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Trouble making a long dado

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Forum topic by DocFluty posted 10-31-2017 02:18 PM 468 views 0 times favorited 14 replies Add to Favorites Watch
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DocFluty

3 posts in 42 days


10-31-2017 02:18 PM

I am trying to rip a 66” dado about 4” from the edge, using the fence, on 1/2” birch plywood on my table saw. But I barely got a foot before I noticed the board wasn’t tracking straight and my cut was crooked.

So now that board isn’t good for that project anymore and I am reluctant to cut a new board and try again until I ask around for a better method than me standing behind it and trying to slowly push it through.

This is my first attempt at working with a dado stack, so I’m trying to find out what I am doing wrong. Youtube isn’t very helpful on this subject like it is with many others. So what do you suggest I do?

Would it just be smarter/easier to set up a router and bit to make this length of a dado?

Thank you.


14 replies so far

View bbasiaga's profile

bbasiaga

1005 posts in 1829 days


#1 posted 10-31-2017 02:22 PM

Sheet goods can be hard to handle on a table saw. But with good technique you should be able to do it. Maybe try setting up some supports to hold up the piece so you can focus just o. Keeping it tight to the fence.

Another option is to use a fence on your router. Since it is only 4” from the edge you might find it easier to move the tool across the wood rather than the wood across the tool.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View Tony1212's profile

Tony1212

146 posts in 1569 days


#2 posted 10-31-2017 02:33 PM

In my shop, I would use a router since my 1950’s table saw lacks a height lock and the blade slowly falls during cuts like that.

However, in your case I would use a circular saw and cut off the mistake and try again. then cut that off and do it again. Then cut THAT off and do it again. Do that until you are comfortable and your dadoes are acceptable. Practice makes perfect.

As for why it happened, most likely you weren’t pushing your stock through the blade correctly. You have to push forward AND into the fence. The blade will act as a pivot point, so if you are pushing too far away from the blade, the piece will rotate and your cut will be crooked.

Mattias Wandel has a good explanation of this. See around the 1:19 mark in this video. https://www.youtube.com/watch?v=ZkvO99lswZg

-- Tony, SW Chicago Suburbs

View Carloz's profile

Carloz

962 posts in 426 days


#3 posted 10-31-2017 03:07 PM

The cut you tried to make is actually the easiest of most work on the table saw. Press the plywood against the fence and move it forward. Even if your saw is not setup perfectly it still should produce the correct cut. Try it again. Learning costs money, in your case plywood.

View Kirk650's profile

Kirk650

513 posts in 583 days


#4 posted 10-31-2017 03:12 PM

I have a real long straightedge I bought from either Woodcraft or Home Depot, and I use that for long dadoes. Be sure the router bit ‘pulls’ into the straightedge or you may again wander. Ask how I know that…..

View MrRon's profile

MrRon

4492 posts in 3078 days


#5 posted 10-31-2017 04:16 PM

You didn’t mention if the fence is adjusted correctly, (parallel to the blade). The previous comments also apply. You should also check if the surface of the fence is perfectly flat. Any bow, hump or dip in the surface will throw the cut off. Is the edge of the board straight?

View DocFluty's profile

DocFluty

3 posts in 42 days


#6 posted 10-31-2017 04:28 PM

I have checked the fence using my woodpecker square and it runs true as far as I can tell. I am using a Dewalt DWE7491RS with a Frued dado stack since I am working out of my garage and need it to take up less space and be portable.

I think the main problem might have been where I was standing trying to push this through. Maybe I was too far back and the pivot was just jacked up like what was mentioned above. I didn’t have the on a table or somethign secure as i was pushing it though and it probably compounded my issues. I like the idea of trying to cut it and if it doesn’t work move the board over and try again and then cutting my final dimensions after I get a cut that I like.

I’m thinking with my limited skills the best course of action would be to set up a straight MDF fence clamped on top and run a router the length of the board to get the proper cut.

thanks everyone for the thoughts on the matter.

View Carloz's profile

Carloz

962 posts in 426 days


#7 posted 10-31-2017 08:07 PM



Be sure the router bit ‘pulls’ into the straightedge or you may again wander. Ask how I know that…..

- Kirk650


It is pretty hard to manipulate router bits on a table saw

View Loren's profile

Loren

9609 posts in 3482 days


#8 posted 10-31-2017 08:22 PM

You may not get a parallel cut if the MDF
fence deflects in the center, so watch out
for that. If doing that I recommend the MDF
straight edge be at least 6” wide.

Another way to do it is attach a piece of
scrap to your router base and screw a stick
to it to use as an edge guide.

http://www.woodsmithtips.com/2011/04/07/shop-made-router-edge-guide/

View clin's profile

clin

751 posts in 830 days


#9 posted 10-31-2017 08:23 PM

It’s technique and practice makes perfect. You didn’t mention how wide the sheet was. If it is narrow enough, you could use a feather board to help hold it against the fence. But paying attention and feed the sheet evenly should be easy enough.

As long as you know where your hands are and can keep them away from the blade area, there’s no reason to look at where you think the blade is under the sheet. Keep your eyes on where the sheet meets the fence. Though I’m pretty sure I keep my eyes moving, sheet/fence hands and back.

While you do need to keep it up against the fence, most of your force should be pushing forward. If you apply too much force on the corner away from the fence, you’ll tend to pull the back end away from the fence and start twisting the sheet. It’s actually pretty hard to do the opposite when you are only 4” from the fence. But the same principle applies.

You are pushing against the blade so the forward force needs to be more or less in front of the blade with just enough side force to keep it against the fence. But the force needs to be straight, not a twisting. Straight, as if you were trying to slide the sheet in a straight line just slightly angled into the fence.

Keep in mind if the near end of the sheet starts moving away from the fence, the sheet itself won’t have moved much at the blade, so you can correct with little or no harm. Your eye should be able to detect very thin gaps before they become big ones and screw it all up.

-- Clin

View DocFluty's profile

DocFluty

3 posts in 42 days


#10 posted 10-31-2017 09:01 PM

Wood was 66”x18”, I’m trying to build a miter saw station.

I was seeing it move from the fence as i was pushing, probably from the wrong corner. Lot’s of learning in this project.

View Sarit's profile

Sarit

549 posts in 2974 days


#11 posted 10-31-2017 10:06 PM

Yeah as clin said using featherboards would help a lot. I have the magnetic ones so you can place them even past the miter slot. If you don’t have them and yours won’t fit then you can flip the board around so that the slot is ~14” from the fence.
Use 2 featherboards, one in-line w/ the blade and one past the blade but not past the end of the fence. W/ 2 featherboards in this configuration you can focus on pushing the wood straight through keeping pressure on top of the dado stack (preferably with a push pad and not your hands).
I usually have to run through the dado twice to make sure the depth is consistent for the entire length.

View Carloz's profile

Carloz

962 posts in 426 days


#12 posted 11-01-2017 02:48 PM


Wood was 66”x18”, I m trying to build a miter saw station.

I was seeing it move from the fence as i was pushing, probably from the wrong corner. Lot s of learning in this project.

- DocFluty


Just as I said above, dont watch it moving away, keep it pressed to the fence.

View MrRon's profile

MrRon

4492 posts in 3078 days


#13 posted 11-01-2017 06:03 PM

When to rip; when to cross cut. When ripping, you should be pushing the wood through the long direction of the board, or plywood. Don’t try to rip a board when the short dimension is against the fence; that is a job for a cross cut. Only rip when the long dimension is against the fence.

View Holt's profile

Holt

166 posts in 2463 days


#14 posted 11-01-2017 07:05 PM

Think on the next attempt, whatever method you choose, I’d cut the board to final width after you cut the dado to your satisfaction. I’d be happier wasting 4 inches than the whole 18!

-- ...Specialization is for insects.

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