SCMS blade drift

[Cliff Holmes]

I'm having an issue with a Makita SMCS that I can't understand.

I've adjusted the blade square to the table and fence, no problem there. But what I'm seeing is that as the blade comes down, it shifts to the left about 1/16". It stays square throughout the trip, it just slides left.

I can't even grasp the geometry of how this is happening, much less how to adjust it out.

Any ideas?

[scott spencer]

Is the blade flexing? What blade and what diameter do you have? A 12" TK will deflect fairly easily.

[Mike Reinholtz]

I've tried a few times to tune for get better accuracy for tighter joints with my 12" Ridgid SCMS and have run into similar problems. For that reason I've been considering getting something like the Dewalt 8 1/2" slider and only use it for precision work, leaving the Ridgid for everything else.

What kind of blade are you using?

Have you tried adding a blade stiffener? I want to try this, just haven't picked one up yet.

[Cliff Holmes]

I'm running a Forrest Chopmaster full kerf

But blade deflection really isn't the issue. I'm seeing this drift when the saw's not even running.

[Myk Rian]

I'm having an issue with a Makita SMCS that I can't understand.

I've adjusted the blade square to the table and fence, no problem there. But what I'm seeing is that as the blade comes down, it shifts to the left about 1/16". It stays square throughout the trip, it just slides left.

I can't even grasp the geometry of how this is happening, much less how to adjust it out.

Any ideas?
I would say the motor arbor is moving out. This has nothing to do with the blade.
With the saw unplugged, see if you can move the arbor in and out.

[Will Overton]

It seems like it could be something at the pivot. It sounds like you are saying the arm moves to the side as you lower it. If it was the arbor, I don't think you would see this with the saw turned off.

[Keith Westfall]

Is it cutting square? If so, it shouldn't be pivot problems. If square, I'd check for arbor movement in the motor.

[James Malcolm]

Assuming there is no slope in the joints, the only way the blade can move side to side is if the axis of the saw pivot pin, the one you rotate about when making a cut, is not perfectly horizontal. Same as if you rotated the head to make a cut across the width of the board. The blade can be adjusted vertically irrespective of the rest of the machine, so it will appear vertical all through its path, but it will shift side to side as you state. You need to adjust the angle of the main upright first, and then adjust the blade. Adjust the main upright until the blade is in the same horizontal position when the blade is up in the stowed position and down in the cut position. There's two pair of bolts on either side of the main slider part. Not sure which one does what.

[Bill Orbine]

The thin blades have a tendency to do that on the bigger SCMS's. And once the blades gets a little dull, the more it wants to ride out from the end of the grain, especially on the sneak cuts and mitres. Which bring up a question I need to ask..... Who makes smaller saw (say.... 9 inch) , preferably non-sliding and non-tilting. I used to have a Rockwell ( a real Rockwell), and boy did that saw ever cut clean mitres! But, no more. Dropped the saw and broke the chaissis years ago.