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trouble with basic dadoes!

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Forum topic by rg33 posted 10-23-2013 05:36 AM 1086 views 0 times favorited 11 replies Add to Favorites Watch
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rg33

83 posts in 1464 days


10-23-2013 05:36 AM

Ok so I finally got around to testing out my 8” freud stackable set on my TS and gotta say Im a bit frustrated. I’ve never used them before and was striving to make a perfect dado on the first try and here’s what happened. I stacked up the dado blades and shims and run a test cut on a scrap. I was close to the width of the plywood (maybe about .015” oversized). Looked around on the forums and all say dadoes are good when they are nice and tight, so decided I could do better and went in to take out about .010” of shims.
First problem: I noticed one of the shims had its ID mangled a bit, looks like it got stuck on one of the threads and as I tightened the nut it sort of got damaged, no big deal hammered it flat, has anyone had this happen? Any way to prevent this?

Ok so I’ve removed one shim, tightened everything up again and second test cut. this time I tested the scrap cut on my plywood and it fit nice and snug so I made my real cut.
Second problem: now my plywood pieces dont fit together. It seems that while the test fit seemed fine with a narrow (2”) scrap, once I made a dado on the actual wider piece (about 18”) there must be a bit of a bend or something on the panels because they will not fit together. This seems quite simple but between shimming and testing and de-shimming I’ve lost my patience tonight. I’ll try again tomorrow and am thinking about just oversizing the dado by .01-.015” and be done with it. Ok enough about my rant. Anyone see a major issue with this? Or any gray beards out there with a completely (hopefully simpler) approach to this whole thing for next time?


11 replies so far

View UncannyValleyWoods's profile

UncannyValleyWoods

441 posts in 1327 days


#1 posted 10-23-2013 06:03 AM

Sounds like cutting dadoes to me. Plywood always raises the trickiness factor, in my opinion. Some may disagree, but I’ve always been a fan of going small and making two passes. Maybe set the blade to half your desired width until you get used to using the blade. shrugs shoulders

-- https://www.etsy.com/shop/UncannyValleyWoods?ref=hdr_shop_menu

View MrRon's profile

MrRon

3926 posts in 2706 days


#2 posted 10-23-2013 05:54 PM

Get a set of magnetic shims. They will stay in place and won’t get caught in the threads. I can’t understand why the plywood won’t go into the dado. Doesn’t make any sense. When you removed the shim and made the test cut, are you sure you tightened the nut before making the “real” cut. Possibly something wasn’t seated properly and when you tigened down the nut, the blades moved, so you got a narrower dado. Also make sure the chipper teeth are sitting in the gullets of the outside cutters and that each outside blade is positioned correctly. The outside cutters of a dado set are made left hand and right hand. The teeth should bend toward the outside of the set. If they bend toward the inside, you will get an undersize dado.

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1832 days


#3 posted 10-23-2013 06:40 PM

Use a nice round number dado stack and rabbet the mating pieces to fit. I had a similar experience except it was with an undersized plywood router bit, and a sheet of plywood that magically happened to measure 3/4”. My test piece apparently came from the other sheet that was undersized.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View pintodeluxe's profile

pintodeluxe

4854 posts in 2276 days


#4 posted 10-23-2013 07:22 PM

Keep at it. Make one more test cut on longer scrap. Make sure you have a straight-edged board against the rip fence. Add shims until a longer board fits snugly into the dado. It shouldn’t need to be tight, just an easy friction fit.
On my set the .004” shims make a difference how the joint fits.
I keep a sample dado board in my TS cabinet. It has different sized dados from all shim / blade combinations. I find the slot it fits in, and use that setup.

Good luck!

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

View rg33's profile

rg33

83 posts in 1464 days


#5 posted 10-23-2013 08:03 PM

Thanks all for the good advice, I will try again after I get home tonight. On my drive to work today I thought up of an idea that may or may not work. So the problem is that I have to make this dado on 4 different boards the same distance up from the bottom for shelves. Given that I’ve already set the fence and made the first dado on the first piece, Im hesitant of shimming and resetting the stack, blade height, etc. What if instead I did the following:
1) dado the 3 remaining pieces with the slightly undersized blade set.
2)then taking UncannyValley’s advise and putting a bit of a twist do the following. Place one of the boards with the cut dado on top of the blade set to get it exactly positioned in place of the original cut. Loosen the rip fence and using a .005 feeler gauge/shim between the edge of the board and rip fence should get me the right offset for a second pass.

I know I’m probably really overthinking this but in theory it should work no?

MrRon I think the plywood doesnt fit because there may be a slight (.010-.020) out of flatness on the shelf Im trying to fit on the dado currently. The magnetic shims will definitely work better than the ones I currently am using thanks for the tip

View pintodeluxe's profile

pintodeluxe

4854 posts in 2276 days


#6 posted 10-23-2013 08:20 PM

Before you do anything, run the workpiece through the saw again. Sometimes that’s all it takes.
If it still doesn’t fit, cut a few scrap pieces with matching dados. Cut all workpieces before changing TS settings. Then readjust the fence and make a second cut on scrap. Once it fits perfect, make the second cut on your workpieces.

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

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1832 days


#7 posted 10-23-2013 08:23 PM

”I keep a sample dado board in my TS cabinet. It has different sized dados from all shim / blade combinations. I find the slot it fits in, and use that setup.”

I envy you, Willie. This has always been on my to-do list for the shop, but I always feel like it’s going to take too much time and I do something else instead.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View Fred Hargis's profile

Fred Hargis

3935 posts in 1956 days


#8 posted 10-23-2013 08:39 PM

That’s a fairly common problem with the Freud shims, and they are unapologetic about it (at least they were before Bosch bought them). If you have an anvil you can hammer them flat enough to use, though maybe buying a friendlier set might be easier. You are other problem are just the jois of working with today’s plywood.

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

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1832 days


#9 posted 10-23-2013 09:16 PM

Hm, I have a Freud Diablo 8” stacked dado set, and have never had an issue with the shims, I just make sure they’re all the way on the arbor before putting the next thing on.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View gfadvm's profile

gfadvm

14940 posts in 2153 days


#10 posted 10-24-2013 12:41 AM

I’m a fan of the 2 pass method for cutting dados to perfect width.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View kdc68's profile

kdc68

2526 posts in 1739 days


#11 posted 10-24-2013 01:17 AM

I like the two cut method as well.

But here’s a method to achieve a perfect fit in two test cuts. It’s a bit of a pain but works

1.) Install dado with enough chippers to achieve approx. width you want and use all the shims.
2.) Make a test cut. Uninstall dado from saw arbor enough to remove all of the shims
3.) Fit your work piece into the oversized dado and slide in shims one at a time until you get a snug fit.
4.) Set those shims aside. You are not going to reuse these.
5.) The leftover shims are the ones you need and use those to re-install the dado.
6.) Make another test cut and your work piece should fit pefectly

Write down that shim combination as a reference

-- Measure "at least" twice and cut once

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