Are Biscuits Gravy? Can someone make a case for/with glue alone?

[Bruce Seidner]

Most of my experience is building small cases out of 3/4" ply. I am now about to make some larger cases for workshop tool platforms and cabinets. I have used Kreg pocket hole joints with and without glue and I have used glue alone. I am now considering the addition of a Biscuit joiner because I don't like the exposed holes that the Kreg joints leave.

But I have been wondering just how much structural strength a few screws or a few biscuits add to a case. Has anyone with some engineering background studied or commented on the anecdotal experience of hacks like myself? Most of what I build is made of plywood and I know that glue differentially adheres to the exposed laminates. I am happy to use pocket screws where they don't show. But what is the value added of using biscuit joints when making a case. Can I not make a case with glue alone. I am blessed with a silly number of clamps and rolls and rolls of masking tape for stability while the glue dries. How much structural strength does a biscuit or a screw really add to a case?

[Lee Schierer]

As I recall there have been several tests done comparing relative joint strength. Biscuits in edge grain joints only aid in alignment and add no appreciable strength. In end grain to side grain joints they add a slight amount of strength, but are primarily for alignment. I've read instnaces where the swelling of biscuits causes sureface imperfections in panel glue ups. I've also read where woodworkers have misjudged the biscuit location and cut into them when sizing their glue up to final dimensions. I personally don't feel they are worht the investment.

You know you can easily make plugs for your Kreg jig holes from 3/8" dowels. Plugged hoels aren't as obvious as open holes.

[Rod Sheridan]

Hi Bruce, most of my work is with solid materials, although I do use some plywood for cabinet backs that aren't visible, or of course for shop cabinets.

I don't own a plate joiner, or a pocket hole jig.

In solid wood, unless you need to strengthen an end glue joint, such as a mitre, I don't see the need for a spline. Glue is stronger than the wood, so it's sufficient for structural purposes.

When I make cabinets out of plywood, I normally use Baltic Birch, which is very consistent and doesn't have any voids. I use rebates, grooves, and dadoes for those cabinets, glue only, no mechanical fasteners.

I did borrow a plate joiner once from my FIL, who is a retired cabinet maker. He had a brand new plate joiner which he loaned to me for as long as I wanted. That should have raised the warning sign in my head.

I used it to insert plates in the glue up of a white oak cabinet top. When I returned it to my FIL, he asked me how I liked it and I commented that it doesn't align the pieces as well as I do by hand, however it would probably be great for a shop where assembly was performed by semi-skilled labour. That was his experience as well.

I haven't used a plate joiner since, although I do sometimes use shop made splines set in grooves cut on the shaper.

For me, biscuits and pocket screws aren't something that fits well with my work methods, or the furniture I build (Mostly A&C ).

regards, Rod.

[Phil Thien]

For sheet good work, I find the biscuit joiner invaluable. In the time it takes the average user to remove their blade and install a dado blade in their saw, I'm done with the joinery of a cabinet.

I've never had a biscuited joint fail, except for where I've tested them to failure.

In fact, I've built cabinets in the past that I've decided (for one reason or another) that I just didn't like. When I've tried to pound them apart to reclaim materials I've never been able to get the biscuits to let go. I've always had to saw through the joints.

I dare say I use biscuits for all sorts of things besides sheet goods, too.

[Charles Lent]

I use biscuits, but I don't put glue on them. I glue the joint faces and just use the biscuits to help align the joint during glue-up. I got away from gluing the biscuits because I had problems with panel glue-ups where each glued biscuit pulled a biscuit shaped dent in the surface of the panel when the moisture from the glue finally left the boards. Glue on the joint alone is more than sufficient to hold the joint together if the joint isn't starved. I don't use any biscuits where they are not needed for joint alignment or where there is a chance that they might be exposed during final dimensioning. Pocket hole assembly works great, but it also has significant limitations. I hate the look of them, even if they are plugged. I will only use them where they will not be seen in the final assembly. Every joinery method has it's place. You have to choose the correct one for each application based on what best applies to that joint. Each has it's benefits and shortcomings. You must choose the one that works best or is the least offensive for each application.

Charley

[Tom Welch]

I am with Phil on the biscuits. I have made a lot of kids furniture using them and they have held up the test of time and the torture of that only kids can dish out. However if you want strength, then I suggest a floating tendon, like the domino jointer that Feestool sells. I love mine, in fact, after buying mine, my biscuit (plate jointer) jointer gathers a lot of dust. The Donino aligns and adds tons of strength. Although, be prepared for sticker shock, after seeing what they retail for. But mine has been a wise investment.
I know that to wood working purest, the biscuit is considered almost as bad a brad nailer. But I have seen David Marks use biscuits on some of his projects on his show. (although manily to align but also to attach)

[Lee Schierer]

Check out "Wood Magazine Nov 2006 " issue, they did a comparative strength test of different joints including biscuits.

[Chris Padilla]

I'll jump in with my $1/50 (2¢) worth:

In hardwood to hardwood applications, I don't think they add much strength but can aid in alignment.

In hardwood to non-hardwood or non-hardwood to non-hardwood, they aid in both strength and alignment.

That said, I like to use biscuits in ALL picture frames and glued-up casings that I make regardless of the material.

[Chip Lindley]

What Phil and Chris Said!

With sheet goods there is some structural enhancement over a plain butt joint. But the primary reason I use biscuits is for alignment. Your carcass will slip and slide all over the assembly table while you labor hard to align everything before your glue's open time ceases to exist.

I do not enjoy seeing pocket screw holes inside a carcass either. I reserve those for the backs of faceframes and other unseen uses. Biscuits are the way to go making boxes of sheet goods! Lots of clamps are still needed to draw every joint tight; especially plywood! It is notorious for being "almost flat"!

[Cody Colston]

Generally, if dowels, screws or splines will work, biscuits will work.

They are great for joining plywood because, as you noted, plywood has alternating long/short grain plys and not a lot of glue surface. I would not say that they add no strength to a solid, long-grain joint but they aren't needed. They can help in alignment of long-grain edges. They are great for joining miters or end-grain to long-grain butt joints (like face frames).

On shop cabinets, it's probably not an issue but for finer pieces, let the glue cure before sanding the piece if biscuits are used. They will initially swell the wood slightly and if sanded right away, there will be a depression later in the area of the biscuit when the wood shrinks back to normal.

Do pay attention where you place them as they are unsightly on an exposed edge if you saw through one.

Finally, remember, it's your shop. Use the tools that work best for you and disregard the opinions of those who sneer at certain tools/methods "just because."

[Matt Benton]

I used biscuits on one project, and that was enough for me. They are not precise enough to use for truly flush alignment, and just add an extra step.

I use cauls to align glueups, and it works great.

[Bob Wingard]

I use them whenever and wherever I can ... I believe they add some strength to most any joint, much as a short loose tenon would. Most of the time, the biscuits seem a bit loose in their slots, so I tend to apply glue, mostly to cause them to swell to a good, tight fit.

The "telegraphing" some talk about, I feel is a lack of understanding of their use (misuse). When a biscuit swells from the moisture they absorb from glue .. they will actually make small bumps indicating their presence. IF you were to sand or plane that area flat WHILE the bump was present ... later on when the moisture was absorbed back into the wood, the bumps are now depressions ... and there is no good cure for them. I'm rarely in that big of a hurry to finish a project that I can't wait a few days for the whole process to carry out, and I have never personally been plagued by the phenomenon.

I was once very skeptical about using biscuits ... then I got a video by Frank Klausz showing him building a complete set of bookcases built with nothing but biscuits so I tried them, and have never been convinced to give them up.

It's just a matter of what YOU have confidence in ... then honing your skills in the use of that product/procedure.

One other thing ... biscuits DO have a grain to them ... and I try to alternate them along the length of a joint or in thick stock where I would use double biscuits. My experience has been very similar to Phil's ... I have had to cut joints apart to salvage stock because I couldn't break the joint ... to me, that speaks volumes about whether they add strength to a joint or not.

[Jon Endres]

I vote no biscuits. I built an entire house worth of cabinets and vanities without the use of a single biscuit (ok, maybe I ate a few buttermilk ones for breakfast). I bought a P-C 557 with all the accessories, a couple thousand biscuits, thought I was going to use it for everything. I hated it. I sold it for pennies on the dollar and everything since has been done with either routed dadoes or pocket holes. All my cabinets are done with pocket holes. If you're patient and careful and you understand how glue works and how wood moves, you don't need them. I would vote for loose tenons (i.e. Domino) but don't want to spend the money (and don't have much use for one yet).

[Bruce Seidner]

I have been unable to get back to this question for a day and am embarrassed by all of the thought and collective wisdom accumulated. Like most subjects I see that we are all in complete agreement. Much food for thought. Thank you one and all.

[Neil Brooks]

I like using biscuits, for the reasons stated above.

That said, if I hadn't bought my P-C 557, I might not have given biscuits much thought.

Also, for edge joining glued-up panels, for furniture, these days, I'm turning to my Amana glue joint router bit (http://www.amanatool.com/bits-fv/55388.html).

http://www.amanatool.com/routerbits/images/55388-app.jpg

I spent about an hour, with my Milwaukee router and my PRL lift, and some scrap UHMW, and made set-up blocks for the major thicknesses that I work with.

Now, I can set up the glue-joint bit in about five minutes, get dead flat panels, and whatever advantage there MAY be in the increased glue surface.

[frank shic]

i used biscuits for a small chair, a stool and a small children's table. the joints on the chair and the table failed miserably. the stool is still standing although i've warned my in-laws not to sit or stand on it! i sold the pc 557 about 3 years ago on ebay afterwards and got a domino.

[Rob Price]

I bought the freud doweling jig as an alternative to biscuits. stronger joints (according to wood mag), cheaper than domino, and no exposed holes like pocket jigs. I have two friends who have the domino and love it. I couldn't justify the cost- but I'm cheap.

I almost never use it. It collects a lot of dust. The machine is very precise, and you must line it up perfectly on both boards to get the joint perfect, which takes time and energy. I think biscuits have a little more allowance for slop. I bought a good dado set and use dados for my case work. I use pocket holes for face frames because it's faster not having to mark and drill both sides of the joint.

I could see myself using it (doweling jig) for a table apron in lieu of mortise and tenon joints. I have used it to to add a curved piece of solid oak to the edge of some ellipse shaped plywood (front of a boat shaped bed) to reinforce the joint and to line it up since I couldn't clamp it based on shape and size.

So for me it hasn't worked out considering the upfront cost. Biscuits may hold up well for case work, but to me a good dado joint is much stronger/durable. The stack takes a bit of time to set up, but if I'm doing a lot of cases, it takes no time to cut a bunch of dados/rabbets/etc once set up for a tight joint. I have a story board as well, each time I set up the dado I rip a cut off for quick reference down the road.

[Jonathan Spool]

Another ditto for what Phil and Chris said. Biscuits are the quickest way to get some carcasses put up quickly and strong as heck. I agree with Chris not using glue (or just a small amount) on the biscuits when in thin stock, but I'll use glue whenever I can for the swelling of the biscuit adds to the integrity of the joint.

[Mike Cutler]

Bruce

The actual original use of the biscuit joiner was for applications such as yours. It was designed around cabinet ply case work. When people starting to try and make a biscuit take the place of a load bearing joint, that's when it started to get a bad rap.
I'm not sure that I would look at a biscuit as adding structural strength, as much as providing structural integrity.
It's pretty hard to beat the mechanical advantage of a screw. A properly sized screw along with glue will make a joint that will last. Hence the term; "Screwed and Glued".
I don't think "glue alone" will provide a lasting butted corner joint with plywood. Just not enough fibers in my opinion.

[Chris Fournier]

I use biscuits whenever possible if I feel that they will add strength to or aide in aligning the joinery in question. I think that the following points are worth making:

If your biscuits are not helping you align your work then four things are possible. One you have a total POS tool and that's that. Two you have a POS or a good tool that is out of alignment. A decent biscuit joiner will have adjustments for getting the blade parallel to the fence. Take the time to make this adjustment and your biscuit joiner will indeed help you align joints. Three, most guys just reach for their box of biscuits and plop them into the joint. They don't check to see if the biscuits are loose or tight. If they're loose there's no wonder that the technique is not helping align the joint. I make sure that the biscuits go into a dry slot "snuggly" not super tight but snug. I do this by using a plant mister with water to swell the biscuits a bit before I apply glue an clamp up the joint. If you do this your biscuit joint will align beautifully. Four, you are not holding the tool to the wood carefully enough. Make sure that your joiner is properly registered to the joint before you pull the trigger. Properly registered means that you reference your joiner off of the faces or backs of both pieces to be joined not a back and face.

A biscuit adds as much strength to a joint as the surface area of it's faces. For years I had a typical butted rail/style joint made out of pine in my shop. I made the joint with one #20 biscuit and PVA glue. The pine pieces were 3/4" X 2 3/4" in cross section and 12 inches long. I personally tried to break that joint by hand for years. Any time a pal came to my shop I gave them a go at it. It stood the test of time and was never broken until it was forgotten and lost in the rubble. Plenty strong for a horrible endgrain/side grain joint!

Plwood edge joinery isn't that strong relatively speaking because all edge joints are pretty close to 50% end grain! Biscuits will help here plenty.

People seem to dismiss biscuits joinery and often times they're the same people who will extol the virtues of MT joinery. A biscuit joint is a funny looking machine made MT joint. It has all the attributes of the MT joint to scale.

I have a glue joint shaper cutter that gives you a joint like Neil Brooks has shown us. I like it but set up time is a PITA compared to the biscuit joiner. Biscuit joinery is speedy quick and efficient.

The Europeans have come up with all sorts of hardware based on the biscuit joiner - hinges, RTA bits etc.. This stuff is fantastic for given applications and well worth checking out.

Biscuit joinery is cheap. A plate joiner can be had for under $200 easy and biscuits are about $40/1000pcs. (Canada) Add the time factor and there isn't much not to like about the technique if your work can benefit from this cheap and easy to produce joinery.

[Jeff Duncan]

I'll add another vote in favor of using biscuits. Many of the negative votes seem to be from those who have had problems using biscuits. You can't blame a type of joint for one's not knowing how to use it properly. I've done dozens of kitchens, vanities, bookcases, you name it, and find biscuits to be a very easy and reliable method of building casework.

Using rabbets on casework adds very little in the way of a secure joint. It's a bit better than using a butt joint....but that's not saying much. Using a full dado is a good joint, but certainly not practical for many situations. A loose tenon joint (domino) could be a bit stronger, but not worth the additional expense to me. I also use pocket screws when applicable.... with biscuits. I wouldn't use pocket screws alone anymore than I'd use regular screws through the side alone.

Using biscuits allows you to do your casework quickly and easily. I can do the slots for an average kitchen in about an hour. Also makes cutting easier as you don't have to account for the depth of dados in planning your sizes.

that's my two cents....
good luck,
jeffd

[Curt Harms]

What Phil and Chris Said!

With sheet goods there is some structural enhancement over a plain butt joint. But the primary reason I use biscuits is for alignment. Your carcass will slip and slide all over the assembly table while you labor hard to align everything before your glue's open time ceases to exist.

I do not enjoy seeing pocket screw holes inside a carcass either. I reserve those for the backs of faceframes and other unseen uses. Biscuits are the way to go making boxes of sheet goods! Lots of clamps are still needed to draw every joint tight; especially plywood! It is notorious for being "almost flat"!

From what I've read biscuits were invented to add fabrication speed and adequate strength to cabinet boxes made from sheet goods. I used 'em for entertainment center towers that have gotten racked a fair bit when being moved and no signs of failure so far. One thing to watch when cutting slots for biscuits is to be sure the machine is either parallel or perpendicular and not leaning. If the machine is leaning at all the slots will lean and the pieces won't line up like you expect. They'll be off a smidge and you'll wonder why. How do you think i know that? :o For a while biscuits were regarded as the be-all end-all to woodworking joinery. They're not. Like most things, they have uses and limitations.

[Terry Beadle]

I use biscuits on stock that's greater than 1/2 inch thick. They help align and add strength to the table top etc. They speed up assembly on a large glue up too.

Thinner stock situations don't need the biscuits. A spring joint, a bit of glue spread by finger ( best applicator I've found ) and they stay put together.

Thicker stock situations are greatly benefited by more attention to properly made cauls. IMHO. Additonally, getting the stock square, properly sprung, and getting the joint surfaces right, means almost no clamping or very little required.

Of course the final rule is...there's never enough clamps ! Hoot!

[Jay Jeffery]

If you want to try out biscuit joinery without investing in a biscuit joiner, try it out on your router table. A 5/32" kerf cutter and a few biscuits are all you need. Since the width of cut you need is larger than the diameter of the bit, you do have to do more than just plunge the cutter, but you have to move the sock about an inch or so.

[Rod Sheridan]

I use a shaper for cutting biscuit slots on those rare instances when I use them.

Co-incidentally, last weekend I had to make a "U" channel from two pieces of melamine shelving for a friend, used the 4mm Freud slotting cutter in the shaper, perfect biscuit slots, and of course it's large enough in diameter that it makes the slot in one shot.

The only problem with a router or shaper for biscuit slots is that don't work well near the center of a sheet of plywood.:D

Regards, Rod.

[scott spencer]

I rarely use biscuits anymore, and nearly never for joining edge grain butt joints with hardwood. I sold my biscuit cutter, and on the rare occasions I use a biscuit for joining hardwood to plywood, I use a router and cut a long groove.