# How many cauls for table top?



## TravisN (Jan 15, 2019)

Hi all,

I am getting ready to glue a table top. This is my first time doing a panel this large. I went back and forth on using dowels or clamping cauls to make sure my alignment is good and finally settled on the clamping cauls. So the next question is, how many sets should I prepare?

The tabletop will be approximately 40" x 78". I used a planer sled to get the two faces parallel, so I cannot guarantee that my lumber is perfectly flat, but the sled seemed to work in removing any significant twist or cup, and all are milled to the same thickness.

I've used 2-3 cauls on smaller projects, but I'm sure more would be recommended for a large panel. Those of you who use cauls, what do you do? Every foot? More or less?

Also, I've never seen a definitive statement about when to tighten the cauls. Before or after the clamps? It seems like whichever you tighten first will make it that much harder for the other…...


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## JackDuren (Oct 10, 2015)

I don't really use cauls. I alternate every foot but you can only do with what you have….I usually put two close to gether on the ends to keep it flat…


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## nickbatz (Mar 7, 2018)

Speculation since I've never made a tabletop that large or used cauls, but I'd say how many cauls depends on how straight the wood is to start with.

As to when to tighten them, well, right away, no? Why wouldn't you want the boards to be aligned when the glue is drying?


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## TravisN (Jan 15, 2019)

> As to when to tighten them, well, right away, no? Why wouldn t you want the boards to be aligned when the glue is drying?
> 
> - nickbatz


What I meant was which do you tighten first? If you tighten the cauls first, can all that downward pressure prevent the lateral clamps from sealing the joint? If you tighten the lateral clamps first, I don't think the cauls are strong enough to then enforce the desired alignment.


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## JackDuren (Oct 10, 2015)

tighten the cauls to get it flat , then tighten the clamps…


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## Unknowncraftsman (Jun 23, 2013)

How did you prepare the edges square to the faces.
You don't mention what wood it is or how thick. 
I don't cauls never need to because I have a very accurate jointer. I do use spring clamps on just the ends.
The thicker and wider boards get the more clamping pressure. Last thing you want is glue lines showing up 2 weeks after you last coat of finish.

Good Luck


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## CWWoodworking (Nov 28, 2017)

How thick? Are you running it through a sander after or flattening it by hand?

I don't use cauls either, but not saying they don't work. I would tighten before clamps.

Panels that size, I always start in the middle and put enough downward pressure to get any little twist or bow out. Then work towards the ends. That way your working with 3' instead of 6'.


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## JamieAB (Apr 14, 2016)

Be sure to do a test fit up using your cauls and clamps. This will give you an idea of what it's going to take to get it looking "good". You'll know if you need more and how spaced they'll need to be.


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## CaptainKlutz (Apr 23, 2014)

> ...
> I used a planer sled to get the two faces parallel, so I cannot guarantee that my lumber is perfectly flat, but the sled seemed to work in removing any significant twist or cup, and all are milled to the same thickness.
> ...
> - Travis


It takes flat boards to make a flat table top. 
Or put another way: You can not clamp flat twisted/warped boards to make a flat table top.

If your boards do not lay flat to each other when laid out on table side by side, and need top and bottom pressure to 'make' them flat; will most likely have hills and dips in top when clamps are removed.
BTDTGTTS

+1 With flat boards to start, you don't really need clamping cauls. Like others posted before, I alternate my clamps top/bottom and only occasionally need to use spring clamps to keep outer ends aligned on flat boards.

Best Luck.


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## rwe2156 (May 7, 2014)

I agree with Jack, cauls are not necessary. The key to a panel glue up is flat boards and perfect joints.

My technique is to gradually increase clamp pressure, and bring seams into alignment with a rubber mallet. I put clamps on the seams at each end.

If I'm dealing with some minor bows I know I can clamp out, I'll use biscuits.

That said, if you're using cauls, I would put them eveyr 12".


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## TravisN (Jan 15, 2019)

> tighten the cauls to get it flat , then tighten the clamps…
> 
> - JackDuren


Thank you!



> How did you prepare the edges square to the faces.
> You don't mention what wood it is or how thick.
> ....
> - Aj2


I used a router with a straight edge (factory edge of sheet of BB plywood) to get one good edge that is square to the face. I'm hoping to get the second edge on my TS today, but if I can't get a glue line rip with the TS, then I'll use the router on the second edge.



> How thick? Are you running it through a sander after or flattening it by hand?
> ...
> - CWWoodworking


Ash milled down to 1". I was hoping for a bit more but one of my wide planks had significant twist, I lost of lot of thickness getting that piece flat. After glue-up will be flattening by hand (ROS). So my desire for a flat, aligned glue-up is both to preserve as much thickness as possible and to minimize my labor afterward.



> It takes flat boards to make a flat table top.
> Or put another way: You can not clamp flat twisted/warped boards to make a flat table top.
> 
> If your boards do not lay flat to each other when laid out on table side by side, and need top and bottom pressure to make them flat; will most likely have hills and dips in top when clamps are removed.
> ...


The boards look flat when sighting them and feel flat to the touch. But when I stack two pieces on their faces, there are some small gaps, so I know they are not perfectly flat. However, they are as flat as I'm able to get them with the equipment and experience I have. I don't have dead-flat surface large enough to lay them all out side by side and fairly see how flat they lay next to each other. I don't expect the cauls will have to overpower twisting and cupping, that was taken out while preparing the boards. Just keep them in line with each other, especially as they tend to slip around with glue, etc.


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## LeeRoyMan (Feb 23, 2019)

How wide are your pieces and are you going to clamp them all at once?
It's easier to do 2 halves, then clamp the halves together.

4 Cauls should be plenty. 
About 4" in from the edge, and a couple evenly spaced in the field.

Snug the cauls just enough to hold the planks flush with each other, (shouldn't have to bear down on them),
Then put on your clamps. I like to snug the clamps tight, then after about 10 to 15 minutes I go around and give them another crank. It's just what I do.


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## bandit571 (Jan 20, 2011)

What I had to do for this top made out of 1/4 sawn White Ash…..along with rub joints as I built the panel….end cauls outboard of the clamps. Middle caul is centered in the panel


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## TravisN (Jan 15, 2019)

> How wide are your pieces and are you going to clamp them all at once?
> It s easier to do 2 halves, then clamp the halves together.
> 
> 4 Cauls should be plenty.
> ...


Thank you!
My pieces are variable width, I think there are 6 pieces total, final width will be 40". Range is between 5-11" wide. I was planning on doing it all in one glue-up, with the assistance of the cauls. But maybe I should do it in 2.


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## TravisN (Jan 15, 2019)

> What I had to do for this top made out of 1/4 sawn White Ash…..along with rub joints as I built the panel….end cauls outboard of the clamps. Middle caul is centered in the panel
> 
> - bandit571


What size was that panel bandit?
Way to use those F-clamps!


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## HokieKen (Apr 14, 2015)

If you have 6 pieces, I would glue up 3 and 3 then glue them together. Actually, if it were me, I'd do 2+2+2 then glue two of those together then the final glue up. In other words, unless absolutely necessary, I don't like to glue more than two pieces together at a time. If you're doing all 6 at once though, I would absolutely use cauls. Probably no more than 18" or so apart.


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## splintergroup (Jan 20, 2015)

I agree with the 2-step glue up, just makes things less stressful.

As to the cauls, I always apply glue to the edges, place the side clamps and after sliding things around to get a preliminary alignment, I'll *slightly* snug up the clamps to close the gaps. The cauls get laid on (protected on the table top edge with packing tape) and snugged firmly down. Then tighten the side clamps like torquing a cylinder head (do them all in stages, center out). The side clamps will overcome any resistance caused by the cauls.
As to a number of cauls, three minimum (ends and center).

Be sure to alternate the bars of your side clamps top/bottom. As you tighten a bar clamp, the forces will cause the bar to bow, which gets transferred to the top. The cauls will help minimize this, but alternating the clamps is good practice.


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## Dwain (Nov 1, 2007)

Funny! I just completed a new tabletop a couple of months back. It was a smaller kitchen table, 63" long and 45" wide. I built it using five boards. As has been suggested above, I did the following

1) I glued up two smaller glue ups then glued them together. SO MUCH EASIER, even though I had three boards in one glue up. Gluing up all your boards at once can be a stressful job, and this will help to mitigate that.

2) I used three cauls for each glue up, but I would have liked to use four. I applied the cauls and tightened them only enough to close the gaps, then I applied the standard clamps. Once they were applied I put every clamp to final pressure at the end.

3) I used a combination of belt sander to start, then a Stanley #7 jointer plane for any final flattening. I think an ROS would take quite a while, and a belt sander is a rough tool at best. It was nice to have the control of the #7 to finish the table. I know I'm crazy, but I think the #7 is my favorite plane and suggest it to anyone thinking about buying a plane as their first or second purchase

4) I gave the glue ups a SOLID 24 hours or more to cook. Oh, and i use wax paper to protect against errant glue. Dollar store is right across the street, so it's cheap for me. Packing tape works really well also. For my cauls, I just waxed them with Johnson's paste wax before clamping and everything came out suprisingly well…

Good luck!


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## TravisN (Jan 15, 2019)

Great advice folks, thanks.

I'll probably do the glue-up in stages and use at least 4 cauls.


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## TravisN (Jan 15, 2019)

> Funny! I just completed a new tabletop a couple of months back. It was a smaller kitchen table, 63" long and 45" wide. I built it using five boards. As has been suggested above, I did the following
> 
> ...
> 3) I used a combination of belt sander to start, then a Stanley #7 jointer plane for any final flattening. I think an ROS would take quite a while, and a belt sander is a rough tool at best. It was nice to have the control of the #7 to finish the table. I know I m crazy, but I think the #7 is my favorite plane and suggest it to anyone thinking about buying a plane as their first or second purchase
> ...


Yeah, I'm not looking forward to the final flattening with the ROS! I'm not skilled enough with a belt sander or a hand plane, and this is not the project for me to practice on


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## bandit571 (Jan 20, 2011)

Panel is 3/4" x 22" x 39"...as I allowed a little extra for trimming for square.


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## TravisN (Jan 15, 2019)

> Panel is 3/4" x 22" x 39"...as I allowed a little extra for trimming for square.
> 
> - bandit571


Very cool!


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## RichT (Oct 14, 2016)

> Yeah, I m not looking forward to the final flattening with the ROS! I m not skilled enough with a belt sander or a hand plane, and this is not the project for me to practice on
> 
> - Travis


A 4" x 24" belt sander is much easier to manage than a 3×21. The platen is almost twice the area and makes it far more stable. Add a shoe and it becomes a piece of cake to handle. Zero problems with keeping it level. You can adjust the depth as well. Another good choice for flattening a large area is a 1/2 sheet orbital sander.


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## CWWoodworking (Nov 28, 2017)

I guess I'm the odd man out.

I would do one glue up. If I had to hand sand after, maybe my opinion would change.

Have you looked into a cabinet shop sanding it flat for you? Would save you a lot of sanding.

I'd sand your 2 halves for a cup of coffee and a fritter if you were close. Other shops might be slightly more.


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## LeeRoyMan (Feb 23, 2019)

> I guess I'm the odd man out.
> 
> - CWWoodworking


Your not the odd man out.
If I were doing it myself, 
I would use biscuits, no cauls, clamp them all at once,
Then run it through my wide belt.


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## TravisN (Jan 15, 2019)

> A 4" x 24" belt sander is much easier to manage than a 3×21. The platen is almost twice the area and makes it far more stable. Add a shoe and it becomes a piece of cake to handle. Zero problems with keeping it level. You can adjust the depth as well. Another good choice for flattening a large area is a 1/2 sheet orbital sander.
> 
> - Rich


Thanks for the tip, I'll keep my eye out for one. That certainly looks easier!



> Have you looked into a cabinet shop sanding it flat for you? Would save you a lot of sanding.
> 
> I'd sand your 2 halves for a cup of coffee and a fritter if you were close. Other shops might be slightly more.
> 
> - CWWoodworking





> If I were doing it myself,
> I would use biscuits, no cauls, clamp them all at once,
> Then run it through my wide belt.
> 
> - LeeRoyMan


My local supplier offers use of their wide belt sander (for a fair bit more than coffee and fritter), but they cap out at 36", whereas this will be 40" wide, so I'd have to do the two halves separately, then still hand sand the final piece. Which also means transporting my two halves 30 miles each way in my minivan…. All things considered, I'm not sure it would be *that* much of an improvement. Who knows, perhaps after I see the results of my glue-up I'll decide they definitely need the wide belt….


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## CWWoodworking (Nov 28, 2017)

Ok with knowing that, glue the whole thing up and then cut it in half. Take it to them for sanding then glue it back together. I did this with a 45" square top and it worked perfect.


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## Unknowncraftsman (Jun 23, 2013)

Travis have you got it glued up yet don't wait too long or you might end up with a mess. 








I glue my panels right after the final pass through the planer and jointer.
Good Luck let us know how it goes


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## TravisN (Jan 15, 2019)

> Ok with knowing that, glue the whole thing up and then cut it in half. Take it to them for sanding then glue it back together. I did this with a 45" square top and it worked perfect.
> 
> - CWWoodworking


That's an interesting idea, thanks!


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## TravisN (Jan 15, 2019)

> Travis have you got it glued up yet don't wait too long or you might end up with a mess.
> 
> 
> 
> ...


Lol, yikes!
I know, I feel like my wood is a ticking time bomb right now. Besides movement from the initial dimensioning, Phoenix is also about to start our monsoon season, where we can get a sudden influx of humidity. I'm racing to get this glued up and inside as fast as possible. Unfortunately, I have a day job and young kids, so I only get an hour or two in the evenings during the week, plus the weekend. Everything takes me longer since I am getting creative to make do with limited equipment (e.g., using a planer sled to face joint, hand-held router and straight edge for edge-jointing, etc.). Last night I made the reference edge with the router, tonight I ripped a clean edge on the other side so I can begin to play with layout, determine final width for each board, then I can do my final dimensioning. And hopefully glue up right after. I'm trying to get all my prep work done this week so I can spend the weekend on the glue up.


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## CaptainKlutz (Apr 23, 2014)

Oh Travis:
Wood working part time anywhere in world can be very challenging due changes in temp and RH.

Been working wood part time in AZ for over 2 decades now. We have 30°+ changes in temp everyday (37° today), and RH swings from single digits in mid-day to over 35% at night. The RH goes even higher at night when low pressure cell pushes through area. And like you said, monsoon weather makes the place a sauna like summer weather in Florida. 
Will say this much: monsoon season can be benefit as much as problem? If you build drawers with wood slides in July/August; the lumber will be at it's largest size. When winter comes and wood dries out, everything slides perfect with no sticking.  Can have opposite problem with stuff made in dry April/May when monsoon season hits. :-(

Point is: Your wood IS going to move. Have to work around it, especially if your shop doesn't have HVAC.

Here is how I deal with it:

For large panels, or table tops, it is very hard to prep all wood over the course of couple weeks, and then glue it one Saturday; hoping it all stayed flat. Don't do it.
It is much better plan to edge a couple boards, and glue them up the SAME DAY, while you know they are flat and straight during same environmental conditions.

ONLY If you wood has been in shop for several weeks, and has been stored in AZ for several months to reach the less than 4% moisture levels that are common; are you sometimes able to prep wood over a longer time, but it takes patience and practice to let wood tell you (by how much is moves after 24-36 hours).

Yes, Working this way does require a different work flow.

First: Adjust your lumber size in small amounts and let it rest in shop properly supported. Once a face is cut and exposed to air, it loses more moisture than it could before being exposed and it might move. Might not? Reducing the size of your lumber into project parts via small bites is safest way to minimize the movement, and to adjust for any movement you find. With luck and dry lumber, the final size adjustment will have zero movement.

Second: Since the glued up panel sections might/will move after glue up, you do not want to plane it to final thickness at start. Leave each board full thickness, with just enough removed to make it flat. Only after building all the individual panels, giving them ample time to dry, and making the new panel flat again: do you thin the individual panels down on your planer.
I try to be safe: I prefer to leave the glued up panel 1/16-1/8" thicker than final thickness, so I have material to remove after glue up to make it perfectly flat. 

PS - Where in AZ have you checked for width of wide belt sanders to support your work? One of the places in town as a 42" belt sander, as I ran a 39.5" wide top through it a few years ago. Sorry, can't remember if it was Wood Worker's Source, or Timber? Having a brain fart ATM.

Best Luck.


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## rwe2156 (May 7, 2014)

Let us know how you make out with the jointing. I've never had much luck aside from using a power jointer or jointer plane.

If you plan on running the top through the planer or using a hand plane, be sure you've got the grain direction of each board going the same way.


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## TravisN (Jan 15, 2019)

> Oh Travis:
> Wood working part time anywhere in world can be very challenging due changes in temp and RH.
> 
> Been working wood part time in AZ for over 2 decades now. We have 30°+ changes in temp everyday (37° today), and RH swings from single digits in mid-day to over 35% at night. The RH goes even higher at night when low pressure cell pushes through area. And like you said, monsoon weather makes the place a sauna like summer weather in Florida.
> ...


Oh dear CaptainKlutz, that is discouraging! I appreciate the helpful advice, though.

Fortunately, this project wood has been in my garage for about 1 year, so I'm assuming it has dried and equalized by now. That said, I did just plane all the boards flat, which took off about 1/4", so they may be inclined to move again.

WWS is the place I know has the 36" belt sander. I haven't checked anywhere else. I'll look at Timber. A quick look on their website doesn't mention milling services and they are only open during regular business hours (M-F), which is exactly when I work . I'll keep looking. It sounds like you would recommend just getting everything flat and square, glued up, and then belt sanding to final thickness?


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## TravisN (Jan 15, 2019)

OK, sorry to revive this thread, but help me work through one more thing….

If I am going to do what others recommend-glue up in stages (stage 1: 2 halves, stage 2: join 2 halves), run the 2 halves through a wide belt sander before doing the stage 2 glue-up-then I should not mill my boards to final thickness before the stage 1 glue-up, right?

That means my pieces won't be uniformly thick when I do my initial glue up. In this case, does it still make sense to use cauls for the stage 1 glue up? I'm trying to imagine how cauls will work if pieces aren't the same thickness. Will it still help alignment? If some pieces are a little thinner than others, presumably they might not have contact with the cauls, and therefore can't be pressed "flat." Is my line of thinking correct?


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## HokieKen (Apr 14, 2015)

If it were me, I'd still mill all my boards to the same thickness prior to starting glue up Travis. Just makes it easier IMO. Leave some allowance for final thicknessing but I'd plane them all to uniform thickness personally.


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## TravisN (Jan 15, 2019)

Thanks Kenny! I agree it would be easier if they were all the same thickness. I'm just worried about losing more if I bring everything down to my thinnest piece and then run through the wide belt sander again. It's also hard for me to imagine how I would get a flattish glue-up if the pieces are not all the same thickness….. Catch-22.


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## shampeon (Jun 3, 2012)

The flatter and more uniform you make it now, the less work you're going to have to do later. If I know I'm going to have to remove 1/4" from my thickest board, I'd much rather run it through a surface planer before glue up than bring it down to the level of another board later after it's glued.

While it's true you don't absolutely need cauls, if you aren't super experienced with milling the pieces square and clamping and aligning them evenly, I'd use them to ensure the panel is as flat as you can get it.

It's a little bit like golf. If you insist on playing like a pro when you're not, you're going to be hitting from the weeds all the time and not learning how to actually play golf on the fairway. Make things as easy as possible so you have some success doing things the right way, instead of hacking your way through it.


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## TravisN (Jan 15, 2019)

> The flatter and more uniform you make it now, the less work you re going to have to do later. If I know I m going to have to remove 1/4" from my thickest board, I d much rather run it through a surface planer before glue up than bring it down to the level of another board later after it s glued.
> - shampeon


I think I misinterpreted previous advice about leaving extra thickness for subsequent planing as "just get everything flat, don't worry about uniform thickness." What I think I will do is plane the boards in each half to a consistent thickness for that half, and then let the wide belt sander get the two halves to match. That seems like an appropriate compromise between preserving thickness during the intermediate stages as well as facilitating a successful glue up.


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## farmfromkansas (Jun 16, 2019)

Kind of late to the party here, but I use cauls all the time, and since doing so, my panels are much flatter than prior to. I use cauls in pairs, buy 2×4 fir, they are very strong, but for a big table, would be tempted to make some from oak for strength. I also wrap packing tape all the way around on the edges, so the glue does not attach the caul to your table top. lay out your pieces, put a bar clamp in the center to make sure you have no gaps what so ever. Then lay your cauls about 12" oc, one a little in from each edge, then lay your boards out on the cauls, apply glue to the edges then set another caul stacked on top of each lower one, put your clamps on the cauls, not completely tight but snug, apply your bar clamps, and if you can't pull the panel up tight, loosen your caul clamps a bit, then after the boards are pulled up tight, tighten up the caul clamps. If you have an offset end, use a C clamp to even it up. I take a rubber hammer to bad joints to try to even them up, even with cauls they are not always perfect. Get as even as possible before you give up. Wait a few minutes and use a putty knife to scrape off excess glue. If you have your boards even and get a good glue up, you can probably just sand with a ROS. I hardly ever need a belt sander since using cauls.


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## TravisN (Jan 15, 2019)

> Kind of late to the party here, but I use cauls all the time, and since doing so, my panels are much flatter than prior to. I use cauls in pairs, buy 2×4 fir, they are very strong, but for a big table, would be tempted to make some from oak for strength. I also wrap packing tape all the way around on the edges, so the glue does not attach the caul to your table top. lay out your pieces, put a bar clamp in the center to make sure you have no gaps what so ever. Then lay your cauls about 12" oc, one a little in from each edge, then lay your boards out on the cauls, apply glue to the edges then set another caul stacked on top of each lower one, put your clamps on the cauls, not completely tight but snug, apply your bar clamps, and if you can t pull the panel up tight, loosen your caul clamps a bit, then after the boards are pulled up tight, tighten up the caul clamps. If you have an offset end, use a C clamp to even it up. I take a rubber hammer to bad joints to try to even them up, even with cauls they are not always perfect. Get as even as possible before you give up. Wait a few minutes and use a putty knife to scrape off excess glue. If you have your boards even and get a good glue up, you can probably just sand with a ROS. I hardly ever need a belt sander since using cauls.
> 
> - farmfromkansas


Thanks for the synopsis. I did the glue-up in stages and used cauls about as you described. I made my cauls out of fir and they worked pretty good. I think my construction left a little to be desired but it was certainly better than gluing without them. I didn't need the wide belt sander, but I did have much better results using a hand-held belt sander than the ROS to even out my seams. I got little peaks and valleys with the ROS-invisible to the eye but easily felt. A few passes with the belt sander and it felt flat again.


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## farmfromkansas (Jun 16, 2019)

My ROS works a lot better since getting a new Bosch, with vibration control. Now I can sand one handed.


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