Best way to rout this rebate..?

[Iancd]

I'm going to be making timber sub-frames to fit windows into heavy section oak main/outer frames. The windows are to be fitted from outside, sealing against the sub-frames.

The sub-frames are 17mm thick oak, rebated 5mm deep and 35mm wide; I can choose the overall width of the sub-frames, depending on how much I want to be seen on the inside of the window, but they're likely to be between 60mm and 70mm. The longest piece of sub-frame is 1.5m.

I have a router table which I haven't used yet and am wondering whether these rebates are best cut with a long straight mortise bit, holding the width of the sub-frame sections vertically against the fence, or with a smaller straight cut bit in two or three passes, with the width of the sub-frame flat against the table?

Many thanks,
Ian

 

[Phil Pascoe]

There's little to be gained by doing it vertically, 35mm x 5mm is a fair chunk so you'll still need more than one pass. it's easier and safer done on the flat.

 

[marcros]

I recently bought a 6mm grooving sawblade- I bought use the 5mm version of that. It was a cmt from biven and was about the same price as a decent router cutter

 

[Iancd]

There's little to be gained by doing it vertically, 35mm x 5mm is a fair chunk so you'll still need more than one pass. it's easier and safer done on the flat.

Thanks Phil,
What diameter straight cutter would you recommend using - largest I have is 19mm - and how many passes?

 

[deserter]

I'd agree with Phil on this.

As a rule of thumb don't cut deaper than the diameter of your cutter. Obviously there are exceptions, butvim a good starting point.

 

[RobinBHM]

I would choose a 1/2" cutter as they are often cheap -at least in 1/2" shank as they are std kitchen worktop cutters. If you are using a small router then buy a short bit.

If I was cutting a rebate 35mm wide, I would do about 2mm width x 5mm deep to trim the start of the rebate cleanly. If you are confident with the router this first cut can be done climb cutting if the routing is creating a lot of chipping. Do not attempt unless you are sure you can control the router without snatching -Id hate to recommend unsafe

Then set the fence for cutting to 35mm, rout a groove to depth, re set the fence and repeat passes until you get back to your first cut. That way your router is fully supported until the last cut.

 

[andersonec]

Have a piece of scrap to make test cuts as you adjust your fence for each cut.

Andy

 

[Iancd]

I would choose a 1/2" cutter as they are often cheap -at least in 1/2" shank as they are std kitchen worktop cutters. If you are using a small router then buy a short bit.

If I was cutting a rebate 35mm wide, I would do about 2mm width x 5mm deep to trim the start of the rebate cleanly. If you are confident with the router this first cut can be done climb cutting if the routing is creating a lot of chipping. Do not attempt unless you are sure you can control the router without snatching -Id hate to recommend unsafe

Then set the fence for cutting to 35mm, rout a groove to depth, re set the fence and repeat passes until you get back to your first cut. That way your router is fully supported until the last cut.

Great, thanks Robin.
I've assumed I'll be doing this on the router table. There's about 11m to be worked in total, with the two longest pieces each 1.5m. Am I right that it'll be easier (and safer) on the table? There will be just over 1.5m of workbench at the same height either side of the table. The router is a Trend T11EK.

The advice re a small first cut, then a groove and work back to that first cut all makes sense... not sure re the climb cut, so I guess I'd try it on some practice material to see if it works.

Ian

 

[dejaa]

Hi

Are the sub-frames already assembled? I'm guessing not?

If so why not consider using a table saw? I have made dozens of oak frames windows including their oak frames. I always cut the rebates on my table saw. Doing this you always get the offcut which can be used as a glazing bar which matches perfectly the colour grain of the subframe. More than happy to send photos if your'e interested in this approach

David

 

[Iancd]

Hi
Are the sub-frames already assembled? I'm guessing not?
If so why not consider using a table saw?
David

No, they're not assembled yet...
...but I don't have a table saw..!! :lol:

 

[Eric The Viking]

A kitchen worktop cutter (1/2" shank, 1/2" width) is an inexpensive choice for this - they are so common you can get good ones cheaply (Freud, Wealden, Axminster, etc.). A new cutter will make everything easier - cleaner cut, less strain on the motor, etc. A rebater will give a better finish, but the rebate isn't seen, so it's probably not worth the extra cost.

That said, you're doing frameS. A rebate block will work faster and probably need fewer passes. But make sure the threaded mount for the bearing doesn't stick up above the knives, as your cut depth will be limited by this. The Wealden one is recessed, so you can go deeper (further from the fence). I find a proper rebate cutter is better behaved (the knives are slanted).

As for doing it, the key thing is what you have left when you finish the rebate. Will the cut piece support itself, or is there a risk it will tend to tip over into the spinning cutter? And will you be able to use a push stick easily?

As suggested, your first pass defines a clean edge to the rebate. After that, each pass can be as chunky as the router and cutter will allow. Assuming you're keeping the cutter height constant (at 5mm), if you screw a narrow batten, 5mm thick, to the outfeed side of the table, it will support the stock and prevent it tipping over into the cutter.

My first attempt at frames involved bigger rebates, but exactly the same problem. I came up with a complicated jig I could clamp to the lip of the table on the outfeed edge, which did the same thing. What a numpty!

Two holes, for 4mm countersunk machine screws, in the outfeed side of the table top, on the cutter axis (so all three centres are in a line parallel with the fence), would do it much more easily, with no clamps needed. I hate clutter where whizzing knives are involved!

So, do a 5mm thick batten of something* , almost reaching into the cutter, with a slight bevel on the end, so the stock leads onto it easily. When your rebate gets to the width that the stock may become wobbly, bolt the batten down onto the router table before the next pass, and the rebated stock is safely supported. Different rebates only need different thickness of batten...

I am SOOO glad you raised the question: it's birthday time (October is 'month-of-impoverishment' here), so I have small picture frame mouldings to make. Going to mod my own table and ditch that silly jig!

Sorry for a bit of a ramble. Hope it makes some sense.

E.

PS: djaa's advice re tablesaw is much better generally, but safety considerations apply: the waste will be inaccessible initially when it's cut free , and there are blade guarding issues. You can't use a batten as support either as the waste is in the way, and you have to remove or lower the riving knife. I like the idea in principle, as glazing bars are a PITA and using fresh stock is wasteful, but I'd have to think it through carefully. I have a tablesaw but rarely use it.

*(can you make the rebates 6mm? That's standard MDF thickness, so v. easy)

 

[dzj]

A jointer with a rebate 'ledge' would do the trick.

 

[Iancd]

Well, I only just got round to doing this... As it worked out, the sub-frames needed rebating to different depths to accommodate the windows and fill the space between them and the large oak frames.
So, against all the advice here (!!), I went with Bill Hylton's advice ('Ultimate Guide to the Router Table') and did the rebates vertically with the 16mm mortise bit, using two horizontal featherboards fixed together one on top of the other to hold the (60-65mm wide) sub-frames against the fence, and took maximum 2mm cuts at a time.
It went fine, seemed very straightforward this way and was really easy to adjust how deep I needed the rebates. I'm wondering what the concerns were about that method..?

...and aren't router tables... Brilliant..! (Paul Whitehouse.. )

 

[woodchip]

Well, I only just got round to doing this... As it worked out, the sub-frames needed rebating to different depths to accommodate the windows and fill the space between them and the large oak frames.
So, against all the advice here (!!), I went with Bill Hylton's advice ('Ultimate Guide to the Router Table') and did the rebates vertically with the 16mm mortise bit, using two horizontal featherboards fixed together one on top of the other to hold the (60-65mm wide) sub-frames against the fence, and took maximum 2mm cuts at a time.
It went fine, seemed very straightforward this way and was really easy to adjust how deep I needed the rebates. I'm wondering what the concerns were about that method..?

...and aren't router tables... Brilliant..! (Paul Whitehouse.. )

Wait until you get a spindle moulder