Recently, I could not resist getting an adjustable dado from Habor Freight. It is 40 tooth for $10. I think it is #36912.
I already have an old one (Disston?). The thing is almost useless. The setup cannot be repeated. Every time it was tedious adjustment.
I just wanted to see what this dado can do. To my surprise the design is so much better. This is a great deal, IMO.
Later, when I look at a picture of a Freud adjustable dado, I realised that this much better design is not new. It is just that the design of my old adjustable is very bad. Now, my opinion of the adjustable dado has been revised.
The better design has set screws. First, at a minimum, once set the thickness of cut is repeatable. For example, every time I need 31/64″ for plywood, I slip on my 31/64″ dado head. Second, if one uses the adjustment feature, it is not too inaccurate. I managed to repeatedly get to within about 1/100 th of an inch at various thicknesses. Pretty good. This blade cuts solid stock quite well.
Of course, there is always the bad round bottom that cannot be fixed. This is not too desirable especially if one uses a dado to cut tenons, IMO.
Replies
Woodenfish,
Even if the bottom appears to be flat, it isn't. The nature of adjustable dado's is that they can not make a square'd cut, a problem that is more evident as the width of the cut increases. For many uses they may not be a problem but the when you put clamping pressure to a piece with dadoes that are not perfectly square, you run the very real risk of throwing the entire piece out of square. The other obvious problem is that you can not leave the joint exposed since it is a poor mate. Stacking dado's avoid these problems but at a much greater expense.
Doug
Doug,
You are correct in regards to adjustable dado cutters that "wobble". The Freud SD600 series adjustable dado sets are stacked like a conventional dado and have an adjusting hub that eliminates the shims so you get the same flat-bottomed cuts you would from our Super Dado.Charles M
Freud America, Inc.
Charles,
Thanks for the clarification. Can you contact me offline at [email protected] regarding my super dado? Thanks
Doug
I agree and my last post does says so.
This type serves well in making cuts parallel to grain. In this case, a slight curve at the bottom does not matter much.
This dado would last MUCH longer than "plywood" router bits, to say the least.
That "bad round bottom" is not necessarily due to the dado set (and if you're using the Freud set, probably isn't, I'd say). Any deviation from "flat" on your table can create the same problem. For instance, if your throat insert is just a smidge high or warped. I've had exactly that problem (with a regular Freud safety dado set) and traced it to a problem with the saw table/insert, not the dado set.
Another culprit can be inconsistent pressure on the stock as it goes over the blade. The stock has to be held snug to the table.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Forestgirl,
The condition you cite will cause a equal decrease in the depth over the entire width of the cut in the case of applying unequal downward pressure. If the throat plate is higher on one side is will cause an uneven cut from side to side. The bottom of the dado should still straight although not parallel to the board. It seems reasonable, IMHO, to conclude that if the bottom cut is either concave or convexed the the problem lies with the design of the dado.
Doug
This forum post is now archived. Commenting has been disabled