Test fitting the primary joinery. Note the horns will remain until we paint the sash.

Making a Window Sash Part 1

Building a window sash by hand can sound intimidating, but with some practice it can be an enjoyable experience. Early window sash were built by hand designed to be maintainable — if a component broke or rotted out it could be replaced — something that is not possible with most aluminum and vinyl windows you see on the market today.

Continuing Education Department at the North Bennet Street School, Boston, MA
Continuing Education Department at the North Bennet Street School, Boston, MA

A few weekends ago I taught a two day workshop I developed on building a window sash at the North Bennet Street School. This post and the next are a high level recap of the course with some photos from building the prototype in my workshop and what we did in the classroom

Nice quarter-sawn stock for muntins.
Nice quarter-sawn stock for muntins.

Stock selection is important. My wood of choice is Eastern White Pine, preferably quarter-sawn heart pine which is easy to work, weathers well and historically appropriate in my area — the greater Boston area.

Sticking Knife Profile in the Williams and Hussey
Sticking Knife Profile in the Williams and Hussey

A profile can be run by hand using sash planes or using a router table. For larger runs a custom molding knife can make fast work of this often tedious task using a machine like the ‘Williams and Hussey’ molder. (Shown above and below)

Profiling the stock
Profiling the stock

We make a few passes to get near the finished size wanted and then a final cleanup pass at the end to leave the piece with a nice finish.

Profiled stock coming out of the molding machine
Profiled stock coming out of the molding machine

Rails, stiles and muntin stock are run using the same setup on the machine — this way all the profiles are consistent.

Rails, stiles and muntin stock profiled.
Rails, stiles and muntin stock profiled.

Next up is the use of a story stick — this traditional device is effectively a set of plans laid out on a piece of stock that matches the rest of your milled stock. Key locations like mortises are transferred to the work piece by using a marking knife and a combination square. The knife allows for accurate and consistent transfer of measurements to the work-piece.

Using the story stick to transfer measurements to the work piece
Using the story stick to transfer measurements to the work piece

Shown below are mortises cut either with a hollow chisel mortiser or by hand with a mortising chisel. Also note that the work pieces are deliberately left long. These ‘horns’ allow for more relish to support mortise walls from blowing out and also allow the sash to sit in the shop and not ding or damage the piece as it is worked on and eventually glazed.

Mortises cut
Mortises cut

Once the mortises are cleaned up its on to cutting the tenons. Once the piece is laid out I start by cross-cutting the shoulders. (See below). I then use a chisel to pop off the waste or for larger tenons will make a second saw cut (This time ripping down to the shoulder cut) and clean it up with a chisel.

Cutting in to reveal the tenon
Cutting in to reveal the tenon

With the shoulders in place I can dry fit them (using the square shoulders that are on the exterior side of the sash) to make sure I have a tight fit as seen below.  Note that I am not fitting the tenon yet, just the shoulder to start.

Test fit the central muntin
Test fit the central muntin

Next up was the coping. I make use of a saddle block with a 45 degree ramp and some in-cannel chisels to cope the muntin stock as shown below.  With the cope in place I can now test the fit of each of the tenons into its mortise.

Tenon complete and profile coped
Tenon complete and profile coped

This creates a nice tight joint that allows the pieces to mate together in a pleasing manner that allows to profile to make that 90 degree transition from the horizontal to the vertical.

A nicely coped joint
A nicely coped joint

I use a similar process for fitting the horizontal muntins — starting first with the center joint as this can be fussy at times. I want each horizontal muntin to meet cleanly in the center and have both tenons fill as much of the mortise as possible. I leave the stock long so if something goes wrong with the joint I can cut off that inch or so and try again without wasting a whole piece of stock. With the center joint in place I’ll cut the other shoulder and fit it as we did with the vertical muntin and then cope the joint and test those tenons.

Test fitting the shoulders for the horizontal muntins
Test fitting the shoulders for the horizontal muntins

With all the primary joinery completed its time to dry fit it all together and check for square. All the joints should fit together well and the shoulders and copes should be nice and tight.

Test fitting the primary joinery. Note the horns will remain until we paint the sash.
Test fitting the primary joinery. Note the horns will remain until we paint the sash.

If your joints close up with some mild pressure don’t worry too much as the draw bored pins will help pull the joints together and keep them closed. With each stage in this process the sash becomes more and more rigid.

In the next post we’ll talk about making pins, draw-boring, cutting glass and glazing.

Take care,
-Bill

7 thoughts on “Making a Window Sash Part 1”

  1. Thanks Bill. I am fascinated with making windows by hand. I have all the antique tools and I hope to cross this project off my bucket list. I look forward to Part II. Mark

    1. I don’t have the dimensions for that sash handy as my shop is half in storage as I am building a timber framed barn at home. But given its unlikely you have the same profile the dimensions are not all that useful to you. Unless you are trying to replace an existing sash I’d say you should start with a profile you like and then define a lite (the window glass) size you want to use. For that workshop I used 5″x6″ panes — an odd size historically, but efficient for use as I can easily get a 10″x12″ pane at lower and the students only have to make 1 cut to get it down to size. So with the profile and glass size defined you can create a story stick, work out the size of each piece and use that story stick to lay out the sizes without having to do additional measurements with a ruler. (I think the sash was about 12″x 14″) At some point I need to write up the part 2 of this post, but it may be a while given the barn build. In the meantime you may want to check out this book reprint by my friends over at the Lost Art Press as it echoes many of the same techniques I use when building a door or window.
      https://lostartpress.com/products/doormaking-and-window-making
      I hope this helps.
      Take care,
      -Bill

  2. Hi Bill, I took the 3 Month furniture course at NBSS last March. I always volunteered to go check on the dust collector just so I could walk through the preservation carpentry shop to see what they were up to. I was most intrigued by the window sash construction. I need to make a few custom windows for a project I am working on now and was hoping to take your workshop, but unfortunately it looks like the timing isn’t right. I have made a set of sashes once, but I milled the stock on a table saw so was limited to an angular profile. This time I would like to do it right. Luckily, I recently picked up a Williams and Hussey molder on Craigslist for a song. Were you able to buy your knives stock or did you have them custom ground? Thanks for the post, I look forward to part two!
    Ian

    1. Hi Ian,
      I buy my custom knives from W Moore profiles (As does the school) http://www.wmooreprofiles.com
      I’ve found the prices to be reasonable and the quality exceptional.

      I also recommend this book reprint by the Lost Art Press on Door and Window Making. The content is originally from the UK so some of the styles/details are distinctively English, but many of the tools, designs and techniques are similar to how I was taught to make windows and doors.
      https://lostartpress.com/collections/books/products/doormaking-and-window-making

      Part 2 is in the queue to be written up, but with a new baby, a recent death of my grandmother and a timber frame barn build going on I am way behind on my blogging. If you are not already following the blog I highly encourage you to follow it via email, wordpress, Facebook or twitter (all of which are available via widgets/links on the left and right side of my blog/webpage)

      Good luck with your project and I hope to see you in a future class.

      Take care,
      -Bill

      1. Thanks Bill,
        I actually picked up that book last summer on a trip to Lie Nielson, and I have a set of knives in the mail right now from W Moore. Once those arrive I guess I have no more excuses… Thanks!

      2. Great to hear. Once you finish some of your sash you are welcome to post a picture of it here in the comments or send it to me and I can post it on your behalf.
        Good luck.
        -Bill

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