Flattening workbench

Robert Engel

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28
I have a bench from a piece of bowling alley lane that is relatively flat, but I would like to have it a little flatter. I've already hand planed it and used a belt sander the best I can, but my back can't handle it.

I'm looking for other ways to produce a flat bench without getting too crazy with it.

And I'd like some opinions on just how important is a perfectly flat bench top?
I already have a torsion box assembly table and it is really nice, but I don't anticipate using the bench for assemblies.


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Having the bench flat aids in all sorts of things. Your vise jaws are in plane, you don't pull things out of square when clamping to it and so forth. How flat is flat for a workbench? That question will get some different answers. My construction grade KD fir trim around my 4 layer MDF top contiued to shrink despite being kiln dried and setting for over 2 months, stickered in my shop. This actually squeezed the outer edge of the top and it now "drops" almost 1/16" at some places starting about 2" in from the edge. This really bugs me and I have to watch for it but the top is about 30" x 84" so I have lots of flat area. It does not bug me enough (yet) to build or re-size the top as a rebuild is more likely due to dog hole positions and so forth. I heave dealt with it for years but, will get that feeling you get when you finally get the splinter out when I go to a new top. YMMV.
 
Turns out the slab is a shallow tongue and grooved and nailed together. I recently built a proper base for it, but when installing the top I thought I detected a little flex. Then I remembered how it was put together.

In retrospect, I think maybe I should have taken it part, removed all the nails, and glued it back together (sure would have made drilling the dog holes easier!).

So looking for an easier way out, I'm thinking through bolts using threaded rods would stabilized the top.

But drilling a hole across 36" is a daunting task.
Is there a drill bit or extension that long? I thought I once saw bits that were up to 5 feet long maybe an electrician had one.

Any advice? The bench seems fine, but in thinking about flattening it, I know it has to be rock solid unit.


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I have an idea and suggestion, but first my get out of jail free card.....i am not a pro or super experienced woodworker, so take my idea for what its worth, nothing. I have just finished my second workbench if that means anything.

So i just built a double layer ply workbench top surrounded it by rock hard maple and put a 1/8 layer of mdf on top.

Then i had the dilemma of how to attach it to the frame i made for it.

I did not want to go too deep into the top and end up with some fastner either poking through or being beneath the surface.

So i used pocket hole screws and drilled through my frame supports into the bottom of the workbench top.

They pulled it up nice and snug to the frame i had made for it to sit on and the frame is supportive on 4 sides.

Now all that said why dont you look to brace it as a single surface from below through say cauls of a kind that would then be the bars you would use to attach it to whatever structure you going to mount it on.

Once you have that done the cauls strung and attached to the bottom would hold the whole top rigid and you could then deal with flattening it.

My approach with my other heavier and bigger workbench made up of 2x4 sandwhich face to face essentially giving me a 3.5 inch thick slab, which has since been whitlled away with a #7 handplane to probably less than 3" by now I made sure was as flat as i could get it with my #7 stanley. Took a bit of work but my thought was same as Glenns add to that the fact that I knew it was going to be my only reliable flat surface.

When it comes to the work effort involved in using a large plane i think its worth mentioning there is tremendous value in how you approach the task and the condition of the plane blade.

Set the edge of the blade up with a bit of a curve or use two planes. Maybe if you can get your hands on one a Jack plane. Then set the edge of the jack up with a large radius make it sharp and use it like a scrub plane to cross the top and get grooves going that are at least flat across. Then take the #7 again with a sharp sharp blade and with slight radius on the corners so you dont have it producing railway lines and work longways. Now you just knocking off the bumps the scrub plane effect left.

Its a bit of work but if the blades are sharp and you present yourself physically with the right approach to the bench and plane you will find you efficient in your application of force and then its a pleasure to do.

This would be far less complex that trying to drill through the slab and put a bolt all the way through to pull it flat when in essence that is really just compressing the various pieces together. Support from the bottom across gives them something to rest on.

Hope some of this at least makes some sense. Post pics of your problem it may make it easier to help with ideas. Good luck.
 
With a flat assembly table I wouldn't worry too much. Like Glenn's, mine is almost off by 1/16" (maybe 3/64", across the short dimension) but it doesn't seem to impact much, the important squaring work is done on the assembly. It is getting close to time to replace the assembly table though, 8 years of great service has it showing it's age.
 
With a flat assembly table I wouldn't worry too much. Like Glenn's, mine is almost off by 1/16" (maybe 3/64", across the short dimension) but it doesn't seem to impact much, the important squaring work is done on the assembly. It is getting close to time to replace the assembly table though, 8 years of great service has it showing it's age.

Oh but it is, for example, if you're face planing a piece of wood and have it dogged down, the board, especially if it's under 1/2"' will flex and not be planar and you end up with an unlevel board.

My plan (when I've got less to do) is to take the top apart, remove the nails (BIG problem when I drilled the dog holes) run each board thru the jointer, and either glue back together or use threaded rods across every 3'. Then re drill dogs holes (came out like crap on ones I hit nails).

Then I will make sure the base is planar, attach top, and level top using the router sled method.
 
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