Under whaat conditions of board width, thickness, and type of wood do I need to consider biscuit joints vs. just butt joint gluing with clamps? This applies for end tables and for large desks, for example.
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Replies
Barney, I use biscuits for most of my glue-ups and laminating, no matter of the thickness. Just remember that biscuits are for alignment, not for strength of the joint.
Len (Len's Custom Woodworking)
Thanks for your reply.
Barney
Barney, I knew I'd open a can of worms, but I wrote you as to what I do and believe. I'm sure if you asked 10 people you'd get at least 15 different answers. I think we all do what we have previously done that worked, and trashed what didn't. I think all will agree that it's not the tool or material, it's the craftsmanship that makes or breaks how we turn out fine furniture.
Len (Len's Custom Woodworking)
Barney - Biscuit jointing helps with aligning two boards. Not such a strong bond with biscuit jointing alone. Butt joints offer more substantial strength, but this usually requires some additional fastener to the butt joint besides glue, nails, screws or some other type of fastener. End grain which is weaker than long grain joining does not bond well at all with glue alone.
Lar
Thank you for the info.
Barney
Barney,
A butt joint has almost no physical strength because glue will not adhere well to the end grain of the butted piece. Contrary to the other two posts so far, biscuits not only offer alignment they also contribute considerable strength to the joint. In tests I have seen the only joinery stronger is mortise and tenon. I use biscuits for most joints where m&t is impractical (or I'm too lazy). I have even built kitchen cabinets with nothing but biscuits for the entire carcasses. I assure you they were quite strong and the only problem I encountered was having enough time to align the joints and apply all the clamps before the biscuits started to swell (I now use plain ol' white glue so i have longer working time). That brings me to another benefit which is that biscuits align the joint in one plane but allow for fine adjustment in the other so you can get the joint just right.
Charles M
Freud, Inc.
I agree that biscuits greatly strengthen a butt joint. That's because a simple butt joint has no inherent strength at all, and eventually will always fail. The biscuits in the joint form a kind of floating M&T joint.
There was an article in FWW which showed amazing strength of biscuited joints of this kind.
I also agree that biscuits contribute no additional strength to joints that are proper long grain to long grain joints. The inherent strength of those joints is potentially higher than the strength of the wood itself and in such joints, biscuits serve only to align the joints.
In a related topic, dowels also do not strengthen a long grain to long grain joint. They are equally useless in giving much strength to a butt joint.
R
"They [dowels] are equally useless in giving much strength to a butt joint." Granted, I'm very much a novice, but I find this statement a little hard to believe. They may not be as strong as using, say, finger joints or dovetails, but "useless"? I don't think so.
One of the recommendations I've recently seen is to angle the dowels used in a butt joint, thereby pulling the joint together. Works with through-dowels only, not blind dowels.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I think the method you are referring to is more akin to loose tenon than to dowels. I rate blind dowels as "useless" due to the difficulty in accurately aligning the joint and minimal strength. A through dowel that is drilled after the joint is assembled is easier to drill accurately.
Charles M
Freud, Inc.
As much as there are several alternatives to your average dowel joint (m+t, floating m+t, spline biscut etc.) I think they are not totally without merit. As far as accurate placement a simple doweling jig (a small cast clamp with a self centering, diameter selecting barrel) used with a hand held drill is as simple as it is effective. It does no to need to be a struggle
I will concede that dowel jigs and dowels can be an inexpensive way to do basic joinery and that there are some uses for but the advantages of biscuits over dowels are many. For one, in a joint with more than one dowel it is difficult to get the dowels to align. Biscuits, on the other hand, allow for lateral movement so there is some margin of error. Secondly, dowels and biscuits both vary in thickness but biscuits swell in the joint to make the joint more secure with less mavement during clamping. A biscuit joiner also eliminates the need for jigs.
In regards to the original question concerning thickness of stock, I don't use biscuits for less that 1/2" thick stock because the swelling of the biscuit can distort the wood. I don't use the smaller face frame biscuits very much but they are thinner and could be used for thinner stock. As to width of the material it depends on whether the edge of the wood will show. I generally choose the biscuit size based on how wide the slot is. For instance, if a #20 biscuit slot cuts into the side of the wood and will show I try a #10.
Charles M
Freud, Inc.
Jamie,
Dowel joints are little more than useless for giving strength to any joint. They are a means used by industry for years to speed alignment of parts in a production work flow. Somehow the idea of a doweled joint being a "good thing" has crept into the wood working world.
No joint is sufficiently strengthed by a dowel to recommend doweling for that purpose. Prior to the article about biscuits strengthening a butt joint I would have recommended a saddle or M&T in such a situation. The doweled joint in that article failed as easily as the butt joint. When the joint failed, the dowels' saving grace was that they kept the two pieces of wood in the same vicinity slightly longer.
Dowels are for alignment (similar to biscuits) and little else. They do not add long grain to long grain gluing surfaces of any significance in any joint. They have uses other than alignment as in a pegged joint, but even there, I avoid them and make square pegs (for round holes!).
Your reply is most helpful.
Barney
I agree that the biscuits are only good for alignment when edge gluing (long grain to ling grain) and offer no additional strength in this type joint. I don't even use them for edge gluing. I use biscuits for butt and miter joints mostly. And I, like you, have found dowels to be almost useless in a home shop. A production shop with dowel driling machines can use them effectively but it's very difficult to mimic their results with a drill press or hand drill.
Charles M
Freud, Inc.
Vey helpful.
Barney
You can make a jig that will align dowel joints for face frames in about 2 hours that will last for years. Take a small benchtop drillpress & bolt its base into a 3/4" plywood stand made in an H shape bolt it to the cross piece at a height so that the drill bit is pointed toward you coming through the back fence of the table much like a Radial Arm saw would be if you put the drill chuck on it so you could draw it toward you. The table doesn't need to be as deep as on a radial arm saw. Make a hinged handle with rubber on it to come down against the top of the material to hold it in place as you reach over & pull the quill handle & drill the hole. My Dad has one like this that he used for over 25 years in his cabinet shop to drill 3/4" face frames. It will carry on in my shop someday. My Dad will be 81 in January & as far as I'm concerned he can keep it for a long time yet, I hope.
Thanks, the vaious replys were helpful.
Barney
I think you all need to read the original question again, and then tailor your answers to that instead of going off on interesting, but unrelated tangents.
Here is the original question again. "Under whaat conditions of board width, thickness, and type of wood do I need to consider biscuit joints vs. just butt joint gluing with clamps? This applies for end tables and for large desks, for example."
Here are some things to ponder.
There is no question of joining end grain to end grain here.
A butt joint is a very specific joint.
What is the role of an alignment aid such as a tongue and groove, slit feather, dowel, or biscuit in such a joint?
What is subtracted from a plain butt joint by adding a dowel, biscuit, tongue and groove, or slit feather, and what is added-- think of glue line length, and its relationship to the overall strength of a 'butt' or edge to edge joint.
How do you eliminate the chance of the reinforcement aid, e.g., the biscuits telegraphing through to the top surface as rugby ball shaped dimples after polishing? And should you glue dowels, tongues, biscuits, etc., in place at all in a butt joint?
There is really no need for any sort of alignment aids or reinforcements in a butt joint, unless your joinery preparations are somewhat suspect, and you use a creepy glue, like PVA. I use alignment aids from time to time. I can think of work surfaces that are highly stressed in use at the join line where the alignment aid is useful.
Now go to it.
Slainte, RJ.
Sgian,
What's this?!?!?
How do you eliminate the chance of the reinforcement aid, e.g., the biscuits telegraphing through to the top surface as rugby ball shaped dimples after polishing?
I've never heard of it being a problem. If the biscuit is centered in 3/4" stock (oak), should I worry?
Jeff
Jeff, not worry, but but allow for it. Reinforce a butt joint with a biscuit, and use a water based glue, like PVA or hide glue. The joint 'pooches' either side of the biscuit due to the moisture introduced. Next day the glue has gone 'off', and you're in a hurry to do final preparation, sanding, scraping,----and polishing. That material 'pooched' (i.e., swollen) parallel to the show surface by the introduction of moisture remains raised for a while-- about 5---7 days in my experience, and it'll shrink into an oval 'rugby' ball shaped depression if you hurry up on the polishing front.
It doesn't matter much on vertical faces, but they look like shirt on table and cabinet tops. Slainte.
Edit mode. The language police don't like ####, or s-hite without the hyphen, so I changed it to shirt, ha, ha.
Some stuff I've made.
Edited 11/21/2002 10:32:35 PM ET by Sgian Dubh
Sgian,
I prefer to say "what the bird left on the pump handle" - a bit verbose but folks usually know what I mean and it brings a laugh.
I generally wait a week between assembly and finishing, so I guess I'm safe.
BTW, there's a post over in the Cafe (Do you wear and apron... #27) from a chap called scots_chippy who's a new member from the Land of the Thistle.
Thanks, Jeff
So I see, Jeff. He'll ken what Sgian Dubh, and Slainte stand for.
Sounds like you're fairly safe on the preparing for and polishing steps after the glue-up. Not hurrying is the key.
Slainte.Some stuff I've made.
http://forums.taunton.com/tp-breaktime/messages?msg=24955.1
That Mongo's a skookum guy...listen well.
No body has spoken about stock thickness. Obviously don't use biscuits if the boards are thinner than the biscuits. Consider biscuits when thickness is at least 3 to 4 times biscuit thickness. 1 biscuit for 3/4" is good, 2 biscuits in line with thicker stock is good too.
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