Clam
Clamps
(1-800-966-4837 )
P.O. Box 812
Holden, Maine 04429
Miter Clamps
for
Perfect Miters ...... Fast
An Article
"Perfect
Miters Every Time"
by Jim Chestnut
Article First Published
in "Fine Homebuilding
Magazine"
issue #164, July 2004
Edited by Jim Chestnut for web site publication.
All pictures are courtesy of "Fine Homebuilding Magazine", though most were not used in the orignial publication. Any inaccuracies, omissions, advertising, or inappropriate verbiage that may appear in THIS article did NOT appear in "Fine Homebuilding" and are solely the result of my own ineptitude and/or megalomania, greed, perversity, or any other of a wide range of diverse character defects.
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The Story of the Story Pole
The story pole method of measuring came about because a builder I was subbing from had a huge "completion date" penalty clause in his contract and was behind schedule. Every available experienced man was needed for innmuerable built ins, kitchen cabs, pediment heads, moldings, library, entertainment centers, communications room and the like.
The builder's solution was to give me his kids' Nanny and a college kid on vacation to help. The Nanny, a Russian gymnast from right off the plane, who had proved "temperamentally unsuitable" as a Nanny, spoke volumes of indeciferable English, yet followed directions and mimicry impeccably - unlike the college kid. He had never even seen a miter box, nor used a retractable tape measure.
The Nanny ran the casing show, measuring, cutting, slotting and assembling the casings; the college kid cut back rock and installed the units. The results amazed the builder. This exercise taught me a few things as well. Since the story pole was made from the casing itself, the Nanny's head reveals were more consistent than what are routinely obtained with a tape measure. Since both story pole and casing had the identical wide footprint, on slightly irregular flooring the final casing sat in very nearly the same position as the story pole which took the measurement (only a quarter inch difference).
In cases where doors crowded inside corners, it was immediately apparent when using the story pole, and those casings didn't get glued up prematurely.
Important too, in my case at least, is that I could record the measurement as I was taking it rather than afterwards, which proved more reliable and less random than my Random Access Memory. And when my "Where are those measurements at ?" neuron was on break or had expired suddenly, I could relocate a seven foot story pole more quickly than a little scrap of primed base or casing among the hundreds of primed scraps of base and casing on the job. So, for these reasons, and to save increasingly scarce RAM for more important things, I switched to the story pole myself.
Plinth blocks are used under the casing legs on most of the homes I have trimmed in recent years. On these jobs, we cut all the door legs identical lengths from stops ( no story pole or measuring of legs required) , and make up length differences with the plinths.
If we are using plinths averaging 7 inches, we cut the stock in 15 inch lengths, have the apprentice bevel each end on a router table, and set one length on each side of a door or cased opening. That way, there is always a left and a right for each side of each door. Then they are cut to fit by the apprentice - not me or you – since todays builders are putting all their floors down much lower than they used to.
For this article, we shot all the plinths on first so we could use the story pole technique just as we would have had there been no plinths. It can be done either way, depending on Murphy and the tempo of the job. Done this way, the base , base cap, shoe, and wainscoting can go in before the doors and windows are cased. For more on this check out my Philosophy.
Incidentally, I find it easier - and better looking- to install paneled wainscot before the doors and windows are cased anyway. But that's another article I haven't had a chance to put on the site.
WindowsNearly all the windows I have trimmed which are the same nominal size are close enough to the same height and width that the casings can be cut directly from stops. Indeed, many of the double hung jambs are fabricated with the left jamb (for instance) butting into the bottom of the head jamb, and the right jamb being butted into by the head jamb. With this configuration, the right head jamb can be pounded up slightly to increase the length of the right side to match the left, or it can be shimmed down to shorten the length to match the left - whichever adjustment is required (if any). And the left side jamb can be moved either in or out to widen or narrow the width of the head jamb, and consequently, the side casing reveals.
In any case both the window legs and heads can usually be cut to length directly from stops.
Biscuiting the Joints
We have bought high quality trim, controlled its moisture content prior to assembly, cut perfect miters on the ends, and will soon be installing them. We now need to mate them together so that we achieve a perfect miter that stays together longer than the next heating or cooling season. Our solution is to assemble the casings on a workbench with biscuits and glue, and clamp them together before installing them as a complete unit.We slot from the bottom of the casing, using thin plastic or formica glued back to back (cut on a 45) between casing and jointer sole and held back from the line of the miter cut (see picture). The plastic spans the void caused by the back relief cut into the back side of the casing, and reduces the tendency of the biscuit jointer to rock.
This fuzzy photo shows the jointer cocked where the fence or "shoe" has fallen into the back relief.
Notice how little of the near side fence is actually in contact with that portion of the casing it needs to sit on. You can see that the bottom of the fence is beveled, further reducing contact with the stock.
That small triangle is all the bearing surface you get on the right side of the casing. Thus, the initial approach into the stock is apt to be cocked, and the pins which bite into the end grain just prior to contact with the housing get started into the stock in the wrong place. Some carpenters simply make a jig for the jointer, and then move the stock into it.
I find this way to slow when dealing with volume. For every hundred doors you will be cutting 800 slots and I find it easier to move the jointer than 7 foot stock, and much less space is required as well.
So, I span the back relief with two pieces of formica glued back to back as shown below.
This gives a solid bearing surface which is slick enough to easily slide the jointer "shoe"or fence on so that your initial approach into the end of the stock is dead on. The illustration in the FHB article is wrong, and shows the formica filling in the back relief - not spanning it. The publication schedule was so tight, I never got to see the illustration before it was published. Filling in the back relief will not work. Here is a video in 320 x 240 (4.5 Meg) or 640 x 480 (25 Meg) showing it in action.
I have done many thousands of slots this way without a problem with cocking the biscuits. If you are new to it, I would suggest making a left and right miter on the formica, and putting sticky back 100 grit paper on the bottom to keep it from sliding around on you. Keep the formica back from the miter edge so you don't wind up bottoming out on the formica, and winding up with a shallow slot.
We align the outside edge of the biscuit jointer fence with the inside edge of the miter (as shown in the first pholto) and plunge. There is no need to make any marks on the casing. This puts the biscuit close to the inside edge of the joint for maximum effect in preventing the inside corners from opening when the wood shrinks.
In dealing with many brands of biscuit jointers over the years, we have learned a few things. For instance the slot cutter in many DeWalt's makes for an extremely tight fitting biscuit - so tight that it is difficult to insert a glued biscuit then align the miter details along the length of the joint. The slot can be widened by cutting a shim from a feeler gauge and inserting it between the cutter and the arbor flange underneath one side of the blade - simulating the operation of a wobble dado.This video shows the proceedure in high resolution for DSL or Cable connections. In a pinch, biscuits can be swiped over 80 grit sticky backed sandpaper stuck to the glue up table.
We also check the depth of cut the following way (also illustrated on the video). We bottom out a biscuit into a slot, scribe a line with a sheet rock knife, pull the biscuit out, spin it end for end, shove it back into the slot, make sure the scribe line is totally within the slot, scribe a new line with the knife and pull it back out again.
The distance between the two scribes is the total amount of extra space left over with the biscuit inside. This space, if large enough, can fill with glue and not dry for weeks in primed poplar - retarding the cure time for the joint itself. The gap between scribes should be no more than half what you see in the picture (see video). If the jointer you use does not have a fine adjustment, you can often shim the fence out with (you guessed it) sticky back sandpaper, or have a pro grinding shop take a little off the diameter of the cutter. It will probably cut better then anyway.
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