Episode 18- Assembly Table Torsion Box

31 Responses to “Episode 18- Assembly Table Torsion Box”

1. Andy Hobbs on June 3rd, 2007 1:47 pm

   As always, awesome podcast!!! That assembly table looks to good to get dirty. Maybe it could be a rustic dinner table!!!

2. Randy Klein on June 3rd, 2007 6:10 pm

   Marc,

   I’ve always heard that interior doors are torsion box design with cardboard innards and about an 1/8th” skin on both sides.

   Do you think its possible to simply throw on the 1/2″ MDF (that is what you used for skins, right) on both sides of an interior door (or 2 interior doors ganged up) as a way to accelerate the assembly table build-up?

3. thewoodwhisperer on June 4th, 2007 10:10 pm

   Thanks Andy.

   Randy: I know many folks who have used doors for workbenches and assembly tables with great success. The issue here is whether or not the doors are dead flat. Most likely, they are not. But are they flat enough for most things? Perhaps. Do you have a really high quality and very long straight edge? If so, check the doors and try to find the flattest ones possible. Joining two doors together and keeping the whole assembly flat could get tricky too. So is it a perfect substitution? No. Will it get the job done? Yuppers.

4. Paul Comi on June 5th, 2007 12:59 am

   Nicely done. Ironically, my torsion box assembly table needs to be redone right now and I’m inclined to scale down from 4 x 6 to 4 x 4 to conserve shop space.

   Did you find 4 x 4 was too small for many projects?

5. Colby Hubler on June 5th, 2007 8:15 pm

   Marc - great podcast! I have been needing to build one of these and have been putting it off - especially since I heard you were working on one for Fine Woodworking. Quick question with respect to the torsion box: The plans call for 3/4″ skins on the top and bottom, yet in the podcast you say they are 1/2″. Does it matter? What do you suggest? By the way, thanks for the drawer sizing tips on the base - great ideas!

6. thewoodwhisperer on June 5th, 2007 8:18 pm

   Hey Colby. I looked over the drawings and I dont see where it calls for 3/4″ skins. I did use 1/2″ material, but you certainly could use 3/4″ if you wanted to. The main difference is the whole table would be even heavier than it already is. Please let me know where the misprint is and I will try to have it corrected.

7. Matt Berger on June 6th, 2007 4:40 am

   UPDATE: We corrected the downloadable plan on Tuesday afternoon after discovering that it called for 3/4-in. skins rather than the correct 1/2 in. skins. This mistake also affected the width of the hardwood trim. The new plan is available on the site.

   Mark: Maybe you can print a quick note about this correction for the people who downloaded the plan before the correction was made. Sorry for the inconvenience.

   Matt Berger
   Fine Woodworking

8. Paul on June 6th, 2007 4:54 pm

   Another awesome installation Marc!

   But.. Marc.. oh Marc… how could you let your dear old step dad stand there sucking up all that MDF dust while you wore a full respirator?? Poor poor step dad.. :-)

9. thewoodwhisperer on June 7th, 2007 12:43 am

   Paul Comi-

   I actually found the 4×6 to be fine for most projects. I went to 4×6 for two reason: because I could and because I usually have other crap on the table. I just needed more room to accomidate the crap and the projects. :) I think you will be satisfied with a 4×4 on most projects.

10. John Cooper on June 11th, 2007 9:16 pm

    Hi Marc,

    As a beginning amateur woodworker, I’m in deep-learn mode, and I feel so lucky to have found such a generous online teacher. You rock!

    I’m the guy with the incredible disappearing garage workshop :) All my tools stow in cabinets, and my workbench is my assembly table and it rolls into the corner at the end of the session. The laminated particle board top of my workbench was sagging in the middle. So I built your torsion box this weekend. Your excellent instructions and video gave me the confidence to try it! I shrunk the plan a bit to 24×48, 2 1/2″ inserts and 7 1/2″ internal box grid, 3/4″ MDF plus 1/4 hardboard top.

    I’ve got a few questions for you.

    1. I haven’t yet attached a bottom to the box - can I just use 1/4 hardboard to hold it all together, or do I really need the 1/2″ MDF for strength. Trying to slim it down a bit in weight and thickness!

    2. I don’t have all the tools I want yet- no brad nailer or hot glue, but I do have a nice freud 8″ dado set. So instead of cutting individual pieces inside the box, I made a 7.5″ box joint jig, and cut 1.25″ dados across full-length inserts so that it all fit together with just glue, no brads. Got the idea here.

    It worked pretty well, but I may have cut the dados a bit too tight, and while it worked ok in the dry fit- it was a bit tight during the glue-up, and i had some minor high spots. I planed as well as i could, but the final result was that the table turned out to be not quite dead flat. Could’ve also been less than perfect shimming, or the slightly bowed sheet of MDF didn’t want to settle, or just my inexperience. So my next question is, how flat is good enough? :) Using a long straightedge, it appears to drop about 1/32″ across the 24, and about 1/16″ across the 48 (or a bit more). I could conceivably pull out the screws and try your router-sled approach to flatten up the MDF? Might be an interesting effort. Or do you think I’d just screw it up worse?

    3. I’m thinking of trying some more skill-building here and miter the corners of the 4 hardwood sides, rather than butt-joining them. I haven’t been too successful in previous attempts with perfect mitered corners. Hard to get the lengths just right, etc. Any advice?

    4. Do you have any suggestions for how to mount a vice to the side of this 4″ top? I have a little wilton that sat flush with my old 2″ top but this new beast is twice as thick!

    Thanks again for all your great help!
    -John

11. thewoodwhisperer on June 11th, 2007 10:34 pm

    Hey John.

    Glad you are enjoying the podcasts!

    1- I do feel its necessary to go with at least 1/2″ material. I suppose you could use something thinner but I cant imagine the long term results being too good. Not to mention, if you ever clamp something to the table, you could easily punch through it. That would be a shame. :)

    2- That level of error doesnt sound too bad. Its a good idea to memorize the tables flaws, so that you can decide where to place things on the table. For things like chairs, you want to make sure the legs are perfect, so make sure you find a nice flat area, and keep it in mind in the future. So what Im saying is that the table doesnt need to be perfectly dead flat in all areas. But you should get to know the table so that you can predict for yourself how much that error will effect your work. And no I dont think it would be worth all the effort to do the router sled method.

    3- This is generally not the best project to test your skills in this area. The primary reason is that you might not have perfect right angles at your corners. The assembly table really isnt defendant on perfect corners so they might be a little off. If they are, your miters will cause you much headache. So maybe practice them on another project and go for the butt joints on this one. Of course this is just my advice so obviously feel free to do the miters, but dont blame yourself if they dont come out perfect.

    4- The only way I know of to get a vice on there is to make the table thinner or get a bigger vice. :) No tricks that I know of to get a small vice on a thick table.

    Good luck!

12. Tim on June 15th, 2007 12:28 pm

    I have to point out a possible design flaw in your top. The whole point was to make the top hard board replaceable right? The oak sides sit flush to the hard board and so since you glued those on and doweled over the screw holes, how do you get the hard board out to replace it? Also as you mention in a previous post that you don’t know whether or not the table top is 90 degree or not. Trying to fit a piece in later could cause some headaches. Is this correct or how did you plan on dealing with that?

    I do like the hard board top though I work with that material all the time at work but never would have considered it for a work surface. After seeing that idea I think you could take it to the extreme and get yourself a 3/16 phenolic sheet (I don’t think you could 1/8 because it would be to brittle). It is much like hard board except like about 10 times more dense. The stuff I used to work with had a nice melamine finish on it as well. Would probably would never need to replace the top than.

13. thewoodwhisperer on June 15th, 2007 1:28 pm

    Hey Tim. The hardboard top will not be difficult to remove. Its just sitting on top of the table so the removal can be done by simply prying it up. Now when it comes time to drop the new top in, that shouldnt be too difficult. Although I didnt go through any great efforts to ensure that the table was perfectly square, it is definitely in the ballpark. So cutting a new piece shouldn’t be too challenging of a task. Aside from that, and I dont know why I didnt think of this in my other post, you have an exact-fitting sample already in your hands. The old top is a perfect template for the new one. So either figure out a way to flush trim it, or simply trace around the perimeter with a pencil and cut with a jig saw or circular saw. Piece of cake. :)
    Your phenolic idea is a good one. Although there is no surface in my shop that lasts forever. After several years of glue, stain, and finish abuse, that top is gonna look like poo. So as far as Im concerned, the top is always sacrificial. And the cheapest material wins.

    Take care.

14. Tim on June 15th, 2007 3:54 pm

    LOL! Yea didn’t think about using the old one as template!

15. Mike on June 18th, 2007 10:44 am

    Hi Marc,

    First… Great Podcast.. I should say great podcasts, including Woodtalk online as well..

    So was wondering if using Resin impregnated honeycombs such as http://www.vacupress.com/accessories.htm#honeycomb

    Would these be suitable? Thinkin the 3/4″ and I’m asking this because yes I’m lazy!

16. thewoodwhisperer on June 19th, 2007 8:00 am

    Hey Mike. I suppose that could work. At only 3/4″, you cant make a very big table though. Interesting product.

    Marc

17. John on June 27th, 2007 8:23 pm

    Hi again Marc,

    I used #8 3/4″ brass wood screws to attach the hardboard to my 3/4″ MDF top.

    I’ve now learned just how bad MDF holds screws! In some places, the screw went in loose on the first try (won’t tighten to a stop- just starts turning in place). Bummer!

    Any suggestions?

    Thanks,
    John

18. thewoodwhisperer on June 27th, 2007 8:30 pm

    Hey John. I probably should have mentioned that in the video. As soon as the screws are below the surface, you should stop turning.

    The good thing is you really dont need much holding strength for the hardboard. Just something to hold it from flying away basically. :)

    So honestly, my suggestion would be to leave the stripped ones alone and just add a few more. When you replace the top, just yank those puppies out of there, fill the hole, and you will be good to go. But technically you could just throw the hardboard on and not worry about screws at all. I just like to screw mine down for extra security.

    Marc

19. Eric on July 17th, 2007 3:31 pm

    I just built the box. As an alternate method to a block plane to remove high spots, I used a T-bar sander. This is a trick model aircraft builders use to even out all of the ribs on a wing before covering to get a uniform surface. I made a 24″ T-bar by butt-joining two pieces of MDF with glue. Then used spray contact cement to affix some 100 grit sandpaper to the flat surface. Sand the surface with this bar diagonally to the grid. The T bar spans 3 grid boxes or more taking out the high spots first and further flattening the surface.

20. Mike Ward on December 12th, 2007 4:23 pm

    Yo Marc!

    THis must be a very popular podcast, because I can’t download it. Got #19 just fine, but the needle in the record groove seems to have worn it out. (showing my age here). So, any chance you could repost this one? Thanks, Mike Ward

21. Mike Kapotsy on January 1st, 2008 8:22 pm

    Marc,

    My wife and I loved your assembly table podcast so much that we decided to build one for my garage. I am an avid woodworker and although my garage/shop is not as big as yours, the assembly table will help me in many ways including extra storage, table top workspace for projects, and organization. I have purchased the material to build it and will get started this week.

    I did want to ask you where you bought the switch you used for the compressor. I have not been able to find that style switch.

    Thanks, Mike Kapotsy

    P.S. I have ordered the urethane bandsaw tires. Thanks for the link!

22. thewoodwhisperer on January 1st, 2008 8:30 pm

    I got mine from Rockler. Looks as if they only make this slightly cooler one now:

    http://www.rockler.com/product.....;sid=AFN86

    And you are very welcome. Thank YOU.

23. Mike Kapotsy on January 15th, 2008 10:06 am

    Marc,
    I finally got the grid built and glued up this weekend. It was quite a challenge to get the thing dead flat level. I had to use two packs of shims and I still had a sligh sag on one side. Turns out one of my 2X4’s had a slight bow in it even though I ran it through my jointer. I made the mistake of thinking I could then rip it on the table saw and all would be good. Trouble was my jointer is a benchtop delta jointer with a very short bed on it. I wish I had a powermatic jointer like yours! Anyhow, I managed to use a couple of shims to correct the problem and get it pretty darn close. When I wrapped the mdf on the grid and screwed the hardboard on the top, the finished product was dead flat level! I did not have as easy of a time with the oak boards on the outside. I tried your clamping technique and unfortunately I did not have as much luck. I was lazy and didn’t use the brad nails to hold the boards in place and as I drove the screws the board pushed out a bit away from the MDF sides. It still looks nice and the tops are flush with the hardboard. I will send you some before and after pics of my shop once I am done. All I have left is to apply the poly on the base and the table, run my hoses and cords and screw the top in place!

    Mike K.

24. Mike Kapotsy on January 16th, 2008 6:48 am

    Marc,

    I looked in my cabinet and all I have left over is some clear semi-gloss poly and no satin. The only other finishes I have available without buying some is a medium rubbed lacquer.

    Do you think the semi-gloss poly would be okay for this project?

    Thanks,
    Mike

25. thewoodwhisperer on January 16th, 2008 11:50 am

    Semi gloss is fine. You aren’t really building up a big film anyway, so it really doesn’t matter. You basically want to give the material what it will absorb and then remove the excess.
    You could simply use wax, or even nothing at all. That poly was just a little extra detail that makes the top a little easier to clean.

26. Mike Kapotsy on January 17th, 2008 6:12 am

    Marc,

    I bought 4 of the clamp it jigs from Rockler (used my own mini bessey clamps) and they worked great for framing up the torsion box. Thanks for that tip! Do you think the adjustable ones are worth the extra dough? Ever had a use for them?

    Mike K.

27. thewoodwhisperer on January 17th, 2008 9:53 am

    Hey Mike. Haven’t used them and never really had a need yet.

28. Joe on June 6th, 2008 6:06 am

    Marc,

    First, I love the show.

    I was trying to find a cut sheet to build the assembly table and have not been able to find one. Is there one and if so how can I get it?

    Also, now that you have used the table for a while is there anything you wish you could add to it to make it even more useful?

    I am also planning on putting wheels on the bottom. My shop is soooo much smaller than yours, and I don’t think I can put it in one spot without causing problems walking around the shop. If I place a 3/4 inch piece of plywood on the bottom and attach the wheels to that do you thing that would be sufficient to hold the assembly table in a “dead flat” position?

    I am going to be trying this plan this summer!!! Wish me luck.

    Joe

29. thewoodwhisperer on June 6th, 2008 8:13 am

    Hey Joe. Thanks for watching the show. There is no cut sheet. The measured drawing contains all of the measurements you will need to build the project.

    As far as adding things, I can honestly say no. Since this is version 2 of this table, this one has all the improvements I thought it needed from my experience with my first one. That’s not to say I wont think of something as time goes on. I just haven’t yet found anything to improve on.

    As for wheels, I just addressed this in the comments section of the episode on the table base. Check it out here: http://thewoodwhisperer.com/ep.....ble-stand/

    Sounds like a great summer project man. And every piece you build after that will benefit from it. Good luck.

30. Matt on June 13th, 2008 6:50 pm

    Marc,

    I love your podcasts, particularly the two for this project. I’d love to build an assembly table right now, but I have an more urgent, alternative need for a torsion box and was hoping you could offer me some guidance.

    Rather than build a table which is supported by a cabinet base, I want to put up a shelf above my desk that is seven feet long and two feet deep and only supported along the walls on the back side and both ends but not the front. Obviously, I need the torsion box strength so that the shelf won’t sag. I thought a torsion box would be perfect for the application, but I imagine that the internal grid might have to be smaller than the 7 1/4 in. used for your assembly table. Any suggestion as to how to calculate the best size of the honeycombs for this application?

    Thanks,
    -Matt

    PS: This shelf will be above my office desk, so to get some added usefulness out of this shelf and to make up for some of the space lost by the thickness of the torsion box, I plan to add some small drawers along the face, perhaps even a secret compartment or two. :)

31. thewoodwhisperer on June 14th, 2008 10:35 am

    Hey Matt. I don’t really know of any true calculation for this. My advice would be get the lightest material possible, and make the shelf as thick as possible (while keeping the aesthetic you want). Those are the things that will affect the stability of the shelf. And if you are adding a few drawers, the inner grid will be at least a few inches thick which is probably fine for a shelf like that. Very cool idea Matt.

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