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Dodgy dadoes

5K views 30 replies 13 participants last post by  teejk 
#1 · (Edited by Moderator)
The other day in my project comments I bemoaned my lousy dado set. It seems I may have been a little harsh. Last night I was fiddling around making a finger joint jig and a zero clearance insert for a ¼ in dado. While fiddling around I had an epiphany.

The shoulder on my arbor is .625 in. diameter and maybe slightly wider than 1/8 in. Where the threads are cut the arbor is .615 in. Consequently all blades after the first are .01 in. off from the first. Aside from a ragged dado, vibration from the imbalance is disconcerting. Any suggestions? (Grizzly TSC-10 table saw and Avanti dado set)
 
#2 ·
Why don't you add a vibration washer/stablizer as your first component, then add the dado components?

Have you also check the flatness of your table top. I have problems with cuts for ever until I discover the top was warp. If you got warp table, there isn't much you can do. Just make sure the next TS that you get that the flatness is a must check item.

The other thing is wobble blades where the wobble is not actually coming from the blade but from the arbor flange. As you tighten the nut, the compression cause the blade to be distorted. The flange must spin in a plane perpendicular to the arbor axis. Woble could mess up you cuts and dados as well. Here in LJ, there is a post on flatten the flange (search for woble saw blades). You should also flatten the washer too. It know it work, because I have tried it.
 
#4 · (Edited by Moderator)
Muleskinner, hope you get things worked out.

Not trying to throw stones at your dado set, but as a PSA/FYI to would be blade shoppers …. the "Avanti" series used to be manufactured by Freud and was very similar to their well regarded value minded Diablo line, but they discontinued it in June 2009 due to a lot of overlap in the lineups. Since then, HD has been selling saw blades using the "Avanti" and "Avanti Pro" name…..they're not made by Freud, are not associated with Freud, are not copies of Freud's design…they're mediocre blades at best, and are simply cheap Chinese knockoffs that have similar printing on the blades as Freud used. They're poor enough quality that I wouldn't suggest using them for woodworking….aside from the lack of quality, I find preying on unsuspecting consumers pretty distasteful, and will avoid them completely as a matter of protest.

 
#5 ·
hhhopsk - the table's flat and there's no vibration with my regular blades (freuds). It's a stacked set, precisely what knottscott has pictured. I did try adding another washer (off my RAS) and the cut improved a little but the vibration was still present.

knottscott - throw all the stones you want. I fully realize it's not a top of the line set. The teeth on the outside blades are not flat set which causes the corners to be not exactly square or the bottom flat. It's not too much of a problem to clean up in softwood or plywood but more work in hard woods. What I'm wondering, with the .01" difference in arbor diameter, is would I be still be having the uneveness problems with a more professional set.

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pinto - it's a Grizzly TSC-10 table saw (1986 vintage) and a Avanti Pro 8" stacked set.
 

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#6 ·
My guess (and that's what it is) would be that you would still have those problems. That said, my dado set does not cut bottoms that are baby butt smooth, rather you can almost count the number of chippers I'm using looking at the cut…and this is with a Freud SD508 set. A not-so-good solution (but not too bad either) might be to cut your dados a little shallow, then clean the bottoms up with a dado clean out bit in your router. This makes a lot more work, but works well when you do want smoother cuts. I may measure the arbor on my saw later, (Delta) what you have may be the norm and I just don't realize it.
 
#7 ·
Fred - I believe you're right but I'll probably still eventually upgrade to something with flat teeth. I'd be interested to know what you find on your arbor. I checked the arbor on my Craftsman RAS and it was nuts on .625 the entire length and an old Red Star Multiplex RAS only varied a varied from .750 to .747.

Most of the time I don't really care because most of my dadoes end up in case work or shelving units and either wind up in the shop or are face framed. But now I was thinking of making some finger joint boxes and was hoping for a better looking finish. Oh well.
 
#9 · (Edited by Moderator)
Mule - I failed to mention in my first reply that every decent dado set I know will leave minor grooves or "bat ears" along the edges due to the bevel top grind on the outside cutters. Forrest, Infinity, Freud, Ridge Carbide, Tenryu, CMT, Amana, Systimatic, DeWalt/Delta, Onsrud, Oshlun…they've all got them. The bevel grind is intentional to reduce tearout on cross grain dados….in order for that grind to be effective, those pointy tips on the beveled teeth have to protrude slightly above the flat ground teeth of the inside chippers. Some of the better sets reduce the effect of those bat ears by combining a few flat ground teeth on the outside cutters between the beveled teeth, but tiny bat ears still exist to some degree. There are some box joint sets that have flat top ground teeth, but most are intended for cuts with the grain where tearout is less of an issue.

Here's a pic from a set that has fairly typical bat ears:


Here's a pic from a set that has much smaller bat ears (they are there, but they're small):





Seeing as though most dados are hidden, it's usually not a problem.
 
#10 ·
Just an FYI Lowes has clearanced out the CMT 8" 12 tooth stack dado set (same design as the $100 freud diablo) to carry the new Irwin Marples dado set. Last i saw it was down to $34.00. I got one and it works nice. Has the typical bat ears as shown by knotscott's first pic. I almost got 2 of them.
 
#11 ·
Knottscott - thanks for the info. Maybe I'm just expecting too much from mine. It's beginning to look like I'll have to go the router route to get my clean box joints.

Justme - sadly there's no Lowes withing a 2 hour drive or I'd give those a try. Good luck with yours.
 
#12 ·
My arbor is identical to the way yours is. The first blade I put on in the stack is always REALLY hard to get off compared to the others, but I get really flat cuts, and the tiny bat ears. While I kind of find those annoying, I really appreciated them when I had to cut veneered plywood.

That Avanti pro set gets extremely poor reviews almost unanimously. I understand you want to make it work because you own it, but that's likely as good as you are going to get. I have the entry level Freud Industrial set (SD208, 100$) and I don't see that in hard or soft wood.

If you want REALLY flat bottoms with no bat ears, and don't want to buy another dado set, pick up the freud SBOX8 box joint set. It cuts 1/4" and 3/8" widths. You'd have to make multiple passes to get anything more that that, but I usually "seak up" on dadoes anyway.
 
#13 ·
+1 on the Freud box joint cutters! No bat ears and flat bottoms. A little pricy but I love mine and they have been indestructable so far (still scary sharp after cutting hedge,jatoba,pecan, and lots of box joints and dados. The best $100 investment I've made in a while.
 
#14 · (Edited by Moderator)
lumberjoe and gfadvm - I just bit the bullet on the Freud box cutters. $67 through Router Warehouse via Amazon. By this time next week, if I'm still having problems it'll be time to stop blaming the tools and start blaming the workman. Joe, there's no chance that my review of the Avanti blades would raise their rating. My arbor issues aside (for which I can't fault them), they produce terrible tear out which I do fault to them.

Thanks for all the advice and information.
 
#18 ·
Muleskinner, what Fred said about using a dado blade AND router as a follow up is supposed to be THE way to get a perfect dado. You'll see grooves in ANY stacked set of dados.

Milo
 
#20 ·
I'm late getting back to this, today I did measure my arbor, and it was .622" diameter consistent across the length. I also tried a test cut with a new dado set (the CMT set that Lowes has on clearance). Man, was I impressed! the dado had a baby butt smooth bottom, and just a slight set of "devils ears". This was in some very splinter prone luan plywood, and yet there was no splintering at all (cross grain cut). Call me a happy camper.
 
#22 ·
I got my set for $36, they started the clearance price at $54, then went down. That was the store closest to me. The next store (of the 2 in my area) just did go down to $54. I saw on another forum one guy posted a pic of his receipt, he got his for $32.39! BTW, I did some more test cuts comparing the CMT to 1) a brand new Freud SD508, and 2) an older recently sharpened (for the third time) SD 508. You could not tell the cuts apart! The CMT cut every bit as nicely as the much more expensive Freud sets…the only thing was the "devils ears" were just a hair taller, you really had to look close to see the difference.
 
#24 ·
Just to let you know I didn't abandon my quest; a late report on the Freud box joint cutter.

I'm happy with the purchase but it didn't completely solve my issues. The only thing that will do that is a new table saw, it seems.
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The cut on the left is the result of my arbor. I found that if I flipped the board front to back and run it through the jig again I end up with the cuts on the right, which seem satisfactory to my bourgeois standards. There's no bat ears, no tear out, and flat bottoms (tho generally I like my bottoms round and plump). The set is more convenient than messing with my regular dado set.
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Once I got it dialed in, I got a pretty passable box joint. I've got 12 dresser drawers going, by the time I'm done I should have amortized the investment to less than $1.50 a joint.
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A guy couldn't expect more fun for a buck fifty.
 

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#25 · (Edited by Moderator)
Is you throat insert flat/level with your table top? Is your insert flexing down as you cut the dados? Those are the only issues I can see remaining. I don't see an arbor problem giving that stepped cut unless it is not uniform diameter along its length. That is probably what you are saying about your arbor, huh? Could you put a shim/washer on one side of your blades to move them over to a better section of arbor? You have exhausted my ideas now!
 
#26 · (Edited by Moderator)
gf - the problem with my arbor is that where the threads are cut it is ~.01" smaller than the shoulder where your regular saw blade sits. The result is that with a dado set (and my new box joint cutters) the first blade sets on the shoulder but the subsequent blades sit on the threads and as a consequence cut deeper than the first blade. Essentially they're out of round. With the box cutter you get the left most joint in the first picture above. With my dado set it's more erratic the more cutter you use. the cutters are the two tooth type and the staggering produces a cut that looks more like a bar chart than a box joint.

I made a zero clearance insert for the 3/8" joints I'm doing on the drawers. Even put four set screws in it so it's level and flush. Plus the jig I'm using keeps all the pressure on the cast iron.

Your suggestion of shimming would probably work for the box cutter but any sizable dado stack would still have geometry issues. Besides, I'd have to build a new jig and insert and I'm lazy.
 
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