SMT Alignment

[LarryG]

I'm confused about the way the sliding miter table is supposed to be aligned. Right now mine is spot-on but out of curiosity, and for future reference the next time this job is necessary, I'm wondering about the "correct" way to do it.

There's a lot of talk about being careful not to break the eccentric screw adjusters when aligning the SMT. Okay ... but from reading the manual it appears that these screws are there only to adjust the side-to-side free play in the SMT, and not to align it per se. (Obviously if there's too much free play the alignment can be off, or will drift off, as you make the cut.)

Once these eccentric screws have been tweaked to take the free play out of the SMT's side-to-side motion, the entire assembly is then aligned parallel to the blade by using the black, non-eccentric screws on the SMT's black, steel base. Most of the alignment discussions I've seen never mention these screws, or at least that's my interpretation of what's being said.

IOW the method in the manual involves TWO sets of screws, and not just the eccentrics that are recessed into the top of the SMT.

Or have I got it wrong?

[RayintheUK]

No, Larry, I'm with your interpretation all the way. The quote in "Five things a newbie often breaks on a BT3" of "The eccentric screws (they’re real brittle) that set the SMT alignment – know how they work before you adjust them" is incorrect and misleading, in my view.

Ray.

[gmack5]

The Black Screws that you refer to on the SMT Base, the part that attaches to the Rails, are factory set to hold the Base Perpendicular to the Rails and should not need to be "tweaked" at all, ever. The fours Screws that hold the SMT table to it's base consist of three Eccentric Screws and one "Normal" Scew, located at the Right Front corner (it's Silver in color). The Normal Screw should not require any adjustment in order to bring the SMT into allignment with the Saw Blade. The other three Screws, however are a different matter. I've written a proceedure, somewhat different from that in the Owner's Manual, hopefully, easier to understand, with easier to perform adjustments. Because of the recent BT3central crash, the graphics are temporarily not available, but the rest of the proceedure should be of some help.

Let's assume that something is out of square so we'll check everything from the beginning, we'll assume NOTHING, until it's been confirmed.
EVERYTHING , both fences, the front rail (the one closest to the operator), and the SMT all reference off of the SAW BLADE.

So the first thing we need to do is make sure that the FRONT RAIL is square to the saw blade (SMT base references off the front rail). The Saw Blade and the SMT BOTH should be square to the Front Rail and therefore parallel to each other.

Assuming this is true, then the next thing to do is make sure you're locking down the SMT to the RAIL correctly.
Lock down the FRONT two tabs first, then the BACK two tabs.

You just went thru two 90 degree "bends" and the "carrier" (the thing that the SMT slides on) should be parallel to the saw blade, check it and make sure that this is true.
One way to check it, if you've adjusted your Rip Fence to be parallel to the Saw Blade, is to put the Rip Fence right next to the edge of the SMT base and clamp a straight edge low on the fence, so that it will contact the edge of the SMT base. Inspection should reveal whether or not the SMT base is parallel to the Fence, and therefore the Blade.

Next, lets bring the SMT parallel to the SAW BLADE. (This is what you've been waiting for!)

There are four screws envolved, a "normal" shoulder screw and three eccentric screws.
The normal screw is the pivot point and should never require adjustment, since the others use it as a reference point to adjust for parallel and to take the slop out of the SMT, with respect to the carrier.
The RIGHT FRONT screw is the "normal" screw.

CAUTION: the eccentric screws are a little delicate, so be careful that you don't torque them too hard, as they WILL break off.

To make the SMT parallel to the saw blade, be sure the LEFT front eccentric screw is "snug", but not tight, to the base, loosen the LEFT REAR eccentric screw and make sure the SMT is good and sloppy (Don't want it to interfere with the effort to bring the SMT parallel)
The Right REAR eccentric screw is used to bring the SMT parallel to the saw blade, adjust it by applying a slight pressure to the RIGHT side of the SMT as you adjust for parallel by rotating the RIGHT REAR screw.
Once you're sure you're parallel to the saw blade, lock down the eccentric screw by keeping it in it's rotational position with a screw driver (I find that an offset screw driver works very well for this) from the bottom as you snug up the nut on the top of the screw.

NOW take the slop out of the REAR end of the SMT by rotating the LEFT REAR eccentric screw, until the SMT is snug, but not tight, you should be able to push the SMT towards the back with very little effort, in other words, it should "glide" smoothly, with very little or no side to side slop.
Be sure you hold the screw in position with a screw driver to keep the screw from rotating as you tighten the nut on the top of the screw.

Your SMT should now glide parallel to the saw blade!

Your Miter Fence, while not directly envolved in the adjustment, needs to be adjusted also. This is accomplished by adjusting the "Quick Stop", located on the Left side of the SMT, about mid-way down the side. Adjust your "Quick Stop" (the little tab that swings up on the left edge of the SMT) so that it brings your MITER FENCE square to the blade (it's also an eccentric screw) when you gently swing the miter fence up against it.

One other thing to be considered.... The Clamp for the Miter Fence consists of a 5/16-18 bolt that passes thru a plastic bracket that provides the clamping pressure to hold the Miter Fence in whatever position you put it. The hex head on the clamping bolt rides IN a grove on the bottom of the SMT. The groove is sized in such a way that it keeps the bolt from turning as you tighten the knob on top of the bracket. If the Clamping Bolt is properly installed (head in the groove) there is no way that it could deform the Sliding Miter Table, since it merely clamps a piece of Aluminum (the SMT base) between the Miter Fence and the head of the bolt. IF you put a washer under the clamping bolt (on the bottom) in an effort to straddle the the sides of the groove that it was designed to ride in, it might deform the SMT when pressure is applied by clamping the Miter Fence with the Clamping Bolt improperly installed. YMMV

That should do it!

You should be good to go!

[LarryG]

Yes, George, I've seen this write-up before ... many times ... have it my PDA, in fact, and referred to it while adjusting my saw.

However, I found that the black screws on the base DID need to be adjusted, because the SMT's base was NOT perpendicular to the rails, and overall I thought the method in the manual was easier and, ultimately, more accurate. That's the purpose behind my question. I don't under why these alternate methods are supposed to be better when the one is the manual is so easy and straightforward.

[leehljp]

Larry,

Part of my work involves "communication" and boy do I, we all mess up sometimes. Having said that, in the past there have been several people who could not understand the manual's explanations at all. Then several people would join in and add "in other words" in explaining the procedure. One explanation works for some, the other for other people. The result is confusion between the two. []

I had no problem with following the manual's explanation, but as I said, some just could not make sense of the manuals descriptions, and post here or on the Ryobi forum in desperation for help.

Being the helpers that we are, other explanations were given and these seemed to work for some.