Workbench Top

[igor]

Yes, in spite of the subtlety that is granite, I think that photo does suggest the importance of being flat.

And, you do have a good eye. Maybe two.

[Jim]

I built the bench with the 3 layers of 3/4" MDF that woodsmith published a couple of years ago. I'm sure it isn't as nice as a maple bench, but it is dead flat and takes all the abuse I've thrown at it. I do refinish the top every year with a new coat of tung oil and some shellac. I even have put in holes for bench dogs and they have held up nicely.

I mostly build furniture and needed a large bench. A smaller bench wouln't be nearly as expensive to make out of maple, which would have a much larger "OOOO AHHHH" factor.

Jim [e-mail] (Malcolm Webb) wrote in news: [e-mail]:

[Prometheus]

Well, they're not free, but if you have a quarry nearby, sometimes they sell granite sheets with defects for a discount. But why not just glue up a thick hardwood top and plane it down periodically? I can't imagine that your benchtop flatness needs to be within .001" unless you're making jet engines out of maple or something. I made do with a bench made of 3/4" pine plywood and some 2"x4"s from the Borg for several years, and it worked all right for just about everything. I had to screw it to the wall to keep it from sliding around when doing certain things, but once that was done, it was just fine- and it's still flat, even after being moved a couple of times. Total cost was about $40. Aut inveniam viam aut faciam

[Charlie Self]

Prometheus responds:

On occasion, I'll go to a local cabinet shop. Most of them use mobile assembly benches that vary in height (18" to 24"), with space under for the odd tool. I've never seen a torsion box used there, nor a piece of granite. Tops are often plywood on the larger, MDF on the smaller and are reasonably flat. Some are even covered with carpet, a trick I like to use when assembling expensive woods or finished pieces. The flatter an assembly bench top is, the easier it is to keep everything square, but a lack of even .01 flatness is not going to cause a massive out-of-square condition for a careful woodworker. And a careless woodworker isn't going to get a square assembly no matter what he or she uses.

Charlie Self "Health nuts are going to feel stupid someday, lying in hospitals dying of nothing." Redd Foxx

[Unisaw A100]

OK, I'm with where you are but I can't help but to think a thing or two about all of this. Firstly, wooddorking ain't rocket science but one thing I do know is you ain't born knowing all the variables that come into play (1).

OK, stop scratching your head and wondering, "Is he about to go off on some ramble/when can I stop paying attention?". I'll get there.

Torsion boxes are a great thing but aren't absolutely necessary (2). I would start with a good and stout work surface first. Two layers (or for a couple few dollars more three layers) of MDF will make a fine surface to work from. To that I would build a good base beneath it. Four by fours and some aprons/rails going around or full blown cabinets (storage/adds more mass), what ever you want/need. In the end you are concerned about bowing/cupping/twisting you can shim from underneath/pull up/push down until the top is flat(ter). The point here is to have something that won't go rolling around the floor.

As for tolerances, I'm of the opinion that you take a string, pull it taut across the surface and get it trued up by eye. Anything after that is working in the hunnerts of an inch and not worth finding yourself puking up in the corner of your shop over.

Now, something to think hard on, to "successfully" build a torsion box you'll find that it's better/easier if you have a flat surface to start with/build the torsion box on. I'm not saying it can't be done without it, just that it will be harder/you'll be fiddling with it a whole bunch more.

I'm going to interject a thought here on box assembly.

*Normally* a box isn't too huge. We occasionally do a big item though really most projects aren't. When you assemble a box you will/should be checking the parts and pieces as they relate to each other, not to the assembly surface below. In other words, are the sides square to the bottom/top? You can have a gap big enough to drive a Buick through in the table below but that doesn't matter as long as you are squared up.

This is not to say it doesn't help/you shouldn't care, you really should, but...

Now, having said all of that, boxes flex/have some give during constriction. An example. You can put two sides together along with the tops and bottom and depending on the size of the box you can be out of square by a half an inch. It's probably not going to matter because you'll go to fit the back and pull it all to true during that phase of things.

Please do not think for a minute that I'm advocating bad construction/it'll be fixed in the end, just that this is one of the variables you will be thinking of during assembly.

There are two arguments on machine set up. One is that wood moves enough to make any sphincter puckering machine set up not worth the time and then there's the "I would prefer to remove as many variables as I can from the equation/it's my $150 and I bought a TS-Aligner JR so go piss off". I prefer the latter over the former though I can't tell you that all my processes are at zero, just that I'm as close to zero as I can get so I'm not off in the corner of the shop puking my guts up.

(1) Whole books have been written on the subject/a life's time could be spent studying it/I can't right off hand think of a better way to waste my spare time.

(2) Torsion boxes are best suited for spanning long unsupported lengths or when something needs to be light(er) weight. They are fun to make and in the end you'll find yourself showing them to anyone who will stop for three minutes to hear you go on about them.

UA100, who really is agreeing with you more than you might think but thinks that "dead flat" isn't anything to lose sleep over...

[Tom Watson]

(1.) "A man walked along contemplating suicide; at that very moment a slate (roof) tile fell and killed him...."'

Soren Kierkegaard.

(2.)"Current plate movement can be tracked directly by means of ground-based or space-based geodetic measurements; geodesy is the science of the size and shape of the Earth. Ground-based measurements are taken with conventional but very precise ground-surveying techniques, using laser-electronic instruments. However, because plate motions are global in scale, they are best measured by satellite-based methods. The late 1970s witnessed the rapid growth of space geodesy, a term applied to space-based techniques for taking precise, repeated measurements of carefully chosen points on the Earth's surface separated by hundreds to thousands of kilometers. The three most commonly used space-geodetic techniques -- very long baseline interferometry (VLBI), satellite laser ranging (SLR), and the Global Positioning System (GPS) -- are based on technologies developed for military and aerospace research, notably radio astronomy and satellite tracking."

"You can observe a lot just by watching."

Yogi Berra.

[Dennis Slabaugh, Hobbyist Wood]

Here is one last vote for the "Solid Core" door bench.

I picked up a couple of blemished gypsum core "solid" core doors 12 years ago. I built my "temporary" bench from the 48" wide door and it has served me well for all this time. The frame around the door is 2 x 4 under the edges and around the perimeter. The base is 4 x 4 southern pine, untreated done in a trestle configuration bolted together within the dadoes. It is heavy, it is flat and it is strong..... and yes it is pretty dinged up at this point in time. But, I will retain the base and replace the top perhaps with hardwood this time.

The other door I picked up, has been used across saw horses as a great take-down assembly table / workbench. While it is heavy to move on and off the horses, it stores against the wall until another day.

Dennis Slabaugh Hobbyist Woodworker

[jo4hn]

(4.) "Bark of tree look good to squirrel"

Roaring Chicken.

[igor]

[snip]

Agreed. And thanks. -- Igor

[igor]

and will forward to friends' kis of the age where a geo report is needed for school. Some gov't agencies do great stuff.

You can miss a lot just by watching.

Igor.

[Unisaw A100]

A nice thing about gyp board core doors (actually a fire rated door) is they are lighter than particle core doors.

Ua100