Cutting sash to match profile of cill

[fernicarry]

I've just made myself a sash and the last thing I need to figure out is cutting the profile on the bottom to fit into the cill.

Here is the cill profile we use in this part of the world. The outside face of the sash sits in line with the small step to the right and the inner face of the sash overlaps the flat part by about a quarter inch.



Next shows the cill offcut offered up to the underside of an existing sash.

The bevel along the bottom is easy enough, track saw on outer face of sash with (I'm guessing) 5' undercut. What I'm stuck on is how to cut the rebate out of the inner face of the sash where it overhangs the top of the cill. I reckon the angle on the cill is 30' but its maybe half of that on the sash itself.

Best I can think of at the moment is a panel raising cutter. Either feed the whole sash across the table or use a guide rail to run the router across the sash. There are cutters with a 15' angle that would cut the straight edge into the face as well. Multiple passes required to get the depth I imagine.

However I'd prefer not to splurge on yet another cutter for this project (I've purchases at least 10 in the last few weeks....), and those large panel cutters are quite spendy, so can anyone think of another way?



Here's the sash itself awaiting glue up. Its actually going to be a fixed light hence the extra rail in the middle to give the appearance of the meeting rail of a pair of sliding sashes. I'm quite chuffed with it considering its the first I've done with glazing beads!

 

[fernicarry]

So I ended up doing it as I was thinking with a panel cutter on the router table.

I used this cutter from Axminster which was a bit more reasonably priced than similar Trend ones and the angle is a close match to my existing sashes. Good sharp cutter but really big and heavy. The noise from it was quite terrifying!

Feeding the whole sash across the table was not without its trials. One of the stiles being slightly out of alignment with the rail meant that it caught on the edge of the table on the way in and needed a bit of a jiggle to keep it moving. As a result the rebate isn't perfect flat but that is normally hidden when the sash is closed (and this one will be fixed closed).




And here it is filling the hole in the side of the house, sans glass. A bit of an improvement compared the starting point in this thread I think you'll agree.

 

[Janela]

beautiful carpentry skills, bravo.
A lot of time and patience!

 

[frustin]

how did you find out how to make one?

 

[fernicarry]

There's not that much to it tbh. Inspiration probably came from watching too much YT. I highly recommend Bradshaw Joinery, he is outstanding.

I've cheated somewhat to make it easier, purists look away now. For example the corners don't have proper tenons, they are just butted and glued. PU glue is so insanely strong I don't think it will ever come apart. Just have to be careful at assembly time to get the diagonals equal so that it comes out square. This one went a bit wrong actually and the diagonals are 5mm different which turned the air blue at the time but its not at all noticeable in the frame because the slight run in the gap is covered by the staff beads (and I suspect that when I made and fitted the frame a few months back I didn't get it perfectly square either). Reason it went wrong was I changed to a 30 minute glue to give me more working time but it wasn't the usual runny, slippery stuff I use, it was more gel like and it got a crazy initial grab making it very difficult to adjust pieces during assembly. The fan light I did previously went together perfectly square and opens and closes like a dream. Moral is don't change things at the last minute and always test and practice on scrap pieces.

- Rip and plane your material down to size, each piece should be left a little over-length
- Machine the moulded profile on the stiles (verticals) and rails (horizontals)
- Machine the glazing rebate on stiles and rails
- Machine the scribed (inverse) profile on the ends of the rails
At this point you would normally have to make up the mortice and tenon joints, instead I machine away the stub that should form the tenon from the rail so that it butts closely against the stile profile
- assemble and glue up, do a dry run and mark everything so you know what goes where and what dimensions you need to land on
- trim off the stiles with track saw to be flush with outside edge of rails

The glazing bars (muntins, astragals depending on regional nomenclature) follow much the same process but the profiles are machined into both sides leaving you with very little material left. I dropped the moulding cutter a bit lower in the table so that the profile on both sides meets almost at a point to replicate the "feather" astragal used on all my existing windows (this was sanded to a slightly rounded profile afterwards). I was concerned that pushing the second side through the router table would be difficult (or nigh on impossible) because there isn't much flat surface left to run on but it actually went off without any drama at all. Shows that its worth just having a go.

There's some almost real joinery in the glazing bars in that I made a socket in the inner face of the rails for them to fit into. I used a multitool across the grain to get the socket started (because my chisels are never as sharp as they should be) then cleaned it out with a chisel. On the second glazing bar I realised I could have the socket smaller than the width of the bar by taking a bit off the face off the bar with a depth-limited cut on the chop saw. This makes the joint even less noticeable as the bar sits on a shoulder against the rail. Hopefully the pictures explain what I mean. Since I'd left the glazing bars well over length I was able to practice this 10 or 20 times until I was confident I could do it spot on at the correct length.






The last step was putting the bevelled rebate into the bottom edge of the bottom rail as per my original post. If this was a proper sliding sash then there would be some fiddling around with the meeting rails to create the interlocking profile, possibly using the same cutter. I have a top sash with a soggy bottom that will be a chance to try that out, either repair or just make a whole new one, but If I make a new one I'll need to figure out how to cut the horns...

The fact that I'm using soft pine helps hide a multitude of sins as it all sort of compresses together when you do up the clamps and small gaps disappear. The foaming glue will also fill gaps. A trick I learned on YT (from Bradshaw) is to put a bead of caulk around the inside edge of the joint before assembly. The caulk is squeezed out of the joint rather than the PU glue and is far easier to clean up from inside corners as well as filling any little chips from behind. As they say, "caulk and paint makes you what you ain't". It'll be durable enough to see me out so I'm not fussed about not having using hard wood.

So its either the world's cheapest window having cost me about 20 quid for a length of 4x2 dressed from the local builder's merchant plus 60 quid to have it glazed, or the most expensive window given that it needed many thousands of pounds worth of kit and far too much of my time to realise!

Whichever way round it was good fun and supremely satisfying and we all need a bit of that from time to time to keep us going.