Seeking Cutting Board Glue up Jig Ideas

[Richiep]

I've been building end grain cutting boards for about three months now and I'm still on the learning curve.  I built a simple glue up jig using some MDF and some surfaced 2x3 pine boards, I'm using White Oak for the culls. I then clamp the workpiece into the jig using pipe and bar clamps.  I've had some good success with this but it has it's problems. One of which is "cupping" or "crowining" or "arching" of the glue up; i don't know what the term is, I prefer crowning.  

My process is, I'll make a long face grain glue up about an inch thick and cut that up into 2 inch strips.  I'll take those strips glue them up and slap on the clamps and culls and let it set up.  This gives a really tight and flat glue up.  But I still get crowning.

I've come to learn that I need to put the majority of the pressure in the center of the board, which is typically about 12 inches wide.  But even when I crank down the center the edges still need a little clamping to close the gaps.  When I do this the it introduces the crown.  Sorry I don't have good pictures of this because as soon as I discover it I cut it off and try to correct for it.  

I'm on my sixth brick pattern board right now and each one is a little better than the last but the crown persists.  Here's a few things I've tried.

• Glued up the board in several smaller glue ups, about 4 inches deep.  I still get a crown using this method but I trim it off on the table saw before gluing it to the next piece.  This works pretty good but it's not ideal, very time consuming.
• On my current glue up I made it a half an inch wider than normal.  If there are gaps on the edges, which is where they typically are, I'll trim them away later.  

So I'm looking to make my second glue up jig and I'm looking for suggestions from you all.  I've seen some stuff online where jigs are set up using T-Nuts and screws in lieu of clamps.  I like this idea and already have the hardware to set this up but I wanted to reach out and see what glue up jigs are working for you guys,  

Thanks for reading.  Any and all advice is appreciated!

Rich

[pkinneb]

Great looking boards. I would think having all your clamps on one side is going to introduce a cup to that side. Typically you want to alternate one clamp on top one on bottom etc

[gee-dub]

First off, nice boards ;-)

Clamp alternating is what I do as well.  Also, setting proper expectations is always good.  You are going to end up with some surface work no matter how many cauls you throw at it.  I use bowed cauls and this may help with pressure distribution but, does not assure a flat plane.  I plan on at least a couple of passes through the drum sander even on my best glue-up results.

[Richiep]

Thanks Gee!

The "crowning" I'm talking about is related to the pressure of the clamps.  Here's a shot of a board that I trimmed and added a patch piece at the end to address the "crown".  It's not the best picture but notice the edge of the Maple strip is 1/8 of an inch lower than the center of the board.  It would have been nice to have a clear adhesive instead of Titebond III for this "fix".

 

[gee-dub]

Ah . . . compression.  So the clamps are actually distorting the strips?

[Richiep]

5 minutes ago, gee-dub said:

Ah . . . compression.  So the clamps are actually distorting the strips?

Right. So I've been able to address this by cranking down the center much harder than the sides but the sides still need a little bit of pressure to close the gaps and the crown presents itself.

I've thought about getting a thick piece of steel to put between the clamps and the piece; I currently use a thick piece of White Oak. 

 

[Unknown craftsman]

Why so much pressure ? to close up gaps? If that's the case you need to head in the other direction 

[wtnhighlander]

Check out the clamping method this guy uses. Simple and straightforward.

 

https://www.youtube.com/user/mtmwood

[Coop]

Dang, when I first read this, I thought the flat top of the board was bowing where cauls would help. So you're actually squashing/compressing the end boards where the clamps touch? I agree with @Unknown craftsman, way too much clamping pressure. I didn't know you could crank a clamp down that much. You're not making dry ice from liquid CO2!

[treeslayer]

+1 to @K Cooper, if you have to use that much clamp pressure you have a problem at the table saw not cutting the strips correctly (all not the same width front to back) nothing should have that much clamp pressure.

[wdwerker]

I dress all my stock with the drum sander before glueup so it's flat and smooth. Discard any bowed or twisted pieces or cut them into shorter pieces. Then I dress all the strips I rip after the first glue up before the second glue up. The fussier you are about uniform straight smooth parts the better the results will be and the easier the glue up should be.

[gee-dub]

Just a +1 at wdwerker and others comments on stock prep.  Clamping end grain cutting boards is like clamping a bunch of straws standing on end.  The material in this orientation is easily crushed.  Discard or remake any parts that don't fit together correctly without the clamps.  This will let you lower your clamping pressure and eliminate the distortions.

[Marmotjr]

While it's definitely not necessary, consider using all the same type of clamp.  I see you have a selection of different clamps.  If you're on a budget, just fill out your clamp rack with those blue HF clamps, like the one you have there.  That way you can feel the pressure better and more evenly.  Those HF aren't the easiest to crank down, but a couple of those pipe clamps look like they crush a diamond if you wanted to.  If you are having difficulty knowing how much pressure you've applied with different styles of clamps, then maybe you need to get similar ones, and those HF ones will be very hard pressed to over tighten anything.   I use 4 of them, alternating top and bottom for my cutting boards, with calls/culls (which is it?) as needed. 

But with proper stock prep, you shouldn't need lots of pressure, as mentioned. 

[Ronn W]

1) I agree that too much clamping pressure will tend to cause bowing. 

2)  Your gluing surfaces (opposite idea of each piece) need to be exactly parallel to each other to get a flat gue-up.

3)  And I think this could be your problem ------ I assume that the bowing is upward in your second pic.  I notice that the bolts for the cauls are outside of the ends of the cauls.  By ends I mean the surface that bears on the cutting board.  When you tighten those bolts, you create "prying" action on the caul.  The cantilevered end of the caul at the bolt is pulled down by the nut and the center fo the caul will tend to raise up.  This will tend to bow the caul and allow the cutting board to to match.  I think you need to re-design how you clamp your cauls.

One more thing,  I don't see cauls under the cutting board in your pick.  I usually have top and bottom cauls - unless you are using the table as a caul.  I clamp the cauls to each other and the pressrue points of the caul clamps are within the boundaries of the cutting board.

[RichardA]

4 hours ago, Marmotjr said:

While it's definitely not necessary, consider using all the same type of clamp.  I see you have a selection of different clamps.  If you're on a budget, just fill out your clamp rack with those blue HF clamps, like the one you have there.  That way you can feel the pressure better and more evenly.  Those HF aren't the easiest to crank down, but a couple of those pipe clamps look like they crush a diamond if you wanted to.  If you are having difficulty knowing how much pressure you've applied with different styles of clamps, then maybe you need to get similar ones, and those HF ones will be very hard pressed to over tighten anything.   I use 4 of them, alternating top and bottom for my cutting boards, with calls/culls (which is it?) as needed. 

But with proper stock prep, you shouldn't need lots of pressure, as mentioned. 

Caul's.

[Marmotjr]

18 hours ago, RichardA said:

Caul's.

Yeah! That's the ticket!  It wasn't sitting right with me.  Thanks!

[SCPDX]

I was having a similar problem - turns out the resawn strips were not 100% square.  Very slight variance adds up and is compounded over the number of strips.  Looks like you have over 30 strips in your second glue up. .01" variance over 30 pcs is over a 1/4" that then has to be closed up with pressure and results in the distortion.  I started drum sanding the strips to insure all were flat and square.

On another note - what sort of jig do you use to route out the juice groove?  Looking for ideas and it looks like you method works well.

 

[CharleyL]

Be careful. You may be applying too much pressure and squeezing almost all of the glue out of the joints. My experience says you don't need anywhere near that much pressure if the edges being glued are straight to begin with. They need a few thousandths between them for the glue to hold properly. Too much pressure and the glue line is too thin to have any strength. Maybe you should be doing some experimenting to see if a little less pressure is plenty and you won't have the bowing problems that you are having. A good straight joint needs clamping to keep it from moving while the glue is setting. Too much pressure is not a good thing.

Charley