Dados in table saw

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Forum topic by gabo posted 11-05-2012 09:07 PM 1798 views 0 times favorited 13 replies Add to Favorites Watch
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4 posts in 3316 days

11-05-2012 09:07 PM

Hi, I am new to the forum. I did some seaching and could find an answer to my question, so I am posting this to see if you can help me. I am having issues when cuting a groove with my dado blade. I have a 2X1 inch board. I want to make a centered 1 inch groove to the board. The way I am setting up my cut is that I set my dado at 3/4” width, leaving 1/2” space to the table saw fence. This way make a pass to the board against the fence, flip it 180 degrees and make another pass to get my final width on the groove. The issue I am having, is that the groove seems to be cut at a tapered height, 1 mm off. (I do multiple passes to insure i did put pressure to the table saw and get a paralel cut) so when i flip the part and repeat the tapered cut, the groove is not flat at the bottom, it shows to small steps at the end of the board.

I have been trying to understand why this happens with no luck. I use my dado with a zero clearance insert and make sure is completlyl flush to the saw. Also I don’t see an abrut change in the depth on the groove, it seems to be increasing constantly as I push the material thru the blade.

any comments I am going crazy and can find a reason.


-- Gabriel, Mexico, Toluca

13 replies so far

View Swyftfeet's profile


179 posts in 3459 days

#1 posted 11-05-2012 09:38 PM

Warped table?

-- Brian

View sixstring's profile


296 posts in 3531 days

#2 posted 11-05-2012 10:17 PM

or warped wood. was the board surfaced properly? had the same problem cutting dados across some material and it turned out that the wood (which looked dead straight) had a slight upturn which casue my dados to be almost a full 1/8” shallower at one end.

point is… make sure the wood is dead straight and hope it isnt the table.

-- JC Garcia, Concord, CA : "It's easier to ask forgiveness than permission..."

View Gerald Thompson's profile

Gerald Thompson

1305 posts in 3522 days

#3 posted 11-05-2012 10:23 PM

Try cutingg several kerfs with an 1/8’’ combo or rip blade. As an example make 4 rips that overlap. The with a combination square check the depth @ one end and lock it. Go to the far end and see if there is a difference.
If there is the only thing I can tell you there is a problem and I have no clue what it could be.

-- Jerry

View gabo's profile


4 posts in 3316 days

#4 posted 11-05-2012 11:00 PM

hope is not a warped table, I am going to check it again, as for the wood it is dead straight. i’ll some mesuaring and see what else I find.


-- Gabriel, Mexico, Toluca

View Cosmicsniper's profile


2202 posts in 4446 days

#5 posted 11-05-2012 11:27 PM

Is the blade sinking during the cut? I have to lock my blade height with a dado blade, or even when I do repeated depth cuts with a regular blade.

-- jay,

View David Craig's profile

David Craig

2137 posts in 4396 days

#6 posted 11-05-2012 11:46 PM

1mm is not a significant height. What are you using to make sure the zero insert is flush on the saw table? If you are seeing a taper, I can see where a very gradual incline of your insert from left to right could do this and not be immediately detectable.

-- There is little that is simple when it comes to making a simple box.

View teejk's profile


1215 posts in 3972 days

#7 posted 11-05-2012 11:50 PM

besides the fact that you are doing something that I would only do with my eyes closed and a first aid kit handy…

hard to exactly figure out but are you saying the “dip” (taper) occurs in the middle of the board? if so you are dealing with a warped board I think. several lighter passes will help as you try to keep it even over the dado blade (although I still cringe on a 2” board). A feather board mounted to your fence would be better. keeps the pressure at the point of contact with the blade.

View gabo's profile


4 posts in 3316 days

#8 posted 11-06-2012 07:08 PM

David, I am using a square to check the insert, I check in several places around the insert for flushness, do you recommend another way.

Teejk, what do you mean?, how else would you do this type of cut? I use my push block on both my hands and make multiple passes to achieve the desired depth. Now, the issues is at the ends of the board, this is a 15 inch long board and it is flush in the middle and has steps in the ends.

I do have some ideas from all of you and will do some tryouts over the weekend and see what results I get.

Thanks a lot.

-- Gabriel, Mexico, Toluca

View teejk's profile


1215 posts in 3972 days

#9 posted 11-06-2012 08:37 PM

gabo…15” long? that explains some more…TS will generally produce a uniform cut on longer pieces but on a piece that short, you are dealing with flatness of the table and the throat insert (when I was young we had something called a teeter-totter on the playground).

If you have the stock then run a longer piece and cut out the part you want.

or deal with the 1mm…that’s really nothing in the real world but I can see cases where it would be noticable (most likely only to you). so try the feather board mounted to the fence. it seems to work better than push pads for me

2” stock running 1/2” from the fence makes me cringe but that’s just me…bad experience a few years ago on short/narrow stock on my trusted TS…I don’t blame my TS, I blame me.

View cutworm's profile


1075 posts in 4081 days

#10 posted 11-06-2012 08:58 PM

Like teejk you can use a feather board to help with that. I wouldn’t worry about a small amount. If the lumber is crowned you can turn the crown down as well.
And Welcome to LJ’s.

-- Steve - "Never Give Up"

View ETwoodworks's profile


92 posts in 3981 days

#11 posted 11-06-2012 09:14 PM

Is your ZCI flexible plastic or is it ridgid?

-- Building quality in a throw away world.

View RussellAP's profile


3105 posts in 3574 days

#12 posted 11-06-2012 09:25 PM

Having the insert flush is a must. Also go very slowly through the cut and allow the waste to be taken out. Did I say having the insert flush is a must?

-- A positive attitude will take you much further than positive thinking ever will.

View gabo's profile


4 posts in 3316 days

#13 posted 11-06-2012 09:40 PM

ET, my insert is from leecraft, i believe is pretty rigid. and from the feedback i guess the 1mm I am seeing is not a big issues, I guess i am overdoing it…..thats the reason I joined the forum need go insight from experts.

teejk, thanks for the feedback will try to avoid this in the future, i’ll use my roter table instead.


-- Gabriel, Mexico, Toluca

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