Biesemeyer U50 Extension Table is BOWED. How to straighten it?

[Tom Burgess]

I purchased a Delta Unisaw back in 2006 and only now am assembling it (don't ask ;)). No warranty coverage at this late date, and have run into a few problems.

For the record, the Delta 'Customer Service' rep with whom I spoke seemed glad to be
in a position to deny me assistance. Any Delta tools I buy in the future will be
painted GREEN and bear the name 'Grizzly'.


CURRENT PROBLEM: The saw package includes a Biesemeyer U50 extension table that is 44" long. It is BOWED along its length, exhibiting a 1/4" dome.

The front (only) rail of the Delta UNIFENCE is extruded aluminum. It has two channels (like T-slots) that accept bolts set in the front edge of the saw's cast-iron top and Biesemeyer extension table. Of course, the fence rail is straight and it's bolt channels are straight - and the rail must maintain a uniform relationship to the table surface. But the bowed/domed extension table makes this impossible.

The diagram below shows the extension table's construction: 3/4" sheet material with a hard gray laminate covering top and edges, and a purple laminate covering the underside. The underframe is bare wood strips 3/4 x 1-3/4", arranged as diagramed. They appear to be glued to the underside of the tabletop.

I removed the extension table from the saw, set it on support blocks at all four corners and placed considerable weight on it near its center, hoping to flatten the top.

PLEASE TELL ME IF THERE'S A BETTER WAY TO TAKE THE BOW OUT OF THIS TOP. ARGH!

[Frederick Skelly]

Tom,
I wish I had a better idea than the one you're using but I don't.

My (used) saw has the same fence, and a table that looks just like the sketch you posted. My table looks pretty straightforward to make from scratch. (Though it's a stinkin shame to have to do that on a brand new saw.) Keep that option in mind as you get feedback on this, because it's possible to spend more time fixing it than it takes to build new. For example, you might be able to remove the laminate, flatten the bow with a router, then re-attach the laminate. But that is not much faster than building new.

Good luck man. I'm sorry this happened.
Fred

[Paul McGaha]

Tom,

Personally, I think I'd be tempted to make a new table top.

So you have a brand new, 2006 model Unisaw?

PHM

[Tom Ewell]

Can you attach a straight steel 'backbone' under the table and still install it?
Angle iron, square tube etc.

[Ray Newman]

Being stored for nine years and under who knows what conditions, no doubt that there is a great deal of stress in the laminated table top which will not come out or stay flat once the weight is removed.

Even though you have the Beisemeyer fence system, this may give you some ideas: When I moved several years ago, I fabricated a new table and top for my Uni-saw with left and right cast iron wings and 52" Uni-fence. Table legs and apron constructed from 2X4", 3/4" plywood top with a 1/4" tempered Masonite top. Applied internal bracing to support the screwed down top, then screwed down the Masonite. After front fence rail was level, added 'bout an 18" section of 1 1/2" aluminum angle the table apron, then screwed it to the bottom of the fence rail. Has not moved since it was constructed in '02.

Best better fabricate a new table top. Probably Baltic birch or a similar grade of quality plywood and laminated on both sides. Not probably not what you want to hear.

[Tom Burgess]

I wish I had a better idea than the one you're using but I don't...it's possible to spend more time fixing it than it takes to build new. Good luck man. I'm sorry this happened.
Thanks, Fred. I'm hard pressed to build a new one because...(wait for it)...I don't have a working TABLE SAW. LOL! :D

Have you guys noticed how once you've gotten used to having a table saw, not having one is like not having your right arm? I used my old one for EVERYTHING, and thought setup of this very expensive Unisaw replacement would be a delight. So far, it's been a BIG, time-consuming PAIN IN THE ARSE that has forced me to jerry rig a number of aspects.

I appreciate your comments and suggestions, Fred.

I wonder if placing the extension table out in the SUN (on the driveway) with the weight stacked on it would enhance and/or hasten the flattening process? I worry that the table might must spring back to the bowed shape once the weight is removed...no matter what I do.

[Tom Burgess]

Personally, I think I'd be tempted to make a new table top.
I hear you, Paul. But I don't have a working table saw, so I can't make a replacement. 'Catch-22' is the story of my life. :rolleyes:


So you have a brand new, 2006 model Unisaw?
I do, and I thought it might be 'a cool thing', but it's not turning out that way...

[Paul McGaha]

I hear you, Paul. But I don't have a working table saw, so I can't make a replacement. 'Catch-22' is the story of my life. :rolleyes:


I do, and I thought it might be 'a cool thing', but it's not turning out that way...

It's a nice saw. I have one I bought new in about 2003.

This will get resolved and then you'll have a fine saw.

PHM

[Tom Burgess]

Being stored for nine years and under who knows what conditions, no doubt that there is a great deal of stress in the laminated table top which will not come out or stay flat once the weight is removed. [...] Best to fabricate a new table top. Probably Baltic birch or a similar grade of quality plywood and laminated on both sides. Not probably not what you want to hear.
You're right, Ray. Not what I wanted to hear, but that happens everyday. :D The table was boxed and stood on end in my garage, was never horizontal and never bore any weight, so I think it was 'custom made' with that bow.

As noted above, I can't make a replacement extension table because I need a table saw to do that. But of course, I can't set the saw up until I have a flat extension table. CATCH-22. And for the record, I have the Delta UniFence, not the Biesemeyer fence. The extension table is a Biesemeyer U50.

All surfaces are covered with plastic laminate. When I'm sure of no rain in the forecast, I might put the extension table's top OUT IN THE SUN. Mr Sun is very persuasive at getting plastics to 'change their errant behavior'. I'm not sure whether the sun's heat will cause the plastic laminate to expand or contract. Logic suggests that expanding the CONCAVE under-surface or contracting the CONVEX top surface would aid in flattening... Am I right?

If the sun's heat is able to effect the desired flatness, and then I stack the weight on and leave it in place until the table COOLS (when the sun goes down) it might just 'take a set' in the flattened configuration. No?

Can anyone advise me:
SHOULD THE CONVEX (DOMED) TOP SURFACE FACE THE SUN, OR SHOULD THE CONCAVE (DISHED) BOTTOM SURFACE FACE THE SUN?

[Matt Day]

My advice - make another one.
Youve spent too much time on this saw setup to try and fix it. It's simple to make a new one.

[Ray Newman]

Do you know of anyone with a table saw that could cut out a top for you?

Beg, borrow, rent, or buy a circular saw. With a piece of aluminum angle for a straight edge it will easily break down plywood.

[Bruce Page]

I removed the extension table from the saw, set it on support blocks at all four corners and placed considerable weight on it near its center, hoping to flatten the top.


How much weight did it take to flatten it out? Is the dome equal distance form each end?

[John TenEyck]

I don't think putting it in the sun will do anything except perhaps break the bond of the laminate to the base material and that would be a step backwards. But like another poster suggested, you should be able to physically flatten the top by putting a couple of steel boxes channels under it and then bolting the top to them. If you use countersunk machine screws the heads will be flush with the top and it will look fine. More importantly, the top will be flat and stay that way. Oh yeah, you don't need a table saw to do this !

John

[Tom Burgess]

Do you know of anyone with a table saw that could cut out a top for you? Beg, borrow, rent, or buy a circular saw. With a piece of aluminum angle for a straight edge it will easily break down plywood.
I'm the only "woodworker type" I know, and as Dirty Harry Callahan so rightly put it, "A good man knows his limitations." :D I'll be living with whatever extension table comes out of this for a long time, so I sure don't want to rely on my iffy skills with circular saw and straight edge.

[Tom Burgess]

Good questions, Bruce. Thanks.


How much weight did it take to flatten it out?
It must be about 200lbs: 8 half cinder blocks, 3 large pavers, a 5-gal bucket of sand, 5-gal bucket of sandblasting abrasive, two anvils made of railroad track sections - all stacked in an area 16x16" at the approximate highpoint of the dome.


Is the dome equal distance form each end?
The dome appears to be shifted a bit toward the left/saw end. And just to keep things interesting, the front edge of the table (with the fence rail attachments) is more curved than the rear edge.

Ah, but hope springs eternal! :D After it being 'burdened' as described throughout the day, I just placed a 4' straightedge atop the front edge to the table top and NOW THE FRONT EDGE (with weight stack in place) IS BOWED DOWNWARD 1/4". I'm hopeful that removing the weight will 'split the difference' resulting in a straight, flat top...

QUESTION: Should I remove the weights 1) NOW, or 2) AT 11PM BEFORE TURNING IN, or 3) TOMORROW MORNING?
Any educated guess is welcome. :D

[Andrew Hughes]

Defiantly after the witching hour,that's when the magical stuff really happens.👍

[Tom Burgess]

I don't think putting it in the sun will do anything except perhaps break the bond of the laminate to the base material and that would be a step backwards.
That's my natural first approach to these things. :D Thanks for pointing that out, John.


But like another poster suggested, you should be able to physically flatten the top by putting a couple of steel boxed channels under it and then bolting the top to them. If you use countersunk machine screws the heads will be flush with the top and it will look fine. More importantly, the top will be flat and stay that way. Oh yeah, you don't need a table saw to do this!
I'm glad my dilemma in that regard has finally struck home.

Great minds think alike. I've been thinking about steel boxed tubing or angle iron below the table. With the table top face-down, I figured I'd apply weight at the ends to flatten the top, and then tighten the screws - implemented as you described. Countersinking those screw heads would work--as you suggest--but my countersinking is often less-than perfect, so passing material over those plastic laminate holes will likely scape the laminate edges...eventually causing trouble. With that in mind, I was thinking about running some bar stock that I have beneath the existing wood undercarriage, and perhaps screw to those wood frame cross members rather than piercing the work top. The wooden cross members are 1-3/4" deep, providing considerable thread engagement.

Anybody see problems with that approach?

If I can do as I describe above, I may have to add one more wood cross member. CAN ANYONE RECOMMEND AN ADHESIVE THAT CAN GLUE WOOD TO PLASTIC LAMINATE? The existing undercarriage is glued to the laminate, and it's something very strong.

[John TenEyck]

Well you can trying pulling the top down onto the steel box beams by screwing up into those wood pieces. If the screws won't hold or the wood pieces debond then you can always do as I suggested and use machine bolts from the top. If you want a perfectly smooth top, you could countersink them and fill the depressions with wood plugs and plane them flush.

John

[Tom Burgess]

Defiantly after the witching hour, that's when the magical stuff really happens.👍
Ha! :D Hey, the way this project has been going, a little Magic would come in handy right about now.

To be clear, I don't know if length-of-time matters in terms of stacking weight atop the bowed/domed table top. If it does matter, I sure don't want to overdo it, leaving the weight on for too long and then have a top bowed in the other direction...

[Mark Wooden]

Don't overthink this-
No, really
Get a sheet of what you would build it with IF you had a saw
ANY cabinet shop/homecenter/lumberyard should be able and happy to cut you a piece the size you need for a TEMPORARY table board. (If you're in CT, come to my house)
Put it on your saw and MAKE YOUR NEW TABLE BOARD. Put it on your saw and be happy. Use the temporary table board to make a shelf under the saw.