Help with table saw alignment

[Jay Maiers]

I'm having some problems aligning the blade in my Ridgid 3612 (10" contractor model). Raising the blade to 3"+ and using a digital caliper in the miter slot, I'm able to align it to +.oo3" at the rear end: so far, so good. When I drop the blade back down to 1" for cutting 3/4" stock, the alignment dimensions change enough to create a bind at the rear of the blade.

I've confirmed this by cutting a block with the blade at maximum height, lowering the blade, and then checking the clearances with the same block. After the first cut, I shut the saw off, and was able to easily slide the block between the fence and the blade. After lowering the blade, I found it would move past the front of the blade just fine, but would get hung up on the teeth at the rear.

Does anyone know what could cause this?

Thanks,
Jay

PS: FWIW, I've also checked the fence for flatness using the miter slot and digital calipers. My best measuring techniques say that the fence wanders back and forth by +.0005" (away from the blade) and -.0015" (towards the blade) over the entire length, with the area near the blade being a consistant -.001"

[Kent Chasson]

Sure sounds like the arbor is twisting as the blade gets raised/lowered. I would take a close look at the lift mechanism and see if there is something besides poor machining that is causing the twist.

Have you checked to see if it the problem shows up evenly as you lift or is it only at one extreme or the other? If the latter, maybe something is pushing on it as it gets near the end of it's movement.

If it's gradual, I would assume that it's just not made for precision.

[Alan Schwabacher]

The question to answer is whether the blade is consistently following the wrong path, or if there is slop in the mechanism. To check this, raise the blade back up and check to see whether the blade is back in alignment to within .003". If it's not, that may mean that as you aligned the saw, room for movement opened up between the trunnion and carriage. To fix this problem, clamp the trunnions to the carriages with C-clamps as you align the blade to the miter slot. Clean and wax the semicircular grooves where these connect while you're at it.

If the blade is consistently following a precise but wrong path, I'm not sure how you'd fix it.

[Howard Acheson]

It sounds like the trunnions on your saw are out of plane (alignment). Here is the process to check for trunnion planarity and then, how to adjust it.

First, go through the process to ensure that your blade is parallel to the miter slot.

To check whether the trunnions need to be adjusted, tilt your blade fully to the 45 degree position until you get to the 45 degree stop. Then crank the blade back to the 90 degree upright position. Now again check the parallelism of the blade to the miter slot. If the blade is still parallel to the miter slot, declare victory. If not, follow the process below from Delta to adjust them. The process is the same for all Contractor Saws or Hybrids that have the trunnion assembly hanging from the table.

1. Remove the saw blade being sure it was at it fullest height.

2. Place a flat plate (or similar flat object) on top of the two tie-bars. (The size of the plate should be at least 6" by 8", and the flatter the better. A pane of glass works well.) Depress one corner of the plate and if it rocks, the tie-bars are not parallel. This must be corrected as it will affect the alignment of the blade.

3. Loosen the tie-bar locknuts located at the rear of the saw.

4. Grasp the motor bracket and move it left and/or right. Check the rocking of the flat plate and when it can no longer rock, the tie-bars are parallel...re-tighten the locknuts.

5. Remove the flat plate and re-install the sawblade.

6. Again perform the parallelism alignment process.

7. Before tightening the rear trunnion bolts, push forward on the rear trunnion bracket to allow the undercarriage to snugly fit between the two trunnions.

[Joseph Tarantino]

FWIW, also check the face of the fence that registers against the workpiece. some 3650/60 fence faces were not perpendicular to the top of the saw when placed on the rails. probably not the cause, but you never know.

[Jay Maiers]

Thanks folks. I'll check it over this weekend and see if any of these suggestions solve my problem.
Jay