Crosscut Sled – Cut Anomaly?

[Brandt Bolding]

I started to trim some ends off some 14″ w. pieces of Pine recently for a project2022-06-14-14.30.jpg – and noticed that the last few inches of the cut it "bumped out slightly". Cuts made from left side of the blade. I made some other cuts (with different stock) and noticed as the far edge of the piece reached the center - it started to press into the blade plate and the back edge of the blade then started to cut a fresh cut about a 64th. So again, stopping the piece as the blade just finished the cut - leaves a "bi-level" surface - see attached image. I keep the mitre slots consistently parallel using a digital gauge and never had this issue before. Just started with a newly sharpened Forrest WWII which are the only blades used on this saw. I then adjusted the mitre slots so there was a gap at the back of blade on left side from +.005-+.020 and no difference. I also used two other sleds including one that had new runners and had just been calibrated. Riving knife removed. I checked motor and arbor mounts to make sure they were tightened and of course the bolts mounting the table to cabinet. Oddly could not replicate on right side. I did a quick search and the only hit similar also remarked that the WWII blade was being used - and the only suggestion (Bob Rogowski) was to check mitre slot parallelism - and if that didn't work "maybe saw was possessed". When I have blades sharpened I always request that run-out be checked and plate flattened if necessary. Is there anything that I may be missing here? I could make a right side sled but would have to take off fence each time it was used which is maybe minor in scheme of things. Any and all help/suggestions/thoughts would be appreciated.

[Lee Schierer]

From your photo, it looks like the back teeth of the blade is dragging on your wood based on those curved grooves on the cut edge.
2022-06-14-14.30.jpg
I would check the alignment of the blade to the miter slot you are using.

[John Kananis]

Since you checked parallel, try the same thing with another blade. Same results?

[glenn bradley]

In a perfect world the blade would spin perfectly in plane with the feed path. Anomalies abound. Is this a thin kerf blade? If so I would try stabilizers rather than trying for a gap. The offset of the runners or a toe out on a fence may minimize some problems but like aspirin that is treating the symptoms, not the cause.

With a miter gauge or a sled I was surprised at the increase in accuracy and smoothness of cut when I applied sandpaper to the fence to help enhance my grip. It's funny how you watch people do things for years before you try it and realize why. So, here's my first guess . . . Material is shifting slightly due to inadequate grip, sled is shifting slightly due to minor feed path deviations, or blade flutter as the front of the blade is set free from the material during the feed operation.

Blade flutter or oscillation is more common with TK blades but any operation where the blade is not buried in the stock (like just shaving 1/32" of the end of a panel) can experience this. A perfect cut is desirable but not always practical. For highly detailed work a shooting board is your answer. For speed over finesse an edge sander can do the job. You could also experiment with slowing your feed rate for the last few inches of the cut.

[Brandt Bolding]

Thanks. "With a miter gauge or a sled I was surprised at the increase in accuracy and smoothness of cut when I applied sandpaper to the fence to help enhance my grip. It's funny how you watch people do things for years before you try it and realize why. So, here's my first guess . . . Material is shifting slightly due to inadequate grip, sled is shifting slightly due to minor feed path deviations, or blade flutter as the front of the blade is set free from the material during the feed operation." These are things that occurred to me and well considered. I did try slowing the feed rate down but no change. The blade always has a 4" stabilizer as well. I do use shooting boards. Going to try some more tests today and see.

[Brandt Bolding]

Tried with a 80 t Freud Crosscut blade - fractionally better but not gone and this with a gap at rear of blade and mitre slot of +.005 or so.

[Brandt Bolding]

Tried some more cuts just now with different blade as well. Trying cut shaving off bit of end and also "buried" in wood no difference really. I checked parallelism - with right mitre slot 0 and 0 from front to back of blade - left side had gap at rear of about +.0015 which should ideally "work in my favor". For time being am just going to make sled to cut from right as there is no problem. Really exasperating though.

[John Kananis]

How old is the saw? Put a dial indicator on the blade and see if there's any runout. Arbor bearings maybe starting to show a little wear?

[Brandt Bolding]

Couple years old. I have a new WWII blade coming going to check that. The blades I have are about .0025 runout max or so. Forrest spec is .002. It did occur to me about bearings I have a spare set.

[Bill Dufour]

Are you pushing the work and gauge slightly to one side so it rides on one side of the miter slot? Similar to how you have to use a chop saw.
Bill D

[Steve Jenkins]

Agree with sandpaper on the fence. If you have some psa 150 grit it will just take a few seconds to stick a strip on the fence.

[Brandt Bolding]

I was very careful in tests not to do that. When I get new blade, going to make another sled, so I can see if I can get any new insight. That said, I mentioned re. the slots..."right mitre slot 0 and 0 from front to back of blade - left side had gap at rear of about +.0015" so slight discrepancy but not sure that would really have an effect like this.

[Lee Schierer]

Tried some more cuts just now with different blade as well. Trying cut shaving off bit of end and also "buried" in wood no difference really. I checked parallelism - with right mitre slot 0 and 0 from front to back of blade - left side had gap at rear of about +.0015 which should ideally "work in my favor". For time being am just going to make sled to cut from right as there is no problem. Really exasperating though.

Are you measuring off the side of a tooth or the blade plate when you make these parallel measurements.

I put a mark on a point close to a tooth with a magic marker. I rotate that point from front to rear to take out any plate variation. I have applied thin uhmw tape to the side of the bar on my miter gauge to eliminate as much side play as I can. Then I attach a dial indicator to my miter gauge and check the blade alignment. When I take a reading I apply pressure on the miter gauge toward the blade to eliminate any side play. I can get my saw aligned to within 0.001 front to back on the blade. I use full kerf saw blades exclusively. I no longer use any thin kerf blades.

[Brandt Bolding]

I use a EZ Align digital gauge which has a bar that fits the mite slot - made specifically for checking TS blade distance from slots. I measure both the tooth and plate.

[Rich Aldrich]

I have noticed when my blade becomes dull, my cuts loose squareness. This is more with a track saw than a table saw, but it might apply to a table saw since the board can possibly move a bit. Just a thought. Your a new blade may be the answer.