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Window Sash Construction

Easy Window Construction
Step 1: Milling the Stock — To conceal the tenon, this style window uses “stopped” mortise and tenon joints. Always mill enough extra stock to produce at least one test joint of each part from scrap before milling the actual sash parts. Mill the stock for both rails and stiles to finish thickness of 1-3/8". Cut the stile lengths to the full sash height required. Cut the rail lengths to the full sash width required, including the length of the tenon and allow for overlap of the ogees produced by the matching bits (See illustration.). Use a table saw, radial saw, or router to cut the required tenons. 

Mill the stock for the sash bar and muntins to 7/8" finish thickness. When cutting to length, allow for the extra length required for the cope cuts on the ends of each piece.

Step 2: Cope Cuts — The rail cope cuts are always made with the stock face facing down and before making the profile cuts. 

Set the top of the coping bit flush with the tenon bottom as shown by step 2.
Adjust the fence to make the cope cut 1/4" deeper than the tenon shoulder.
Without changing the bit height, make the cope cuts on the sash bar and muntin stock.
To better hold the sash bar and muntins for the second profile cut, make a cope cut on a piece of scrap stock which you will use as a push block.

Step 3: Profile Cuts — The profile cuts are made on inside edge of rails & stiles, and on both sides of sash bar & muntins. Make all cuts with the stock face down. As shown, use the tenon to set the cutter height, the bottom edge of the upper cutter must be set flush with the top edge of the tenon.

Make the profile cuts along the inside edges of both the rails and stiles.
Make the profiles cuts on both edges of the sash bar and muntins.

Step 4: Assembly — Dry fit all pieces before applying glue. Use a minimal amount of glue and do not over-tighten clamps when assembling.