Making Wood Window Sash
A SPECIALTY SASH
Here are a few steps in the manufacture of wood window sash. The method shown here is for the making of haunched mortise and tenon joints. This is the oldest and best method for sash construction. It is strong, time tested, and serviceable over long periods of time. Joints pressed and pinned can be taken apart in order to repair or replace sash parts.
Selection and preparation of the material has already occurred in this illustration. All parts should be face and edge jointed. Then thicknessed. The wood should be free of knots, grain reversals, pitch, pitch pockets, splits, drying defects, and heavy summer wood. Care need to be given to grain direction when laying out the parts. there will be lefts and rights and they need to be arranged so that they will stick without defect. This prior attention must be given before mortising and tenoning.
The machines shown are a hundred years old or more. Their use make up the core activities in making sash parts.
This is mortising with a New Britain Chain Mortiser. This is a Model 2. It a power feed machine, all belted. It uses tooling consisting of a bar, chain, and sprocket which are sized for width and length of mortise. The bar shown is a Renold with .54 pitch chain. The Renold name is legendary in the chain world. The depth is regulated by the amount of table elevation used. Table elevation is achieved with the acme screw in the background. The distances traveled are regulated by a stop rod on the side of the machine which activates a link. The link connects to a yoke which shifts the belts elevating and lowering the table. The table on this model traverses to allow multiple plunges for mortises of lengths greater than the width of the bar. The widest bar I know of is 3 1/2″. The narrowest is 3/4″. Mortise widths range from 1/4″ to 3/4″. This machine is essential for efficient manufacture of mortise and tenon sash and doors.
This is tenoning with a Levi Houston American Single End Tenoner. The work is clamped on the compound rolling table. As the work is advanced the upper and lower tenoning heads cut the tenon. Then the coping head, round disc in front on the saw, copes the shoulder of the tenon. Lastly, the adjustable saw cuts the tenon to precise length. The upper cope spindle is removed on this machine. It is not needed in sash work unless desired to slot check rails. Both copes are required in door work.
The tenoner is equipped with appliances that regulate the distance between tenon shoulders thus establishing the desired glass opening size. Theses are spring stops which locate in a dovetailed rail in the rolling table. Traditionally, glass sizes determined window sizes. The glass rests between the rail shoulders so it is these points which are the control points for dimensions at the tenoner.The tenoning heads are adjustable independently or in tandem. The purpose of this is to be able to retain the tenon thickness while locating the tenon on the desired elevation of the rail or bar part to be milled corresponding to the mortise location on the stile. The tenoner has many lateral and axis adjustments which allow for the making of many unusual joints. Offset shoulders, dissimilar stickings, and combinations of stickings — all can be accommodated at the tenoner. With the mortiser, the tenoner is an essential machine for quality machine sash work. It is rare to have one without the other.
Tenon cutters are distinctive in that the knives are skewed for more effective milling across the grain. They are ground with a curve which is an ellipse segment governed by the radius of the cutting circle, the width of the knife, and the skew angle. When in proper condition they will produce an excelsior like shaving which is great for starting the evening fire. Tenoner spindles are set a a slight angle to facilitate the work of the spurs, keeping them from binding and heating.
This is running the sticking on an American No 3 1/2 Sash Sticker. The sticking is the detail milled on the inside edge of the sash parts creating a rabbet into which the glass is set and the moulded detail – ovolo or ogee usually – which visually eases the appearance of sash edge. All moulded details are about easing visual abruptness. This use of profile was highly developed by the Greeks. Square head tooling, as used here, utilizes the components of pattern established by the Greeks. Milling is accomplished by clustering knives around the four sides of the cutter head – block in England – which are cutting components of the complete desired pattern. They somewhat differ from Gothic patterns in the absence of undercutting.
Shown above are stiles passing through the machine with rails and bars waiting on the belt guards for their turn. The parts have been tenoned and mortised with reference to which edge will be milled here at the sticker. The sap side must always be the milled edge in sash. Otherwise the grain will raise. Additionally, the part must be put to the sticker so that it will be milled with the grain to avoid tearing of the grain. Good sash material is quite expensive. Any steps to reduce milling defects are well worth the time. It is not necessary to lose any parts to defect at the sticker if one pays attention to the material and if the material is of sash quality.
Stiles are always made in lefts and rights. Parts must be stacked at the sticker for ease of manipulation because a pause in the feed while fooling around sorting parts will polish the wood at the contact with the spinning knives creating a defect for stained finish and creating heat which alters the temper of the knives. Taking the temper out of the knives shortens the time between sharpening.
This is an American Single Motion Clamp. It makes quick work of sash clamping. There is a technique in the hands and feet required in the using of it which I may elaborate on at some point. Sash are pressed in the clamp, squared, and pinned.
In the clamp is a storm sash. The stiles are pressed at the joints. Tenons are cut shy of stile width at the tenoner so that they will not interfere with the closing of the joint. I have always favored a slight compression of the fiber. Some very large plants deliberately skew the flats on the sticking to create a compressible contact. On the clamp beams are sash dogs. Also suitable with lighter blind or cabinet work. Doors require the more robust door dogs which are on the rack below the machine. For muntined doors, a heavy iron clamp rests between the beams. This puts a squeeze on the vertical muntins of a door or sash adequate to close joints and parallel the rails.
Here we see the beveling of the bottom of a storm sash on an American Clement Jointer. The Clement “Perfection” Jointer is the best jointer design ever manufactured. It is copied to this day.
Rails are edged first, then the stiles.
Here is the same jointer rabbeting storm sash. It’s a 5/8″ by 1/2″ rabbet best done in one pass. The Clement has no problem taking off a half inch. In this case, we are running against the grain. The deep pass greatly reduces, actually eliminates, tear out. The sticking was run with the grain which is why we are against the grain on the opposite edge. All jointers are made for right handed use.
Here we are glazing the sash. In this case, glass is bedded and set with glass bead, a small moulding often made in multiples.
DIVIDED LITE SASH
Divided lite sash are made by placing bars and muntins into field created by the stiles and rails. Bars run through from side to side or top to bottom. Muntins are the short parts that lay between the bars and the stiles or rails.
Here we see a rail being mortised for receiving bars. It is not a through mortise.
Here are the stiles after sticking and before haunching and relishing.
This is the fitting of muntins. I do this at the tenoner. A sash of each size in the run is put together and then I fit the muntins to suit. The object is not to have them too loose or tight. Too tight will deflect the stiles and bars which is embarrassing. Too loose will show an open joint. Also embarrassing.
Here are muntins going through the little sticker. For real short muntins, I run the tenons longer to add stability in the machine and trim them at assembly. This is the first pass.
And this is the second pass. In a sled this time. This particular pattern rocks slightly when run upside down without a sled. The sled keeps things nice and sweet.
The muntins tenons are the same as bars on each side but are trimmed to just less than half the bar width between the glass rabbets. This is the Houston Saw and Dado Machine at work here. I pull the table away to let trimmings drop to the box.
Muntin between bars, bars into rails.
In this case, bars vertical for strength in an awning sash. Also good for double hung sash. You know, the kind people don’t know how to use. On a casement sash, the bars would run like rails from stile to stile.
All knocked together now. Muntins straight the way we like them. Accuraccy and consistent points of reference are the key to straight muntins.
And off to the big clamp.
DECORATIVE or CUT WORK SASH
This is cut work. Miters, coped miters, and mitered copes. This was once common in many plants. A statndard sash could be divided in any number of patterns to add decorative features to the home or building.
Parts are cut to length from muntin stock prior to coping. A mating profile needs to be run for the tables on the trimmer to support the muntin and the same is also useful when clamping against the profile in assembly.
In a large field like this, I have selected a bar with crown up towards the top rail. The fit has to be somewhat loose in order not to distort the bar.
This is an American Sash Trimmer. These were made be several firms. They were not an AWWMCo product. These are essential for slicing the cope.
This is a mitered cope. The joint this cut is part of is in the background in the photo.
I have yet to master the machine. I also have yet to learn how to grind the mill to pattern profile.
DOUBLE HUNG CHECK RAIL SASH
Double hung sash require check rails, upper and lower, which have beveled surfaces that meet when the window is closed. They meet to close the gap between the sashes required by the parting bead which secures the upper sash in the jamb and prevents the surfaces of the sashes from rubbing on one another in operation. Double hung sash without check rails are called plain rail sash and are common on earlier and simpler homes, usually hand made.
Solid milled check rail sash require much more work than plain rail.
A groover or slotter is helpful. One can make the requisite slots for the open mortices with the morticers, but a groover makes a cleaner cut. Groovers can be run on shapers or heavy tenoner cope spindles. In my early career I did them on the table saw which I found was the least preferable method.
This is a shaper grooving set up. Set here for slotting the upper and lower stiles to receive the check rails.
There are several methods for the check rail joints. This method requires an additional rabbet on the check side of each stile.
This shows the lower sash stile metting the lower check rail which has not yet been beveled. I bevel last because I want the squre reference surface for notching the parting bead notch.
Which I am doing here at the pedal saw.
The check rail joint shown above is made at the tenoner with the upper tenon head removed. Then the part goes to the shaper for the slot, using the exact same elevation setting as the stiles, but referencing off the check side rather than the face.
The check bevel is the same on both parts and the parts are the same width so uppers and lowers are made at the same saw setting. The lower sash rail is run through the sticker while the upper rail is rabbetted for the glass at the table saw.
When closed together, the distance between the sashes should be slightly greater than the thickness of the parting bead in the jamb. This will prevent the sash from rattling.
The ogee detail in this sticking needs to be blanked off for the joint to assemble.
This is the joint required for bars or muntins into the upper sash check rail. the bar in this shot has not yet been stuck (milled).
This is a bar showing how I fit them to the glass rabbets. And to make sure the muntin mortices are perfectly aligned. This part has not yet been stuck.
A last step before assembly is to shorten the tenon equal to the depth of the stile plow which provides clearance for the sash at the rope and pulley in the jamb.
This is how it all goes together. The ouside edges are made 1/32″ proud to accomodate clean up passes at the jointer. The plow and bore is done at a sash sticker.
And off to the clamp for pinning.
INSULATED GLASS SASH
Insulated glass requires a large rabbet to accommodate the glass unit and to house a stop adequate in size to secure the glass, shield the unit sealant from the sun, and be sturdy enough to remove and replace without breaking.
In this example the haunch is housed into a slot in the stile.
Multiple sided sash can be made using splines.
The double spindle shaper with slot cutting saws makes this easy.
The spindles cut in opposite directions. The work can enter from either side without the need for backing and without running against the grain.
The work is attacked to a template. The template guides the work against the fence.
The vertical splines are longer into the stile and assist in clamping by allowing the slide only into the mating shoulders of adjacent parts.
Coping by hand. A reference cut at the meeting angle is made. The intersection of the sliced plane and the profile determines the “line” to cope to.
After removing a generous undercut with a saw, the finish is filed to the line with a round and a flat file.
There are two angles involved. The peak angle, and half the plumb angle.
In the entries (links) for the machines mentioned here you may find additional set up and operation information.