Filling in scratches after stain and lacquer

Hi all. Rookie woodworker here with a rookie mistake. After gluing and bisc uiting my first table top, I had a few seams that were not flush (kinda far off). I used 40 grit sandpaper to sand down the joints and then proceeded up to 400 grit. It felt smooth to the touch and I went ahead and stained an d put a coat of polyurethane on. After the poly, the subtle rough edges bec ame very apparent. Is that normal? (ie for a poly to enhance mistakes)
I thought a couple more coats of poly would smooth them out since they are not too deep, but did not do much. Any recommendations? I am not sure if t here is a special lacquer that could fill in the scratches, or if I just ap ply a heavier amount poly and sand out, or just go back to square one and r esand to the way it should've been.
Any feedback would be most welcome. Thank you.
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Here's my 2 cents, and remember you get what you paid for. I'm jumping in since it is almost 1am central time, and nobody else is likely to give you bad advice this late at night.
If you have an end table, just put a doily on it and no one will notice the scratches. Table cloth for a dining table, and if it is a coffee table it will soon be cluttered with magazines and no one can see the defects.
If I had deep, 40 grit scratches, I'd sand down until smooth, doing the entire top to keep things level. Start with 80 grit and remove all scratches, then go to 120 then 180. You could go as high as 220, but a lot of folks here on the wREC seem to think that is plenty when top coating with PU. If the scratches are in the 120 grit range, I'd be tempted to let the top cure for a few days, then sand 120-180-220 and try another coat. Using PU as a grain filler is not what it was designed for and will probably end up looking like a piece of plastic.
Some of the experts will chime in later today. FWIW, make yourself some cauls for the next table top, buy lots of clamps and see if you can get a straighter glueup to reduce sanding. I used to use a belt sander, but frankly, I'm not very good with it and tend to leave gouges in the wood using one. I do better with hand planes and scrapers. In a moment of weakness a few months ago, I bought a Performax 16/32 at an estate sale, but have not needed it yet.
Before you start finishing again, set up a bright light almost horizontal to the table top and look very closely for any defects. A raking light will make them show up well. Use the light from all directions. If you can see or feel a defect, it will almost certainly show up int he finished product. Fix every defect you find before you start applying finish. Make that last sentence into a chant for all your future finishing.
Welcome to the group, and don't do anything until Lew, Swing, Leon and some of the other much more experienced folks (who do this for a living, not a hobby) can weigh in.
Someone will surely suggest Plastic Wood and yellow paint, but I won't. Where is Joat when we need him?
Regards, Roy
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On Tuesday, July 23, 2013 12:04:37 AM UTC-5, djc wrote:

scuiting my first table top, I had a few seams that were not flush (kinda f ar off). I used 40 grit sandpaper to sand down the joints and then proceede d up to 400 grit. It felt smooth to the touch and I went ahead and stained and put a coat of polyurethane on. After the poly, the subtle rough edges b ecame very apparent. Is that normal? (ie for a poly to enhance mistakes)

e not too deep, but did not do much. Any recommendations? I am not sure if there is a special lacquer that could fill in the scratches, or if I just apply a heavier amount poly and sand out, or just go back to square one and resand to the way it should've been.

I'll add a penny's worth: After I glue up a table top, I take it to the loc al lumber yard and have them run it through their wide belt sander at 80 gr it. I get a much better result in 10 minutes on their machine than a coupl e of hours of hand work in my shop for less than $10.
Larry
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Hi Larry. Thanks for advise. What is interesting, I never thought of this idea before, but after reading your post, I passed my local lumber yard tod ay and they had a sign out that I never noticed before, which advertises mi ll work. Weird coincidence or am I now just aware about mill work, I'm not sure! Thanks again. Dan
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djc wrote:

are

To follow on from Ray. When clamping ALWAYS use the "over/under alternating clamp" method. In other words, put your first clamp on top, your second one under, the third on top, etc. Watch you tension and keep an eye out for any warping of of the joints or bowing of the piece. That will produce a very flat work piece.
I just finished gluing two panels, and am working on a third, 3/8 x 11 x 144" using this method and have three flat panels. The fun will begin with I glue those three together, after running them through the planer. But the same method will produce the same results..
Also, after your final pass with the sander, whether 200 grit or higher, wipe the piece with Naptha and view it in a raking light. The Naptha will make your scratches AND and glue show up very plainly. It also dries very quickly and does not raise the grain.
Deb
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On 7/23/2013 6:58 AM, Dr. Deb wrote:

Is this typed correctly? You glued up panels 11" x 12 feet? What's the intended use?
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On 7/23/2013 12:04 AM, djc wrote:

The question to ask is, when you went through 40 grit to 400 grit did you progress through all the grits with out skipping a grit?
Did you wipe down the surface between grits to insure that no grit was left behind from the previous?
If you skipped grits, actually you can normally skip "1" grit, you have not removed the previous grits scratch marks.
And FWIW you can normally stop sanding at 180 or 220 when applying poly.
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"djc" wrote:

I thought a couple more coats of poly would smooth them out since they are not too deep, but did not do much. Any recommendations? I am not sure if there is a special lacquer that could fill in the scratches, or if I just apply a heavier amount poly and sand out, or just go back to square one and resand to the way it should've been.
------------------------------------------------------------ Sounds like in the process of sanding down the joints you now have a top that is no longer flat.
If so, the only solution is to re-sand the top FLAT and then finish.
Without access to a drum sander, the lowest cost approach is to use a fairing board and a fairing batten to get a level surface.
You can build a fairing board by getting a mason's wooden float and replacing the board with a piece of 3/4" plywood that is 4-1/2" wide x 22" long.
You now cut a 9" x 11" sheet of sand paper into two (2), 4-1/2" wide x 11" pieces and attach to the plywood with rubber cement.
While you are getting the mason's float, buy a 3/4" x 3/4" x 1/16" x 96" aluminum angle which will be used as a fairing batten.
Start with 80 grit and sand at +45 degree bias to the long dimension of the top.
Check your work frequently using the knife edge of the aluminum angle against the work surface.
If you rub the angle against the work surface, it will leave black aluminum oxide marks across the high spots showing you where to sand.
When your arms feel like they want to fall off, your top is flat <Grin>.
Seriously, you can probably get the top flat and smooth in 3-4 hours depending on top size.
Once you are satisfied that the top is flat and smooth, change to 100 grit and sand at a -45 degree bias just until are the 80 grit marks are gone.
A hand held light can help here.
Once you are satisfied the 80 grit marks are gone, change to 150 grit and sand on +45 degree bias until 100 grit marks are gone.
Keep increasing grit (220, 320, 400) and alternating bias until you are satisfied.
Sounds a lot more complex than it actually is.
Took 4 years, but faired out a 55 ft sailboat hull using the above method.
Have fun.
Lew
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