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Discussion Starter #1
First post here. Lurking for a while and need your guys' brilliant minds to help me out.

I recently built a bench. It is u shaped and crazy sturdy. Used 2x6 frame, 4x4 posts, and Simpson RTC42 brackets. After all that, I decided to go low bid and top the entire thing with 2 layers of 23/32 CDX plywood, screwed and glued with Titebond. Because it is u shaped and pretty sizable (6' legs of the u, 13' center width), seams in the plywood were unavoidable. Through some careful design, got it down to 3 seams.

Built the thing and everything went together great with one exception. There is a seam at the center of the 13' wide section, that didn't match up height wise. The other two seams are perfect. Upon closer inspection, it appears that the plywood was actually thicker at one end! I'm not kidding, it looks like one ply of one sheet is double thick the last couple inches. I swear, no joke, you can see it by looking at the sheet installed.

Long story short, there's a 3/32" to 1/8" difference in height between the two sheets at the seam. It is driving me nuts (did I mention I'm OCD?)! When you try to slide something across the surface, it catches every time. It's about the thickness of an entire ply so I'm not sure sanding would turn out looking good. Any ideas to even it out?

Most of my buddies just tell me to deal with it. Maybe I will if there is no good fix.

Please keep in mind I am trying to preserve the rigidity of the bench (long story).

TIA for all the help!!!

P.S. I can attach photos if necessary.
 

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John
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First post here. Lurking for a while and need your guys' brilliant minds to help me out.

I recently built a bench. It is u shaped and crazy sturdy. Used 2x6 frame, 4x4 posts, and Simpson RTC42 brackets. After all that, I decided to go low bid and top the entire thing with 2 layers of 23/32 CDX plywood, screwed and glued with Titebond. Because it is u shaped and pretty sizable (6' legs of the u, 13' center width), seams in the plywood were unavoidable. Through some careful design, got it down to 3 seams.

Built the thing and everything went together great with one exception. There is a seam at the center of the 13' wide section, that didn't match up height wise. The other two seams are perfect. Upon closer inspection, it appears that the plywood was actually thicker at one end! I'm not kidding, it looks like one ply of one sheet is double thick the last couple inches. I swear, no joke, you can see it by looking at the sheet installed.

Long story short, there's a 3/32" to 1/8" difference in height between the two sheets at the seam. It is driving me nuts (did I mention I'm OCD?)! When you try to slide something across the surface, it catches every time. It's about the thickness of an entire ply so I'm not sure sanding would turn out looking good. Any ideas to even it out?

Most of my buddies just tell me to deal with it. Maybe I will if there is no good fix.

Please keep in mind I am trying to preserve the rigidity of the bench (long story).

TIA for all the help!!!

P.S. I can attach photos if necessary.
Sounds like one H*** of a bench:thumbsup:
Judicious application of a belt sander would take care of the bump in short order but, you're right, it probably wouldn't look that good. You could top the whole thing off with a layer of 1/4" MDF, very smooth and hard but may be lacking in durability. Just screwed down it could be replaced as needed though.:smile:
 

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Discussion Starter #3 (Edited)
Sounds like one H*** of a bench:thumbsup:
Judicious application of a belt sander would take care of the bump in short order but, you're right, it probably wouldn't look that good. You could top the whole thing off with a layer of 1/4" MDF, very smooth and hard but may be lacking in durability. Just screwed down it could be replaced as needed though.:smile:
It is pretty stout. Had a bad run in pounding out some taper pins on one of my AR15 rifles recently and learned the hard way about the value of a solid whacking surface. So I decided to go overkill in case I ever have to do it again.

Agreed about the sanding.

You think the MDF would work well without creating a pronounced "slope" in the surface that would look just as bad? Trying to temper my OCD.

On that note, do I need to pre drill the MDF for screws? I've heard that if you try to screw anything into MDF it just strips out because it's sawdust and glue. But I guess that doesn't matter since I'm screwing through it and into the CDX beneath.

That being said, if I got a nice even surface, I'd consider putting Masonite on the top to take care of the durability. Might have done it already, but I know it won't turn out with that stupid gap there.

Thanks for the input.
 

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John
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It is pretty stout. Had a bad run in pounding out some taper pins on one of my AR15 rifles recently and learned the hard way about the value of a solid whacking surface. So I decided to go overkill in case I ever have to do it again.

Agreed about the sanding.

You think the MDF would work well without creating a pronounced "slope" in the surface that would look just as bad? Trying to temper my OCD.

On that note, do I need to pre drill the MDF for screws? I've heard that if you try to screw anything into MDF it just strips out because it's sawdust and glue. But I guess that doesn't matter since I'm screwing through it and into the CDX beneath.

That being said, if I got a nice even surface, I'd consider putting Masonite on the top to take care of the durability. Might have done it already, but I know it won't turn out with that stupid gap there.

Thanks for the input.
I'd sand the lumps down and then top it off, Tempered Masonite would be just as smooth and more durable than MDF. I would lay it out so none of the Masonite seams would align with the plywood seams. Small pilot holes would help with either. As you observed, you are going through the top layer so the threads are really not gripping anywhere in there but both Masonite and MDF are extremely dense and the material displaced by an unpiloted screw will tend to "erupt" around the screw leaving a small bump. :smile:
 

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Discussion Starter #5
I'd sand the lumps down and then top it off, Tempered Masonite would be just as smooth and more durable than MDF. I would lay it out so none of the Masonite seams would align with the plywood seams. Small pilot holes would help with either. As you observed, you are going through the top layer so the threads are really not gripping anywhere in there but both Masonite and MDF are extremely dense and the material displaced by an unpiloted screw will tend to "erupt" around the screw leaving a small bump. :smile:
Now why didn't I think of that?!?

I want it to be even but also look good. So as u proposed, sand it down to make it even. It will look like sh!t but then top it with either Masonite or MDF. Problem solved! U da man!

When I drill holes for the Masonite/MDF, do I need to drill the holes to be "free fit" or is a small pilot hole sufficient to prevent "eruption"?

Also, I've read that a good way to attach Masonite is to drill pilot holes and counter sink screws to make it easier to replace later when it wears out. Thoughts?

Lastly, what kind of pattern would u recommend for screws? My bench top is 24" deep.
 

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John
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"When I drill holes for the Masonite/MDF, do I need to drill the holes to be "free fit" or is a small pilot hole sufficient to prevent "eruption"?

Also, I've read that a good way to attach Masonite is to drill pilot holes and counter sink screws to make it easier to replace later when it wears out. Thoughts?"

I'd drill so the threads have minimal encounter with the Masonite/MDF. The bugle head on drywall screws will do a nice job of making a countersink so I don't think that operation is necessary.

"Lastly, what kind of pattern would u recommend for screws? My bench top is 24" deep."

Not sure what you mean by "pattern" but screws every 6 or 8" along the seam(s) should be sufficient. May need to play that one by ear.
Good Luck:smile:
 

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Discussion Starter #8 (Edited)
Lots of good ideas here.

Yes, on pattern I did mean spacing for a grid of screws.

At the outset of the project I bought a 25 lb bucket of #8 x 1-1/4" Bugle Head Drywall screws. Needless to say, I have a few left over. I might countersink them anyways to be sure. I've come this far.

Thanks all for the ideas. I will proceed the sanding and masonite route. I will update the thread when done.

In the meantime, feel free to float other ideas.

Attached are some photos to give you an idea of what I'm dealing with.
 

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