Does anyone know how this happens

[edward]

While cutting Steve Goods pattern of the soccer Moms pattern I noticed that the back breaks out and the front looks good, any suggestions .

[fredfret]

Blade not at 90 degree to table, side pressure. Front to back alignment could also be at work.  It only takes a very small amount of offset like .25 degree to cause this.

[kmmcrafts]

kind of looks like it could be possible two things.. First.. check to be sure your saw table is square to the blade... second possibility if the blade is square. be sure you are not pushing the blade too hard and making it flex.. suppose not enough tension might be a possibility too..

At any rate the way the picture looks.. it looks as though the bottom side it thinner than the top.. which is why I suggested looking at the table to be square to the blade..

Quick and easy way to check it.. get a fairly thick piece of wood maybe 1 or 1-1/2 inch and make  a cut just deep enough into the wood to get the blade all the way into it.. then back it out and try to insert the back part of the blade into the slot you just cut... if the table is square to the blade it should line up.. if not then you need to adjust the table and make another test cut.. keep doing the process until you get it to line up... Or if you have a small machine square you can also use that.  

[OCtoolguy]

Also check to make sure your blades are center in the clamps in a way that the blade is perpendicular to the table. Everything has to be square and aligned so that the blade is cutting at the same point both top and bottom. It looks like either the top or the bottom of the blade is ahead of the other.

 

[jollyred]

Looks to me like there are short grain issues involved, also.  The pieces broken out are at right angles to the grain, which means the section will be weak.  When the grain is aligned with the cut, the parts of the pattern are good, since that is a stronger orientation.  Those pieces also look to be slightly narrower, which would again weaken it.  If you recut it, try making that part thicker to strengthen it.

[WayneMahler]

Keeping your blade at 90 Degrees is critical. Make sure everything is square and take your time cutting. 

[CharleyL]

I agree with the others, but could probably help more if I knew what saw you were using. Getting the front/back angle of your blade at 90 to the table isn't quite as easy as  getting it 90 to the table in the side to side direction. A lot will depend on what saw you are using.

Charley 

[edward]

I am using a Dewalt 788 and a#5 blade, and the table is level and so is the blade tight and straight.

[John B]

39 minutes ago, edward said:

I am using a Dewalt 788 and a#5 blade, and the table is level and so is the blade tight and straight.

Edward, It looks like narrow, short grain is the problem. When cutting any timber and these 2 things come together you will more than likely have the back (underside) breaking away.
Reverse tooth blades, mitigate it to a certain extent and a zero tolerance blade surround will also reduce it some. A sharp blade also helps and a slow cutting speed, not the speed of the blade, the speed you feed the piece into the blade.