I tried the SMT again

[d_meister]

Fascinating thread, this. Going back several pages and answering Sailor's question about what is "West", I meant that the "track" of the "sled" along the "non sliding Base" of the "SMT" in the nicely done illustration went "left" instead of parallel to the blade. That, as Sailor describes his issue, is exactly what he is experiencing: Push some wood past the leading teeth on the spinning blade, and the kerf is away from the back end of the blade to the left
Whoops! I might have seen what I wanted to see in Crybdr's top illustration. That most excellent diagram shows the potential of the (insert favorite name for the thing that clamps to the rails here) to veer either left or right (West or East, Sailor). Ultimately, it is not possible to obtain an accurate cut of 90 degrees, or any other angle, unless the sliding portion of the SMT is as nearly as absolutely possible, to parallel with the saw blade. As others have said, it doesn't matter if the sliding portion is triangular, trapezoidal, round, or mounted diagonally or sideways; you can't calibrate an angle of a cut unless the SMT passes by the blade as nearly as parallel as is possible.
What is really amazing about this thread, is that we don't have a common nomenclature, yet we all have the same saws. Then, we have practical answers to the issue at hand, but we're unsuccessful in communicating them.
There have been some truly innovative and thoughtful efforts at clarifying the answer, and I think you're all exceptional for not abandoning the effort. Kudos to BT3

[d_meister]

At this point, I think the culprit might be a worn plastic pivot on the bottom of the miter fence. I will try it again tomorrow evening. Does anyone have any suggestions for shimming this hole as a temporary fix to test? I tried a wrap of aluminum tape, but it didn't help much.

If this is the cause, I will officially curse Ryobi for using plastic on a part that is integral to accuracy.

Cool; We're onto something, here. Unfortunately, I don't think it's the fault of the plastic piece. I've been watching the fence on the "SMT" wandering on my BT3000 for some time. As mentioned before, "Don't push on the fence". That doesn't solve the problem either. If I clamp a piece to the SMT fence, and push on the SMT deck, with hands off the deck, the SMT fence migrates away from the 90 degree stop, after some multiple cuts. The fault must be in the clamping fixture arrangement. If I wasn't so Bad-News-Averse, I would take the whole SMT rig apart and look at where the hex-head center clamp obtains it's purchase, and very likely create a new project. But I won't. I'll intuit the error and hand-clamp the fence more aft then center when I use it.
Ultimately, though, I think that one must develop work-arounds for any piece of equipment, software, personal relationships, ad infinitum. When I think about tuning my BT3000 Sliding Miter table, and then think about using one of those puny sliding miter squares that other saws have: Count me out. I love my SMT. My double miter track is only good for mounting featherboards.
OK, maybe not: It's perfectly aligned and I can use a miter guide in it, but why?
Thanks for including me,
Dirk

[LCHIEN]

I don't know if sailor wants any more advice at this point.
Some BT3 miter fences are easier to knock out of square than others.
Things I know can contribute are for example:
1. The SMT can be crowned at the center slot being higher than the rest of the SMT. This may be a factory defect (not likely since the casting is machined flat) or because at some time an owner torques the locking knob too tight. or maybe some other abuse. If thi is the case you can check it with a good straight edge. Sometimes the black clamp on the back of the miter fence is too tall if modifedo messed with.
2. If you have a miter clamp, tightening that excessively can lift and rotate the miter fence due to the compound action of the miter clamp. If yo u have oine of these put it aside fro now and I'll advise you how to use it later.
3. the pivot can move... it has a sprung side and a fixed side, if the spring side is toward the operator, pushing the back of the miter fence can rotate the fence a bit when pushed off-center; I think you should have the spring part away from the operator so the fence when pushed has no give.
4. Pushing the SMT in a bad place. Nos this may seem strange but I have leaerned to try and push the SMT using the knob to place my hand. This both keeps it away from the blade but also pushes on the miter fence where ths well supported and will not twist the miter fence. pushing on other parts of the fence tends to move it when heavy handed.

I would definately encourage sailor to do this: Use his normal technique but put the Zero stop properly adjusted so it kisses the miter fence at exaclty 90 degress to the blade (using a known perfect square to set the miter fence and blade angle.
The zero stop shold have absolutely no daylight between it and the back of the miter fence. Then make a few cuts. Observe if theres any gap now between the zero stop and miter fence. I say this beause he claims to have aligned and locked the SMT base and the SMT itself to the blade properly. I can only then assume that the miter fence is shifting on him.

[sailor55330]

Loring, I appreciate the advice and will take it willingly Thank you.

My pivot has the "sprung" side facing the user. Based on your post, I will reverse it and see if that makes any difference.

Let me try to describe what I mean by the miter fence is moving.

I do have the left edge of the miter fence adjusted so that is it just touching the zero stop and in that position, the fence is at 90 to the blade.

The center hold down knob is tightened securely, BUT when it is tightened, it is not holding the fence motionless, it is acting as a pivot that allows the blade side of the miter fence to move towards the front of the saw about 1/16 of an inch (I am able to move the blade-side of the miter fence towards me).

I will have to check the table to see if it crowned. Obviously, since the saw was purchased used, I have no idea of what the previous owner may have done. I have the miter-clamp hold down, but I have never used it

Thank you again.

[LCHIEN]

Sailor,
having heard your most recent experiences sort of nails it down, to me, anyway, that the miter fence is somehow your problem, not the slide or the SMT alignment.

I guess there is love and hate for the SMT system, it was one of the reaosns i bought my saw but for some reaosn some people hate it - maybe there's a percentage that weren't made just right or they have some technique issue.

As you narrow it down to the miter fence, here some things that have worked for people:
glue a thin sheet of some fine sandpaper on the bottom of the miter fence, When you lock down the knob this will really keep it from moving, provided the SMT itself is not crowned, again check it with a straight edge.

If its crowned, then a couple of things come to mind (I don't really recall how anyone solved this othern than it being a discussed issue) you could shim the ends up and then put sandpaper over the shims. You'd probably want some feeler gauges - a couple of bucks at the auto parts store - to see how much you need to shim, might only be a few layers of sandpaper glued up. obviously you'e got the skills to measure paper thicknesses. This will be prefereable to trying to grind down the table, in my book.
I suppose its also possible the miter fence is warped altho this sounds unlikely. If that's the case, it MIGHT be possible to turn it over (not sure if its symmetrical top and bottom).

The black pivot is generally a second point for the miter fence to keep from rotating, but, its not perfect. It can have some give due to the spring thing which is why i suggest pushing on the knob, not the back of the fence.

Clearly, too, when crosscutting long, heavy items like 8' 4x4s, its really easy to twist the miter fence, this is also a problem with traditional miter slides. - however, the BT3 with adjustable rails and movable SMT you can position the SMT so its centered behind the workpiece and not being twisted. If you can't reposition the SMT then Personally on long crosscut items I push the item from the knob AND somewhere else on the workpiece that takes off most of the twisting load. Better yet, I take the workpiece to the compound miter saw which has a moving blade and stationary workpiece.

Another possible reason for rocking miter fences is that the black center support under the knob and in back of the fence is too tall for some odd reason. The knob tensions the support but the fence itself is not under tension. Sometimes i have heard the fence rocks front to back as well as side to side. Shimming up the fence with sandpaper will also help this out. If its way off either way (black piece too long or too short), then the face of the miter fence will not be perependicular to the table which is also bad. Again, it seems to me that this must be rare, how do molded parts and extruded parts get so out of tolerance??? yet, its something to consider.

Again, remember its not a heavy duty saw, its a hobbiest/craftsman saw, it requries a bit of finesse to work well for you. It doesn't like to be forced, gotta let it glide thru the work.

good luck to you.

[sailor55330]

Loring,

Based on what I saw last night, I agree that the miter fence itself is a likely suspect and not the SMT assembly as a whole. It's funny you mentioned gluing sandpaper to the bottom of the miter fence. I was looking at some sandpaper and superglue last night, but decided that it was late and I didn't want to make a judgement while fatigued. I definitely don't like the idea of planing the table.

I've got some good feeler gauges, so I'll see just how far off I am.

Thanks again

[pelligrini]

The SMT miter fence has been a great source of consternation for me. It's a love/hate thing sometimes. I love the ease of use of the SMT, but I hate the inaccuracy I get at times too. I have the some problems with movement of my miter fence too. I believe most of it hinges around the pivot. I think I'm going to try to fabricate a solid one in the near future. I have 3, and one is pretty tight, but I still can get a little movement. I'm also thinking of picking up some of this high friction tape from Lee Valley next time I place an order. http://www.leevalley.com/US/wood/pag...110,43466&ap=1

The T-bolt mod for the fence clamp helped a little with mine:
http://www.bt3central.com/showthread.php?t=38224

I also made a bracket for stability for 90 degree crosscuts.
http://www.bt3central.com/showpost.p...01&postcount=4
It really comes in handy with my box joint jig:
http://www.bt3central.com/showpost.p...83&postcount=9

[SteveR]

No measure jig?

Sailor, I applaud you not giving up yet.

I am getting to this thread late and have just skimmed over it, so apologies if this has already been suggested. Do any of the long time members recall Lonnies no measure jig? Would this help Sailor? It was pretty slick and eliminated a lot of potential variables.

Here is the thread: http://www.bt3central.com/showthread.php?t=33234
Good Luck !!!
Steve

[sailor55330]

Well, I spot glued a few small peices of sandpaper to the bottom of the miter fence to see if that would eliminate the "pivoting" of the fence on the bolt that holds the fence snug. Bottom line, it did. Now when I set up the fence, it is square to the blade. Because of time, I didn't get to actually make some cuts, but I'm hopeful this was the issue--the fence itself.

I did take a closer look at the black pivot on the bottom of the miter fence. It appears that at some point, there have been small fins on the pivot, mine are worn almost smooth. Whe I put the pivot in the hole, it is definitely sloppy, to be kind.

I'll make some test cuts over the weekend and we'll see. If this isn't the issue, then I am truly at a loss. I don't even want to think about the time spent on this---now you understand why I have been called a perfectionist


Also--just as a follow up, I did check the flatness of the SMT top with a known straight edge and it doesn't appear to be warped or crowned.

[gjat]

I've glanced through this thread over time and didn't pay much attention because my SMT has always worked fine HOWEVER, long ago I noticed my fence was never 'stable', and I rigged up a supplementary bolt down that I think I copied from a thread here.

Maybe someone remembers the thread and provide a link for Sailor?

[LCHIEN]

my black pivot is very snug even after years. I have to lift pretty firmly on the miter fence to make it pop out.

[Black wallnut]

my black pivot is very snug even after years. I have to lift pretty firmly on the miter fence to make it pop out.

Ditto!

It is not plastic but glass filled resin. Based on the sheer lack of volume of this being an issue and tousands upon thousands sold I surmise that this is simply a rare occurance. Add that Sailor purchased the saw used IIRC and it is hard to know exactly how much abuse the previous owner(s) may have subjected the saw to. Kudos to Sailor though for not giving up long ago. Add in the price point of the BT3 saws for all years other than early ones and I conclude that Ryobi is not at fault. This is not a defect but simply abnormal wear.

This is not the first problem a member of our forum has had that required exhaustive searching before finally determining the answer to the puzzle. I also doubt that it will be the last. The older these out of production saws get the more likely it is that abnormal wear will show up. We must remember that not all users are gentle to their tools.

[Uncle Cracker]

Kudos to Salior though for not giving up long ago.

I agree. Hopefully, his persistence will result in many years of fun together...

[Norm in Fujino]

I feel sure this issue can be licked if the real problem can just be identified, but I'm as clueless as the next guy, so. . .
One thing I would add is that when clamping down the SMT, the registration surface is the back edge of the front rail; when clamping down, I do the following: with all four clamps loose, I gently pull on the front two clamps to assure the table is drawn into contact with the registration surface of the front rail, then gently push down the clamps. Only then do I fasten the rear two clamps. This raises the issue of whether the rails are adjusted in parallel, but that somehow doesn't sound like the OP's problem.