SMT strikes again

[sailor55330]

I had my SMT aligned to the point that I could not see any difference when peforming the 5 cut method with a 12" (approx) panel. I performed this 3 times with repeatable results.

I had not touched the saw for about 4 days and no one else was in the basement (I was the only one home that week) I used the table top as a work surface to edge glue and clamp a couple peices of wood. There was no banging, no bumping, and no use of the saw whatsoever.

Tonight I was making a featherboard and was squaring a piece of 1x6. I checked the cut end and it was not square. I checked the miter fence with my drafting triangle. It was dead on. I procede to test again with another 5 cut method. I have nearly 1/8" of variance between the two ends. I was able to perform this 3 times with the same result.

I've heard of sensitive saws, but this is ridiculous. I really don't understand.

[dbhost]

This is honestly stunning...

My saw gets bumped into quite a bit, and the SMT stays square... Is there a member near you that might be able to help you through this?

[crybdr]

I've followed your threads over the last couple weeks. I'm astonished by the amount of trouble this saw has given you - mine has been very accurate from day one.

If you're seeing 1/8" non-square cuts across a 5.5" piece of wood while the fence to blade angle is 90 degrees - seems like the sliding portion of the SMT is out of line - the sled itself. I hesitate to even offer advice in this area as I am not as expericenced with this saw as others on this forum. But, geometrically, what you are experiencing doesn't add up - as your frustrations clearly indicate.

The only other thing I can think of (and I'm sure others have suggested it) is that your front or back rails (the big horizontal extrusions - the front one has the inch markings on it) may be shifting - not tightened enough, or worn fasteners? Otherwise, if the rails aren't shifting, could the SMT clamps be shifting on the rail?

I went downstairs just now and gave my current saw setup a little shove in certain directions - I need to do an alignment anyway, it's good practice.

After some focused pushing, I was able to bump the rails slightly out of alignment (they were probably not tight enough) AND shift the SMT clamps relative to the rails (this is plastic on aluminum - it WILL move if you force it - they don't see lateral forces during the normal use of the saw) I'm not surprised by these results and it doesn't concern me. Just gotta tighten the rails more and make sure I don't overstress the SMT clamps.

I have made many furniture pieces on this saw. Don't lose hope - it's a very capable tool.

[sailor55330]

Trust me, if you're stunned and or confused, how do you think I feel? The Base sled is/was aligned within .003", which is less than your average peice of copy paper. It just doesn't seem possible that this minute error is translating into the variance I am seeing over 12 inches, especially when things were fine 4 days ago


All of the rails are tight and the SMT clamps do hold with no slipping when engaged. There was 1 thing that I did do as I think back. I moved the SMT from the left side of the table to the right side to support a 23x23 piece of MD that I was squaring up. That was not a problem. I moved the SMT back to the left side, clamped it accordingly (fronts first and simultaneoulsy, then the backs) and left the saw until tonight. Now it's out of alignment.

If I was abusing the saw or pushing it's capabilities or forcing something, I would expect issues, but the bottom line is, I'm just not. I was always taught that you let the tool do the work, never be heavy handed.

As much as I can see the saw does have some unique properties, the one in my basement just has so many gremlins that they are overshadowing anything positive.

I am really at a loss

[Uncle Cracker]

I use my BT as a workbench, sawhorse, practically everything but a hammer, and I have no such issues. (Caveat: I don't use the SMT anymore, because I like a sled and good miter gauge better, since I have slots on both sides of the blade, but my SMT never acted up like yours...). Maybe you can catch one cheap on a part-out somewhere, and just change the whole thing out to see if the problem goes away. Something is obviously wrong somewhere... Wish I had the magic answer for you.

[leehljp]

I have seen this before but it was with a heavy handed hold. But this would not apply to you since you were using a light hand. However, I do have a question about that? What did you use as a hold down for the 6 inch piece of wood? Is your blade clean and sharp? Reading your tenacity for detail, I figure they are, but I had to ask.

You once mentioned loosening the rear clamp bolts or something, were those reset and tightened?

[charliex]

I had this same problem and was getting frustrated also. At times it cut perfectly square and other times it was not even close. What I eventually noticed was that when the cut was not square, it was always with more material removed from the lead edge. What I then deduced was that my saw had an issue and my feed technique was taking advantage of this issue. The technique issue was when I feed the SMT forward I placed my left hand on the fence to left of the hold down bolt. The saw issue was that when I did this the SMT fence moved ever so slightly. I'm not sure why it did this but to fix it, I put 120 grit PSA paper on the bottom of the fence and I now feed the SMT forward by the hold down bolt. No more a problem, though occasionally, I catch myself with my feed hand in the far left position.

Hope this helps

Chas

[sailor55330]

I checked everything again and there are no loose connections anywhere. To hold down the 1x6, I was using the supplied accessory clamp. When I did the 5 cut test, I used a stop block to keep the wood from sliding and the accessory clamp. I also have some sandpaper on the miter fence face (150g I think).

Because of the things that i have read about the miter fence possibly slipping, I don't really apply pressure to the miter fence, but try to use the rear edge of the SMT top to apply pressure evenly with my left hand (I usually push just to the right of the lock down tab that makes the SMT not slide) with my right hand on the wood. The blade is new (40T craftsman carbide). It may not be the best blade, but while I am learning the saw, it is fine, plus, everything was fine a few days ago with it and my measured runout is .004.

I absolutely admit that I am not perfect when it comes to using the saw, but when I can make 3 sets of cuts and the parts are interchangeable, then 3 days later, same technique, but with the variance, I am stumped. If on the test cuts, the variance is repeatable and the test cut pieces are interchangeable with the variance, then that means something mechanical has changed. I don't believe anyone can make the same exact mistake 3 times in a row, there will always be a little variance if it is a human element.

Again, this morning checked all clamps, fasteners, hold downs, and looked for culprits like saw dust or chips that could explain it. I came up with nothing

[cgallery]

The strange thing is that if your blade is 90-degrees to your miter fence, then misalignment of your SMT base would have to account for the 1/8" error. And if the saw was that far out of alignment over 6", it would be fighting you as you cut the wood (because you'd be forcing the stock into the blade plate).

There would be binding, burning, and everything else. It would, in fact, be a dangerous situation.

So I'm surprised you are mentioning that the cut is off by 1/8", and not that the saw seems possessed and dangerous to use?

[LarryG]

I've heard of sensitive saws, but this is ridiculous. I really don't understand.

It is ridiculous, and I don't understand, either. I occasionally had similar problems with my saw mysteriously cutting out of square, but nothing approaching 1/8" in 5-1/2".

Have you checked the motor shaft for excessive end play that could be allowing the blade to move laterally?

Have you tried making these test cuts without the accessory hold-down clamp? I'm wondering whether tightening the clamp down is somehow pulling things out of whack. Try some cuts without the clamp, to eliminate that variable. Like charliex, I found I got the best results by pushing the SMT with my hand on the hold-down bolt on the miter fence.

[LCHIEN]

I checked everything again and there are no loose connections anywhere. To hold down the 1x6, I was using the supplied accessory clamp. When I did the 5 cut test, I used a stop block to keep the wood from sliding and the accessory clamp. I also have some sandpaper on the miter fence face (150g I think).

Because of the things that i have read about the miter fence possibly slipping, I don't really apply pressure to the miter fence, but try to use the rear edge of the SMT top to apply pressure evenly with my left hand (I usually push just to the right of the lock down tab that makes the SMT not slide) with my right hand on the wood. The blade is new (40T craftsman carbide). It may not be the best blade, but while I am learning the saw, it is fine, plus, everything was fine a few days ago with it and my measured runout is .004.

I absolutely admit that I am not perfect when it comes to using the saw, but when I can make 3 sets of cuts and the parts are interchangeable, then 3 days later, same technique, but with the variance, I am stumped. If on the test cuts, the variance is repeatable and the test cut pieces are interchangeable with the variance, then that means something mechanical has changed. I don't believe anyone can make the same exact mistake 3 times in a row, there will always be a little variance if it is a human element.

Again, this morning checked all clamps, fasteners, hold downs, and looked for culprits like saw dust or chips that could explain it. I came up with nothing

you did not mention the accessory clamp before. Its a tricky thing.
It has a compound motion, in that it clamps both down and pulls the work towards the face of the miter fence.

If you clamp the clamp too hard and do not thighten the miter fence enough, its downards force will hold the work on the SMT and pull the fence forward. I detail this fault/problem in detail in my FAQ if you've read it. As I state in the FAQ, the BT3 does not respond real well to force, In this case, too much miter clamp pressure will overwhelm the miter fence hold down knob and allows the fence to come forward some - you can actually see a gap openinig between the miter fence and the zero stop. Its really insidious because the more trouble you have with square the harder you tend to tighten the miter clamp which just makes it worse, not better.

Ther real trick using the miter clamp is to
1. tighten the miter fence tighter than the miter clamp will be tightened, taking care not to tighten the miter fence handle/knob too much since that may warp and crown your SMT - remembering the BT3 does not respond well to excessive force, and
2 then using just a smigeon of force on the miter clamp, clamp the workpiece; its actually quite effective without a whole lot of force. Watch the gap (there should be none) to see if any opens up at all between the zero stop and the back of the miter fence.



I thought this a way back, you really need to start with you saw bare naked... just the splitter, no guard, no miter clamp, nothing else and make your adjustments and test cuts. The BT3 responds best to gentle pressure and not to force... I don't know how else to say that but i think its said several times in the FAQ.

I've never had any problem making square cuts with my saw (OK, after I learned about the miter clamp!). I'm surprised at your endless trouble. Have you read my FAQ? It details the miter clamp problem and a bumc of other things making non-square cuts.

Addressing the other recent comments - his 1/8" error is not a single cut but after making five cuts around four side of the square so this is an amplifier of the error. With a 12" square and five cuts, that's about 0.025 per cut per 12", if you take the miter fence to the zero stop that's about 6" or half the error .012" THat's about the opening I see between the zero stop and the back of the fence when cranking on the miter clamp.

Charliex also points to the method of feeding the SMT forward. I agree you should push on the handle/knob of the miter fence, this being firmly clamped to the table at that point will not put any rotational torque on the miter fence. Or better, push the right end of the SMT behind the buried black pivot point. Pushing on various other points can induce torque that wants to make the miter fence knob slip and the fence rotate.

Now there's a whole other range of issues that can arise if you are doing more than a 12" piece of wood crosscut:
Lets assume a 8' 2x4 being crosscut, the SMT on the left...

1. Crosscutting a short offcut to the right. you'll have a long piece on the left hanging off the SMT unless you shift the rails so the piece is supported mostly in the middle. You need to support the free end to the left but in such a way it doesn't drag and cause the piece to want to rotate and put force on the miter fence.

2. Crosscutting and cutting near the middle - then you put the SMT near the blade and just to the left so as not to cut off your miter fence end. Push the handle/knob forward but be prepared that the 4' piece hanging off the left is going to fall after being cut unless you support it. The right cutoff should be held up by the aux table you pushed all the way to the right!


3. Crosscutting a short offcut off the left - the offcut will ride on the SMT and won't go anywhere but the right piece will be falling off the saw after being cut unless you have the wide rails option and its draggingon the table will make the miter fence want to rotate.

A long miter fence attachment may help keep the wood against the fence but in the end the geometry still puts the torque in the same place to rotate the miter fence.

You have to be carefull with one and three about pushing to minimize the effect of dragging the long end. When I have to do this I usually take a stance and push evenly as i can on both sides of the blade, yes this violates the rule of don't stand in front of the blade except this is not really a kickback prime situation and i think its OK. Actually I rarely make such a cut - its exactly what my miter saw was made for and I have right and left supports for it; the blade moves and the work stays put, this way there's no twisting motion from the wood dragging anywhere. Right tool for the job, y'know.

[phi1l]

I stopped by Sears last night, & glanced at the Craftsman Version of this saw. They had the table on backwards, & there was a lot of play in the in the table too. Then they had the pivot located in the slot of the tightening bolt.

I think there has to be something really badly set up on you saw. If you can, I would try & find one that is working right & take a close & careful look. After doing that I expect that the problem will be obvious. If it is set up wrong, we can only make guesses as to what the problem is. ... or maybe .. do you have the capability to post somereally detailed pictures of you saw?

[sailor55330]

Guys, I appreciate the help.

I don't even know where to begin to answer all the questions. I did mention the miter clamp in a previous thread. I only went to it after it was suggested that I was possibly causing the wood to to shift during feeding. This last round of test cuts was done bare (no guard, splitter, etc). There is no wobble in any of the saw arbor or bearings as far as I can tell. There is absolutely no slop in the blade or any movement at all up down, sideways, etc.

I have gone over the FAQ repeatedly and I thank you for the time you took to put that together. I have broken down the saw and re-assembled according to the manual with new eccentrics and slides. It's really a very simple procedure. I am familiar with table saw operation and understand the importance of supporting the piece, but I am not working on anything big enough for this to be a factor at this time. Also no binding, burning or kickbacks, well, one kickback when I was ripping a narrow strip and had the fence adjusted wrong, but that's my fault.

I can try to take some pictures. I won't be able to get to the saw again until the weekend. I am really stumped. This just shouldn't be that difficult. Thanks for the patience

[crokett]

If you want to verify that the SMT is sliding true, use this method. Credit goes to Lonnie_In_Orlando. It is brilliant and all I've ever used. Take a piece of milled stock at least as long as the base to the SMT. Ply is preferable since it moves less. I use a double thickness of 3/4 ply. Fix magnets to one face at one end so that they will stick to the blade on the face but not on the teeth. On the opposite face and end, drill a hole big enough for an 8 or 10 penny nail. Cut off the head and epoxy the blunt end into the hole so the point is sticking out.

Now stick your new alignment jig to the blade with the magnets so the nail is at the front of the saw. Slide the SMT all the way forward. Slide the miter fence over (or use a block sitting on the SMT) so the end just touches the nail tip. Now flip the jig end for end and slide the SMT all the way back. If the SMT is sliding true to the blade, the end of the fence should just touch the nail tip.

I use the same method to align the rip fence.

[shoottx]

Check for wear on the plastic pivot on the miter fence.

On mine as the pivot wore out the consistancy of square cuts would vary. It was annoying. The fence would appear square until pressure (even light pressure) while cutting was applied to the fence. I would use a Quick clamp on the outside of the fence until the part is replaced.