Internal glazed units

[RogerS]

At last I can finally get around to doing some woodwork for the cottage.

There is an internal wall (which was the original external wall) between the new orangerie and the open-plan living area. There are two empty holes that will be filled with double-glazed units in mullion type oak frames.

Each hole is roughly 850mm high by 1385mm wide and have been squared up after a lot of faffing about. The centre post was all over the place and I squared it up by fitting a vertical template and then running the chainsaw down both sides. In the picture below you can see where the original beam (shown black) remains smaller than the template. Hidden metal, nails etc were first detected using the Lumber Wizard and either removed or hammered below the cut line.

The plan is to split up each window into two glazed units with the verticals turned around 45 degrees to make it look like a mullion frame.

Past experience tells me that cutting square material down the diagonal isn't that easy. The size of the mullion posts (75mm square) is also going to push the limits of my kit.

A quick trip to Good Brothers produced some kiln-dried oak albeit very pricey. Typically a length of 2.3m of 75mm x 80mm was £28+VAT.

Mistake no 1 - I forgot to take my moisture meter with me and while choosing the timber by eye, when I got home I found that one of the pieces was around 15%, the rest in the range 10-11%.

Mistake no 2. Because I don't particularly like seeing the joins in planks, I always like to have wide whole pieces of wood. So as the windowsills will span across the width of the wall and overhang slightly, I was after something about 12" wide. They had some nice prepped material but that was only 6" wide. A search in one of their sheds produced a length of oak that was 13" wide but in need of preparation. I wasn't quite sure how I was going to plane something that wide - various jigs and routers came to mind as I drove home.

I needn't have bothered and actually made a rod for my own back. There was no reason why I couldn't have gone for the prepared 6" stuff and joined them together since the join line is going to be hidden anyway! Close inspection of the wood showed it to be bowed along part of its' length

so I had no option but to rip it down. Only to discover that it's lively.

. That cutline was straight off the table saw.

A few passes through the planer tidied it up but I'm going to wait and see what happens overnight before I do any more work.

CONSTRUCTION

The actual construction is still up in the air. I think that I will make it up as a frame and sit that onto plasterboard up the two verticals and along the top. That way I should be able to pack out the plasterboard to be a snug fit against the frame so that the plasterer can make a tidy job. I want to keep the verticals and top of the frame fairly sparse (ie not have a large piece of flat oak onto which the mullions will fit) as the room is already heavily oaked. There is no need for real structural strength as it will effectively float inside the houses' oak frame.

If I make the frame in one half vertically I think that I should be able to make it reasonably square and sufficiently strong. The two outside mullions will be left whole and the one in the middle cut in half. One half will be already fitted to the frame. I can then slide in the glazing units into the two outside mullions and then fix the centre mullion half later. Somewhere along the line some old oak floorboards will be pressed into service to finish off the top and bottom.

KNOWN PROBLEMS

1/ I've never had much success cutting square stock cleanly down the diagonal. My table saw goes to 45degrees but the blade isn't deep enough. So I think it will have to be the bandsaw and some sort of jig to keep the cutline in the right place ....but what?

2) I need to cut a groove into the triangular mullions to take the dgu (double glazing unit). How? These are long heavy lengths of oak.

Put a dado on the table saw? Never cut a dado in my life and not sure if the dado I have actually fits the arbor.

On the spindle moulder? But I would need to buy a groover which at over £100 is a bridge too far.

On the router table? Support for the stock is questionable perhaps.

Any ideas?

 

[Steve Maskery]

Hi Roger
You do make life difficult for yourself, don't you?

OK, initial thoughts.

45deg cuts. I'd mak a V-cradle for the bandsaw, but I know you don't like your saw very much. You could cut it partway through on the TS, perhaps from both edges, just leaving 1/2" or so wood in the middle. Then finish though with the BS, much less challenging.

Personally I would probably have fabricated the moulding - you could have used thinner - and therefore probably cheaper - wood, bevel-ripped it on the TS with no problems and, when glued up and the arrises removed you would not be able to tell the diference. Probably more stable, too.

For the groove, even I, who am reasonably pro-dado, would baulk at using one for this job.

This is a job for SuperJigMan;

12mm baseboard 200x150 or thereabouts. Ends have support pices for you router fence rods. The router sits on the rods in roughly the centre of the board.

Ont eh underside of the board are two triangular fillets, so that the jig an sit on a corner without wobbling. You can then jun a router along the edge. Groove width is increased by moving the router along its rods. You'll need to decide how to clamp the workpiece, but if you have an older workmate with the grooves in the jaws, that should do, I would think.

If I have any other ideas I'll let you know.
S

 

[RogerS]

Thanks Steve for the suggestions.

I tried a cut on the bandsaw by tilting the table to 45 degree but the cut went offline fairly quickly. Thinking about it, it only needs the fence to be a tiny bit out of square and that will be enough. I'll give your idea some thought.

I like the idea of using the stock to support the router. Will give that some thought as well.

 

[Steve Maskery]

 

[RogerS]

CUTTING THE DIAGONALS
Following Steve's suggestions, I tried part cutting on the table saw. Lining up was very tricky. The fence really wants to sit tight against the blade to ensure that you cut down the diagonal but the kerf of the blade fouled the fence. Luckily I realised that before firing it up. Tried a sacrificial piece between fence and blade but the following result was disappointing. Guess I could have persevered but decided to try Steve's Plan B - the sled.

Ripped some spare stock down and fixed it to a piece of spare kitchen plinth and decided to make it a decent length.

An initial trial run proved encouraging and so I went for broke and at £25+ per piece of stock you kind of keep your fingers crossed.

Cut 1 - perfect

Cut 2 then proceeded to go really pear-shaped

and I really struggled with this one stopping the cut and coming at it from the other end. Still disappointing but some sawdust and glue will have to fill the gap. I even tried unclamping the sled and handguiding it from side to side to try and keep the cutline true but without much success.

Then I realised that I could get a heck of a lot more tension in the bandsaw blade and Cuts 3 and 4 were perfect again - phew.

CUTTING THE GROOVES
Next to cut the groove for the DGUs. The choice of DGU is either 4-6-4 (4mm glass, 6mm spacer, 4mm glass) which is perfectly permissible as it's an internal window. Add a couple of mm for glazing stuff (although I'm tempted to mount them dry) means a 16mm router cutter. The thicker DGUs (4-12-4) would need a 22mm cutter which I reckoned was a lot of oak to hog out.

Again, using Steve's suggestion my lightbulb moment came when I realised I could use a bit of the sled upside down.

Drilling two bolt holes exactly through the centre line, I bolted the router on top. I also made sure that I gave myself a generous amount of lead-in and lead-out support.

Holding the stock down was a no-brainer as I clamped it between a couple of bench dogs and the tail vice checking first that the router cutter wasn't going to try and mill through the top of the dog.

A trial cut using a 16mm cutter created a huge amount of sawdust compacting in the groove even though I was making lightish passes. So I decided to precut the grooves using a kitchen worktop cutter and even then I cut each groove in five passes.

Lots of sawdust later, ready for the final cut using the correct width cutter but I need to measure the depth of the DGU spacers etc so that they get lost inside the groove.

I need to double check with the suppliers that toughened glass comes in 4mm thickness and also how much depth I need to cut to lose the DGU spacers etc. Rather frustrating that I need toughened since the bottom of the windows are 770mm off the ground and the limit is 800mm. Normally I wouldn't bother but as the cottage is being done under Building Control notice I can't afford to chance it even though I know they probably won't pick it up.

WINDOWSILLS
The stock hadn't moved anymore since last weekend so I decided to prep them some more. Planing the 6.5" boards on a 6" planer is not ideal but they are coming along. I realised that I made a mistake in ripping them down the middle since the window line that is intended to hide the join is not on the centreline. Not too sure where it is so tomorrow I'm going to take a few more accurate measurements and decide just how much material I can remove from the windowsills as my early planing efforts resulted in the material being a tad uneven across the width. I can see me leaving the underside unfinished (as it won't be seen) so that I can keep a reasonable finished thickness.

NEXT MISTAKE aka PPPPPPP

The original plan was for the middle mullion upright to be in two halves so that I could slide the DGU into the side mullions on the left and right and then fix/glue/whatever the second half of the middle mullion down. Only I've cut the wrong diagonal for the middle mullion and it is exactly the same as the ones on the outside. It should have run down the groove . You think you've planned these things through only to realise you haven't.

So now I have to glue the middle mullion back together and hope that the joint line on the diagonal is good or sandwich a thinnish (10mm?) piece of contrasting wood between them.

Assembling the window and getting the DGUs in place is now exercising my mind. I could try and cut down the correct diagonal after the glue-up but it has to be 100% spot on to accomodate the DGUs. The current preferred plan is to make the frame up without the middle mullion, instal in the window opening then offer up the DGUs into left and right outers and gradually ease them into the middle mullion which is then slid and glued into position taking the DGUs with it.

CORNER JOINTS

The easy way is to simply cut a triangle out of the windowsill halves that match the upright mullions and glue them in place. But that assumes that the way I cut the windowsill down matches where the uprights need to be. Not convinced either that that will be strong enough and really fancy cutting a triangular piece that is 2/3 deep so that the uprights sit on the windowsill. Unnecessary work though??

 

[RogerS]

Planed the cut faces of the centre mullions a tad and glued them back together. The end result wasn't too bad.

Decided to abandon any thoughts of being clever and making proper joints since there is no structural strength needed and too many other demands on my time. So opted for a couple of dowels to locate the mullions and foamy glue.

Accurately locating the dowels proved to be a bit of an art. For the first ones, I used an offcut from the mullion and then tried to plunge rout where the dowels would go. Controlling the router proved to be a bit feisty and so opted for a simple drill and 10mm bit. Rushed it. Used the wrong (too fast setting) glue and the result was a pigs ear. The centre mullion rotated (I was too lazy to use two dowels), the end mullions didn't sit square. If the DGUs don't fit then I'll cut through the joints and remake.

The next day, I took a lot more care over the second window. I used a Triton drill that has a built-in 90 degree steady, two dowels per mullion and the end result was a nice tight joint.

Next I needed to make some oak fillets to conceal the top and bottom of the DGU's. Each one needed to be individually tweaked as the angles of the mullions relative to each other were all over the place. I used some cartridge paper folded into the angles as a template and then adjusted the mitre on the saw. Some were beyond the adjustment on the saw so these were handheld in the right position. Got there in the end but to be honest I wish I'd never gone down the angled mullion route....damn sight more difficult to work with then nice square stock.

So popped one empty frame into its' proper location and it actually fitted - now there's a first. The DGU's arrive Tuesday so we're good to go.

Thanks for looking

Roger

 

[JonnyD]

Looking good so far. I am slightly confused as to how you are going to get the units into the frames or replace them if they get broken.

Jon

 

[RogerS]

The frames aren't fixed in yet and so the DGUs will slot in from the top (it's only screwed on at the moment. As for breakages, well, no kids so that eliminates one risk. If they get broken...well....worry about that then :wink: