Replies

1. 
   Frozen | Sep 08, 2004 07:28pm | #1

   It can be done, but it is very (very!) easy to screw it up. It is significantly safer (for the surface) if you use a sanding frame: this is a levelling surface that attches to your belt sander that prevents it from digging in. 

   I would look around your area for a shop that would put it through their wide-belt sander. 

2. 
   HowardAcheson | Sep 08, 2004 08:04pm | #2

   In the shop I was involved with, we flattened all our panels with belt sanders. The steps are:

   o scape off any glue

   o using a long straight edge (a 4 ft aluminum level works well) mark the high spots. Move the level side to side lengthwise, widthwise and on both diagonals.

   o Use just the weight of the sander and 80 grit, diagonally sand the high spots.

   o Check, using the level, for high spots again, and make some more pencil squiggles.

   o Again lightly sand the high spots.

   o Check for flatness--it should be pretty good by now.

   o Change the belt to a 100 grit and sand any remaining high spots.

   o Sand the the whole panel gently on the diagonal to remove the sanding marks from the 80 grit belt. Than lightly sand with the grain to remove any remaining sanding marks. Be careful to keep the sander moving smoothly and evenly.

   o New change to a 1/2 sheet pad oscillating sander with 100 grit. Smooth the top sanding with the grain,

   o Change to 120 grit, sand then move up to 150 and 180. Finally, hand sand with the grain using 180 grit and you are ready for finishing.

   The top should be dead flat by now and it should take you 15-30 minutes to do it. Be sure to do some sanding on the bottom side depending on how flat it needs to be. Sanding the other side to some extent will help the keep the panel flat over time.

   Oh, I avoid ROS for flattening. The do not take of material evenly and tend to dig it leaving swirl marks and depressions. Flat pad sanders are much better at getting and keeping a surface flat.

   Howie.........
3. 
   Jellyrug | Sep 08, 2004 08:22pm | #3

   Mark,

   A belt sander is the quickest and easiest method, but you will NEVER get perfect results.

   It depends on the standard of finish you require. If you have mat finish, you will get away with close to perfect, but if you have a gloss finish and you look at the top standing about 15 yards away at the right angle, with proper lighting, you will always see an uneven surface.

   In conclusion, if you want a solid wood top to be as flat as a Plywood, or veneered top, a belt sander won't do the job.

   Willie 

4. 
   dpw32 | Sep 08, 2004 09:58pm | #4

   Mark,

   My humble opinion: Don't do it!!!

   Find a shop who will plane or sand the glue ups for you.  The money you will spend on this is far outweighed by the aggravation you will bring on yourself with your beltsander.

   Good luck

   Dave

5. 
   robkelly | Sep 09, 2004 02:06am | #5

   Howie is right on. If you're not real good with a belt sander, glue up the top in 12" widths a bit too thick, flatten the bottoms the best you can, run the pieces thru the planer, and then final glue one piece at a time, paying close attention to how the edges register. This way the amount of wood to remove from the top is minimal, you can even finish the seams with a scraper.

   I just finished a 39" x 82" top built like this, and the trick for keeping it flat in gluing is to build the table base 1st, then clamp to the aprons and stretchers of the frame as each successive piece of the top is glued on, thus stopping the clamps across the face from making the top curl up. Protect the table base with waxed paper.

6. 
   nikkiwood | Sep 09, 2004 04:39am | #6

   If you follow the steps outlined by Howie, sure you can get a good result with a belt sander -- expecially a 4 X 24 model.

   The real trick is to get a straight glue-up in the first place. Then use your "winding sticks" meticulously as you sand.

   Finishing up with a pad sander gives too many swirl marks for my taste, so I favor a ROS -- followed by a fair amount of hand sanding with a block.

   But all this is a lot of work, and if you have easy access to someone with a sander that will handle your 40" table top, by all means, have them do it.

7. 
   BG | Sep 09, 2004 01:55pm | #7

   Mark,

   It sounds like it'll be a beautiful table...will you fill the pores to achieve glass smoothness or let the texture come through?  Assuming you start with flat boards, the primary cause of non-flatness would be where the seams line up.  Flattening the seems is very easy with a #80 scraper, smoother or even a block plane...doesn't require too much skill...expecially with the #80.  Lumps in the wood can appear around the seams where you have not planed....and all things being equal..the size of the lumps is determined by the glue-up quality. Personally, I always leave some minor lumps because I like the country look and it adds a bit of character...but I only make for my family..   My point is why don't you just go for it...try planing...your fall back position is Howie's process...and worse comes to worse, bring it to a shop with a wide belt sander. 
8. 
   Napie | Sep 09, 2004 05:43pm | #8

   Our local millwork shop charges about $60.00 an hour, (1/2 hour minimum), that top should take about 30 min. sanded to 150 grit.  That’s money well spent if you ask me.

1. 
   Jellyrug | Sep 09, 2004 07:30pm | #9

   Napie,

   What is the widest you can go?

   Anyone out there know a place close to Central California?

   Willie

2. 
   MarkinNY | Sep 10, 2004 02:09am | #11

   Wow, that sounds really reasonable.  Anybody know of any shops in the Long Island, New York area that can do the work.  By the way, I appreciate all of the great advice, and at some point when I have more free time for woodworking, I will probably face my fears and flatten a table myself.  But I really want to get this table finished in the relatively near future, and I really don't want to experiment on 32 square feet of the most expensive wood I will probably ever buy.  Mark

9. 
   Midnight | Sep 10, 2004 01:39am | #10

   Personally I'd forget the power tools altogether; use a good #7 plane and a good straight edge (I use a 6' builders level), get the blade real sharp and take your time... QSWO is about the most user friendly material to learn on; it's hard, but it shouldn't have any demons concealed inside it. Work both across and along the grain, stopping frequently to check your progress with the level. Adjust the depth of cut to take finer shavings as you get closer to having the top both flat and true, remembering to keep the blade sharp. Once it's done, you should be able to go straight to finish.

   Mike Wallace

   Stay safe....Have fun

   
   

   ---

   Edited 9/9/2004 6:40 pm ET by Mike

10. 
    Clay | Sep 10, 2004 02:26am | #12

    This table was flattened with scraper then belt sander then random orbit then by hand.  I have never seen a flatter one.  Gloss surface too!  Obviously it can be done.  It is a lot of work ... but not too tricky unless you get too impatient and try to rush it or quit before you get there.  The random orbit sander is actually excellent for minor flattening of surfaces but on a piece this size the flattening is done before you get the random orbit out ... it is just for rough smoothing.  I sanded this table to 120 grit with the random orbit and then to 150 by hand.  After the first varnish coat it was sanded with 220 grit and then steel wooled between coats (000 steel wool).  It has about 6 coats on the top and 4 or 5 everywhere else (tinted polyurethane).

    Oh BTW I rarely am able to buy a piece of plywood that is anywhere near this flat.

    
    

    ---

    Edited 9/9/2004 7:33 pm ET by Clay

    
1. 
   HowardAcheson | Sep 10, 2004 07:23pm | #13

   >>Obviously it can be done.

   Of course it can as your photo shows. I was at the Steinway piano factory years ago and they were flattening panels with a belt sander. Using a belt sander to flatten panels was the way most shops did it--and, many still do--20 years ago.

   In the shop I was involved with, it was one of the first jobs we taught to apprentices and they could do it with only a couple of hours of practice.Howie.........

2. 
   Jellyrug | Sep 10, 2004 08:37pm | #14

   Clay,

   Don't want to break your speed, but I have achieved the same kind of result with a belt sander and on a photo it looks flat.

   If you look carefully at your picture, and you look at the reflection of one of your wall wood moldings on the top, the curvature shows that the top is not perfectly flat.

   It's kind of like comparing a motor car body panel, which was repaired in a body shop, with a new panel.

   Willie

1. 
   Clay | Sep 11, 2004 08:46am | #15

   You may be correct ... at the moment when this photo was shot.  I have noticed that the whole top tends to flap it's wings a bit with seasonal changes.  The movement is minor though and I can assure you that you can go through every sheet of oak ply in Lowes or HD withut finding a flatter specimen.  Since you can do better I would appreciate seeing a photo of the really flat stuff that you make.  It might inspire me to do better next time.

1. 
   Jellyrug | Sep 11, 2004 05:59pm | #16

   Clay,

   Don't think I can do better, but I gave a 5' x 5' Satinwood (Pau Amarillo) my best shot, starting with a belt sander. Everyone thinks it's perfect, but I don't, because if I look at the top from a distance, with exactly the correct light reflection, I can see the slight uneven surface.

   To me it also looked perfect, measured with a straight edge, no gaps. Once I applied the finish, my opinion changed though.

   This was expensive wood and I won't use a belt sander again.

   You can look the project up under gallery, "Formal Dining Set"

   Willie

1. 
   Clay | Sep 11, 2004 10:17pm | #17

   Perhaps your expectation of perfect is unrealistic.  Certainly I can spot the flaws in plywood panels from the factory with no need for a glossy finish as an aid.  some of the chipboard or MDF core laminate panels are indeed extremely flat but that is most emphatically NOT so for fir or SYP core plywoods.  I have also been making some casework recently with baltic birch plywood and it too has some very noticeable flaws (mostly humps caused by overlapping interior plies).  Nonetheless the table pictured has been vocally admired by every one who sees it for the first time and I've often been asked to make more of them.  A common comment is "the most beautiful table I've ever seen".  You are the first to have suggested that it has any flaws.  So that should help you gain perspective.  No one else looks at tables the way that you do.  I would suggest that it is unlikely that a wide-belt sander or any other system is going to acheive a significantly superior result.  After all ... plywood MFR's use such systems and I can examine their results and easily tell you that my belt and ROS and hand sanded result is FAR superior.

   PS: Your formal dining set is beautiful and I think what you are encountering here is the inescapable fact that solid wood is actually not TOTALLY stable.  It moves with the weather and even the application of a finish can have some effect on the shape (therefore flatness) of glued up panels like tabletops.  No one can get them to always be perfectly flat because they are moving.  This is also true for composites that are built up of plies (re; plywood) and explains why the factories also cannot acheive perfect flatness.  Even so, with all it's flaws wood is far more beautiful than metal or plastic as a tabletop material.  Embrace excellence and reject perfection ... excellence is truly superior.

   Edited 9/11/2004 3:35 pm ET by Clay

2. 
   Jellyrug | Sep 11, 2004 10:41pm | #18

   Clay,

   Maybe you are right and I'm being over critical.

   Didn't mean to criticize your table, looks like a nice job.

   Think somewhere in this forum I have read that Rob Millard, who makes real high end pieces, also hates a belt sander. Mine is up for adoption.

   Next time I go to a furniture store, where everything is veneered and stained, I'll have a careful look at the quality of finish on their table tops. Next one I do has to be better than that.

   Willie