Undersized Router Bit Question

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Forum topic by deucefour posted 01-04-2011 09:42 AM 1748 views 0 times favorited 10 replies Add to Favorites Watch
View deucefour's profile


285 posts in 3888 days

01-04-2011 09:42 AM

Topic tags/keywords: question walnut router joining

I was wondering how much “slop” is too much when using and undersized router bit on 3/4” walnut ply. the dado cut seems just a bit wide for the ply. this is my first furniture project and I dont want to mess up this expensive wood. thanks for any help you all may provide.

the project is the wood whisperers low entertainment center.



10 replies so far

View FirehouseWoodworking's profile


769 posts in 3907 days

#1 posted 01-04-2011 09:57 AM

You should probably look into buying a Plywood Dado Bit Set. Mine is a three-bit set for (NOMINAL) 1/4”, 1/2”, and 3/4” plywood. Each bit is actually undersized and is sized to match the ACTUAL rather than NOMINAL thickness of plywood. You get nice tight dadoes that way.


-- Dave; Lansing, Kansas

View deucefour's profile


285 posts in 3888 days

#2 posted 01-04-2011 02:09 PM

My router bit set is an undersized plywood dado set from eagle america, my guess is that the walnut ply is just a little thinner than regular oak ply etc. because of the cost they could save by making it slightly thinner. I have read that plywood thickness can vary slightly from different manufacturers, I just dont know how much is too much.

thanks for the reply


View Big Ben's profile

Big Ben

87 posts in 3524 days

#3 posted 01-04-2011 02:36 PM

You might want to look into making a jig that would be the thickness of the material. Here are two that I am looking at making.

View GaryL's profile


1099 posts in 3464 days

#4 posted 01-04-2011 02:41 PM

bomisore has the solution for getting a precise dado. You can use bits you probably already have.

-- Gary; Marysville, MI...Involve your children in your projects as much as possible, the return is priceless.

View eruby's profile


79 posts in 3408 days

#5 posted 01-04-2011 03:03 PM

I agree,
bomisore is dead on. I have learned, just because you have a plywood bit doesn’t necessarily mean the groove it makes will be the correct size for your plywood. I used a plywood bit on a bookcase that I built and the dado was actually a tad too tight. The bit is 23/32 but my plywood ended up being wider than that.

-- Eric - Baltimore MD

View Gregn's profile


1642 posts in 3617 days

#6 posted 01-04-2011 03:53 PM

With as much changing in dimensioning between Imperial and Metric in the woodworking industry and the quality control of imports. The jig that bomisore referred is the best solution. I have noticed variances in plywood thickness’s over the years in my woodworking as well.

-- I don't make mistakes, I have great learning lessons, Greg

View fussy's profile


980 posts in 3685 days

#7 posted 01-04-2011 04:59 PM

Bomisore is right on, and here’s another—they all work the same way. Make one pass up, and the other down and you have an exact fit. Now what color you going to paint that walnut?


-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

View makedust's profile


53 posts in 3551 days

#8 posted 01-04-2011 05:33 PM

I have used the jig that Bomisore is talking about with great results a number of times. With the plywood that is sold today it is the easiest way to assure a good fit…Ron

-- "Happiness is creating dust"

View deucefour's profile


285 posts in 3888 days

#9 posted 01-04-2011 05:37 PM

Thanks everyone for your help. I will check out that jig.

fussy: I’ll probably paint the walnut with a heavy coat of metallic purple! :)


View childress's profile


841 posts in 4176 days

#10 posted 01-04-2011 06:20 PM

Another easy solution is to make a 1/2” dado and then rabbet the other piece to fit the 1/2” dado. you can do it all on the tablesaw with the same blade set up…

-- Childress Woodworks

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