SMT Clamp question during alignment

[sailor55330]

Hi again,

I tried again to work on the SMT. I loosened the 3 appropriate nuts on the SMT base. I had the front rail clamps in the locked position and solid. I had the rear clamps loose.

I have a question that I hope someone may be able to answer

The smt clamp assembly is made up of brackets, cams, and an aluminum u-channel that pushes against the larger rear rail to lock in place. When my rear SMT clamping assembly is loose, the whole clamping assembly has approximately 1/8" play if I wiggle it front to back (between the underneath u-channel and the larger front or rear rail--more so in the rear). I know there is some room necessary. Does this sound right. The reason I ask is that when I go to align the SMT base, the whole clamp assembly ends up moving along the larger rear rail before I get any movement on the smt base itself I am wondering if this excessive play is part of the problem. I would guess that with the rear clamps open and the front clamps locked, I can easily move the SMT base an inch left to right without putting any real pressure on it. Think of it as the rear of the SMT base "torquing" against the front clamps

I have not been able to figure out how to keep the clamp assembly from shifting while adjusting the smt base or while tightening it. The only way I can get the SMT base to move is by holding the clamp in place with pressure.

I wish I could post some pics, but I didn't have any luck with that. My words probably aren't very good descriptions on this, but they are the best I can do.

I can't tell you how frustrated this has made me

[crokett]

Hi again,
had the front rail clamps in the locked position and solid. I had the rear clamps loose.

I wonder if this is part of your problem? When you are setting the base in place to cut, do you tighten the front or rear clamps first? You are supposed to tighten the rear ones first, then the front ones.

[Salty]

Sailor, what you described didn't sound good so I just had to go check mine for the same situation. What I found is that with ALL SMT clamps fully UP, the unit does not move side to side at all. In fact, the only movement is the slide part from the lower section and that is because I don't use it for cutoffs and do not have it adjusted correctly.
Here are some pictures of mine both from the top and from under.
See if there looks to be something dramaticlly different from yours.
I'm guessing there is something not the same between yours and mine.
Hope this is of some help.

[Salty]

I wonder if this is part of your problem? When you are setting the base in place to cut, do you tighten the front or rear clamps first? You are supposed to tighten the rear ones first, then the front ones.

Hummmm...I thought it was front first then the back!

[Salty]

Sailor, does yours have the bright aluminum U-channel on BOTH the front and rear of the SMT?

[Black wallnut]

Front first; then rear.

[Black wallnut]

It is difficult for me to follow what you are saying. With the front clamp locked and the three SCREWS loose yes it should pivot on the front screw and the rear clamp assembly should float along. The two screws that secure the base to the front clamp are what do the lions share of the alignment work. The rear just rides along and its screws are tightened only after the base is parallel by pivoting off a front screw. So yes, some slop is normal but not much. Surely not even enough clearance for a spark plug gap gauge.

[sailor55330]

Thank you for the pictures and thank you for the ideas and questions. I'll try to answer clearly on each.

1. When I lock down the SMT, I do lock the fronts first and then the rears, each pair simultaneously.

2. My clamps look exactly like the pictures. A

2.5 The 3 screws for adjustment are loose and the rear clamps are in the open position while I trying to align.

3. When I put the smt on the rails with the clamps in the open position and all adjustment screws tightened, I can stand on the left side of the table, put my left hand between the clamps on the rear of the smt assembly, my right hand on the front of the smt assembly between the clamps, and I can shift the whole assembly between 5/8 and 3/4 of an inch. By shift, I mean that the rear of the smt will move towards the blade and the front will move away from it (the whole assembly). It actually only takes 1 finger on the front and back to do this. There is that much slop between the locking cam and the shiny aluminum channel on the underside of the clamp assembly. It will actually rock to the left and to the right on the main rails. When all 4 clamps are locked, I can actually move the whole saw by the smt--it locks down that tight.

4. If you look at Salty's picture in the lower right, the distance between the u-channel and the cam is large enough to allow the shifting I am trying to describe above

I know there are set screws on the clamping assembly that seem to be able to control the gap between the shiny aluminum channel and the cam that locks everything to the rails. I was going to try and adjust this gap with that set screw, but all 4 of them have been set with a locktite type compound (it's blue). What I am wondering is if over time, the plastic cams have worn causing the gap between the cam and the shiny aluminum channel to increase, which would cause the excess play I am seeing while the table is sitting on the rails.

I hope my descriptions are ok--I have never seen a 3100 in verified working order

[Black wallnut]

Quick question: Have you seen the pics of the front and rear rail profiles that I have posted somewhere on our site?

I just braved the cold rain and wandered out to my shop to look at my saw. I have less than .005" play between my u-channels and the rail when unlocked. I can not measure it any closer since I do not own a dial gauge and my thinnest feeler gauge is .005".

[sailor55330]

BlackWalnut,

I certainly didn't mean for you to head out into miserable conditions tonight--that's way above & beyond.

As for you pictures of the rail profile, I honestly don't remember.

I can tell you that the gap between my rails and u-channel is enough that when the smt is resting on the rails with the clamps open, I can move from front to back approximately 1/16 of an inch in a straight line which isn't far from .005.

[Black wallnut]

You might try just closing the gap so that the SMT will still move smoothly when the clamps are open. Then you will have to readjust.

[sailor55330]

That's what I'm going to try later today,provided I can break the set screws loose

[Brian G]

I read in a different thread that you're in Minneapolis. I'm in Bloomington. I'm willing to help solve your problem, if you'd like.

I decided to check the alignment of my SMT this morning. I haven't felt the need to do so since I first assembled it in 2003, but I figured it was a good idea to check anyway.

My SMT was out of parallel by 0.5 mm, so I took care of that. I also corrected a slight amount of side-to-side play that probably sneaked up on me over the years of use. The SMT fence is now re-squared to the blade.

That's not meant as a brag, just that the process is fresh in my mind.

Let me know if you'd like some help. You can send a private message and we can make the arrangements that way.

[sailor55330]

Update:

I removed the clamp assembly, cleaned everything and re-assembled. That removed about 95% of the slop I had in the clamp assembly when they are open. That was enough finally allow me to get the smt base aligned within 1/1000th and it seems to stay aligned if I move the assmebly to other parts of the rail. Apparently over the years, things had just worked loose. I aligned the miter fence to square using 2 different squares. I tested the cuts again and still not square. Nearly 1/8th over 12 inches again with the 5 cut method. I began examining the miter fence. It wiggles about 1/32 of an inch when tight. I tightened it as much as I dared. Still able to move it. So I guess that the pivot pin is shot.

On to the next weakest link I guess. This was the worst tool purchase I have made (not bashing 3x000's, just pointing out this one). I have learned that used tool purchases aren't the way to go.