Really struggling, need help with table top glue ups

[Scott Brandstetter]

Not sure what in the world I am doing wrong but in the middle of building a bedroom set and I just can't get the tops to come out flat with my process. Would really appreciate any help you might have.

My process for the rough cut lumber.........
Jointing rough cut poplar on one short side and on long side to get flat. Check my work, perfect
With flat long side down, run through planer to smooth other long side. Check my work, perfect
Go to table saw with the 3-4 pieces, run through the above process, and put the good short side against the fence and square up the other short side, perfect
Return to the jointer and smooth the short side just cut on the table saw, perfect

Time for glue up, my process........
I use bisquits (I realize there is a debate about strength) and match the boards up for this process, seems perfect
Glue each side of each board and insert bisquits, seems right .......... see, this is where I am losing confidence (went from perfect, to seems perfect, to seems right)
Put multiple boards, with bisquits, glued on each mating side, on the verticle clamping station (a clamp every 12 inches or so)
Leave it set up for approx an hour and remove, not perfect
I continue to have a gosh darn bow in my table top

Tonight I made a set of cauls and re-did the tops. It seems to have helped a lot but still not perfect......and I don't mean, off by a 1/32 of an inch.

I would really appreciate any help you might give to simplify the joining of boards for a table top. I am at a point that if I have to spend money on something I will. I don't remember the name but I believe there is a "wall clamping station" that can be purchased. Please feel free to suggest anything.

Thanks in advance and sorry for the long thread.....frustrated.

[Bob Carreiro]

Is it cupping? You must alternate grain patterns of each board for the glue-up.
Is it warping? Allow lumber to acclimate. If warping still occurs, glue up alternating warps and use cauls to straighten (although this may leave some twist/warp). If possible, don't take down to final thickness - leave as thick as possible. This way you can flattern, or hand-plane out the twist on one side, then send it through the planer for the other side taking it to final thickness.

[John Lankers]

I assume you mean tops for the night stands, they should be fairly small so not to difficult to pull flat when you do the assembly. To prevent cupping you could mill the lumber in stages over a period of a week or two after it had time to acclimatize in your shop for a few weeks (depending on your location and moisture content of the lumber). You could also alternate the clamps (one from the bottom one from the top and so on), cauls will definitely help. Gluing up narrower boards can sometimes make a difference too and try not to clamp the ... out of it. If you're still having issues, dowels instead of biscuits can sometimes make a difference.
Just my 2 cts.

[Andrew Hughes]

Hi Scott,My guess is your vertical clamping stations is flat along its length or width.
I clamp table tops up on a flat surface, that I check for twist before I mill my parts square.
I also have a good square that I am sure is accurate and set the fence on the jointer.Never needed bisket or cauls,i do use spring clamps on the ends were the joint is.Dont give up you'll figure it out.

[Mike Schuch]

Biscuits are not needed for strength, they are an alignment tool. I never found them particularly useful for keeping the boards lined up so I went back to dowels to keep the boards lined up. For me dowels work much better. If you can keep the boards lined up without the use of biscuits or dowels there is really no need to use them. For me dowel holes are quick on my horizontal boring machine and eliminates one more thing I need to worry about when glueing up.

Are the glued up boards cupping across the grain of the wood or are they bowing with the grain of the wood?

Clamping too tight often leads to cupping.

Go to this page: http://www.wwgoa.com/article/master-the-jointer/ and read the section about half way down titled "Compensating for an out-of-square fence." Always use this method to joint the edges of boards and you will never have to worry about whether your jointer fence is perfect or almost perfect. Your jointer fence can be way off from square and this method will compensate for any variations from perpendicular.

If you are having problems with the glue up bowing along the length of the grain I would suspect your wood is the problem.

I picked up three of these pipe clamps off of Craigslist for really cheap. They are supposed to help eliminate cupping. I haven't tried them yet.
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I am usually able to get acceptably flat glue ups without any fancy glue up racks or clamps. I do look forwards to giving these double pipe clamps a try though!

[Don Frambach]

I've had good luck with this system. I cover the wooden cauls with shipping tape so the glue doesn't stick. I also do glue ups on a flat surface (usually my garage floor). By starting with flat cauls and then pulling them against the work my table tops end up nice and flat.

314408
here's a source:

http://www.woodcraft.com/Product/125392/WoodRiver-Clamping-System.aspx (http://www.woodcraft.com/Product/125392/WoodRiver-Clamping-System.aspx)

[Bill Adamsen]

You clamping station ... are you alternating clamps top and bottom? Most clamp arms bow when tensioned, so alternating helps counteract that force. Of course it requires almost twice as many clamps. Using well seasoned and shop acclimated quartersawn wood removes the material as a possible culprit.

[Sam Murdoch]

Your milling method is "perfect". Don't know about the lumber you are using.

I process lumber just as you do and have not had any issues that could not be corrected when attaching my top to its base.
No need to alternate faces in my experience. Just match your faces for the best look after processing as you do.
The biscuits are a perfectly useful tool for alignment - Festool dominos are even better and easier but biscuits are a useful aid.
DO MAKE CERTAIN that your biscuit slots are perfectly parallel to your top faces. This could be a source of your problem.

"Clamping too tight often leads to cupping" A good caution from Mike Schuch. Your boards are already straight - light pressure to pull the joint together is all you need. Cauls are a great option too. Those that Don recommends , though they have limitations appear to be excellent. Important in any case - as you do your glue up check your panels for flat - loosen and move clamps accordingly until your straight edge shows the panel to be flat.

Also - glue up your panel as close to the finish size as possible - maybe within 3" extra on both ends and 1" overall on the width. Sometimes you can't follow this rule but when you can, why glue up more than you need?

Sounds like you are doing everything right. I'm frustrated for you. Good luck.

As for the lumber question -
I suggest that you mill a few extra boards and then wait - at least an overnight - from the flattening/straightening stage to the glue up stage. Should not be needed but this will allow you to check your lumber again and eliminate the worst offenders before the glue up.

[Jim Matthews]

Perhaps a verification in terms is appropriate.

Bow is a defect along the length of a board.
A board with a bow in it will rock on a flat surface.

http://www.woodmagazine.com/woodworking-tips/techniques/skills/dealing-with-wood-defects/?page=2

If the boards start out flat (verified with a straightedge as on your table saw or jointer)
then the distortion is induced - either by mechanical misalignment on a surface that isn't flat
or because the wood isn't taking up glue evenly.

I'm suspicious that the biscuits are swelling and forcing the board into an arc.

FYI - Many of us don't use anything beyond clamps and glue to align boards like these.

[Steve Jenkins]

When gluing up a panel I alternate the clamps above and below and check flatness with a straight edge as I tighten them. Also I glue on a flat surface. I've found that pipe clamps are the worst for bowing with bar clamps next. Bessey k bodies stay flat up to about 36" then they also bow some. So for panels less than 36" wide I can use k bodies sitting on my work table without alternating above and below.
I stopped alternating grain many years ago when it became nearly impossible to find lumber that was clear on both faces. I go for the best look. My panels or table tops are still flat and remain flat.
Just a note on terminology, boards have faces and edges.

[Phil Thien]

Ditch the biscuits, use cauls to keep the glue-up flat.

Also, before applying any glue, do a test run with the clamps and cauls to make sure your panel is flat without any gaps between the boards both on the top and bottom surfaces. You said your machining is perfect but you never really know for sure until everything is pulled tight and there aren't any gaps anywhere.

[Robert LaPlaca]

What kind of clamps are we using for the glue up? Any chance they are pipe clamps? I have found they really deflect in wider glueups, especially if one really cranks them up.. If glueups are a challange, you will always get much better results from parallel clamps like Bessey k body style

I do do agree that doing a dry run of your glue up before actually putting glue to the wood is always a great idea. Don't really see any issue with using biscuits, or dowels or nothing at all.. Alternating clamps on the top and bottom is always a good idea

[glenn bradley]

Time for glue up, my process........
I use bisquits (I realize there is a debate about strength) and match the boards up for this process, seems perfect
Glue each side of each board and insert bisquits, seems right .......... see, this is where I am losing confidence (went from perfect, to seems perfect, to seems right)

-- Adding biscuit slots to correctly milled edges should not cause any change in the mating surfaces. Are your biscuit slots deep enough?


Put multiple boards, with bisquits, glued on each mating side, on the verticle clamping station (a clamp every 12 inches or so)
Leave it set up for approx an hour and remove, not perfect
I continue to have a gosh darn bow in my table top

-- I don't worry about alternating grain patterns arch up, arch down, arch up, etc.). I position boards for the best appearance. If the biscuit slots are not preventing the edges from fully seating together, I would look to your clamping station as the culprit. Is this a pro rig that performs a 4-way pressure when clamping or is it just a row of clamps? I learned to clamp alternating under and over. I also clamp on a flat reference surface with clamps that set flat and stable. This means that the bars of the clamps are also flat so I can use them as a reference surface. You don't mention alignment issues so it sounds like the biscuits are taking care of that for you. I think clamps on the alternate side every other clamp position will be your solution.

[Bill Huber]

I am sure not any type of expert but this is what I have done for panels.
I know this is not what is said about making panels but it works for me.
I have a very small shop so I can not handle really long boards.

Starting with 4/4 boards.
A lunch box planer.
A Freud glue line rip blade.

Cut the boards to length plus an inch.
Run them though the planer to get both sides smooth and flat.
On the table saw rip one edge of a board, taking off maybe 1/8".
Flip the board and rip the other edge, again about 1/8".
Now I lay the boards out like I want them for the panel, alternation grain patterns of each board and mark them 1-to what ever.
I now mark the edge of each board with a U or a D for up and down, each board will have a U and a D on it.
On the table saw I now rip about 1/8" off the edge with the U side up.
Now on the table saw I flip the board over and cut all the D sides with the D down.
(The up and down cutting is so that if my blade is not exactly 90° they will still go together flat.)
Now on a flat surface I set up my clamps with half the clamps on the bottom and the other half on the top.

Again this is how I do it and it works great for me.

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[Prashun Patel]

If your finished panel is bowed, my instinct is that the edge of your boards are not perfectly jointed. You mentioned they are 'flat', but are they perfectly square to the faces?

In my limited panel glue up experience, I can say that cauls, biscuits, clamps all play a distant second to two flat,square mating surfaces. Biscuits will help with alignment; cauls along the edges will help with distributing pressure to give a gap-free surface. But if your boards are not jointed perfectly, then the error magnifies over each successive board - even if you use cauls along the tops, once released, the board will bow.

A trick people use is to joint mating board edges with the opposite faces towards the jointer fence. This will cancel any error in the fence position. It however, relies on each board having perfectly parallel top and bottom faces.

Another trick people use is to joint boards 'bookmatched'. Line up the boards in order of assembly, then fold up adjacent pairs (face to face on boards 1, 2, then bottom to bottom on boards 2,3, then face-face on 3,4, etc.). Clamp and joint them as a pair. Again, this way any error is cancelled.

Also, it really helps me to glue one board at a time. It allows you to work cooler, and neater. It's also easier to nudge boards into vertical alignment and to add more clamps to remove any gaps. If you are a hobbyist like I, you may not mind the sacrifice in throughput.

[Roy Harding]

I make glued up panels every day (I make a lot of cedar blanket chests). Everybody above has made very valid observations, and provided excellent solutions to your possible problem. In my own case, I use alternating top/bottom clamps, every 10 - 12". I don't use biscuits, but I have the luxury of being able to run my panels through a 24" drum sander - so perfect vertical alignment is not vital to me.

Personally, given that you state when you check your jointed pieces they are flat and square ("perfect" was your description) I think the most likely problem is that you're over tightening the clamps. Try not tightening them so much on your next glue-up. If the problem remains, then move on to the next solution, etcetera.

[Jeff Ramsey]

Time for glue up, my process........
I use bisquits (I realize there is a debate about strength) and match the boards up for this process.

I would not debate the strength of biscuits; I'd debate their usefulness in alignment. Biscuits have too much tolerance on the flats (to permit glue to enter), and thus aren't very good at alignment (on their own) on the flat surfaces. I use dowels. A proper fluted dowel is firm at the high flute points against the inner walls, yet the flutes permit glue to flow. They are also stronger than biscuits, although the face glue surface should be sufficiently strong.

Others have mentioned their techniques. If properly milled (and dried), with grain altered, you should be able to get flat glue-ups with cauls+clamps on a flat surface.

[Pat Barry]

First off, what you are describing is fairly common. I do not think its reasonable to expect that the glue-up will be perfectly flat, even under the best conditions. I also think its typical to have to do some work on the top and bottom surfaces after the glue-up to level the boards to each other although there are tricks to minimize that such as cauls, dowels, biscuits, and the like. I think that small amounts of bow can be managed during assembly.

[scott vroom]

The first thing you should do is check your jointer fence to make sure it's dead on perpendicular to the bed. If not 90degrees, then you're already starting in a deep hole.

I don't use biscuits and rarely use cauls. I use quick grip clamps to align the boards at the panel ends. I alternate clamps top and bottom and avoid over tightening. I've never worried about alternating the grain (not convinced it helps, and it would often interfere with the desired face grain pattern).

On extra wide panels I do the glue up in sections, e.g. if it's 6 boards I'll glue up 3 pairs of 2 boards, joint and plane each before doing a final glue up of the 3 sub-assemblies. I've found that doing this improves my chance of flatness.

Even with the best practices, it's darn near impossible to get all panels dead flat. I don't worry about minor deviations; most of my panel work gets attached to an apron which makes it easy to pull flat.

Hang in there and keep tweaking your process...you'll get it figured out.

[Kent A Bathurst]

Another trick people use is to joint boards 'bookmatched'. Line up the boards in order of assembly, then fold up adjacent pairs (face to face on boards 1, 2, then bottom to bottom on boards 2,3, then face-face on 3,4, etc.). Clamp and joint them as a pair. Again, this way any error is cancelled.

Also, it really helps me to glue one board at a time. It allows you to work cooler, and neater. It's also easier to nudge boards into vertical alignment and to add more clamps to remove any gaps. If you are a hobbyist like I, you may not mind the sacrifice in throughput.

Do these. The "bookmatched " final edge joint has proven critical for me.

I do one joint at a time, so I can focus on that one thing.

I disagree re: pipe clamps. That is what I use exclusively - up-down-up-down.....but - I do use cauls religiously.

It is all "doable". Took me a while, but my joints require nothing more that [a] junk card scraper dedicated to glue removal, and [b] good card scraper to even the joint - there is no difference that cannot be taken care of by a card scraper.

Biscuits add nothing in terms of structural or alignment. A waste of time, IMO.

[Prashun Patel]

I'm with Kent on the pipe clamps. Cheap and effective, and honestly easier for me to manipulate than cab clamps.

[Erik Christensen]

Dump the biscuits and use cauls to keep things flat as others have said. If the glued-up panel is < width capacity of your planer don't plane before the glue-up. Joint one face & both edges, make sure all jointed faces end up on the same side and glue that sucker up. Light pass through the planer either side post glue-up and as long as the edge mis-match is less than what the planer is removing... you can't goof it up (as they said in the navy "sailor-proof")

[Roy Harding]

Dump the biscuits and use cauls to keep things flat as others have said. If the glued-up panel is < width capacity of your planer don't plane before the glue-up. Joint one face & both edges, make sure all jointed faces end up on the same side and glue that sucker up. Light pass through the planer either side post glue-up and as long as the edge mis-match is less than what the planer is removing... you can't goof it up (as they said in the navy "sailor-proof")

This is another excellent solution.

If your glued-up panel is > width capacity of your planer, do it in sections that DO fit in your planer, then glue the sub-assemblies together to form the final product.

[Sam Murdoch]

You guys are way to hard on BISCUITS. I have never had a glue up fail because of biscuits, (and I used them for many many years) on the contrary they have been immensely helpful as an easy alignment tool. YES, you can use them improperly - to close to the top face or misaligned - but when used correctly they are great. As I noted above, the Festool Domino is more precise and just as easy but the biscuits are more than useful even with consideration to their limitations. Even used with cauls or other top/bottom flattening clamping systems, biscuits help a glue up by getting the top surfaces in very very near alignment prior to clamping. Glue up failures occur for lots of reasons but biscuits are not at the top of the list.

Just sayin'

[Dave Cav]

I've done quite a few larger glue ups and my experience mirrors a lot of the advice above. Alternate faces against the jointer fence so any error on the edges is cancelled out. Alternate clamps top/bottom about 8 or 10 inches apart. Don't overclamp. I always clamp on my flat work table and then when the clamps are tight I lean the glue up against the table or wall. I use cauls when necessary, but a lot less since I got my widebelt. My cauls are just 2x4s ripped down the middle and faced with blue tape.

I have a biscuit jointer. It's a Freud I got when I didn't know any better and all the WW'ing mags said you HAD to have one. I haven't used it since the 90s.

[Kent A Bathurst]

You guys are way to hard on BISCUITS. I have never had a glue up fail because of biscuits, (and I used them for many many years) on the contrary they have been immensely helpful as an easy alignment tool. YES, you can use them improperly - to close to the top face or misaligned - but when used correctly they are great. As I noted above, the Festool Domino is more precise and just as easy but the biscuits are more than useful even with consideration to their limitations. Even used with cauls or other top/bottom flattening clamping systems, biscuits help a glue up by getting the top surfaces in very very near alignment prior to clamping. Glue up failures occur for lots of reasons but biscuits are not at the top of the list.

Just sayin'


Yeah, yeah, yeah..........yawn....;)

[Judson Green]

Is your jointer set to perfectly 90°?

[Kent A Bathurst]

Is your jointer set to perfectly 90°?

Key point, Judson:

If you do the bookmatched edge jointing, you can be off dead-nuts by a few degrees and you are groovy. But - you gotta be using cauls to keep it all copacetic.

[Mike Schuch]

You guys are way to hard on BISCUITS. I have never had a glue up fail because of biscuits, (and I used them for many many years) on the contrary they have been immensely helpful as an easy alignment tool. YES, you can use them improperly - to close to the top face or misaligned - but when used correctly they are great. As I noted above, the Festool Domino is more precise and just as easy but the biscuits are more than useful even with consideration to their limitations. Even used with cauls or other top/bottom flattening clamping systems, biscuits help a glue up by getting the top surfaces in very very near alignment prior to clamping. Glue up failures occur for lots of reasons but biscuits are not at the top of the list.

Just sayin'

I drink beer when I am doing my glue ups. I have never had a glue up fail when I drink beer during the glue up! Everybody should drink beer during their glue ups if they don't want their glue ups to fail!


My apologies for being such a smart a$$. ;)

[Judson Green]

True, the edge jointing can be off by many degrees and still make a flat panel but the boards need to be glued in the proper way. Those of us in the hand tool camp know this all to well and often joint for panel glue up two boards at a time, so any angle inconsistencies are corrected automatically.

[Jim Matthews]

The OP is describing a bow in the assembly.

I don't mill by machine, so I can't figure how the lateral alignment
would effect the vertical and cause the deviation described.

It would be easier to help if the OP posted some photos.

I can remember having a lower tolerance for error when I started out.
It isn't necessary to be within the same range as a machinist when working wood.

Something doesn't add up in this thread, and it's probably a simple misconception.

Those of us that don't use biscuits see them as a simple element to eliminate,
as gluing two boards together doesn't require much.

I've seen sixteen foot spars glued up by hand with nothing but twine.

[Judson Green]

The OP is describing a bow in the assembly.


It would be easier to help if the OP posted some photos.


Something doesn't add up in this thread
.

1. Despite numerous requests the OP (at least to my knowledge) hasn't cleared up weather its a bow or a cup.

2. Sure would or at least participate in his own post.

3. Truer words have not been spoken.

[Scott Brandstetter]

To all that have replied, I really appreciate you taking the time to respond. Jim, I always do my best to respond once I post but I have been out of town on business and not able to until now. After reading through the responses, I feel strongly that I have done several things wrong. I am certain I am putting way too much pressure when clamping the boards. I don't really know, how to know, when enough is enough but I am going to spend this weekend doing a few tests. I also realized that in the past, before my clamping station, I had clamps on both sides of the boards, alternating. Add the fact that the clamps are all on the same side as the glue up and over clamping, it must equal problems.

My goal moving forward is to minimize clamp pressure, use cauls on a regular basis (can't hurt), and alternate clamps on both sides of the panel.

I am also going to do a home made strength test on the difference between using bisquits and nothing. I've always had it in my mind that bisquits will add strength to the joint.

Thanks again for all of the responses.

[Stanley Powers]

You probably don't have square edges on your boards as you glue them up. Orient them as you want. (Alternating grain patterns really doesn't make a difference if they are properly dried). Mark the lay out with a carpenters triangle. When you joint the edges, alternate the faces of every other board against the jointer fence. This will take care of your fence not being exactly 90 degrees. Works like a charm!

[roger wiegand]

I've found cauls to be a completely unnecessary complication in glue-ups of panels. It's worth a fair amount of effort to make sure your jointer and table saw are giving you edges that are exactly 90 degrees to the faces, that way you can align boards for looks rather than maintaining alternating directions. (measure the squareness of the boards, not the tool) Alternating sides, enough pressure to give a little squeeze out of the glue, and squared up boards and it should be OK. I will confess to using biscuits to keep things from sliding around.