Thread: Cutting dadoes for bookshelves

Originally Posted by havenoideaatall

Thoughts?

For a nice finish you can take a shallow cut with the saw to within 2mm of the size (depth and width). Then finish it with the router using a parallellogram jig.

Make the jig out of four pieces of mdf, two about 300mm and the other two long enough to span the job, plus about 400mm. Insert one bolt in each corner so the width can be adjusted. Clamp one side down as a guide for the router, sit router in place then close the other side to touch the router base. Then clamp the other end and rout the dado.

fantastic!!

I anticipated originally that dadoing would be easy - test cuts of course were a doddle, but the wood was easier to control.

I now will look to the use of the router to complement/replace the Triton.

Try a few of these for help too, you might find something you like:

Woodworking Tip: Dado Setup Jig
router dado
Router Dado: American WWer

Whilst not wanting to hijack this thread, I am interested in the answer...

All this talk of cutting dadoes reminds me that until a few years ago I had never heard this term in Oz. My old dad (in his eighties now and a keen woodworker when younger) always referred to them as trenches (and while on the subject, also referred to 'rebates' not 'rabbets').

I never use the terms 'dado' and 'rabbet' when talking about 'trench' and 'rebate'.

So is this simply just just another case of a couple of Americanisms that have infiltrated the lingo (now there's ANOTHER Americanism - lingo), particularly since the advent of the US handyman programs on pay tv?

Or have these terms always been used interchangebly in Oz in the chippie trade, and I've just been unaware of it?

Jeff.

The search for additional knowledge should never be considered a hijack. I looked up the terms in Wikipaedia, I hope this helps. As for who originated the terms, my personal view is I don't care anymore. I would rather a common language where I can be understood whether I am speaking in a shop here in Oz or on a phone order to the US. A tool for 'trenching' there will cost a lot more than one here does .

Dado

Groove or plow cut

Rebate

Originally Posted by Swagman

So is this simply just just another case of a couple of Americanisms that have infiltrated the lingo (now there's ANOTHER Americanism - lingo), particularly since the advent of the US handyman programs on pay tv?

Or have these terms always been used interchangebly in Oz in the chippie trade, and I've just been unaware of it?

Don't know that I've got the answer for you, but I can chip in and say that the Felder factory in Austria refers to it as a dado. The Europeans are less likely to adopt Americanism's than we Aussies are, given that English is usually their second language, so I would hazard a guess and say it has been around for a while, but you have only recently heard of it.

Originally Posted by Swagman

Whilst not wanting to hijack this thread, I am interested in the answer...

All this talk of cutting dadoes reminds me that until a few years ago I had never heard this term in Oz. My old dad (in his eighties now and a keen woodworker when younger) always referred to them as trenches (and while on the subject, also referred to 'rebates' not 'rabbets').

Or have these terms always been used interchangebly in Oz in the chippie trade, and I've just been unaware of it?

Jeff.

As a chippy I've always known dadoes as trenches and rebates as rebates. In carpentry, the term trench was most commonly used when we used OBHW framing and the top and bottom plates had to be "trenched" so as to provide for a common stud length and to minimise the risk of a green stud twisting itself out of a wall as it dried.

Rebates were what joiners cut into window and door sills. We never cut 'em.

Now that I've added woodwork as distinct from building to my list of hobbies I've had to learn to use the American terms somewhat interchangeably with the Australian ones as so much information on woodwork comes from America.

HTH,

Mark.

Originally Posted by havenoideaatall

Thoughts?

If you're going to cut them using a circular saw the cross cut mode you should contemplate using a dado blade in your saw. A dado blade has a wide, often adjustable kerf so you can cut a dado in one or two passes (a dado blade won't fit in the WC in table saw mode though).

Otherwise if you do have a router you should consider buying the sliding router base that fits in the WC sliding channels - if your using pine and your router bits are sharp then you can probably route the dados in one pass if they are not too deep. Make sure to clamp 20mm or so wide lengths of scrap to both sides of the cut to avoid tear out though and if your router starts screaming run through in a couple of passes of increasing depth.

Lastly - make sure you support the length of timber both sides of the machine with some sort of adjustable stand and clamp each cut in two places (per board - you should be able to cut both boards at once as you've indicated if you've supported the timber adequately). As you've noted any movement in the timber you're cutting will create a bad finish.

Happy chippying!

Originally Posted by toddles

If you're going to cut them using a circular saw the cross cut mode you should contemplate using a dado blade in your saw. A dado blade has a wide, often adjustable kerf so you can cut a dado in one or two passes (a dado blade won't fit in the WC in table saw mode though).

Otherwise if you do have a router you should consider buying the sliding router base that fits in the WC sliding channels - if your using pine and your router bits are sharp then you can probably route the dados in one pass if they are not too deep. Make sure to clamp 20mm or so wide lengths of scrap to both sides of the cut to avoid tear out though and if your router starts screaming run through in a couple of passes of increasing depth.
Lastly - make sure you support the length of timber both sides of the machine with some sort of adjustable stand and clamp each cut in two places (per board - you should be able to cut both boards at once as you've indicated if you've supported the timber adequately). As you've noted any movement in the timber you're cutting will create a bad finish.

Happy chippying!

Indeed I had too much movement - but I only used one clamp per board and no extention table - one went on ebat fairly cheaply the other day I forgot about..

i didn't know you could get a sliding router base- any idea what the part no is?

Originally Posted by havenoideaatall

i didn't know you could get a sliding router base- any idea what the part no is?

Router mounting plate is AJA150. Fits both MK3 and 2000 models
http://www.triton.com.au/accessories...20#accessory_9

Originally Posted by havenoideaatall

Indeed I had too much movement - but I only used one clamp per board and no extention table - one went on ebat fairly cheaply the other day I forgot about..

i didn't know you could get a sliding router base- any idea what the part no is?

The weight of the overhang of your workpiece (I assume it's reasonably long being a bookshelf) will apply upward leverage on the area you're cutting in crosscut mode so you have to support the weight on both sides so that your WC is not acting like a pivot. I use a couple of $19.95 cheapo 4-roller stands from bunnies for this. Whilst I'd love a sliding extension table the roller stands are probably more useful if you've got one either side for this kind of cut, move along, cut... sort of stuff. Just be aware that you need to angle them slightly inwards if using them in table saw mode or they have a tendency to ever so slightly pull the workpiece away from the saw blade.
In cross cut mode the blade is spinning up into the workpiece (have a look at the way the blade spins) and has a tendency to push the workpiece up off the table so two clamps are neccessary to stop the workpiece pivoting on the single clamp. This applies to a lot of situtations where you use clamps in woodwork - two are general needed to hold something firmly that could otherwise pivot with one. Between these two factors your work piece is probably moving enough to give you the bad results you described.
You can also over come this latter issue by "climb cutting": Where you start with saw pushed away from you, turn it on and slide it back towards you to cut the workpiece. You'll need to pack out the fence by clamping a scrap of wood so that the saw can start all the way in past the work piece. You'll get far less tear out with climb cutting - if that's been an issue - as the back of the saw cuts down an pulls the work toward the fence (NEVER climb cut with the saw freehand!).

Secondly: The part refered to is called the "Router Mounting Accessory" Part # AJA150 and is designed with this type of dadoing purpose in mind.
You'll find a picture at the wonderful Holmsglen Triton site:
http://www.tritonwoodworkers.org.au/
under the Triton Equiptment: Specs, Spares, parts, videos section.
Hope this helps.

Originally Posted by toddles

Otherwise if you do have a router you should consider buying the sliding router base that fits in the WC sliding channels

Toddles
I have the sliding router base to cut the bulk out of the trench, but do you need to cut the trench sides with a saw in cross-cut mode first or is the router (with good sharp blades) good enough for the whole of job. I'll be using Qld Maple as the timber of choice.

Originally Posted by Markw

Toddles
...do you need to cut the trench sides with a saw in cross-cut mode first or is the router (with good sharp blades) good enough for the whole of job. I'll be using Qld Maple as the timber of choice.

No you shouldn't cut the sides with the saw before routing - the router with a straight edge bit is ideal for this sort of work. I've had no experience with QLD maple but would be fairly confident you will get the best results buy making three or four passes of increasing depth with the router to cut each dado trench. Routers work very hard to remove a lot of wood so the harder the wood the more passes needed for one cut. You can actually hear when a router is in distress, if it sounds like it's struggling - it is. As above: clamp some scrap wood to either side of your work piece if tear out is a problem and get the feel of the job by experimenting with some scrap of the actual wood you'll be using before you attack your work piece.
And if you can make the cut in one pass without any issues then that's fantastic. If this seems so then make the pass slowly - burning the sides of the cut doesn't really matter too much in a dado trench and the slower feed rate makes it easier on your router.
Depth of cut, hardness of wood, size and sharpness of bit and the power and speed of the router all influence what will be the best approach so always experiment before making your good cuts.
Have fun!

Thanks Toddles