Replies

1. 
   Mumda | Nov 03, 2006 02:18am | #1

   Why do you need double biscuits? They are used for alignment, not strength.

1. 
   quietude | Nov 03, 2006 02:25am | #2

   Not sure really. It seemed like a good idea at the time. I'm pretty sure it's a stronger joint, but I'm sorta new to this side of the business.

1. 
   steveky | Nov 03, 2006 02:51am | #3

   Biscuit joints are about strength. The biscuit absorbs the water based wood glue and swells in the hole and makes the joint stronger than the wood itself. I have never heard of a double biscuit joiner, but just give them time.

1. 
   Mumda | Nov 03, 2006 02:06pm | #6

   "Biscuit joints are about strength..."Sorry, that is incorrect sir. Biscuits are for alignment.

2. 
   Bolts | Nov 03, 2006 03:48am | #4

   Festool make a joining system called Domino that uses loose tenons,but you may have to save up.

   Regards from OZ 

   You can make it fool proof but not idiot proof 

1. 
   QCInspector | Nov 03, 2006 10:04pm | #11

   "Festool make a joining system called Domino that uses loose tenons,but you may have to save up."You and the Europeans have the Domino available. They have not been released to the North American market yet. I was at a local woodworking show a couple weeks ago and asked the Festool rep when it was coming. He looked at me like I was from another planet and asked "What's it called?" "It does what?" "Are you sure that's a Festool?" "Festool doesn't make anything like it." Then he turned away to deal with a sane customer.I wonder if he will remember our brief conversation when the Domino is released and they can't keep up with the demand? ;-)Quietude. You may find it easier to double biscuit by cutting the first row of slots with the tool and work registering flat on the table. Then the second row, by putting a plywood spacer in front of the board and registering the tool from it. It isn't as others have said needed for long grain joints, but works well for butt and miter joints in thick stock.

   Edited 11/3/2006 3:14 pm by QCInspector

3. 
   RickL | Nov 03, 2006 02:01pm | #5

   Using curved cauls for alignment is the best way. I never use biscuits for edge glue ups and thats based on 35 years in the trades in factories and custom shops. There is no strength in biscuits and limited alignment help. I've glued up 4' x 8' panels myself with perfect alignment with curved cauls.

1. 
   JMartinsky | Nov 03, 2006 02:08pm | #7

   What is a "curved caul" ?Best,John

1. 
   RickL | Nov 03, 2006 02:29pm | #8

   http://www.bowclamp.com

   I don't advocate buying them by any means. Cauls have been mentioned in FWW lately.  A really old concept actually. Using a pair of cauls avery 18" on a glue up will give perfect alignment. I plane to size before the glue up and onlhave to sand the planer marks off.

2. 
   Lataxe | Nov 03, 2006 09:31pm | #10

   Rick,

   If you have never used biscuits to add strength or aid alignment, how do you know they provide neither?  That's a rhetorical question, incidentally, as by your own admittance you can't know - at least not via experience, which means you must be going on hearsay.

   I can tell you from experience that biscuits do add a great deal of strength (eg when gluing  long grain to end grain) and they aid mightily with alignment (eg when jointing long, thin boards that have a tendency to bend).  In fact, biscuits are an exremly useful and time saving technology.

   Of course, this does not mean that traditional methods, including curved cauls, are superceded or inferior.  But why do you feel that alternative methods are somehow wrong or irrelevant just because you prefer something else?

   Lataxe, biscuit user.

    

1. 
   Mumda | Nov 04, 2006 04:23am | #12

   He was referring to gluing up panels as was the original poster's question. It's well documented here and many other places that biscuits add no additional strength to properly prepared long grain joints.Yes, they help add strength in many other applications, but not the way the OP is asking for his job.

1. 
   Lataxe | Nov 04, 2006 08:17pm | #13

   Mumda,

   You're right that long grain joints are usually strong enough to stick perfectly well with only glue and no biscuits.  However, there are some cases where biscuits do help with long grain joints.

   I have made a number of panels from teak and afromosia, both of which can be rather oily woods.  Where they contain a lot of oil, ordinary glue can and does fail in edge joints. 

   After suffering a couple of such failures, I now strengthen the joints of teak and afromosia panels with biscuits.  The strength does not come from the increased glue area but from the mechanical grab of the biscuits when they swell in their slots, so that their cross-hatched surfaces act internaly like miniclamps.

   The "minclamp" effect is useful in all cases, should you want to get on with a job rather than wait 24 hours befor taking off the real clamps.  Using biscuits allows you to declamp sooner rather than later.  In fact, if you want to use no glue at all, you can employ the toothed plastic biscuits, which grip very well indeed all by themselves (but not nearly as well as glue of course).

   There is too much "certainty" around statements such as "biscuits are no use for this or that".  Unless those uttering biscuit-related statements have experience and associated evidence I feel they should keep thei prejudices to themselves - unless they want their utterances to be regarded as mere BS.

   Lataxe

1. 
   PADDYDAHAT | Nov 05, 2006 01:04am | #15

   Mr.axe, I am one of the true belivers in biscuits after building an extension to my son-in-laws kitchen cabinets for a built in dishwasher that they thought they had a bay of cabinet for it to go into? . Just a 3 1/2  sided cube to be faced with maple face rails to match the existing and real butcher block top. All done with various size biscuits and a PC 557.

   They did have more than enough space at the end of the counter top for the new bay, so I built a the side walls and top of 3/4" birch ply but in a senior moment or due to the poor dishwasher documents provided made the dam thing 1 7/8 too narrow. I split the top, cut the required spacer from the ply biscuited the socks out of it and used Gorilla glue.  You can now sit engine blocks on that top ,no worries.  The rest was built with no further excitement, all with a cs.js. chop saw and router in his front yard. BISCUITS RULE. Paddy

2. 
   RickL | Nov 06, 2006 04:05pm | #20

   I'm going by evidence from several articles in FWW. Also I've a woodworker professionally so have other sources of information such as technicians in various commpanies to draw from.

   I've used the plano enough to compare it to the curved cauls. What's wrong with a method that uses existing tools most guys have and doesn't cost any extra money????   I firmly believe that many of the gadgets being peddled to woodworkers are totally unnecessary.  I've used the plano but have you tried the cauls????  The cauls go back to the early days of veneer work for folks who didn't have expensive elaborate presses. I first saw them in an English woodworking book years ago. We were using them before we saw the reference but all jisgs are based on necessity and will be discovered anyway. Necessity is the mother of invention and practicality is the father as the saying goes. I think the plano is fine if you have the cash to spend, but for the money I get more results from my cheap caul method.

   Also I've been in the business professionally for 35 years working in factories and custom small shops so have gotten to hear opinions and seen evidence from other professionals. Have you a copy of the Wood Handbook put out by the non-profit group in Wisconsin, Forest Products Laboratories. The book is online. Unfortunately it's somewhat out of date but it does get into edge joints and such. The two FWW articles elaborate on the biscuit strength. Perhaps you've seen them???

   A good butt joint on edge grain is supposed to break anywhere but the glue line so how would a biscuit add noticable strength????  (Forest Product Laboratories)   Biscuits are good in certain places but they add time to do edge joints and I would rather put that time in other areas especially if there is no added value in strength and my cauls make up for alignment.  Obvioulsy they would add strength to a long grain and end grain but a dowel or mortise and tenon is better. I'm not saying biscuits don't add strength to all applications, just long grain to long grain. We're on the same side. I'd rather use a power tool than a handtool.

    

   Edited 11/9/2006 9:26 am ET by RickL

3. 
   Rackman | Nov 05, 2006 06:04pm | #18

   RickL, what glue do you use to get best results. Cherry and red oak types. Thanks

4. 
   charlesm | Nov 03, 2006 04:04pm | #9

   AFAIK, there is not a "Double" biscuit joiner available. For edge gluing (long grain to long grain) it is correct that a properly prepared joint will not gain appreciable strength from the biscuits. However, for every other biscuit joiner application I can think of they DO add considerable strength to the joint.

   Charles M
   Freud America, Inc.

   
   

   ---

   Edited 11/3/2006 9:05 am ET by CharlesM

5. 
   dwolsten | Nov 04, 2006 10:00pm | #14

   What you want is a Porter Cable 557 biscuit joiner. It's pretty much the top of the line of biscuit joiners, and is famous for its fence which can do 135-degree reverse-bevel biscuits. But the reason you want it is that it has a plastic attachment that slips onto the fence, and is exactly the size of a biscuit, and is intended for exactly what you're looking for: double-biscuiting.

   To use it, you set the fence depth to make the lower biscuit slot, and cut it as usual. Then you slip the plastic piece on the fence, and immediately cut the upper biscuit slot. Very simple and effective.

   The MSRP is $199 I believe, but you can frequently get better deals from Amazon, or using price-matching, holiday sales, etc. I got mine near Christmas time at Lowe's for $144 I believe a couple years ago, because of a sale and a price-match with their online store.

1. 
   byhammerandhand | Nov 05, 2006 05:18am | #16

   Correct on the PC 557. When I only had a 555, I simply used a plywood spacer.

1. 
   charlesm | Nov 05, 2006 04:12pm | #17

   So why not just use a biscuit as a spacer wjth any joiner?
   Charles M

   Freud America, Inc.

1. 
   dwolsten | Nov 06, 2006 12:29am | #19

   Because biscuits are rather small. Why not make a biscuit joiner with a fence only as large as a single biscuit (and football-shaped, too, not rectangular)? It wouldn't be very stable, would it? Sticking a biscuit under a full-sized fence would work, but would require some extra effort in making sure you don't tilt the joiner in some direction because of the odd shape of the biscuit.