Replies

1. 
   hammer1 | Oct 01, 2010 09:04am | #1

   An easy way to solve such problems is to draw it out full size. Since you have the glass, lay it down on a piece of paper, posterboard, plywood, whatever, and trace around it. Decide how far the frame will cover the glass and draw lines. It may help to use a different color or use a dashed line. From that point make lines to show the desired width of the frame pieces. If you have done this carefully, you can just connect the intersections of the lines at the corners. The intersection points will designate the long point, short point and meeting point of the rabbet or groove.

   When working with glass, you need to leave a little slack. Often glass work isn't perfectly square, after you trace it on your layout, make sure the two opposing sides are equal in length and you are starting the layout with parallel lines and square corners. Also be careful not to make the fit too tight on the glass. In making picture frames, having the opposing sides absolutely identical in length with accurate 45s makes all the difference.

2. 
   RalphBarker | Oct 01, 2010 10:59am | #2

   Remember high-school geometry?

   It's a right-triangle geometry problem.

   http://en.wikipedia.org/wiki/Triangle

   Roughly, the frame-member length would equal the pane side + 2x the remaining frame width. Think of an inverted right triangle, one point of which is touching the corner of the pane. The vertical side of the triangle is the remaining frame width (after the dado is cut), and the horizontal side is equal to that, since the miter angle is 45°. So, if you start with 1 1/2" material, cut a 3/8" dado, the remaining frame width is 1 1/8", so one side would be 9" + 2 1/4", But, you also need to allow for a little slop in the fit, perhaps a 1/16" on each side.

3. 
   Eef | Oct 01, 2010 12:37pm | #3

   hi michael,

   1)size of picture (or glass pane)

   2)desired width of frame parts

   3)width of rabbet (into which fits the " frameable")

   knowing these three things, one can easily determine the length of the frame parts.

   eef

1. 
   MichaelDavid | Oct 01, 2010 03:10pm | #4

   1)size of picture (or glass pane)  10 X 18

   2)desired width of frame parts   1  1/4

   3)width of rabbet (into which fits the " frameable")  3/8"

   I would love to know your secret

1. 
   Eef | Oct 01, 2010 04:21pm | #5

   hey michael,

   not my secret.  simply borrowed knowledge.

   it helps to draw things out on paper as hammer suggested.  1 1/4 minus 3/8 equals 7/8.  7/8 is what's left over when you subtract your rabbet width from the 1 1/4 frame width.  now double that 7/8 and add that (1 3/4) to 10 which makes two parts at 11 3/4 and then add that 7/8 times 2 to the 18 and get 19 3/4.

   i was math trained at gun-point by a host of very unpleasant nuns.  i am truly happy when these little formulae work.

   eef

    

4. 
   JohnWW | Oct 01, 2010 05:40pm | #6

   Work From the Inside Out

   Simple solution: You calculate the dimensions for the inside of the frame.  The length of the inside edges of the frame for the short side will be 9 inches less the depth of the two grooves : 9" - 3/8" - 3/8" = 8 1/4"  Using the same formula the inside edge of long side will be 11 1/4".

   Now all you need to do is mark the inside edges of your frame stock and then draw 45 degree lines to the outside, if needed, to mark your cuts for sawing.  You might add back a bit, like 1/8", to the length of the inside edges, cutting to 8 3/8" and 11 3/8" respectively, to give yourself some wiggle room if the glass is out of square or fat somewhere along an edge.