Basic tabletop milling question

[Ken Cohen]

Hi-

A rookie question. My first tabletop.

I'm milling stock for a 28x70 trestle desk top. I was lucky enough to find wide boards that exceed my 8" jointer capacity. I built the FWW planer sled and did my best to flatten each board. I started with generous 4/4 (1 1/8) and am hoping to end at 7/8 or better.

The reality: one dead flat board and two boards slightly bowed lengthwise (1/16+ gap in center of 75" board). Thinnest board just under 1" with several light passes still required.

Before I return to milling (and making a mess of things), a couple of questions:

1. Is the 1/16 gap worth worrying about? Will it evaporate into the noise after glue-up, sanding and mounting? (my guess is that it's a problem)

2. What's the best way to achieve dead flat from here? Stay with planer sled? Bring out the old planes? Other
techniques?

Thanks in advance for the advice. I appreciate how this group finds a way to help beginners like myself.

Ken

[Matt Day]

I used a more basic planer sled at one time and it worked okay, but was finicky I thought. I'm never doing that again after I did this the first time:

What I do now is remove the blade guard on my 8" jointer and joint 8" worth of the board. The remainder of the board (for instance on a 11" board I did the other day I had 3" of un-jointed wood) will be full thickness but there's a nice lip where the freshly jointed wood meets up with the full thickness. Using a piece of baltic birch ply (about 8" wide), put the jointed 8" of wood on top of the ply and put it through the planer to give you one full width flat surface parallel to the 8". Screw a stop at the front of the plywood so the planer pushes the hardwood against the stop and pulls the whoe thing through. Flip it over sans plywood, and plane off the thin strip and you're done.

Some might be worried about the lack of blade guard, but the entire cutter head is covered just be careful at the start and end of the board.

[david brum]

I personally wouldn't worry about 1/16" over 70". Even if you could mill your stock perfectly flat, it could easily be out by that much by the next morning anyway. I would clamp it up then use cauls and smaller clamps to flex the boards so they are on the same plane. If this is your first big glue up (or any time) it is a good idea to dry clamp everything to make sure you have the clamps ready, and that you'll get the results you want. If you do a dry run, you can find any problems without the stress of trying to move pieces which area covered with glue and want to stick together.

After the glue dries, you'll invariably have to flatten the table top anyway. The better you align the boards, the less work you'll have to do, but there is always some flattening. You can do the work with sanders or hand planes, whichever you've got.

[Chuck Wintle]

I would have ripped the boards so they fit on your 8 inch jointer. wide boards can be less stable over time and I was told once by an old timer never to use boards wider than 4 inches for a table top. The grain should alternate up and down from one board to the next.

[John Lanciani]

I would have ripped the boards so they fit on your 8 inch jointer. wide boards can be less stable over time and I was told once by an old timer never to use boards wider than 4 inches for a table top. The grain should alternate up and down from one board to the next.


This advice has been around for ever and I cringe every time I hear it. My shop teacher used to preach it like it was the gospel. The fact of the matter though is that it is not neccesary at all.

One of my staples is making tavern tables with three-board tops. All of the boards are wider than 12" and I always orient them heart side up. My own table is 15 years old and it is as flat as the day I made it, and none of my customer pieces are any different. The three keys to success are; careful stock prep and joinery, proven design, and patience when selecting and preparing the stock. It often takes me 6 weeks to flatten wide boards so that they stay flat, taking a little off at a time and then putting the boards away to relax and adjust. It is a pain sometimes but the results are worth it and my clients are thrilled ($$).

John

[Chuck Wintle]

This advice has been around for ever and I cringe every time I hear it. My shop teacher used to preach it like it was the gospel. The fact of the matter though is that it is not neccesary at all.

One of my staples is making tavern tables with three-board tops. All of the boards are wider than 12" and I always orient them heart side up. My own table is 15 years old and it is as flat as the day I made it, and none of my customer pieces are any different. The three keys to success are; careful stock prep and joinery, proven design, and patience when selecting and preparing the stock. It often takes me 6 weeks to flatten wide boards so that they stay flat, taking a little off at a time and then putting the boards away to relax and adjust. It is a pain sometimes but the results are worth it and my clients are thrilled ($$).

John

Do you need to make relief cuts on the underside to counteract the tendency of the boards to cup?

[Peter Quinn]

The critical Part of a table top glue up is the edge joint. Stock will bend to conform over 70"' and frankly if that's maple you are working with it's about as stable as a barrel of drunken monkeys anyway, so flatness is both relative and temporary at best. Get the faces cleaned up, get the mating edges well joined, use good cauls across the grain and glue it up. As long as all the thicknesses are the same it's not a problem IMO. Tops, like tables, counters, etc, need to be in one plane at the end of the day with no steps in thickness, but need only be flatish, not truly flat, except maybe a very thick bench top. Once you screw it to the tressel frame all will be well.

[John Lanciani]

Do you need to make relief cuts on the underside to counteract the tendency of the boards to cup?


No, I use breadboard ends and thick (1.25") aprons to keep the tops flat. Traditional tavern tables typically have fairly thin tops - 3/4" to 7/8" - and the overhangs on the sides are only 4" to 6" so they are relatively easy to keep under control.

Also, by orienting all of the boards heart-side up, the top has a natural tendancy to want to cup up in the center. This is much easier to deal with than the opposite. A strong attachment to the apron in the middle of the top keeps everything flat and slotted holes outboard allow movement. My personal table is red maple and is a full 1/2" wider in summer than winter.

[Ken Cohen]

Thanks to all for the great ideas.

My take-away (knowing that there are differing opinions)

1. Don't worry about the 1/16. It's within the margin of error.

2. Finish rough milling the board faces to equal thickness

3. Figure out board alignment for best aesthetics

4. Joint edges (using reverse direction through jointer to address any jointer angle error). Take a harder pass in the middle of the boards to help spring the joints.

5. Add biscuit holes to ease alignment (probably should dry fit before this step to make sure boards have enough spring to align against top reference surface)

6. Dry fit and confirm clamping strategy

7. Glue up

8. With a little luck, hope things are close -- then refine top with plane, etc.

One question from the posts: one recommendation was to align the boards heart side up. I'm actually working with curly maple which I believe wants heart side down alignment. Thoughts.

Thanks again to all. Welcome any additional thoughts.

Ken

[Chris Fournier]

I think that you've recieved some good and not so good advice here.

The tavern table builder John Lanciani gave the best bit of advice but it was very easy to gloss over. Read his post again and look at how long he gives the boards to aclimate and then remachine in multi-step process on his way to flat and stable. If you take the time to reduce your stock to finished dimensions in a careful and considered manner you can pretty much do anything you want with your stock. This being said a wonky piece of lumber will most likely remain wonky forever.

I would not worry about heart orientation scheme with the figured maple that you're using - figure and grain matching are most important in this case. Glue the table top up as it looks best.

Make sure that your trestle base can support and "gently" restrain your top as much as possible.

The 4" rule has it's merits if you are a factory builder of furniture buying the cheapest materials and pushing product out the door to meet quarterly sales projections. For guys like us I would never even consider this "rule" unless you want your handcrafted efforts to look like factory work.

Lastly, finish both sides of your top with the same product and process, this will help insure that moisture effects both faces similarly. Now direct sunlight...

[Frank Drew]

Lastly, finish both sides of your top with the same product and process, this will help insure that moisture effects both faces similarly. Now direct sunlight...

Important piece of advice from Chris; the underside doesn't have to be smoothed and sanded to the same degree as the top, but it does need to have as many finishing coats.

Chuck, what the heck, I'll pile on :D; your old timer was full of old beans! With only a few exceptions, narrow board glue-ups for a table top are totally factory looking, as noted, and that heartside up/heartside down orientation of the boards guarantees a stripey effect.

[Jay Allen]

And biscuits are of no use in this type of glue-up. They do not add any strength and all they really can do is cause a fight with alignment. Good clamping and maybe a few bumps of a dead-blow mallet are all that is needed.

Like the opthers said, align you boards for the best appearence. The only time I worry about which side is up is when book-matching