Carbatec CTJ-381X thicknesser blade misalignment

Hi Woodies.
I have a Carbatec CTJ-381X thicknesser that I purchased in 2010 along with a full set of replacement blades. I have been very happy with the planing finish obtained with this machine and the longevity of the blades. I have recently undertaken my first full blade change and am not completely happy with the results. The timber is left with visible cutting lines that need to be sanded out after thicknessing. I have studied the blades more closely and found that there is a slight rotation of the blades as they are tightened on the cutter head. This causes one corner of the blade to be slightly forward of the other which would also result in it cutting slightly deeper.
Has anybody out there experienced a similar problem and found a way to overcome it? At this stage the only solution I have come up with is to wedge the blade somehow while tightening the retaining bolt and using a straight edge to check the final alignment across several blades on the head. This is a very tedious process given that there are 72 blades.

Don't the inserts register solidly against a raised edge to prevent them from turning? Is the surface below the inserts really clean with no build up that would stop the insert pulling down flat against it? Is the underside of the screw head in good condition with no gouges or score marks?
Does your head look like this one from the later models?

Attachment 492494

I don't have your model thicknesser but I do have the Carbatec helical head 8" jointer and lunchbox spiral head thicknesser. I found that some cutters had gunk buildup around them that wasn't an issue until I loosened their holding screws, the gunk prevented good registration against the index on the head. The issue was similar to what you describe, where tightening the screw down meant the cutter edge was slightly skew compared to the index. Cleaning off the build up allowed the cutter to register properly.

If you're still having issues and there is no build up, I'd say your cutters might be the problem. Did you have any issues when you turned to a new edge in the past?

This was my method of insert rotation, worked perfectly for thousands of rotations:

Loosen the screw enough for the insert to freely rotate
Blow out the seat with compressed air
Visually inspect the seat for any resin that's stuck on and remove it
When retightening the screw, hold the insert down and away from the rear seating edge; this ensures that it is seated flat at the bottom and allows the screw to pull it back to the correct position

Blow out with air
check for resin build up.

Just came across this video from SJE with something that sounds very similar to your problem TassieRob - Accu-head Insert Screws - YouTube

Apparently worn screws can cause an issue with the cutters being skewed too.

Quote:

---

Originally Posted by Treecycle

Don't the inserts register solidly against a raised edge to prevent them from turning? Is the surface below the inserts really clean with no build up that would stop the insert pulling down flat against it? Is the underside of the screw head in good condition with no gouges or score marks?
Does your head look like this one from the later models?

Attachment 492494

---

Thanks for your thoughts Treecycle. I have been cleaning the surfaces to ensure no grit or buildup. The head does look like the picture. I have checked the size of the old inserts compared to the spares that I have installed. There is a 0.12mm difference in the size with the spares being the slightly smaller size. This allows a small amount of movement. I have been able to minimise movement of the inserts as I tighten them by using a feeler gauge between the recess and the insert. I have used a straight edge across the face of each row of inserts to get them in line. I haven't checked the screws closely for wear or poor manufacture but will do this and let you know.

Tried this but didn't improve the installation. Thanks for your suggestions.

Did you get your replacement inserts from Carbatec or from a third party?

Quote:

---

Originally Posted by Treecycle

Did you get your replacement inserts from Carbatec or from a third party?

---

I bought a complete set of replacements from Carbatec at the same time as I bought the thicknesser. This was about 10 years ago so I don't think there is much point in trying to make a warranty claim.

Are you over torquing them by chance? I found that last little 'nip up' where i was over torquing the screw twisted the insert just enough to cause the issue you have.

You are right in saying that the last little nip up twists the insert but my thinking is that they are too loose if I don't go to this point. Maybe this is incorrect. What do you use to gauge the correct torque?

I used to do them with an impact driver (slowly, of course), 4 clunks and they're good. If the insert is seating properly at the back, it's physically impossible to twist them; that's the whole point of the seat.

Thanks. You are torquing them more than me. I am using a manual screwdriver handled torx driver to do them up. I don't believe my hand and wrist strength would be enough to overtorque them.

Yeah...I used to do them by hand, but that got old REALLY fast with 250 tips on the thicknesser and 128 on the buzzer :rolleyes:

Impact drivers can be surprisingly gentle if you're light on the trigger. I was definitely more than normal hand-tight, but they could still be undone by hand if needed.