Still having SMT/alignment troubles

[sailor55330]

Hello,

I am new here and new to the BT3100. I purchased last week and attempted to give the saw a thorough tune up. I quickly realized that the SMT was missing some of the slides causing excess play. I decided to order all new slides and eccentrics just to be safe. I installed everything and adjusted according to the manual and at least 2 of the other "methods" listed in these forums. After going though all that, I still do not have square cuts happening. I'm going to try and describe what I have done. I really need some help.

1. Marked the blade and put a framing square against the blade.
2. With the SMT all the way to the front of the saw, I marked a reference point on the table.
3. Rotate the blade, flip the square, move the SMT to the back of the saw and compare to reference mark. It was off

4. Loosen rear rail clamps and slightly loosen the table adjustment screws as listed in the manual along with 1 of the front screws. Adjust table to mark to make it parallel to the blade.

When I tried to move the SMT assembly, it did not want to "shift" on the adjustment screws. Instead, the movement was coming from the whole back of the table assembly moving on the rails. (think of it as torquing the table with the front clamps locked). I ended up using a quick clamp to apply just enough pressure to hold the assembly until I could tight down the adjustment screw in the fron and the 2 in the back. (I did try without clamping it also). I was never able to get the saw aligned at the back of the blade within 1/64 of an inch. Every time I would get it lined up, it would slip when I tighted the adjustment screws. I must have done this 30 times.

5. Mount miter gauge and set to "0" as per the manual.
6. I set a square against the blade and loosened the back two locknuts on the top of the table
7. I adjusted the left eccetric for maximum side to side play and then slowly brought the miter gauge back to square while applying pressure to the left side of the SMT (bungee cord was a good idea). Once I had it square, I tightened the left side lock nut while holding the eccentric as still as possible.

8. I used the right rear eccentric to remove any additional slide-to-side play in the table (it was stiff, but still moveable with just steady pressure.

I double checked the fence for square again and it was dead on. I then adjusted the quick stop as well.

Here's the problem---I did several test cuts and NONE of them were square. over a 12" span, I was off about 1/32 of an inch. I am stumped.

Next, I took a piece of wood and drove a nail into the end to make a "feeler" gauge. With the blade marked, I put the nail so it was just touching between the teeth and clamped it on both sides. I then rotated the blade and moved the SMT to the back of the saw----1/64 of an inch gap.

I have spent at least 8-10 hours trying to get this saw aligned (including replacing the slides) I am starting to get frustrated with the saw.

I really could use some advice here. I have read every post and FAQ on this subject and nothing seems to be working. I am getting nervous that if the saw takes this much time to set, then I might end up spending more time keeping in it tune than using it and that just won't work.

Sorry for the long post. Just trying to be thorough.

Thank you in advance for any advice or thoughts.

[LCHIEN]

I have not had to align my SMT in a long time, but it seems to me that you should NOT be unlocking the rear rail clamps when making the adjustments. The adjustment you are making should be the slide to the SMT Base so you want the SMT base locked to the rails.
There is a proper way to lock the clamps - always front two first, rear two last. always at rest (no force applied so its naturally amd repeatably squared to the rails).

Once you have aligned the slide to the blade, use a square to set the miter fence and zero stop square to the blade, this of course should set the fence square to the travel of the slide as well due to the laws of geometry.

The key thing I hope you should know is that placeing a square against your blade you need to be careful about the teeth... either use a square that fita agaist the body of the blade between the teeth or else touches both front and back teeth. Because the teeth stick out from the body using the teeth on one end and not the other will give you a slant.

FInally there are some conditions for using the miter fence. is there any gap deveoping with your workpiece against the fence before, during or after the cut?
The following can cause this slippage to happen:
improper use of the miter clamp
allowing the wood to slip sideways. Some people glue a sheet of fine sandpaper to the face of the miter fence to prevent any slip.
long piece of wood off balance on the miter table will tend to skew
improperly set or adjusted miter locking knob, screw and washer
crowned SMT
is your square proven good? if you don't know how to check, ask us.
etc.

if your miter fence is square to the blade, regardless of the SMT to the blade alignment, you will get a square 90° cut. There will be some other issues regarding the lack of parallelism of the SMT/Blade but for the most part the miter fence setting rules the squareness of the cut.

[sparkeyjames]

Suggestion. Forget about the miter table (the one that slides in the track) and align the underlying track to the blade. If the track is parallel then even if the miter table is off a little it will still travel parallel to the blade. After you have the track parallel then adjust the table to the track so the 90 degree marks on the table provide a perfect 90 degree cut.

[sailor55330]

Lchien
Thank you again for taking the time to respond.

I agree with you that it seems the rear table clamps should be locked when doing the adjustment, but my manual states very clearly that the rear rail clamps should be unlocked. This seems totally counter-intuitive to me as well.

I am taking into account for the teeth on the blade as I am familiar with the offset the teeth will cause.

I am also stumped by the fact that the cuts are not 90 when the fence is set to 90 to the blade. I have tried 3 different squares, so if they are off, they appear to be off by virtually identical margins.

My next steps are a new blade and finding a straight edge to verify the straightness of my miter fence. The only other thing I can think of is that perhaps the miter fence is warped, damaged, or just not true.

I'm also going to give your method of dial gauge alignment a shot this afternoon.

stay tuned I guess

[Black wallnut]

As Sparky is hinting at I think you are not first aligning the SMT base (track). If the base is not parallel to your blade no amount of fiddling with the table will produce a square cut. Reference this manual, Figure #53, you need to loosen screws "L". both at the back and the left one at the front of the base. Then with the rear of the SMT clamps open or unlocked pivot the base until the one single spot on the SMT table is parallel through its whole range of travel. Rest assured if you measurement is the same at the front as it is at the rear it will be parallel all along the track.

Once you have done this repost and we'll move to the SMT table and fence adjustments.

[sparkeyjames]

I forgot to add check and make double sure your rails are mounted correctly and tightened down.

[sailor55330]

Again,

Thank you all for the patience. BlackWalnut, the procedure you outline in the linked manual is exactly what I have done at least 15-20 times. With the screws "L" loosen and the left front screw loosened to form a pivot, there is simply not enough play in the table base to allow the base to align parallel. As I try to align the base of the table to where it would be square, the adjustment slots simply run out of room and then the locking mechanisms begin sliding along the track.

I thought I had it correct earlier today, but when I rechecked, it was incorrect. I'm sorry I dont' know how else to describe it. I am beginning to wonder if the entire SMT base might be warped or something similar.

I am trying very hard not to get frustrated, but I'm losing the battle. I am going to work on the saw again tonight and tomorrow, but if I still struggle, I may sell the saw. I've been around to many tools in my life for this to be this complicated. I even built a 12" bandsaw with my father once that worked perfectly for almost 9 years. This shouldn't be this frustrating.

Thank you

[Black wallnut]

With screws "L" removed and screw "N" removed you should be able to pivot the base on screw "O" to make it parallel. The front stays firmly attached to the front rail. Once it is parallel by the checks replace screw "N" You should then be able to slide the rear clamp assembly to where you can see at least one of the attaching holes for "L" screws. Also notice where you may have to remove material from the base for the other screw to also connect.

I've not heard of anyone having to do this but it is possible that you have one made out of spec.

Where are you located? There may be a BT3 Central veteran that might be willing to come over and help you.

One other item is to check that your framing square is square.

[sailor55330]

Again,

Thank you all for the patience and advice.

I gave it another shot at aligning. I purchased a dial gauge and used the method described by Lchein here http://www.cgallery.com/jpthien/3k.htm.

I am able to loosen all the necessary screws and pivots and get the base of the SMT to align on the dial gauge. When I tighten down the adjustment screws, I am only able to keep it within about 5 1/000 between front and back when referencing the marked spot on the blade . When I then go to clamp the rear of the table, the alignment now jumps to well over 35/1000 out.

I think I may have discovered something. I did remove the two adjustment screws on the back of the table and looked into the holes. It appears that there may be some play in the holes. Actually, it doesn't even look like there are holes in the locking clamps under the SMT. It looks more like there is a slot that runs perpendicular to the SMT base. I am wondering if over the years if the adjustment screw mounting holes could have worn and are no longer holding true. The other option is that the table itself was just made out of spec or has been dropped/damaged. It's hard to tell what the true history of the saw was (it did have 2 missing table slides).

I guess tomorrow I'll take the SMT base completely apart and see if anything is showing wear. If that doesn't work, I give up unless someone has an epiphany.

FWIW, I'm just outside Minneapolis.

[sailor55330]

I think I have figured it out.

I took apart the rear end of the sliding miter table where it attaches to the clamping mechanism. In this manual http://bt3000.com/Manuals/BT3100-Manual.pdf on page 46, illustration 59, there is a part # 15 which is listed as a guide bar. For those of you who aren't familiar, it appears to be the bar that runs between the clamps on the inside of the rear rail. There supposed to be 2 screw holes according to the diagram. On my saw, there are no screw holes, but rather a channel cut into the underside of this guide bar. The hold down screws are then designed to "cut" threads into this aluminum guide bar in the channel, allowing for infinite adjustment. It appears that I have 2 or 3 sets of threads that have merged into 1 set of threads over time where it has been adjusted. The result is that the SMT base will definitely still tighten down, but it will always tighten down to the same location, effectively eliminating any adjustments that were being made. (think of it as wagon wheels follwing deep ruts).

Not sure if this makes any sense, but this what I think is the issue.

[Black wallnut]

What you are describing is normal. As long as the holes in the SMT base allows for lateral adjustment of the screws that is what you need. As you adjust the base that part is supposed to move side to side along the rail. With the SMT base adjusted with only the front two screws tightened then do you tighten the rear screws "L" once they are also tightened then you lock the rear clamp to the rear rail, then recheck.

[sailor55330]

BlackWalnut.

There is NOT enough lateral adjustment in the holes in the SMT to adjust the base into alignment. The lateral adjustment runs out before the SMT rails are in alignment with the blade and the entire clamping mechanism begins to move along the rear rail.

That is the trouble I'm having--the difference in alignment between the front and back rails is more than the movement allowed by the holes (and clamping system) in the SMT. As I said, the closest I have gotten it within 5/1000's, but when I engaged the rear clamps, the alignment jumped to 30/1000's with everything tight.

If there is a picture that I can take that will help, please let me know.