[Bill74]

I am building a 40" x 7'0 x 1-3/4" walnut farm table. The boards are already surfaced. I will be gluing up two boards at a time, then glue the pieces together. My issue is with keeping the tops aligned to minimize hand planing.

I recently built a workbench out of 2X6 on edge using the same method. I used biscuits to keep the pieces aligned but still had considerable planing to flatten the top.

I am thinking about getting a good doweling jig to keep everything better aligned. Any thoughts? Also I could get a Festool domino tool if necessary but would prefer to avoid that cost.


Thanks

 

[bilyo]

One method that I usually use is battens clamped together with the top sandwiched in between. Use hardwood about 3/4" to 1" thick and 1-1/2" wide for half of them and 2" wide for the others. Cut them to length about equal to the width of your table. On the narrow half of them, cut a curve on one edge so that they are about 1/4" less in width at the ends than they are in the center. Once your panels are glued, place them together on the straight set of battens. Then lay the curved set on top directly opposite the straight ones. You will likely need a pair of battens spaced every foot to 18". Clamp the ends together until the bow is taken out of the curved ones. this should apply fairly even pressure across the width of the top pushing all of the edges to alignment. Now, put your pipe clamps or bar clamps across the width to pull the table edges together. Use waxed paper or clear packing tape under the battens to keep from gluing them to the table top.

 

[calabrese55]

There are several ways to handle this.
A simple method is to use a spline like a tongue and groove . Your top is 1 3/4 thich so a 3/8 or even 1/2 inch thick spline could work.Dowels are great but you have to have enough clamps, (in any method) and you should alternate the clamps top and bottom will help prevent cupping the assemply. It is a good idea to duild it in sections as you stated . Managing several boards / joints can be a problem especially if you are sparce on clamps or your clamps are not raek sturdy. Be sure to add some packing tape or blue tape or even wax paper under your clamp bars to prevent glue stain fromthe clamps especially if you are using pipe clamps.
If you use dowels be sure to cut a saw kerf in at least two places alond the dowel stoch to give the glue a way to exit the dowel hole othewise you may hydrolically lock the dowel going in and split the wood. Some commercial dowels are kind of splined all around see picture attached . These work great as the offer several advantages to working successfully in the glue up and automatically allow glue to escape and mechanically let the dowell conform some for a little misalignment..Additionally the ends are chamfered and that feature is important. There are all kinds of doweling jigs here is one example that works very well and will not bend your check book.
have all your clamps set to fit the width of the glue up plus some extra so you dont have to fiddle with fitting them to size whail the glue setting up decides to make your assembly more difficult.
BE SURE to use some culs on the edge of the board that will become your next join up surface or the clamps will possibly leave dents if you have to strong arm the clamps.
It is a little nerve testing to do this overall just plan and set up first and kind of dry run the process.
Lastly Festools are nice if you want to show off. They are great tools but for the $$ you can buy a bunch of other tools to support your work for the price of one fancy tool.
Good luck
calabrese55

 

[JackDuren]

Use wood cauls…

 

[MFled]

Before spending money on new tools, I'd try to figure out why things aren't in alignment. No matter what system you use, if your underlying techniques aren't sound dominos or dowels aren't going to solve the issue. I've made doors and table tops with biscuits and not had alignment issues. Did you dry fit everything to make sure the mating faces are meeting 100% parallel to each other? One face off slightly from 90 degrees could cause misalignment. I like to dry fit things and then mark the pieces so I know that there is full contact between the faces without needing a lot of clamps to pull everything together and the marks help me make sure the faces that I confirmed fitting correctly are the faces that will get glued together.

I agree with using cauls to help keep things flat and in alignment. Clamping pressure can skew things, especially if your clamps don't have parallel faces, cauls will help overcome the shortcomings of your clamps. There are clamps out there that exert force in both the vertical and parallel direction, but I think just some cauls like what Jack has posted are going to be a lot less expensive than anything else especially a Festool machine!

 

[redlee]

Glue is slippery, you need something to keep things flat.
Good advice already given.