Tooth Marks from an Upcut Saw

      A cabinetmaker troubleshoots a cut quality issue with an upcut saw. April 2, 2015

Question
I have a Powermatic upcut saw. The cut quality doesn't seem to be good enough to butt joint face frames with pocket screws. The blade is freshly sharpened and the sharpening guy checked to see that there weren’t any teeth out of alignment. I turned down the air pressure to slow the cycle. It is at 40 psi and is just enough to complete the cycle. That has helped the cut quality but it still isn't up to miter saw quality. Am I expecting too much or is that a normal cut?

Forum Responses
(Solid Wood Machining Forum)
From contributor X:
I don't know about the Powermatic but my Omga upcut saw cuts as good as a miter saw. If I am cutting finished pieces that aren't going through the widebelt sander later then I will always cut face down to avoid tearout on the face, otherwise I don't worry about door and faceframe parts since they go through the widebelt anyway.



From contributor B:
Check the runout in the spindle and try a different blade. We use a FS tool FST1L06450 18 x 120t on our upcut saws with good results. It is a thick stout blade and very high quality.


From the original questioner:
I meant to post about that initially Contributor B. We've tried it on two blades. They are both the Frued 18"x108t blades. I can't feel any terrible runout on the spindle but there may be a little.


From contributor B:
What does it do - tear out or saw marks? What is keeping you from having clean butt joints?


From the original questioner:
I guess you'd say saw marks. It almost looks like it is a chain saw (for lack of better description) but not near as bad. I thought maybe the blade was wobbling from deflection and that's why I turned down the air pressure.


From contributor V:
It really sounds like a high tooth, but you said you tried two different blades. How about the collar on the right way? Has it spun and is it galled? Pull the blade and stick a dial indicator on the shaft and fixed flange, also grab a hold and see if it wiggles indicating a bad bearing. They are pretty simple machines so I would just keep eliminating possible problems.


From contributor S:
Try a 0 deg. or neg hook ATB 4+1.


From contributor D:
I wonder if it is possible the blade is not square with the travel like a radial arm saw does when the arm is traveling square but the motor blade assembly is cocked causing the blade to heel on the cut.

From Contributor S

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We had trouble with our upcut a few months ago. We slowed the cycle time and that helped a lot but wasn’t quite perfect. Then when I moved the guard/clamp closer to the wood and that really helped. If I left an inch or two between the pieces we got the "chainsaw" marks again, but with only a half inch or so clearance we got great cuts.


From contributor B:
To contributor S: Do you mean before the cycle started?


From the original questioner:
I adjusted the guard down to less than 1/2" above the wood. Slowing the cycle has given me a cut I can live with until I can investigate further.


From contributor K:
I would suggest going to more teeth on the blade. Is yours an ATB tooth pattern? The blade I would suggest would be 18" x 1" bore (I am assuming Powermatic have a 1" bore) 0.134" plate, 0.180" kerf and 120 teeth. I wouldn't lower the air pressure. Likely on the cylinder itself I would adjust the flow control valves. Lowering the air pressure may cause other issues (stalling in the cut etc.). I wouldn't suggest the negative hook angle but a 5 degree should do the job. Negative hook angles are usually for double sided melamine or plastics.


From Contributor T:
We had the same type problem when we purchased our first upcut saw about ten years ago. It was a Kit Cam with an 18" blade. We do our frames the same way and had exactly the same issue. After trying everything everyone mentioned in this post, we found the problem was in the 18" blade. In my opinion that blade is just too large to make a finish cut and the least bit of wobble out at the rim will give you the "chain saw" marks you refer to. We modified the machine slightly and made some adjustments so we could use a 14" blade, problem solved!



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