Flat bottomed Blade differences?

[Sam Marrocco]

I'm working on some box joints of various widths and looking to purchase an appropriate table saw blade. Freud seems to offer a variety of well-respected blades at decent prices. However, I'm a bit confused as to the differences in some of their product line....

The Box Joint set they offers seems perfect, but limited to a max of 3/8" wide cuts. This seems a bit limiting and I'd prefer something with more width options. Most of their blades seem to promise "flat bottom cuts", as does the Super Dado set, which also offers more variety for future cut sizes. The super seems like a better buy, but I'm wondering if it is missing anything that the Box Joint set provides...?

Also, a router is not an option...this is strictly for my table saw.

Any suggestions or comments between the Box Joint set and the Super Dado for my needs?

[Rod Sheridan]

I owned a box joint set and it made perfect joints as it’s a true flat tooth design.

A dado set will not produce a flat bottom as the blades normally have a few Scoring teeth to prevent chip out which results in tiny grooves at the shoulders.

If you want wider box joints take the box joint set to your local tooling manufacturer and have them make an infill cutter to take the set to the width you want...Rod

[Jim Becker]

As an alternative to Rod's suggestion, you could dedicate a dado set for box joint work and have the two outer blades reground so that their scoring action is level with the flat chippers. Many of the better dado sets have this scoring action to preserve the edges of both solid stock and veneer sheet goods but it results in a visible, slightly deeper mark at the inner and outer edges of the cut. The box joint set you bough presumably doesn't Another option would be to either buy a second box joint set that's exactly the same and just use the extra chippers or see if you can buy them individually from the manufacturer.

[Sam Marrocco]

Jim, I actually haven’t purchased one yet, I was noticing that Freud claims flat bottoms on both the box joint and the super dado. So if they both did flat bottoms, it seemed silly to buy the limited size box joint blade if the more versatile super dado is just as flat by can make wider cuts. It sounds like we are implying that the super dado might leave bat ear....? It would be worth it to buy two box joint blades but u don’t think they are ‘stackable’.

[glenn bradley]

I have the SD-508. There are very slight bat's ears due to the ATB outer plates. These are pretty insignificant on a shelf dado every 14" for a book case. On casework dados are often stopped prior to the visible front edge or are covered by trim. Every 1/2" for box joints that will be right in your face would be unacceptable to me. Here's box joints with a 50 tooth, ATB + FTG blade that I have.

Plane Till (5).jpgDave-Urn (12).jpg

[Andy D Jones]

If you use a Sawstop, beware of their limitations on dado set types and wide blades. Check the manual to be sure.

Flat Top Grind (FTG) and Triple Chip Grind (TCG) will give square bottomed cuts.

A zero clearance insert on the table saw, and/or a wood backer on the miter gauge is usually necessary to prevent tearout with these type blades, unless you are cutting with the grain (e.g. ripping).

-- Andy - Arlington TX

[Sam Marrocco]

So in summary it seams that.....assuming I stick with a table saw blade.....

If I want perfectly flat bottomed box joints with no bat-ears, and can live with smaller than 3/8" width I have to go with the Freud Box Joint set.
If I want almost flat bottoms and can live with the bat-ears and need wider than 3/8" joints, I can go with the Super Dado set.

I looked at a couple other manufacturers and it seems they have the exact same options--limited size box joints or dados with bat-ears. And I couldn't find any box-joint options that were stackable to get wider width.

Per Rod's suggestion, I'm surprised they don't sell inserts/infill cutters for those box joint sets to give you the option for wider cuts.

[John C Bush]

I used the Freud 6" dado set before the new SS needed an 8" dia. set. I got the Infinity Dadonator and it leaves flat bottom cuts. Both work great for box joints.

[Tom Henderson2]

I have the SD-508. There are very slight bat's ears due to the ATB outer plates. These are pretty insignificant on a shelf dado every 14" for a book case. On casework dados are often stopped prior to the visible front edge or are covered by trim. Every 1/2" for box joints that will be right in your face would be unacceptable to me. Here's box joints with a 50 tooth, ATB + FTG blade that I have.

Plane Till (5).jpgDave-Urn (12).jpg

Nice looking boxes Glenn...

[Jim Becker]

A thought occurs to me that you might check out a "cheap" dado set...they may not have the "bat wings" because doing that kind of precision grind likely costs more to manufacture. A proper backer board as used for box joints will help keep things clean for you as you cut.

[Mark e Kessler]

I have heard/read that the Freud box joint blades are not consistent in grind, also the freud dado leave the largest bat ears, Ridge carbide bat ears are much lower and lower than Forrest, I don’t recall all the dimensions but that is why I bought the ridge set

So in summary it seams that.....assuming I stick with a table saw blade.....

If I want perfectly flat bottomed box joints with no bat-ears, and can live with smaller than 3/8" width I have to go with the Freud Box Joint set.
If I want almost flat bottoms and can live with the bat-ears and need wider than 3/8" joints, I can go with the Super Dado set.

I looked at a couple other manufacturers and it seems they have the exact same options--limited size box joints or dados with bat-ears. And I couldn't find any box-joint options that were stackable to get wider width.

Per Rod's suggestion, I'm surprised they don't sell inserts/infill cutters for those box joint sets to give you the option for wider cuts.

[John C Bush]

Indeed-nice looking boxes Glenn. How did you (does one) do the curved sides and fronts. I'm guessing you cut box joints on flat stock then mill curves with a shaper round over panel cutter after glue up. Don't have a shaper and haven't done large panel cuts. Very nice design, thanks for sharing.

In regard to Jim's mention of tearout --I make my own jigs and if the ZC slot isn't ZC after changing cut depth or wear I CA a tight plug in the slot and have an new ZC for the new depth.

[Andy D Jones]

I used the Freud 6" dado set before the new SS needed an 8" dia. set. I got the Infinity Dadonator and it leaves flat bottom cuts. Both work great for box joints.

The 8" Infinity Dadonator is precisely the type of dado set that SS warns will void their warranty. The solid disc, multi-tooth chippers have too much mass, resulting in too much momentum, for them to stop sufficiently quickly, and can damage the saw. I have read (I believe here) of a user who bent the SS arbor when the emergency stop mechanism triggered with such a dado head in use. SS does not cover such damage under warranty.

I'm not sure if this exception was noted in the early SS saws produced, but was added in a revision to the manual which was supplied with later saws. Supposedly SS sent notices to owners of earlier SS saws. I am not sure whether the warranty voidance was retroactive to earlier saws or not. I'm not even sure that would be legal (changing the terms of a warranty supplied with purchase, in the supplier's favor, notice provided or not).

-- Andy - Arlington TX

[Doug Garson]

I have the Freud box joint set, haven't tried it (yet) but looks like you could add shims out to about 1/2". Can't test it as I have some wipe on poly drying in the shop. I have used a single blade (which Freud says you should not do ) which gives about 3/16" kerf with no problem.

[Dan Cameron]

Sam, you didn't mention what style of jig you are using (or plan to use). I made a jig which uses a 3/8 -16tpi threaded rod to control the left/right movement of the boards, with a 3/8 zero backlash nut and a hand crank that has a retractable stop/detent at a fixed position. That is, I always advance the material in exact increments of 1/16". I usually have my dado blade set (AND PRECISELY SHIMMED) for a 1/4" dado. So if I'm making 1/4" box joints I advance 8 turns between cuts. If I want ,say, 1/2 inch box joints I usually leave the dado set at 1/4" and use multiple OVERLAPPING passes. That is cut, advance 2 turns, cut, advance 16 turns and repeat this sequence. There is really no limit to how wide the box joint sections can be other than your patience.

Now, I don't really turn all those turns by hand nor do I count turns one at a time. I have ruler with 1/16" divisions and the 1/4",1/2"and 1" divisions are identified with different length markings which helps me keep track of how far I have advanced. The advancement crank has a hex net it the center and I drive it with a small power drill to within a half turn or so of where I want to stop. Finish the last half turn, engage the detent, and cut.
Lots more I could say about the construction of my jig but the clocks running out on me now.