Routing windows for extra depth

[Horaldic]

First of all hello, this is my first post :). I hope this is in the right place.

I'm finally going to be able to get my workshop properly set up again after a hiatus of several years having purchased a house with some decent shedding. As a result of this house purchase I have a bunch of jobs I'm going to need to complete and gear I will need to buy.

The job I'm thinking most about at present is changing the depth that the glass is set in the old 1930's timber windows to accept 8.5mm laminate glass as opposed to the current 3mm glass. I'm doing this to improve the sound deadening from a nearby railway line. This is along with a number of other measures including: good ceiling insulation, thick carpets and heavy drapes. For a number of reasons we cannot install double glazing.

I have owned an older-style 3600 Makita plunge router for a number of years . It is the constant speed model from before they brought out the variable speed type. I was thinking of using this to rebate out the frames to the depth required. However, I suspect it may be too unweildy in this application.

Do any of you have a suggestion for a more suitable tool? I was thinking that perhaps a laminate trimmer might be ideal in this application? Or perhaps a smaller/lighter router may have more stability over the thin rails of the window frame and not be so difficult to keep level?

I will be removing the windows to replace the sash cors and increase the weights so access to the frame is not going to be an issue.

Any thoughts on this would be appreciated.

[Papa]

If all the windows are about the same, frame width, it should not be
hard to build a simple jig to do the rabbits.

I have had a one speed router so long, I see no need for any thing
else. You may need to do some test pieces to get comfortable doing
the real ones.

Be sure to prime the rabbits before installing the glass to prevent
rot down the road.

[orraloon]

Welcome to the site Horaldic,
This may be pointing out the obvious, but will the deeper rabeted frames be sturdy enough to hold the new glass that is going to be 3 times the weight of the old glass. Timber windows that old are often in a quite fragile condition. If they are the old puttied kind look out for small panel pins in the putty.
Regards
John

[Horaldic]

Thanks for the advice. The frames are of varying width which makes a jig a bit of a challenge. I think I may need to spend some time finding an appropriate router bit for the job.

The frames should be sturdy enough. I've played about a bit with this type of window construction in an even older house from the "Victorian" era before and so long as the window weights are balanced correctly for the new panes I can't see any engineering reason for the structure to fail.

If there are any failing timbers I'll replace them as I go. I've found these old windows to be "over-engineered" and made of higher quality timber when you compare them with the modern cedar framed windows installed in homes today. Though, of course, seventy years of weather and sun takes its toll.

[joe greiner]

Welcome aboard, Horaldic. Yes, I think you're in the right place.

As I understand it, you're concerned about riding on the pane openings to increase the depth of the rabbets, and the ribs aren't wide enough to assure stability of the router. A jig would facilitate the process, but the variable dimensions of the openings could require many separate jigs.

I think you could build an adjustable jig, by placing four wide strips in a pinwheel pattern. A threaded rod could protrude from the end of each strip, to engage a slotted hole in its companion, with a nut or wing nut and washer. The slotted holes would have lengths long enough to cover the range of sizes you need. The far end of each strip would reach far enough to enable clamping to the sash, out of harm's way for the router plate. This may only work if the sash is a constant thickness; otherwise, shims might be needed.

The jig dimensions may need an offset from the pane openings, depending on the profile of the bit with respect to its bearings, and a long bit may be needed to reach beyond the jig. The corners may need additional attention. A corner chisel could sharpen the deeper rabbets. Mortised hinges are made with rounded corners to match router bits, but that's probably not available for your new glass. A better way could be to allow the bit to slightly over-run the opening, just past the rounded location.

If my explanation isn't clear, I think I can draw a cartoon.

Joe

[Horaldic]

Thanks Joe. Though I think my imagination is failing me slightly on what you describe. It's given me another idea though, I could make an appropriate jig using a couple of sheets of MDF and just move and adjust it for each cut.

Some of the rails on the windows are most definitely too narrow to support my router but if it rides on the MDF and I can just change where I clamp it to the frame, that would work.

[joe greiner]

You're very welcome, Heraldic.

If you only have a few different size openings to deal with, separate sheets would definitely be superior to the fully adjustable contraption. Have a sharp look at the corners of the openings, though. A corner chisel would work, or your glass supplier might be able to nip the corners of the glass, to clear the rounded corner and be covered by successive moulding or sealant. Upon reflection, the notion of over-running doesn't look so great.

Joe

[Horaldic]

Hmm, yes, overrunning would make it sort of messy. I think I'll talk with the glass supplier tomorrow, all the sheets have to be specially manufactured from the Pilkington factory in Geelong so I'm guessing there will be minimal options. However, it's worth asking.

[joe greiner]

If the glass is NOT tempered, you or the supplier might be able to grind a chamfer on the corner at half the diameter of your router bit. Individual sheets could be nipped, but grinding is likely better for laminated in your thickness. The smallest bit available would need the smallest amount of grinding. Have a chat with your glass supplier to illuminate your options. The corner chisel might end up the winner, after all.

Joe

[GraemeCook]

Hi Horaldic

I did almost exactly what you are planning. My house was built in the 1870's and has huon pine sash windows. I put in 15mm double glazing - 2x3mm glass plus a 9mm gap, and used my old Makita 3600BR router to cut the rebates with a carbitool rabetting bit with ball bearing guide.

My method was:-


smash old glass. By about the fifth window I decided it was impossible to remove old glass without breaking it.
remove all old putty, glazing pins, dried paint, etc. Viciously/ruthlessly scrape rebate to ensure there are no nails, etc remaining to damage router.
lay sash flat on bench and make a spacer exactly the same thickness as the sash and slightly shorter than the shortest inside edge of the sash. This spacer is laid inside the sash and ensures both sides of the router are supported.
set router depth to cut about 3mm deeper than existing rebate. Check. Then deepen rebate.
Reset router 3mm deeper, check, and cut again deepening rebate. Repeat until desired depth is reached.

We found that new glass, because of its weight, had to be held in place with glazing strips and not putty. Should the strips be utilitarian or decorative?

We also found that we had to increase the sash-weights by so much that iron ones would not fit. I cast new weights in lead - same weight as gross sash weight (wood + new glass). And we took the opportunity to replace the sash cords with new super strong stuff from a yacht chandlery, and cleaned & oiled the pulleys.

Hope this makes sense.

Cheers

Graeme

[Horaldic]

Graeme, that makes perfect sense. Thankyou.

I have a roll of sash cord somewhere in my shed, well it was new when my dad bought it 30 years ago. Perhaps a trip to the ship chandlers might be in order.

Did you use the outer edges of the windows to run the router guide up?

I hadn't thought of anything other than putty. I'll have to find a source of glazing strips.

Making lead weights is going to be way beyond the week I have off work to get this done. I'll have to think of another solution.

My windows have some decorative elements on one sash which will mean I cannot use the router guide over more than three quareters of the width of that sash.

I am now thinking of using a top, flush-mounted, guide plate and a spacer.

I can use one of the Carb-i-tec "inverted flush trim" bits http://www.carbitool.com.au/routing_catalogue_popup/pic6/page10.html

The bearing would run along the edge of the guide plate (template I guess) and the spacer will support the router on the other side. As I'm planning on making two 3mm cuts and the existing rebate is probably only 10mm, the depth of the guide will allow me to use this kind of bit and be a guide for that top bearing.

Wednesday is action day, but at least I now have some semblance of a plan, provided I can find some suitable weights.

Many thanks!

[GraemeCook]

Graeme, that makes perfect sense. Thankyou.

I have a roll of sash cord somewhere in my shed, well it was new when my dad bought it 30 years ago. Perhaps a trip to the ship chandlers might be in order.

Did you use the outer edges of the windows to run the router guide up?

I hadn't thought of anything other than putty. I'll have to find a source of glazing strips.

Making lead weights is going to be way beyond the week I have off work to get this done. I'll have to think of another solution.

My windows have some decorative elements on one sash which will mean I cannot use the router guide over more than three quareters of the width of that sash.

I am now thinking of using a top, flush-mounted, guide plate and a spacer.

I can use one of the Carb-i-tec "inverted flush trim" bits http://www.carbitool.com.au/routing_catalogue_popup/pic6/page10.html

The bearing would run along the edge of the guide plate (template I guess) and the spacer will support the router on the other side. As I'm planning on making two 3mm cuts and the existing rebate is probably only 10mm, the depth of the guide will allow me to use this kind of bit and be a guide for that top bearing.

Wednesday is action day, but at least I now have some semblance of a plan, provided I can find some suitable weights.

Many thanks!

Hi Horaldic

The marine braid is seven or eight times stronger than ordinary braid and slipperier (less friction) so I reduced the size from 6.5mm to 4mm.

I ran the router bit bearing along the inside of the window sash.

The glazing strips were just strips of bevelled timber about 5x10mm - its raining so I'm not going outside to check - and were mitre cut to fit inside sash frame. Glazier emphasised that putty was not strong enough for double glazing.

I just used very skinny aluminium pep-drink cans and poured molten lead into them - set cans in dry sand in case Al melted but there was no deformity - labels disappeared.

I find it best to nibble away with a router rather than trying big cuts. Without seeing your windows its hard to comment more specifically. Just think/act everything through first as an error may be difficult to recover from.

Biggest downside was the 48 hour time at the glaziers and the three days wait while I waited for my paint to dry. (3 coats). Would have been a little easier if I had painted the frames before sending them to the glazier. No glass to paint then.

Cheers

Graeme

[Horaldic]

Ahh, very good. I'm sure I can pick up some glazing strips somewhere here in Melbourne.

I think I'll try and fiddle with my weights before getting into casting lead. Last time I did that was when I had access to a gas fired furnace, with my dad *ponders time interval* probably twenty-five years ago.

:D

Cheers