workbench construction help - leg joint

[Robert Trotter]

People I would like to pick your brains about what kind of joint to use for the stretchers to legs.

although not completely decided yet I am tending toward a bench something like this.
61258

But I will probably not initially use the twin vice for a tail vice. I might try some wonder dogs at the right end incombination with some round bench dogs.

I am thinking of using all the same material for the top and legs and stretchers. That is 105mm x105mm face laminated spruce beams/posts.

I am currently thinking like Roubo style , where the top is morticed onto the legs, so I have no top rail/stretcher.

Top is about 550mm x 2000mm at the moment but if I use the twin screw for a face vice then I will have to add an apron type of piece(s) so the rear jaw is in line.

Anyway...
I have not done any big work like this before so could you let me know how to connect the stretchers to the legs.
Some ideas I have are below:-

Any commments or suggestins welcome. I will have to do it all neandre. So chisels and saw.

1.612592.612623.4.

Robert

[Andrew Williams]

I'd go with tusk tenons, as I have on my bench. In retrospect I would have made the upper and lower shoulders much larger since that is the main protection against racking. Someday I may make two new stretchers.

[John Schreiber]

I think any of those would work. Keep in mind that what you want to emphasize is long grain to long grain glue surface and/or a mechanical connection.

The designs you show all have the stretchers intersecting the legs at the same level. Typically the longitudinal stretchers and the lateral stretchers intersect the legs at different heights. That makes the joinery less complex. Another option is to have the lateral stretchers join with the longitudinal stretchers (or vise versa) rather than the legs if you choose.

[Hank Knight]

Robert,

My bench has only one long rail strecher along the lower front and back and two short rail strechers - one bottom and one top. The short rails are through tenoned. The bottom long rail is attached at the same level as the bottom short rail with a stub tenon and two bench bolts for each joint. The bolts go through the short rail tenon. I've posted photos previously here:

http://www.sawmillcreek.org/showthread.php?t=53372

The shoulders on the long rail stub tenons are wide to provide a lot or resistance to racking forces; and the wood is oak, which is very tough. The two bench bolts insure the joint is drawn tight all along it's length, so there's no play in the joint whatsoever. I don't expect it to fail any time soon. I've been using the bench heavily for three years and I've expereinced NO loosening of the joints. If I built the bench again, the only thing I'd do differently is to wedge the through short rail tenons. I don't know that it is necessary - so far, I've not seen the need for it - but it would be an extra measure of assurance that the joints would remain tight.

EDIT:

I should probably also mention that the drawer case in the base of my bench fits tight against the legs on either end, front and back. I'm sure it will instrumental in keeping the base from racking over the long term. But I used the bench to build the drawer case and I didn't notice any racking of the base before I installed the case, so I'm confident it is a stong construction.

Hank

[Bob Smalser]

I am currently thinking like Roubo style , where the top is morticed onto the legs, so I have no top rail/stretcher.



Not so good. When the humidity changes from something different from when you assembled the joints, the top will go slightly out of flat and over time will wreck the lower rail and stretcher joints. That's a promise. And if the stock for that thick top isn't already well acclimated to your shop, it can go greatly out of flat and eventually crack if you tie it down tight.

http://pic20.picturetrail.com/VOL12/1104763/5536778/70922267.jpg

Otherwise any common, pinned or drawbored haunched M/T will work both up top and below. If chopping by hand, leave the legs overlong until final assembly or you can break the fragile endgrain at the top of the mortise. Tusk tenons are for pieces to be easily knocked down. To have glued or pinned tenons up top and tusk tenons beneath doesn't pass the common sense test and may some day garner a chuckle at your expense.

http://pic20.picturetrail.com/VOL12/1104763/2594265/216441043.jpg

Multiple tenons will also work, as will sliding dovetails, but you can't beat a large drawbored tenon for bulletproof.

http://pic20.picturetrail.com/VOL12/1104763/2594265/36332508.jpg

Mount the top using buttons in waxed, grooved stretchers so the top can expand and contract freely. That's the only way it will remain flat over the long haul.

[Robert Trotter]

Thanks people,

So maybe I will have to put a top short stretcher in and just lay the top on that. However if I do this and I do put a twin screw end vice on later then I will have to drill through the top short stretcher (What is the correct term? people seem to use "stretcher" and sometimes "rail" ??)
for the vice screws. Or over hang the bench at the right about 400mm or so. Just worried about the base becoming too short and unstable.:confused:

Would the 105mmx105mm stock be OK for the long stretchers? If I don't mortice the legs intot he top then will the stretcher hold up to the racking forces? I suppose that when I put the cabinets under it will stiffen it up.

Robert

[Mike K Wenzloff]

Actually, Robert, the mortised legs will be fine--as long as you do not use an upper stretcher. Regardless of the amount of humidity changes.

The reason is the legs tops being mortised are allowed to move with the top, as long as there is no front to back stretchers tying them together.

The Roubo design is a solid one. One which favors heavy legs and a thick top for the mass.

Take care, Mike

[Robert Trotter]

Thanks Mike for the input.

I was think of the Roubo design because it meant I didn't need the top stretcher so allowing for more experimentation/options for working on the bench and maybe installing a twin screw vice for a tail vice.

BUT...what do you think about the 4" lower stretcher? Combined with morticed top I thought it should be OK.

I want to draw some sketches of the joints and I would liek to ask about actually making them, so don't go anywhere.:)

Robert

An additional thought...While I am asking questions (seems like all I do) in "The WorkbenchBook" with the Roubo bench, it has the legs morticed all the way through. I was thinking of doing similarly but...With a Spruce top 4" thick will the difference in movement between the top and the vertical leg grain coming through be too much making that area uneven at times through the year? (obviously showing my lack of knowledge here) I can see that if I used maple like in the book there might not be too much problem, but softwood will move a lot more, won't they? Because of this I am thinking now of doing the mortice like Chris Schwarz and not use a through mortice.
If I do not use a through mortice can I just sit the top on and have a stable bench or do I really need to fix it on with "drawbore" dowels.

[Bob Smalser]

Actually, Robert, the mortised legs will be fine--


Sure they will. The top just won't remain perfectly flat is all. That's if it's any less than, say, 6 inches thick. And what the legs and top don't take up by flexing, those stretcher joints down below will, eventually breaking the glue joints, and perhaps also those of the top lamination at the mortises. Might take decades to break a glue joint or two, but like in many poor designs it'll likely happen. Will 4 inches thick stay sufficiently flat so you don't notice? Maybe, but 2 inches surely won't.

Roubo didn't originate this. This is the manner butcher block tables have been made since the time of ancient Rome. With 3' X 3', 24"-thick, end-grain-up tops and unglued, pinned joints below, they worked fine for their rather special purpose. Y'all may desire something slightly more precise in the way of stability.

[Mike K Wenzloff]

Hi Robert,

The 4" lower stretchers are probably fine as drawn. I probably would make the front/rear long ones through tenons. In the least I would drawbore them all.

If anyone is worried about the top cupping, they can always use large battens inboard of the ends to allow your use of the Veritas vise without impediment. Just elongate the holes to allow the top to expand/contract.

I have never seen a benchtop remain "perfectly flat" and accept the fact that a large top will need flattened once, twice, thrice [or whatever] over its usable life. It's no big deal. But the battens would lessen cupping if it were a concern.

As concerns the Veritas vise, I instead would suggest adding the wagon vise Schwarz did [in its final incarnation]. Two of my previous benches had end vises. Hardly ever used them, really. But I do appreciate the wagon vise. It in part depends on how you use your bench.

Take care, Mike

[Michael Hammers]

Not trying to hijack the forum but I have a related question.


1.The top just won't remain perfectly flat is all. That's if it's any less than, say, 6 inches thick. And what the legs and top don't take up by flexing, those stretcher joints down below will, eventually breaking the glue joints, and perhaps also those of the top lamination at the mortises

So by mortising out a relief for the tenon of the leg in the underside of the bench top would restrict movement too much?
Also leaving the endcaps to be bolted to the bench ends seems to be how most folks are attatching endcaps, but would this also limit movement causing joint failure in the top?


2.Mount the top using buttons in waxed, grooved stretchers so the top can expand and contract freely

Can you explain the waxed button and grooved stretchers? I may not be familiar with this terminology.

3. Tusk tenons are for pieces to be easily knocked down. To have glued or pinned tenons up top and tusk tenons beneath doesn't pass the common sense test and may some day garner a chuckle at your expense.

After heading your advice earlier on this it still leaves a question for best method to attatch a 4 1/2" x 20" top to the leg system. Plus the configuration itself on the legs and joinery. I would think the long stretchers would be best attatched using the like of the Veritas bench bolts and the short stretchers using thru mortise and tenon?

[Bob Smalser]

1) So by mortising out a relief for the tenon of the leg in the underside of the bench top would restrict movement too much?
Also leaving the endcaps to be bolted to the bench ends seems to be how most folks are attaching endcaps, but would this also limit movement causing joint failure in the top?


2) Can you explain the waxed button and grooved stretchers? I may not be familiar with this terminology. After heading your advice earlier on this it still leaves a question for best method to attach a 4 1/2" x 20" top to the leg system. Plus the configuration itself on the legs and joinery. I would think the long stretchers would be best attached using the like of the Veritas bench bolts and the short stretchers using thru mortise and tenon?

1) The top will move seasonally across the grain, I don't care how climate controlled your shop is. If you restrict it's movement at the corners with leg mortises, it will want to cup when it expands and crack when it contracts. If you want a perfectly flat bench, then bolt the tail vise into a crosscleat mounted to the top's end grain using an unglued sliding dovetail or T&G pinned only at its center. Bolt the vise directly into the top's end grain and you'll restrict its movement

2) I should have said rails instead of stretchers there. The pic above shows the end rails of a table. The leg tops are flush with the rails M&T'd to them, and the top is attached to the rails using buttons that slide into grooves cut in the end rails. These have to move freely. Any vise hardware is mortised as much as possible into the top. If the rails must be cut so vise hardware can pass through, insure they are sufficiently large. As the upper rails are M&T's to the legs, the easiest joint for down below are simply matching M&T's for the lower rail and stretcher. Assemble the ends first.

[Robert Trotter]

OK...thanks for the input Bob and Mike.

The bench could be like this.
61390

Mike my very first idea was to put a wagon vice on the bench. I twould bring the point of contact more toward the middle and away from the end which will be a bit cramped for my small work space.

Then after some search and reading others' comments and looking at pics I thought it might be better to have the dog holes and tail vice closer to the front. This would allow for things lke 'sticking' as Wiley commented and for using a fenced plane. The wagonvice would have to go on the inside of the leg was my first thoughts making it at least 6" in to the cetre line. So then after seeing Wiley's bench I thought, 'Great idea", I'll use a Veritas twin screw. The I could put dogs anywhere along the top of the jaw. Well now since i want to have a twin screw for my front vice, it is getting expensive. So recently I had thought of just have no tail vice and just use Veritas Wonder Dogs at the end and a line of bench dogs to suit. Simple and fairly adjustable. Just make Swiss cheese out of the top.:)
And I wouldn't really need end caps. :confused:

But since your comments, Mike, and my drawing up some sketches again, (SketchUp was a good find- very useful:) ) I think I could go for the wagon vice. And do something like this.
61391 61392

Then, looking at the sketch I did and if I moved the wagon vice a bit closer to the end and beef up the end cap I might even be able to put the wagon vice more in-line with the legs, moving the dog hole line closer to the front.

OR...Leave a wagon vice inside the leg line and if I need to clamp something closer to the front of the bench I could use a Wonder Dog there, with a couple of dog hole situated to allow for most of my work there.

On the last two sketches I also put a top stretcher/upper rail. Then I could just attach the top by maybe a mortice intot he top at the front legs, to maintain the front bench-leg line and let the back of the top float or put some buttons or a bolt through the top short stretcher through a sloted or over size hole.

Also on the last two sketches put the lower rails high up than the front and rear stretchers. These could be through M&T'd and dowelled or wedged (not tried these before).

If I keep the long and short lower stretchers in the same line then I think I see Michael's point, in that the short stretchers would be through tennoned and the long stretchers with a stub tennon and a knock-down bolt.

Or two short tennons drawbored into the legs.

Will one big tennon about 35mm be too big? Or should it be double tennoned for wood movement. (I don't know - never worried too much with my small projects:o )

ANY ideas, comments or thoughts please.

Robert

[Mike K Wenzloff]

Just a couple quick thoughts before I totter off to bed, Robert.

I personally like the position of the wagon vise just inside the front leg. In far anough to help secure panels I think and near enough to the edge for much sticking of a board. May still need to build actual sticking boards for narrow moldings, which themselves could be held by the wagon vise.

I also don't think a 35 mm tenon is too big.

The bench drawing looks nice. And at nearly an 80" length to the end cap...I'm jealous!

Take care, Mike