heaven!
yes,check the catalogs,there are a few makers that size their bits plywood thickness OR you could use a smaller bit and make two passes to get the right size groove,just use a piece of plywod as a gauge and move your fence to get the perfect fit.also use a bit that has an up twist to get cleaner cuts and remove waste

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