Because the pieces of wood that slide out to support the leaf wouldn't e able to slide past the hinge. Also, a piano hinge won't support weight as well since the screws would be in the same direction of the force of anything on the table. The screws would eventually pull loose.
----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, December 21, 2007 4:47 AM Subject: Re: [BlindHandyMan] Installing a Drop Leaf Table Hinge I can't see why going through all this trouble. Why not use a piano hinge from underneath and install it while the boards are snugged up tight on horizontal? On Fri, 21 Dec 2007, Boyce, Ray wrote: > Installing a Drop Leaf Table Hinge > > Drop leaf table hinge in the dropped position > > Drop leaf table hinge in the raised position > > Drop Leaf Rule Joint > > While at first glance the rule joint seems simple, the realities of this joint can be frustratingly troublesome. A first attempt will often result in a > joint that scrapes and binds or leaves unsightly gaps. To get it right the first time requires both an understanding and application of the geometry at > work. > > These days the majority of us will cut the rule joint profiles with a router. Though this tool can quickly produce a very accurate pair of matching cuts, > it can just as easily cut a good looking but unworkable joint. > > Because different hinges will require different settings for your router, hinge selection must be your starting point. A rule joint hinge is specially manufactured > with an extra wide leaf to span the joint. Because it is screwed into the underside of the table with the barrel facing up it is countersunk on the reverse > side. > > Start by opening the hinge and laying it barrel upward on a flat surface. Accurately measure up from this surface to the center of the hinge pin. In the > case of our standard drop leaf hinges this measurement will be 1/8" (Alternatively, and assuming the hinge is a traditional flat back style you can simply > measure the hinge barrel and divide by two). When this hinge is mortised into the underside of the tabletop the center of rotation of the table leaf will > be 1/8" up from the bottom. > > Most tabletops are built of 3/4" thick material and so it seems reasonable to select a 1/2" radius cutter for the joint. Many woodworkers cutting a rule > joint for the first time will fail to take into account the center of rotation described above and will assume a 1/2" radius cutter will leave a 1/4" fillet > in 3/4" stock. If a 1/2" radius cutter is set correctly, with the center of its described circle raised 1/8" above the underside of the table, the fillet > will actually be only 1/8" not 1/4". An 1/8" fillet is a workable minimum because, while the fillet is cut into the tabletop, the table leaf must match > its profile with perhaps 1/32" clearance. With a full 3/4" material thickness, that will leave an edge of 3/32" which should be regarded as the absolute > minimum. If the tabletop is thinner due to planing or sanding, then a 1/2" radius cutter will be too large and must be abandoned in favor of a 7/16" or > smaller pair of bits. > > After having established the center of rotation as defined by the hinge choice and having selected the cutter, you can run the profile on the table top. > If you are using a 1/2" radius cutter you will need to set the base of your router to cut a fillet of a thickness that is the result of the following formula: > > Tabletop thickness (3/4") minus 1/2 hinge barrel diameter (1/8") minus cutter radius (1/2") > > With this profile cut you can run the mating profile in the table leaf. Ideally you would select a cutter with a 1/32" larger radius to provide a little > clearance at the joint. Such cutters are not generally available, so in order to create the needed clearance, you will separate the leaves by this much > when installing the hinges. > > The hinges can now be mortised. The first cut will be in the table top and will accommodate the hinge barrel. This is best cut with a ΒΌ" straight cutter. > The center of this cut should be a 1/64" outboard of a line drawn down from the vertical cut left by your radius cutter. With the table top upside down > and with its leaf nesting in place but separated by 1/32", lay the hinge barrel in it's mortise and with a sharp knife scribe its outline. Finally route > a mortise to set the hinge flush with the table underside and screw into place. Make sure the table leaf remains firmly in place during this operation. > > ********************************************************************** > This message and its attachments may contain legally > privileged or confidential information. If you are not the > intended recipient, you must not disclose or use the > information contained in it. If you have received this e-mail > in error, please notify the sender immediately by return > e-mail and delete the e-mail. > > Any content of this message and its attachments which > does not relate to the official business of Eraring Energy > must be taken not to have been sent or endorsed by > Eraring Energy. No warranty is made that the e-mail or > attachment(s) are free from computer virus or other defect. > ********************************************************************** > > > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] To listen to the show archives go to link http://acbradio.org/handyman.html or ftp://ftp.acbradio.org/acbradio-archives/handyman/ The Pod Cast address for the Blind Handy Man Show is. http://www.acbradio.org/news/xml/podcast.php?pgm=saturday Visit The Blind Handy Man Files Page To Review Contributions From Various List Members At The Following address: http://www.jaws-users.com/handyman/ Visit the archives page at the following address http://www.mail-archive.com/[email protected]/ If you would like to join the Blind Computing list, then visit the following address for more information: http://jaws-users.com/mailman/listinfo/blind-computing_jaws-users.com For a complete list of email commands pertaining to the Blind Handy Man list just send a blank message to: [EMAIL PROTECTED] Yahoo! 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