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Need advice on cutting dadoes in plywood.

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Forum topic by TheChadshowalter posted 04-17-2014 07:12 AM 594 views 0 times favorited 10 replies Add to Favorites Watch
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TheChadshowalter

4 posts in 257 days


04-17-2014 07:12 AM

Topic tags/keywords: dado plywood maple newbie

I am attempting to cut a dado in maple veneered 3/4 inch plywood. I am using a mibro set and if I am going with the grain it is flawless. When i cross the grain things do not got well at all… I am new to woodworking >1 year and this is my first project for my wife to convince her the table saw she bought me was well worth it. and pointers would be appreciated.


10 replies so far

View Jake's profile

Jake

460 posts in 386 days


#1 posted 04-17-2014 08:22 AM

Try scoring the dado lines with a marking knife before you go at it, otherwise your plywood will tear like crazy, especially going across the grain.

Scoring the dado lines before will eliminate that problem. That’s what i did anyhow.

-- Measure twice, cut once, cut again for good measure.

View Paul Maurer's profile

Paul Maurer

146 posts in 310 days


#2 posted 04-17-2014 10:30 AM

Scoring is your best bet. Of the other things that help, a zero clearance insert or a zero clearance table saw sled are both good. With it you might try a shallow first pass (like the thickness of the veneer)- scoring with the table saw blade or packing tape along the cut line.
“Scoring the dado lines before will eliminate that problem”(jake) If it dose not, then you probably have not cut deep enough or something is out of alignment.

-- Psalm 62: 11 Once God has spoken; twice have I heard this: that power belongs to God, 12 and steadfast love belongs to you, O Lord. For you repay to all according to their work

View lab7654's profile

lab7654

254 posts in 1002 days


#3 posted 04-17-2014 11:21 AM

ZCI’s help quite a bit, and a shallow cut will also reduce the tear out. Most dado stacks make “bat ears” in the top of the cut in the corners, and with a skimming cut they will do the scoring for you. The Freud stack I use has given me very little tear out so far even without taking the skim cut, and I’m very pleased with it.

-- Tristin King -- When in doubt, sand it.

View Fred Hargis's profile

Fred Hargis

2058 posts in 1248 days


#4 posted 04-17-2014 11:22 AM

The scoring pass idea might be the easiest, though all of the ideas above should help. Slow down your feed rate a little and see if that helps as well. Cross grain cuts on plywood can always be a pain, the veneers of today are so thin it’s very tough to do. I’m not familiar with the Mibro dado set, but give some thought to upgrading yoru set if this will be something you will be doing a lot.

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

View squaretree's profile

squaretree

156 posts in 327 days


#5 posted 04-17-2014 11:51 AM

+1 for zero clearance, scoring and shallow cut. I’m in the middle of a cabinet build myself (oak veneered ply). I used my dado stack for some cuts, and used my router with an exact-width dado jig for cross-cuts on pieces that were too large to run across the tablesaw safely. The jig makes it super easy because you can actually use the jig as a guide to score both sides of the cut. Just don’t tell the wife you used a router :)

-- if you can't find me, just follow the extension cord

View TheChadshowalter's profile

TheChadshowalter

4 posts in 257 days


#6 posted 04-17-2014 01:43 PM

Tonight, I shall try scoring…. today I will look for an upgrade on dado blades. Mibro was a box set purchased at lowes several years ago I just finally got a saw that will run them! I also use my router to do some dados I just have a cheap bit and and that needs upgraded also… the joys of just starting out.

View Vincent Nocito's profile

Vincent Nocito

455 posts in 2119 days


#7 posted 04-17-2014 01:44 PM

Scoring (sharp utility knife) and ZCI works for me.

View HorizontalMike's profile

HorizontalMike

6968 posts in 1669 days


#8 posted 04-17-2014 02:51 PM

Here is how I cut dados into my 3/4” Maple plywood using a router and a shop-made router based dado jig:

The best part about this jig is that it adjusts to the exact size of the piece you want to insert in the dado.

-- HorizontalMike -- "Woodpeckers understand..."

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TheChadshowalter

4 posts in 257 days


#9 posted 04-17-2014 03:07 PM

what is ZCI?, never mind i figured it out…

View pintodeluxe's profile

pintodeluxe

3580 posts in 1568 days


#10 posted 04-17-2014 03:57 PM

My Freud dado set will cut grooves and dados in plywood without any splintering at all. I do use ZCI’s, but never bother with scoring cuts. I think it boils down to tooth geometry. You need a good dado set that features angled teeth on the outside cutters. Orient the cutters so the outside blades make square shoulders, and the angled teeth face inward toward the chippers. Does your dado set have angled teeth?

To be 100% honest with you, years ago when I used a dado blade for the first time, I put the blades on backwards. It actually still cut a dado!

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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