Guido Henn’s box-joint jig has butt joints reinforced with biscuits. Not having a biscuit joiner, what would be a good way to put the box together?
At first I considered using long thin strips instead of biscuits, because it would be easy to make grooves to fit. But a FWW article says that biscuits are designed to swell in thickness, to add strength. Homemade splines wouldn’t do that.
Would glue and wood screws work? It’s a jig, so looks don’t matter.
Janet
Replies
I think the general consensus is that biscuits don't really add any strength, but are useful for aligning parts. Before biscuits, dowels were commonly used for essentially the same purpose, but do add some strength. A good doweling jig and a set of dowel centers will be helpful. (Drill centered holes on one side, insert dowel centers, press the other side against the point on the dowel center to locate the hole on the other piece.)
Depending on the design of the jig you're making, you can also reinforce the butt joint with glue blocks. The little triangular cutoffs from miter joints are useful for this. You do save your cut-offs, don't you? ;-)
Metal corner braces can also be used.
I save everything, much to my husband's chagrin. Problem is, the recycling center here doesn't accept lumber. i can't bear the idea of sending clean wood to a landfill when it could be composted with yard waste, but the scrap box is almost full.
Any suggestions?
Janet
scrap disposal
Are you allowed to open burn ?? Potash (wood ash) works well in the garden.
Or, If the lumber is hard wood, you can roast marshmallows and make sumores. Open cooking is legal in most places.
Saving
The downside to saving too much is the potential of ending up on that TV program about hoarding. So, the frugal, but creative woodworker must think up projects that will use the scraps. Making children's wooden toys is one potential target. Bird condos might be another. Not the usual one- or two-bird variety, but hundreds of tenants. And, since they are not likely to pay rent, you might even qualify for some sort of tax write-off. ;-)
i use almost entirely hardwood........... my cutoffs go in my food smoker for when I make jerky or smoked salmon. I use walnut cutoffs only to get the fire going ......not when it comes to the smoking. I also use the cutoffs in my fireplace.......... I try not to discard much other than sawdust
Biscuit myths sometime are wrong
Biscuit joinery actually does add strength to many types of joints despite the "common wisdom" at Fine Woodworking. There are tests done by labs that show that biscuit joinery can have almost as much strength as the vaunted mortice and tenon. I suppose that's why European manufacturer's invented and then used the things.
One can google and read some of these tests if you're curious. I've attached one for reference. When people say they don't add more strength than glue they are talking about edge to edge glue ups of table tops. But even then i wonder if they aren't talking about a certain failure method while ignoring other ways the joint could be stressed. It is a mistake take lessons gleaned from that joint and think they will be the same as end grain to end grain or others.
The alignment thing with biscuits I have found is a bit dicy to actually achieve. There are no magic bullet and I've often found adjoining boards joined with biscuits not flush at the surface due to a slight misplacement of the plate joiner or a very dry biscuit that leaves a certain amount of play in the slots. On the other hand dowels are precise in alignment if frustratingly unforgiving in execution.
Peter
I'd have to agree with Peter
A biscuit joint would provide a larger glue surface area than just a glued butt joint so it seems logical that it would be stronger.
I often use a full length spline when adding a solid wood edge to plywood, typically a 1/4" or 1/8" spline about 3/8" deep on each side. This more than doubles the glue surface area. Seems like it would have to be stronger and helps with alignment.
Bret
I like the glue surface thing, too, but I also feel we need to think about where the glue and the surfaces are in relation to the stress vectors that a joint might be subjected to. The same holds true with splines and grain direction. Dowels and dominoes, for example, add much more strength because their grain is running perpendicular to the joint line.
I sit corrected
Thanks for the correction, Peter. I should have said, "much strength". Since biscuits are made of formed wood chips, and rather thin, they are pretty easy to break, though. On the other hand, most of the joints in which a biscuit might be helpful probably don't really get a lot of multi-directional stress. Unless one sub-contracts with the Samsonite luggage-testing gorillas. ;-)
I keep being surprised...
Ralph, It's not a correction, just a seemingly overlooked observation that tests find that biscuit joints can achieve (if I remember correctly) 90 or 95 percent of the strength of a mortice and tenon joint. Put another way, biscuits can add considerable strength to certain joints. The study I read was done by a man who manufactured stile and rail doors using biscuits. He wondered how the strength of his methods compared to the traditional methods. So he had tests run at the Sandia laboratories. Some of his joints used multiple biscuits, but still the results (as well as the other study I linked to earlier) fly in the face of much that is said here. His ultimate test, is easier to digest: he simply had never seen a failure in one of his doors.
I know biscuits are thin. But then the first time I looked at the spindle coming of the exposed hub of the front wheel in an auto, I said you mean that's all that's holding us up?
If the force vector is in line with the length of the biscuit, as it would be with a downward force on a cabinet door, that becomes its effective thickness. The amount of glue surface also works to the advantage of the joint in that situation. With a downward force on an otherwise unsupported edge added to a table, it's more like breaking a cracker. So, what I'm sugesting is that it may be better to consider the nature and placement of a particular joint, along with the force vectors that it is likely to be subjected to, and then select the most appropriate joinery.
Ralph,
" consider the
Ralph,
" consider the nature and placement of a particular joint, along with the force vectors that it is likely to be subjected to, and then select the most appropriate joinery"
Now, that's so crazy, it might just work.
Ray
re: crazy
Ray, I'm sending a copy of your comment to the head doctor (pun intended) on my ward, in the hopes that I'll get an extra dose of meds as a result. ;-)
An extra dose????
Oh my.
:-)
Regards,
Even a spline will swell some if you use water based glue but
that's not what I came here to offer . . .
I don't know if you can use it but this is a joinery technique I use when making jigs. Drill and insert short cut off of dowel, drill for clearance for screw diameter, drill dowel to take threads of screw, wax screw and drive it,
I orient the dowel before fitting it in the hole so the screw threads across and through the grain layers as opposed to threading between the layers. No need to glue the dowel or the jig components.
Alternatively you could epoxy your jigs together if you can keep the parts in perfect alignment until the epoxy hardens. Maybe with accurately cut blocks of wood and some clamps. Wax paper so it doesn't all stick together. Use very little epoxy. Doesn't take much at all. Other wise a hopeless mess with squeeze out that is hard to remove.
Maintaining 3D alignment is big challenge for me. I wish I had some specialized clamps!
Janet
Combining a handscrew with a C-clamp is one way to do 3-D clamping. Attach the handscrew to the item, a vertical part on a jig, for example, then clamp the clamp that to the base, the bench, or whatever. Handy little devils, they are.
http://www.adjustableclamp.com/handcat1.htm
Or, if you want to "go Hollywood", photographic lighting gear, clamps, etc. can sometimes work when nothing else seems to fit the task. Need a helper? A C stand, a Hollywood arm, and a Mafer clamp may be just the ticket.
http://www.msegrip.com/
Look in the "Hardware" section. Be aware, however, that this stuff is even more epensive than woodworking tools.
Butt joints and screws is fine for shop fixtures
I usually do not use glue when building shop jigs and such. using screws makes for easy adjustments and refinements or total disassembly.
As far as keeping everything as you say "in 3D alignment", this is why it is important to keep all your cuts square and acurate. It also helps to have a flat surface for assembly. Check and adjust all your saw settings and re-check them occasionally.
Bret
Just be sure that placement of screws will not be in the way of blades or cutters when the jig is put to use...
Ray
Jig alignment
I'm not sure about your specific alignment issues, but you might give some thought to Miller Dowels. These are stepped, hardwood dowels that are a snap to insert and can provide alignment and strength. The special stepped drill bit comes with a package of dowels.
Frosty
a spline runs the lenght of the joint and a biscuit doesnt. The spline has a lot more glued surface. select a piecs of hardwood for the spline with the grain running at about 45 degrees to the joint and it will be darn strong. If you mark the matching surfaces when you assemble, youll get the alignment that a biscuit offers with the strength of a hardwood spline.
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