Replies

1. 
   Northboundtrain | Mar 21, 2006 10:16pm | #1

   I've never built a bench with dovetailed aprons.  Mine just has the end pieces bolted on.  But I've never noticed any differential expansion/contraction between the end caps and the rest of the bench.  I think that this is mainly due to the way I oriented the boards.  They are in the quarter sawn/vertical grain orientation, i.e., if you could see the annual rings on the end grain of the boards (the end caps hide the end grain of course) they would be vertical.  The wood expands side to side much less in this orientation.  I have a 13" wide maple cutting board that I built the same way.  It obviously goes through major moisture content changes as it is washed and then set out to dry over and over.  The end caps have stayed put and I've never noticed any differential expansion/contraction. 

   That said, the dovetail joint can accomodate any expansion/contraction just fine.  Cut the pins in the end caps, use half blind dovetails, and make the cut out between the pins a little deep to allow for the benchtop to contract without prying the apron board away.  Even with expansion/contraction of the top, the joint will hold firm and serve it's purpose of keeping the end cap tightly in place.

2. 
   ring | Mar 22, 2006 02:24pm | #2

   Houston,

   If your apron is attached under the top as in most tabletops, that is, allowing for some movement, then you won't have any problem at all. For something this heavy, I'd prefer elongated holes in the apron, and large lag bolts screwed thru into the top (but not tightened all the way).

   It's still an unusual construction for a workbench, mainly because it doesn't easily allow for the vises, but as a table it will certainly work.

   DR

1. 
   HoustonHeights | Mar 22, 2006 09:41pm | #3

   In this case, the apron is not under the bench, it surrounds the bench top.  In other words, the top of the apron is flush with the top of the bench.  The apron is necessary to attach vises to the side of the bench. 

1. 
   ring | Mar 23, 2006 03:52am | #4

   Oh, that's something else again...I'd say 3 things -1. Make sure the material for the top is quite dry and acclimatized. I don't know where the stock is coming from, but thick pieces are very often not fully dried, unfortunately. Their slow shrinkage will not open your joints, on the contrary, you may end up with gaps in places if the stock is still in the process of drying.2. Make through dovetails that can move in the cross-grain direction. Pins on the short part of the apron, tails on the long pieces. Maybe you could even leave them unglued and free to move if the joints are tight fitting.3. No matter what you do, you're probably going to get some effects of expansion/contraction in the joints. Probably it won't really detract from the bench's utility. But don't expect that it will stay exactly as it was when you built it.DR

3. 
   BG | Mar 25, 2006 01:24pm | #5

   HoustonHeights,
   I do get some expansion but not so much, the trick is to keep the expansion where it won't hurt performance. Usually, those aprons are 'Breadboarded' on to the table edges...and just the ends are shaped as dovetail. Glue the dovetail into the breadboard on the vise end(front vise) only (about 2-4")and let the rest of the end apron float using dowels(drawbore) to hold on. This way as the top expands the end apron stays flush with the front apron on the side where you need it flush..near the vise.
   You might want to consider a 6" apron on the front to better accomodate the depth of your front vise.(obviously that depends on the vise your using)

   
   

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   Edited 3/25/2006 6:29 am ET by BG

4. 
   BilljustBill | Mar 25, 2006 06:09pm | #6

      Houston,

       I've gotten to see, first hand, how thick laminated Maple moves.   From a surplus place, about 8 years ago, I bought two glue-ups that have the stamp, "USN, General Dynamics" on a label.  They are 24"X 48"  and vary in thickness from 2-1/2"-3-1/2".   The boards glued together are 6/4 and glued to each other on their face grain.  The quality of the Maple is flawless.....

       On each end, the mfg. company took a piece of 6/4 Maple and used long, harden, drywall screws to fasten it across each end.  It actually locked the boards together.   I've had them in an unheated and dry storage building.  Even though the end pieces are tightly screwed to the ends of the lamanated block,  EVERY glue joint has failed.  When the wood isn't allowed to move, the only place the expansion/contraction can take place is at the wood's weakest grain area or the glue joints.

       To give you an idea of how to mount and endgrain apron or one of the Veritas Twin Screw wooden jaw vises, look at the instructions in one of the twin screw vise kits.    They use 4 machine bolts, not lag bolts, to mount the first jaw to the work bench.  Their procedure allows for wood movement.

      Bill

   
   

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   Edited 3/25/2006 11:10 am ET by BilljustBill

5. 
   BigK | Jun 09, 2006 11:05am | #7

   Most workbenches ar emounted to the base with 1 or 2 (in line) bolts tightly and all other mountings allow for wood movement. Reccomend that you read up on workbench construction first. There are several excellent books out there on the subject. Lon Schlening wrote an excellent book a couple of years ago.