Replies

1. 
   jharveyb | Dec 14, 2022 09:12pm | #1

   As far as I know, your only option is certain ripping blades. Glue line rip blades don't create a flat bottom, as every other tooth cuts a bit deeper in the middle. I recently bought a narrow rip blade that does produce a flat bottom. I don't think a cross-cut blade can give a flat bottom, as it needs the sharp points of an ATB to sever the fibers cleanly.

2. 
   john_c2 | Dec 14, 2022 09:39pm | #2

   I use a Freud LM72R010 24 tooth rip blade. Perfectly flat bottom. It seems to be the most popular choice.

3. 
   geedubbee | Dec 17, 2022 09:32pm | #3

   I have a Carbide Processors blade called a Groover. ATB with a raker that leaves a flat bottom. Others may make them. It is my go to for miter keys, drawer bottom grooves, etc.

4. 
   DRBWWing | Dec 18, 2022 07:39am | #4

   There are specialized blades such as box blades.

   Grooves 1/4” or less I use a FT rip blade. Wider than 3/8 if there’s enough to do, I break out the dado.

5. 
   user-7627473 | Dec 18, 2022 08:09am | #5

   Forrest makes a WWII with flat grind (#1 grind) that I use for splines. I'm sure many other makers produce them as well...do web search and you will probably come up with several options.

6. 
   chuckvandyck | Dec 18, 2022 11:34am | #6

   The freud box joint set is money

7. 
   russ_rva | Dec 18, 2022 02:18pm | #7

   I replaced the original SawStop blade with a Forrest recently. I had the SawStop blade reground at a local shop. Cost $10 for the flat regrind.

   Now sharp and flat. I use it primarily for thin corner splines in small boxes.

8. 
   user-7513127 | Dec 18, 2022 06:58pm | #8

   I really like my Freud Industrial blade, just got a new one. It is a 10" 60 tooth 1/8 with flat bottom teeth. Freud item no. LU82M010
   Better than getting one of the blades from the box joint set. Came from Amazon.

   
9. 
   phantomtrapper | Feb 26, 2023 11:03pm | #9

   I had the same need about a year ago. Just sent a good shape combination blade to the sharpeners and asked for a flat top grind-FTG. Works well and it is a dedicated blade. I don't really recall but I don't think it cost much more than a regular sharpening.

10. 
    bilyo | Feb 27, 2023 10:15am | #10

    Specific to your question, combination blades (at least the ones I'm familiar with) have mostly alternate top bevel (ATB) grind with a flat top grind (FTB) "raker tooth" on every 5th tooth. These will usually give a flat bottom cut. At worst, the ATB teeth may leave a small triangular groove at the edges (some call them bat ears). So, as suggested above, check out combination blades. Most every brand has them.

11. 
    carbide_tipped | Feb 27, 2023 12:28pm | #11

    +1 on a combo blade when a flat bottom is needed. I use the Freud LU84 because it is the same kerf size as their glue line rip blade and their ultimate plywood and melamine blade, which works well for sheet goods and solid wood crosscuts. Having all blades with the same kerf means your zero clearance insert works for all, and your table saw measuring tapes are always correct, regardless of which blade is installed. If I'm doing a large number of deep grooves I will often remove most of the waste with a rip blade first, and then finish with the combo to flatten the bottom. The rip blade cuts faster and burns less than the combo would if you are hogging out a deep groove.

12. 
    Pete99353 | Feb 27, 2023 01:25pm | #12

    I use the 24 tooth Blade of a Forrest dado set. 1/8" wide and flat.

13. 
    revbob | Feb 28, 2023 07:59am | #13

    If you decide to have a blade sharpened to achieve a "FLAT" bottom be sure to specify your requirements for a "Clean Flat Bottom" to the sharpening service. Else wise you may end up with something that meets their "tolerance spec's" but is not a clean flat bottom. Someone mentioned "bat ears" earlier which is what might fall within their 0.005" tolerance but is definitely not a clean flat bottom. Good luck.