Popular Woodworking 2001-06 № 122, страница 4
Out on a Limb Getting It Right Weighing in once again on woodworking's little miracle joint-making machine. We've devoted several pages of reviews and techniques in this issue to the oft-maligned biscuit joiner. Yes, you can conclude that this magazine is on the biscuit joiner bandwagon. There's nothing new about that. We've been an advocate of these clever machines for years. If you aren't aware, there's a vocal group of woodworkers who trash this tool at the drop of a chisel. Generally, these woodworkers hold to more traditional techniques. Their argument is like this: the biscuit joint is a substitute for the mortise and tenon, and the usually thinner biscuit can't be as strong as the thicker tenon. The mortise and tenon has been used for centuries, and fine antiques have survived hundreds of years using the joint. (We won't get into how many pieces of old furniture didn't stand the test of time.) Now, I'm not harping on traditional joinery. Like Rodney Dangerfield, I'd simply like to see biscuits get a little respect. They deserve it. They are fast, easy to use and the joint produced is strong. How strong? Six years ago a respected woodworking magazine published an article on just this subject. In the article, the authors tested different types of joints used in door-making on a hydraulic ram. One tester builds custom doors; the other is a structural engineer who wrote his doctoral dissertation on timber joint strength. The test measured the deflection in each joint before a gap appeared and at what pressure the gap appeared. Then they measured how much pressure it took before the joint failed. And the winner was? Well, from my reading of the article all the joints won, with the exception of the one using two lag bolts. For all the other joints, the wood failed before the joint failed. As to how much pressure it took before the joint failed, the statistics show the biscuit joint outperformed the rival joints. Yet the article concluded the loose tenon was best, closely followed by the traditional mortise and tenon. Huh? Why didn't the biscuit joint get its due? The article cites the ill-effect freeze/thaw, wet/dry cycles would have on the joint and that when it failed, it failed completely. So let me get this straight — I shouldn't use biscuit joints for cabinets and furniture that go outdoors, on entry doors for my house or if I'm timber framing a building? Otherwise they are stronger, deflect less and gap only under considerably more pressure than traditional joints? I can live with that. Heck, I can continue using them with confidence for the dozens of everyday applications for which they were always intended in the first place. This article has always stuck in my craw because those involved appear to be prosecutor, judge and jury. And what the article really proved is what we've always known, that modern adhesives and properly made joints will always be stronger than the wood it's holding together. And so I say, once again, "Pass the biscuits. And this time, with a little respect." PW contact information Steve Shanesy Editor & Publisher Specialties: Projects, techniques, article and project selection 513-531-2690 ext.238 steves@fwpubs.com David Thiel Senior Editor Specialties: Projects, new products and tools, tricks of the trade 513-531-2690 ext.255 davidt@fwpubs.com Christopher Schwarz Senior Editor Specialties: Author liaison, website, projects, photography 513-531-2690 ext.407 chriss@fwpubs.com Jim Stuard Associate Editor Specialties: Projects, carving,turning, project illustrations 513-531-2690 ext.348 jims@fwpubs.com Tricia Barlow Art Director Specialties: Magazine and cover design, photo direction 513-531-2690 ext.599 triciab@fwpubs.com Got Questions or Problems With Your Subscription? To report problems with your subscription visit our website at popwood.com, call our subscription offices at 515-280-1721, or write to Popular Woodworking,P.O. Box 5369, Harlan, IA 51593. Our Privacy Promise toYou We make portions of our customer list available to carefully screened companies that offer products and services we believe you may enjoy. If you do not want to receive those offers and/or information, please let us know by contacting us at: List Manager, F & W Publications, 1507 Dana Ave., Cincinnati,OH 45207 SAFETY NOTE Safety is your responsibility. Manufacturers place safety devices on their equipment for a reason. In many photos you see in Popular Woodworking, these have been removed to provide clarity. In some cases we'll use an awkward body position so you can better see what's being demonstrated. Don't copy us.Think about each procedure you're going to perform beforehand. Safety First! JOINT SIZE OF JOINT GAP PRESSURE DEFLECTION* FAILURE PRESSURE 3 biscuits #20 ! 1,700 lbs. i W- 3,000 lbs. 2 biscuits #20 1,700 !/«4"+ 2,800 Loose tenon j /,2" x 3 x 5 j 1,200 i Vu" i 2,700 Mortise & tenon j /,2" x 21/2" x 2|/2" ! 1,200 ^g" 2,700 2 dowels '/2" x 59/i«" 1,200 not given 1,800 Tongue & groove i |/2" x V8" not given not given 1,300 2 lag bolts I '/V x I^V' I not given I not given I 300 * Deflection is- the amount the rail and stile had moved as a gap appeared in the joint. Source: Fine Woodworking,April 1995 6 Popular Woodworking June 2001 |
