165-066 - Biscuit Basics

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  • hen I started my first job inwoodworking in 1984, the biscuit

    joiner, also called a plate joiner,was just arriving on the shop scene. Thecompany where I learned the trade stillwas using rabbet and dado joints to assem-ble plywood case goods. Its a tried-and-true system but one we abandoned foreverafter discovering the manifold benefits ofbiscuit joinery.

    First, by using biscuit joints instead ofrabbets and dadoes, every joint is a buttjoint, which makes calculating dimen-sions from a measured drawing much lesspainful and error-proneno more addingand subtracting to account for dadoesand rabbets. Second, biscuit joinery al-lows you to move a stack of freshly cut parts directly from the tablesaw to the workbench, where all of the joinerywork can be done (maybe not a big dealin a one-person shop, but a definite ad-vantage in a shop where coworkers arewaiting to use the saw). Third, theres noneed for dado blades and the finickyprocess of getting the fit just right. Fourth,biscuit joinery eliminates the frustratingtask of sliding large workpieces across thesaw to cut joinery. Sure, you can avoid


    66 F I N E W O O D W O R K I N G


    This versatile and speedy system

    handles all the joints in plywood casework

    B Y T O N Y O M A L L E Y

  • S E P T E M B E R / O C T O B E R 2 0 0 3 67

    these last two problems by cutting rabbetsand dadoes with a router and T-squareguide, but biscuiting is much faster. Fifth,assembling a case with rabbets and da-does, no matter how finely fit, always re-quires some extra effort to get the caseclamped up squarelythe joints just seemto lean a little bit on their own. A biscuit-joined case, in contrast, almost alwaysclamps up squarely right from the get-go (assuming your crosscuts are square,of course).

    But the biscuit joiners usefulness goesfar beyond joining carcases. From strength-

    ening miters to joining panels, from assem-bling face frames to attaching them to cab-inets, this versatile tool can be a majorplayer in your shops lineup. As a col-league recently observed, the biscuit joinermay be the most significant tool develop-ment for the small-shop woodworkersince the invention of the router.

    I should point out that dovetails and mortise-and-tenon joinery remain the best

    approaches for solid-wood furniture con-struction. But the biscuit joiner can handleall of the joints in a basic plywood cabi-netfrom the case to the shelves or di-viders to the face frame, the base molding,and even a drawerwith the exception ofthe door, which requires traditional joineryfor additional strength.

    What to look for in a biscuit joinerMost of the time, the base of the machinecan be used as the reference surface formaking a cut. In most machines this posi-tions the slot in the center of 34-in.-thick

    Photos: Asa Christiana

    Try to rely on the base of the machine as thereference surface. This generally is a betterapproach because the distance between theblade and the base does not change, whereasthe fence is movable.

    The standard position isshown at left. To cut themating slots, the work-pieces or the tool (above,with the help of a jig) mustbe positioned vertically.

    Fence adds conve-nience. If the fence isused for both cuts (leftand above), the work-pieces can remain flatwithout the need for jigs.


    Make sure your fence is reliable, and be surethe base isnt getting hung up on thebenchtop or another workpiece below.


    The base serves as thereference surface.



    Biscuit slot

    Fence must be parallelto the blade.

    A L I G N I N G B I S C U I T S L O T S

    Watch it on the WebFor video tips on using a biscuit joiner,

    go to www.finewoodworking.com.

    Use a spacer or hang theworkpiece off the edge of thebench to ensure that the base isnot resting on the benchtop.

  • 68 F I N E W O O D W O R K I N G Drawings: Jim Richey

    Cut slots for a sin-gle shelf or dividerall at once. Afterlaying out all of thepieces and cuttingslots in the divideror shelf, clamp thecase parts togetherand use a longstraightedge as afence for the tool.

    Two ways to locate dividers and shelvesTwo ways to locate dividers and shelves

    A jig to locate multiple fixed shelves. For a symmetrical series ofshelves, use a piece of sheet stock that reaches to the center shelf. Asmall cleat at the end locates the jig accurately each time (right).

    Layout tricks. For this carcase, only the center of three biscuits must be marked. To locate theoutside biscuits, line up the edge of the tool with the edge of the stock. Mark the pieces as agroup, first on their ends (left), carrying the marks onto the faces where necessary (right).


    L AY I N G O U T B I S C U I T S L O T S

    A good rule ofthumb for carcaseconstruction is touse at least onebiscuit for every 6 in. of width.Locate them closeto the front andback edges to keepthe corners aligned,unless screws areused for assembly.

    False drawer front,applied afterward,hides plywood edges.

    Use as many biscuits as possible forstrength; configure butt joints asshown to resist stresses of use.

    Screws betweenbiscuits can be usedinstead of clampsduring glue-up.

    Drawer side

    Drawer front

    Drive the interiorscrews first. Then drill

    pilot holes for the screwsat the edges, which areprone to splitting.

    2 in.

    6 in.


  • S E P T E M B E R / O C T O B E R 2 0 0 3 69

    stock. However, a fence mounted ontothe face of the tool provides more versa-tility in positioning the slot. So it is veryimportant that the machine cut a slot par-allel to both its base and its fence; other-wise, joints wont line up properly. (For areview of biscuit joiners, see FWW #151,pp. 58-63.)

    Not all machines are created equal, andits worth the time and effort to check thata new machine is accurate, and return it ifits not.

    Joining cases and boxesWhen joining parts to form a case ordrawer box, the first step is to mark theslot locations on all of the parts. Often, thiscan be done simply by aligning the twopieces as desired and then drawing a smalltick mark across the mating edges. How-ever, for casework, where there are sever-al of the same type of piecesides andshelves, for exampleit helps to develop asystem (see the drawings and photos onthe facing page).

    How many biscuits and where?Bis-cuit joints in case goods supplant conven-tional joints like the dado, the rabbet, andthe splined miter. These are long joints,and it seems logical to cram in as many bis-cuits as possible, but its not necessary. Biscuits are manufactured by compressingthe wood slightly so that upon gluing therewill be a predictable amount of swelling.This swelling makes the joint at every bis-cuit stronger than a conventional wood-to-wood bond. My loose rule of thumb forcase material is to use one biscuit for every6 in. of width.

    This is fully adequate, especially whenusing screws instead of clamps to pull to-gether the cabinet during glue-up. When Icant use screws to clamp and reinforcethe jointwhen the sides will be exposedI dont use more biscuits; instead, I positionthe end biscuits as close to the edge as I can.

    Whenever possible, use the base ofthe tool as a referenceTo cut biscuitslots along the edge of a workpiece, youhave two choices: You can use the ma-chines fence or the machines base to po-sition the slots. Whichever you choose forany given joint, you need to use the samereference for both sides of the joint. Re-member, too, that the reference surfaces


    End grain can drink up glue, starv-ing the joint. Prevent this bybrushing a thinned wash of glueon the joint and letting it glazeover before applying glue at regu-lar thickness. Dont forget to putglue on the biscuits as well.

    J O I N I N G M I T E R S

    To use the trusty base as areference, clamp two pieces withtheir inside faces together,aligning them carefully. Then thebiscuit joiner can rest in the 90notch to cut slots in both miters.


    Clamp down workpieces for safeand accurate results. Be sure tokeep the tool pressed firmly inplace throughout the stroke.


    Biscuits are sized andlocated to avoidbreaking through theoutside faces.

    Locating biscuits closer tothe inside of the miterallows the outside edgesto be profiled or molded.

  • 70 F I N E W O O D W O R K I N G

    on the workpieces should be the outsideface and edge because they must end upperfectly aligned.

    For most biscuiting tasks, you can rely al-most solely on the base of the machine asthe reference surface. Even on inexpen-sive biscuit joiners, the base usually is par-allel to the blade. However, some fencesare less reliable than others in terms of being perfectly aligned with the blade and staying locked in position. Its alsoeasy to rock most biscuit joiners out ofalignment when using the fence on theedge of a 34-in.-thick panel; cutting thosesame slots with the base of the machineflat on a bench is a more stable and reli-able approach.

    When using the base as a reference, abiscuit joiner automatically places the cen-ter of the slot 38 in. from the bottom edgeof the stock. To change that dimension,use thin stock such as hardboard to shimthe machine or the workpiece to theproper position.

    When joining box sides, cutting slots inthe ends of panels is simple using the base,but cutting the opposite side of the jointinto the face of the panelrequires eitherholding the part on end or laying the partflat and orienting the machine vertically.For tall pieces the latter option is easier; somake a simple L-shaped guide to keep the

    machine perpe