How big of gap acceptable for glue ups?

[lcm1947]

I want to glue up some boards for a coffee table top and was wondering just what is acceptable as far as the gap between the boards? The one's I've practiced on so far using the router table with the shim on the out-feed table method is about a playing card wide gap. Is this acceptable or do I need better?

[Jeffrey Schronce]

I would not find that to be an acceptable result on a project I put a lot of time and effort into, particularly if it is going to be in the living room being seen every day. I personally do not find ANY gap acceptable in furniture table tops.
Having said that, I have never jointed with a router table using the shimmed outfeed method. There are those here who do it and get good results. Perhaps your material is not properly face jointed and planed to result in a consistent edge joint?
I would find someone with a jointer and edge joint on that machine prior to making a table top with playing card size gaps.

[TheRic]

The questions is something you have to answer. How big of a gap do you want to show off to people. If you want to put something in your living room and proudly display it with a 1/8 or 1/4 gap then go for it.

The gap your talking about is where??? On the end(s), middle, across the top (tight at the bottom), across the bottom (tight at the top), in spots?? By letting us know, someone here might be able to help you improve.

[lcm1947]

Sorry I guess I wasn't too clear. The gap is along the entire 36"s of the jointed board(s). Now this is before applying clamps which then does close the gap up to nothing. I guess what I'm trying to understand is what kind of gap is expected just butting the boards together without pressure of clamps. Hope this helps?

[Bruce Cohen]

Mac,

Joints (the woodworking kind) should be zero tolerance when dry fitted, without the need for clamps.

Of course, that only exists in a perfect world, which this ain't.

Bruce

[lcm1947]

Thanks Bruce but that's what I trying to figure out. Does a jointer for example product this zero tolerance? Mine was done on a router table so didn't know if this was acceptable or not. If not I'll try some more until I get it perfect but never having tried a top before really had no idea what is considered good or acceptable.

[whitecobra]

Mac
Relook at the router table set up
Assuming your wood is not 1or 2" thick you should EASILY be able to accomplish what you want (zero tolerance) on the table if the table is say 30 inches wide or so

The isuse of a jointer is an EASIER way but it is not a better way

Your router should easily be able t6o be set up to accomplish a "no gap joint"

Try taking off minor amounts at each pass also close the fence up to 1/4" or less adjacent to the bit so that the wood has no place to go but past the flutes

Also set up feather boards if you can to eliminate the wobble your hands are likely going to add in

A good learning lesson for you so stick it out and don't jump into new toys. First learn how to use the toys you have then if you do enough of the procedure buy toys to make the job EASIER or faster

**** I know of a dozen guys that can get a zero tolerance with hand planes

Doc

[jackellis]

Mac, I think we can help you if you could answer a couple of questions:

What kind of wood?

How long between the time you finish jointing and the time you dry fit? Could the moisture content be changing a lot?

After applying pressure with clamps, is the board still flat? Are the boards warped?

Is your stock flat against the router table?

Have you checked the fence for flatness?

A playing card's width is way too much gap.

[ChrisD]

Thanks Bruce but that's what I trying to figure out. Does a jointer for example product this zero tolerance? Mine was done on a router table so didn't know if this was acceptable or not. If not I'll try some more until I get it perfect but never having tried a top before really had no idea what is considered good or acceptable.

Mac,

A properly tuned jointer will do that.

As for the "pre-clamp" gap, I have read a few articles by authors who prefer to plane a very slightly concave edge on boards creating a very small gap along the joint line. They call this a "sprung joint". The rationale is that it creates more tension at the ends of the joint, making for a seamless interface between the boards being glued up.

I have not tried this myself, but it seems to be an acceptable practice.

[lcm1947]

Thanks Doc. Yes the wood I was cutting is 1" thick and 4" wide and 36" long. The table is exactly 30" wide too. Is 1" thick wood a problem? No I wasn't using feather boards but will try using them and see if that helps. Thanks for that tip or I should say reminder.

Jack to give you more info.

The wood is pine. Trying to practice on cheap wood.

It was maybe a couple of hours before I dry fitted them.

The boards really aren't flat to begin with. I am having to push down on them to get them to be level with each other for the dry fit. I figured once I glued them and pocket screwed them they would then stay flat. No not warped just bowed slightly.

Well, I was pushing down on the slightly bowed boards to make sure the board was flat on the table as I slid them over the bit but I suppose maybe I didn't insure that I applied enough pressure and they maybe weren't completely flat. I'll have to watch for this next time.

Yes the fences ( split fence ) are flat/level with each other.

Hope that answered everything.

[drumpriest]

Here is tip, using your router table, joint the first board face up, and the next face down, in sequence. Do this across all of the boards. If your router isn't 100% orthogonal to your table, the error will be cancelled out this way.

This works also on the jointer, alternating faces against the fence.

[TheRic]

Sorry I guess I wasn't too clear. The gap is along the entire 36"s of the jointed board(s).

The gap is along the whole length, top, bottom, middle, top & bottom??

Sounds like the fence (or router) is not at a true 90 to the table top. Alternating the boards like drumpriest says is one solution. I would work on WHY the fence (router) is not at a true 90 to the table top. In other words fix the cause, not the problem. It will save you headaches in the future.

[niki]

Hi Icm1947

Look at the picture and tell me what is the distance between the router bit edge and the router base edge (on your router).

I you have one flat edge on your router base, measure from the bit to the flat edge.

For measuring, use the same router bit that you are going to use for jointing.

Also, tell me what is the width of your straight edge.

niki

[cabinetman]

Everybody has there own way of doing things. I set up a router in a table ONLY for straightedging. Picture this: A straight cutter is sticking up through the top, seated in a cutout. Laminate 1/32" mica to the edge of a 3/4" piece of ply (maple is good) 3" wide by the length of the table. Set the fence so there is 1/32" of bit exposed forward of the front edge of the fence. I use a 1/4" bit so most of the bit is within the fence except for 1/32".Then, the take-up side of the fence laminate 1/32" mica onto the edge. Screw fence to the table top. So, when stock is passed down the fence only 1/32" comes off, and it's straight. Can't think of a reason why the bit wouldn't be 90 deg to the table. The table top and edge of the fence have mica laminated to it so the passes are smooth. This isn't rocket science. This setup doesn't get changed. It's a dedicated setup.

As for edge glue-ups, dry fits should be tight. Over clamping is not the way to solve the problem.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[RayintheUK]

If the gap is consistent along the length, I can think of only two causes - unsquare edge to face, or a non-flat assembly surface. Drumpriest's suggestion on alternating faces will deal with the first cause.

However, if you're pressing down to reduce any cupping effect, then once the board is "relaxed" and on a flat surface, cupping will also induce a gap along the entire length.

Pass a couple of boards through without any undue downward pressure and see if that does it.

Ray.