C-man RAS alignment problem

[Matt Day]

I'm stumped by the cuts I'm getting from my RAS. As you can see in the picture, the blade is square to the table within a gnat's hair, but the cut I'm getting from said aligned blade is out about 1/8" over 6". The table is flat and square to the blade wherever the arm is swung (left, right, center).

How can this be? Am I overlooking something? If I can get this figured out, hopefully it will also eliminate the tearout I've been having.

TIA

[Al Killian]

Have you treid raising the left side of the table to correct the problem? To set it up take the blade off the spindle. Turn the spindle towards the table. Then slide the motor assembly across the table and check the height in several spots, this will flatten it front to back. Next swing the arm from center to the right and check for difference in height. Then repeat for left side. If this is done correct your blade will be 90 to the table. Tire this first and let me know if it does not correct it.

[Jim Becker]

Is the table flat?? (And I hope the "guard is removed for clarity..."... )

[Matt Day]

Jim - Yup, the table is flat.

Al - Yes, I did all that according to the manual. I went through it thoroughly when I set it up, and went through it again after finding this problem.

I did change my technique and it helped a little, well sort of. What I was doing was simply doing one pass with the blade, which I found gave me 90* between the long and end grain faces (in other words, the blade cut 90* to the fence). Doing a pull and a push pass with the blade gets me a little out of 90*, but gets the alignment in question reduced to about 1/16" over 6".

I'm stumped.

[Bill Simmeth]

Just a WAG, but the motor torque will try to deflect the motor assembly in that direction. I'd check for any play in the yoke and arm that would allow for that deflection. It could also be that the design of the arm isn't sufficiently stiff to overcome the torque.

[Les Spencer]

Matt,

Have you checked for movement in the spindle and carriage bearings? As far out as you are, you should be able to see looseness somewhere. Try turning your board over, not end for end, and re cut taking a sliver off. Is the cut parallel to the first cut? Or does the error stay the same?

Is this a new saw? Has saw been wrecked? What happened to cause this?

[Kelly C. Hanna]

You are using two different squares. The first one isn't very accurate for 90* measurements. My bet is the one in the foreground would be a better choice to square the blade with the table.

[Matt Day]

I bought the saw used, and I went step by step through the manual and made a few adjustments. I didn't feel any play in the column when I checked it.

I'll look closer at the carriage when I get home, and try making the parallel cut as Les suggested. I think the carriage might be flexing during the cut due to the torque (it's wired for 220V), so I'll see if I can tighten it up. That's the only thing I think it could be.

Thanks for the suggestions.

You are using two different squares. The first one isn't very accurate for 90* measurements. My bet is the one in the foreground would be a better choice to square the blade with the table.

No, it's the same with both squares I just used both to illustrate what I was talking about. My squares aren't the best, but they're not out by 1/8"!

[Rick Thom]

It appears you are using a TK blade, which is what I also use. Is it possible that it is not stiff enough or of the correct design to prevent deforming and to track correctly when under load?

[Ralph Barhorst]

I have the same saw and the only time that I have a problem is when the motor/blade moves because I had not tightened the knob that is used to tilt the blade.

[Matt Day]

It appears you are using a TK blade, which is what I also use. Is it possible that it is not stiff enough or of the correct design to prevent deforming and to track correctly when under load?

It's a Delta blade that came with my new TS, I'm not sure what a TK blade is (Thin Kerf maybe? If so, it's a standard 1/8" blade). I would think that and blade flex would be negligable, based on the fact that many people do not notice a difference w/ or w/o a blade stabilizer.

When I go home I'll try the parallel cut, check that the carriage assembly is tight, and try a different blade on it.

I'll let you know how it goes.

[Jim Becker]

Matt, 'careful using a TS blade in a RAS...TS blades usually have too agressive a hook angle for safe use on a RAS (or CMS or SCMS).

[Lee Schierer]

Several things come to mind. You say the table is flat, but is the carriage tight on the arm? There is adjustment of the rollers that let the saw carriage ride out the arm. If the rollwers are not correctly tightened, the weight of the saw will make it look square until the cutting action causes the motor frame to tilt on the rollers.

My second thought is that the lever that allows the motor to swivel in the horizontal plane on the carriage is not tight. Again, the weight will keep it in place until the cutting action overcomes the weight and tilts the motor.

Finally. My saw has angles along the edge of the frame that support the edges of the table. It also has a set screw adjustment in the center of the table. to raise or lower the center of the table under the blade when cutting 90 degrees to the fence. This set screw also supports the center of the table under load. If this set screw is not there or not in contact with the table frame the table could be deflecting under load.

I also agree with the comments regarding getting a better square. Go to the local office supply store and buy some plastic drafting triangles. They are low cost and very accurate. You need a longer leg in contact with the table surface to determine if the blade is truly square to the table.

[Matt Day]

Okay, I made some good progress tonight, but still have a couple things I'd like to run by you guys.

I played around with the hex bolts by the yoke handle (the spring loaded vertical post), but couldn't for the life of me figure out what it did. It's supposed to adjust heel and toe of the blade (which I found out was out a bit), but I couldn't see it do anything or figure out what it was supposed to do. What I did figure out was that the carriage bearings on the left side are eccentric, and that they were a bit on the loose side. I snugged them up to remove the heel from the blade, which was enough so there was no play at all even when pulling up hard on the arbor. I made a test cut and viola (sp?), 90* everywhere. Great!

BUT... to remove the heel from the blade, I had to make the bearings tight enough so that the carriage doesn't move freely on the arm. I have to actually push it through the cut (not dangerously so). If I loosened the bearing at all, the heel of the blade would kick out, and I couldn't manipulate the front and back ones to get them in synch.

Is there anything I can do about this? Or do I need to just find the happy medium?

I also changed out the blade to an old, but brand new, crosscut blade (80t I think). Even though this is carbide tipped, it cuts much better.

[josh bjork]

Matt, I had issues with the same kind of thing. The arm was 90 to the fence but the blade was not 90 to the fence. It doesn't sound like you have found the adjustment for that? Maybe it just sounds that way but on my model 100, I think there are some adjustment screws between the top of the carriage and the yoke that holds the motor. I've had this saw for months and still haven't gotten it setup right. There are more adjustments than I would have believed.