Kapex 120 Only square on one side of the blade

[MrBarrel]

I have run into the problem of my Kapex 120 REB only making square cuts on one side of the blade, the other is always a little off but enough for it to matter. To check the angle I use a high quality 20cm square machined to DIN875/00 standard.
First suspect was the fence but its straight as an arrow. I took it off and checked with a straight edge. To make sure, i scribbled on it with a pencil, put some 150grit sandpaper roll on my jointer infeed bed and did a couple back and forths to see if there is maybe some high spots. Its as straight as possible. Logically I dont know what else could it be. I fired an email to festool support but im afraid they will want me to send the whole machine which i really dont want to do. Anything that comes to mind ?

 

[denovo]

I have run into the problem of my Kapex 120 REB only making square cuts on one side of the blade, the other is always a little off but enough for it to matter. To check the angle I use a high quality 20cm square machined to DIN875/00 standard.
First suspect was the fence but its straight as an arrow. I took it off and checked with a straight edge. To make sure, i scribbled on it with a pencil, put some 150grit sandpaper roll on my jointer infeed bed and did a couple back and forths to see if there is maybe some high spots. Its as straight as possible. Logically I dont know what else could it be. I fired an email to festool support but im afraid they will want me to send the whole machine which i really dont want to do. Anything that comes to mind ?

Dull blade causing some deflection when cutting?

or when using the sliding action you could be applying more pressure on one side

 

[Packard]

Check that the fence is exactly inline from left to right using a long straight-edge. If I remember my high school geometry correctly, that would be the only explanation.

 

[smorgasbord]

If you put the two cut pieces back together, aligned with a good straightedge, does the cut line fit perfectly?

 

[MrBarrel]

Check that the fence is exactly inline from left to right using a long straight-edge. If I remember my high school geometry correctly, that would be the only explanation.

It really makes sense that the only explanation if the fence being either misaligned or crooked but i swear to god that thing is straight as an arrow. My straight edge is not beveled but just to make DOUBLE sure i marked it with a sharpie all around the surface and sanded it on my jointer table again, carefully doing each movement without applying any kind of pressure from the top, just slow forward and back strokes. I was initialy glad to see some high spots but after mounting it and aligning a perfect 90° on one side, the other is still ass. Festool called me today (at 8am lol) and as expected he just said to send the whole thing in. Its free but even the best case scenario is a week with no miter saw which is a long time.

 

[ChuckS]

Check the stock you used to make the test cuts. Or, perform another test, using good stock that is flat and straight.

 

[Cheese]

Festool called me today (at 8am lol) and as expected he just said to send the whole thing in. Its free but even the best case scenario is a week with no miter saw which is a long time.

My issue with sending in a Kapex for service is when it's returned to you will it still be adjusted correctly? I have no issues sending in any other tool for service...but a miter saw...there's a risk involved.

 

[kevinculle]

I had the same issue on my Kapex and tracked the problem down to the fence base, which Festool labels as the stop (Part 103). The two flat sides of the fence base were not colinear, such that a straightedge held against the flats showed a slight gap at the inner edges. So, instead of having an included angle of exactly 180 degrees, it was perhaps 179.8 degrees. I lapped the face of the part using a 120-grit self-adhesive sanding roll adhered to my table saw table until the two faces met a high-quality straightedge without any visible gap. I was then able to get very good results on both sides of the blade.