Thread: Stacked Dado Head Cutter...

Greg

1. Don't be tempted by a wobble dado set. They are not as good as a stacked set and generally give an unpredictable finish (or, give a predictably poor finish).

2. 19mm is 3/4" (or close to dammit). I'm sure that most of the metric sizes you see around are just converted from Imperial (otherwise why 19 mm? Why not 20 mm?).

Stay with what you have (or send it to me for careful "analysis").

Regards from Perth

Derek

I have noticed what Bunnings is selling as what was 19mm Melamine is now marked 18mm. I don't know if there has been a general change in the industry or if Bunnings have a supplier that is making different sizes.

The same goes for 3/4 plywood is now sold as 17mm which when I was making my Mitre Saw Station I had to buy a 17mm Router bit to cut the dados, which when you use it I found I had to run the hand plane along the edge and cut a chamfer to get the ply to start in the dado.

Don't do it Barry,

A 3/4 in trench will fit a 19mm board quite nicely (.002in wider)

BUT unless your "dado head" (of which I have no experience) is VERY adjustable you will not be able to do a trench to fit either an 18mm or a 16mm board satisfactorily.

By my (quick) calculation a 16mm board will be .125mm too wide for 5/8" trench (won't fit at all) and 1.46mm too narrow for a 11/16" trench (way too sloppy)

Likewise, an 18mm board will be 1.05mm narrower than a 3/4" trench and .534mm wider than 11/16"

Even if my calculations are not correct (and I'm sure someone will tell me) the fact is a metric cutter in the usual sizes will not make a trench for these boards in one pass. I've tried it.

Trying to use metric tools to cut imperial measurements is a sure route to frustration

Cheers

doh!

I meant an imperial cutter will not make a proper fitting trench in these (metric) boards.

Hi MiniMax

I think you got my post mixed up with Greg Hudson's. I was just commenting on how Bunnings have changed sizes on their products.

And while i'm here Greg,

You shouldn't have to rebate anything when making the boxes for your kitchen. Much simpler to just screw 'em together. This works perfectly for 16mm melamine and saves a hell of a lot of time.

Cheers

Greg, Derek's advice regarding wobbly dado blades is sound. Stay with what you have.

As for sizing your dado cut exactly, this can be done to virtually any dimension within the min/max specifications of your dado set. Most sets come with shims to accommodate this and at least two different thicknesses of chippers. Some combination will work.

However, I sometimes take the easy option rather that fussing around to get an exact fit by shims, etc. I simply mark out the width of the trench on the lead edge of the sheet being trenched and set my dado blade to a dimension slightly below that, i.e. using the two outside cutters and the required inside chippers to achieve a width slightly below that required. I then run the sheet through the dado blades with the left side of the cutter blade touching the left mark, then re-cut with the right side of the other cutter blade just touching the right hand mark. This has the added advantage of flattening out the floor of the trench.

Greg,

A dado set can also be used to cut tenons in a single pass, if you have a table-saw tenoning jig (see Pic below). All you need to do is to replace the chipper blades with spacers made up to yield standard tenon thicknesses. I have spacers for 1/4", 5/16", and 3/8" tenons, which I have made up from various combinations of perspex, MDF, aluminium sheet, laminex, and plastic shims. If you have the 6" Delta dado set, the maximum length of tenon you will be able to cut will be less than !", but an 8" set will allow tenons up to about 1 3/4" long. It is best to use the regular blade on the saw to cut the tenon shoulders first, otherwise you are liable to get some tear-out.

Rocker

G'Day All - thanks for all your feedback. It's been interesting reading.

Derek - Thanks for the advice re the wobbler. I was seriously considering it (until now).

Mr Minimax - Thanks for the Imperial / Metric calculations. Basically it's just as I suspected - the whole shebang is highly unlikely to mate perfectly.

DPB. I like this idea... OK, so you might have to make 2 passes to get the exact dado width - however it appears as though it would do the job.

Rocker. Thanks for the tip re the double cutting tenon - very sneaky.

What grabbed my attention in your pic though was the timber cut-out / spacer you've made for the table / SDHC.

I visited the local Jet reseller today, and explained I wanted a TS that could handle the SDHC, and the salesman said he had never heard of a DODO cutter (Yes DODO). Anyway, the Table that was of most interest was the 10'' Super Saw (at a mere $1900ish) BUT... there are no SDHC sized spacers / thingos - whatever they are called available for the Jet.

The $895 saw I examined at Carbatec though DID have an appropriate slot / spacer, so I guess I may have to re-examine it (and maybe save some moolah).

Of additional interest (and as usual, just 'too' late), was the micro adjustable SDHC I saw in American Woodworker. Check this baby out !!!
http://www.rd.com/americanwoodworker...&contentId=271

And this...
http://www.rd.com/americanwoodworker...DadoBlades.pdf

Again - Thanks to all who have replied. You have added considerably to my limited knowledge on the subject.

Regards, Greg.

there are no SDHC sized spacers / thingos - whatever they are called available for the Jet.

I think you are referring to inserts for the table saw, in which case you can easily make your own, and should replace the standard one on the saw with a "zero clearance" version in any case.

Once you do that you need one for every occasion, but won't regret the safety improvement at least.

I use 10mm MDF and simply use the original metal one as a router template. They are quite disposable, and I probably have a dozen lying around at any given time, so I can use one for every thickness of dado or angle of cut.

As for spacers, I keep a collection of dead CD's (old accounts backups) but at 80c each you could lash out and buy new ones to have an infinite width potential.

Just juggle the different size cutters, a couple of CD's and if you want to get really really precise a few photocopy paper shims between each part. It's really a lot simpler than it sounds!

Oh...and buy the Jet you wont regret it. cheers,

P

Greg
I recently built a kitchen pantry using Melamine. First up Melamine is an extremely disappointing material to use with the standard table saw. I dressed all edges with a straight-bit in the router to remove the chips caused by the saw. My next move was to rebate. I probably could have stacked the dado set and used some shims to get the correct width but as I was across two metre long gables this was a logistics problem on the table saw.

Thinking I had 16mm sheet material I picked up a 16mm router bit to trench the gables. I then found that the sheet material was in fact 16.453408967 something or other millimetres wide! I overcame this by shimming my router jig with a couple of sheets of paper, cutting a trench, removing the shim and trimming the 0.453408967 something or other millimetres off one edge.

A dado cutter is a great asset for many jobs, even if it is imperial, but take the advice of Mr Minimax – butt joint Melamine and screw!

G'Day again.
Well... Norm's just done it to me again. Tonights episode of the NYW featured the micro adjustable SDHC from Freud. (typical - just after I've spent my money on a Delta). Norm was using it to create the dados on a laundry cabinet. Most of joins were butt-joined & screwed - as per the previous comments from others here...

The only possible disadvantage I can see is that the Freud is only a 6'' cutter. No doubt there will be an 8'' version released just after I buy the 6'' (if I do) )

bitingmidge:
Thanks for the tip re the INSERTS. At least I know what they called now. Making them from MDF is an excellent idea.

And the idea of using dead CD's as dado spacers is bloody clever too for that matter !!! It's amazing what info is out there stuck in people's heads... Just a few words & out they pop ! )

Even though I have not as yet made a single cut on a Table Saw - I'm learning a lot here. Hey I've even managed to offer some ADVICE to someone about routing (Which *IS* something I own).

Thanks again everyone.

Regards, Greg.

There is a Dial-a-width adjustable 8" Freud stacked dado head cutter already, called the SD608. I just bought the the the normal Safety Dado SD508, and it comes with steel shims to get the width exactly right.

Dial a Dado

The Super Dado

Even with airmail freight, the SD508 cost me $285 Australian. It is made in Italy, strangely enough. The CMT costs over $400. See anything wrong here?

This is an Australian site that is new and actually advertises at the the top of this forum. They sell SDHC at a pretty reasonable price. Check it Out.

They also have a sets of 4 Brass Shims that go down
to .005"


http://www.northwoodtools.com.au/category101_1.htm