Is this a safe Dado operation?

[Kevin Blunt]

Hello,

I am working on a bookcase headboard for my three year old son. I am at the stage where I just setup my dado blade to uhh.. cut dados http://forum.canadianwoodworking.com/images/smilies/smile.gif. My concern is that my setup isn't quite safe. When I setup the dado blade (1" wide cut), it leaves a small amount of thread on the arbor to install the arbor nut. As well, I cannot use the arbor washer as I normally would.

My two questions are this.

1. Is the arbor nut on enough to be safe? Basically the arbor nut is flush with the end of the arbor itself, so really the entire nut is threaded on.

2. Is it safe to perform any dado cuts without the arbor washer on the arbor?

I have ran a few test cuts to get the right width for a nice snug fit and everything went fine but before I go ahead and do all the dadoing I thought I would check here to see if this is a death wish. I don't think there is much concern but there could very well be something I don't know and would obviously like to prevent any accidents.


Thanks for your help.

Kevin
__________________

[Scott Rollins]

The nut should be fully engaged on the arbor. I do not use the washer if it does not fit with the nut being fully engaged. I would use a router and an edge guide if I felt a little unsafe about it. But thats just me.

[Josiah Bartlett]

As long as the arbor nut is fully threaded onto the arbor, having a longer arbor isn't more safe. The part of the arbor that sticks out past the nut isn't doing anything. However, not having the washer on the stack can result in warping the blade and can do some funny stuff to the cut. If you can't put the arbor washer on there I would use a smaller stack and do two passes to make the slot the right width.

[Steve Clardy]

I use a wabble dado cutter and cannot use the washer either.
Never had any concerns or problems

[mike holden]

Kevin -
One basic rule of woodworking is: "if it doesnt feel right, dont do it!"

This seems to apply here.

As to your setup, it is inadequate. You need to have the nut fully engaged - i.e. threaded completely thru the nut to be safe.

Most dados are maxed out at 3/4" , and few saw arbors will accept anything thicker.

Two passes, or use a router for this job.

Make sure you can count to ten, before and after the job.

Mike

[Tom Veatch]

...1. Is the arbor nut on enough to be safe? Basically the arbor nut is flush with the end of the arbor itself, so really the entire nut is threaded on.

If the end of the arbor is flush with the outer face of the nut, you are fine. Standard specifications for installing nuts in aircraft structure is to have at least 1.5 threads showing. But that is primarily to ensure that self-locking features of the nut are fully engaged and for the convenience of the inspector. That criteria isn't applicable here. None of the thread that extends past the nut contributes to joint strength.


2. Is it safe to perform any dado cuts without the arbor washer on the arbor?
I've never used the arbor washer with my Freud 508 dado set and can still count to 10. 8" diameter blades almost 1/8" thick are stiff and stable enough that they don't require support from the arbor washer.

[glenn bradley]

If you have to ask . . . . just kidding (sort of). As long as the nut threads on the arbor to the point where the arbor is at least flush with the outer surface of the nut (fully engaged), you're OK. No washer required. My saw has a bit of a short arbor so a 7/8" dado is at he limit of what I am OK with. I generally set the dado stack up even smaller and just make two passes.

[Prashun Patel]

The washer is there for a reason.
I don't care what everyone says; doesn't feel right to me, and if it were me, I wouldn't do it.

I'd reduce the stack so you can fully engage the nut AND the washer, and then I'd cut it in 2 passes. I'd cut all the dados and an additional one in scrap first, then I'd tweak the fence and widen the scrap dado until it fits the shelf, then I'd run all the good pieces through for the 2nd pass.

Don't take chances with yr safety. Your son won't forgive you if something goes wrong...

[Andy McCormick]

ok this maybe hard to explain? Heres my question. Can you stack the dado to 3/4 and then clamp a 1/4 plywood to your fence, run your 3/4 pass then remove the 1/4 plywood board therefor giving you a 1 inch dado?

[Rick Moyer]

IMO the washer is not "necessary" and I wouldn't worry about that if it is in fact threaded at least flush. 1" seems pretty wide though? I can only get about 3/4 (23/32) on my old Craftsman, and I prefer to do two passes if I need a wide dado.
btw, why is my thread being italicized?? i must have hit a button wrong?

[Tony Bilello]

The answer is YES.
I do it all of the time. I think it is a safe way as well as a better cut since the saw doesnt have to hog out a lot of wood all at once.
Most times I just move my fence over.

[Peter Quinn]

The washer is there for a reason.....to stiffen a SINGLE 1/8" kerf 10" Blade under load. It does not hold the blade on the arbor, and when you stack a 1" thick dado with an 8" diameter, the washer isn't going to make things any more stiff than they already are. Think about it, 1" of steel plates clamped tightly together by the nut on a hardened steel arbor. Most saws I have used require the washer be left off on any dado stack larger than 11/16", it is standard practice and safe to do.

However, anytime I am spinning a dado on the thicker end of the scale it has my complete attention. While it is not dangerous to leave off the washer and push the on button, it can get dangerous when you start to push wood through it, and even more dangerous going cross grain on long stock as in book shelves. That much blade pushing back at you can cause one heck of a kick back if things go wrong, so make sure you are very aware of what you are doing. I hate reading those "I lost my teeth when my miter gauge loosened" posts. :eek:Check that set up and keep the depth light or take multiple passes. And for God's sake don't use the miter gauge with the rip fence as a depth stop on long vertical members.

[Jim Koepke]

I did not realize at first this was a TS question. I do not own one.

But it seems scary to me to use a fence when cutting a dado. Won't the wood go flying if something goes askew?

Maybe fear of speed is what keeps me doing it with hand saws and chisels.

jim

[Myk Rian]

I've used a regular flat washer that fits the arbor when doing wide
dados, in place of the standard one supplied with the saw.

[Tony Bilello]

When ripping, the fence is the most stable thing you can hold the wood against. This is even more true when using a wide set of blades like in a dado stack.

[Neal Clayton]

Won't the wood go flying if something goes askew?


yeah, but that's with anything on a table saw.

[Kevin Blunt]

I finally was able to get a picture up. Here is what I am looking at.

http://i264.photobucket.com/albums/ii184/arenaranger/IMG_0434.jpg

http://i264.photobucket.com/albums/ii184/arenaranger/IMG_0433.jpg

[Steve Rozmiarek]

I think you are fine, but, you don't have to cut the dado to the width of the stock. The nut on your tablesaw tightens as the blade speeds up or cuts, so the shut down is the only time that it could come apart. If it worries you, just check it often for any sign of movement. You could mark the nut and blade with a sharpie for a reference.

You can cut a dado of say 5/8", then cut a rabbet on the corresponding shelf part so that you end up with a 5/8" end. If your stock is not all the same thickness, cutting rabbets with a dado cutter will be a little aggrivating, but a tenon jig or a shaper with the cutter above the stock would both guarantee consistant measurments.

[Brent Smith]

Hi Kevin,

As long as the nut is fully engaged on the arbor you are good to go. From your pics it seems there may be some of the nut not engaged on the arbor thread. If this is the case I would do the cut in 2 passes. The washer is not neccessary with a dado stack.

[Chris Kennedy]

From the picture, I wouldn't be certain that the nut is fully engaged. If it were me, I would go with two passes. The extra time it takes will pay for itself in peace of mind.

Cheers.

Chris

[Alan Greene]

The nut is not fully engaged. IMHO you should not make the cut. My main reason for this is based on your uneasiness. That niggle in the back of your brain will be the most dangerous part of the operation.
Kevin -
One basic rule of woodworking is: "if it doesn't feel right, don't do it!"


So, as I see it you have 2 major reasons not to make this cut. 1. Nut not engaged! 2. It doesn't feel right!

I would use a router for this it just seems a lot safer.

[Thomas Pender]

IMHO, I would not even contemplate doing what you suggest.

Even though we do not talk about it much, the use of Dados on table saws is not the safest operation in the world (in some places in the world you cannot buy dado blades for table saws). The wider the dado the more dangerous it is. Given the cost benefit ratio (one finger is worth all the wood you will ever cut), I would take smaller bites and slide the wood over untill you get where you are going - you can build a jig that will make it safer. Or, alternatively,you can use a router with a good dado bit and take a series of shallow cuts - much safer.

[Tom Veatch]

... Here is what I am looking at...

Not good. Perhaps it's the perspective, but that nut looks more like a jam nut than a full strength thickness. The arbor nut on my saw looks to be fully twice as thick as that one. Plus it's not fully engaged. As shown in the pictures, I wouldn't trust it.

[Howard Acheson]

>> When I setup the dado blade (1" wide cut), it leaves a small amount of thread on the arbor to install the arbor nut. As well, I cannot use the arbor washer as I normally would.

I'm a little confused. A standard 8" dado set can only cut a groove that is 29/32's. What setup are you using that can get a 1" wide groove?

[Cliff Rohrabacher]

you are fine so long as the nut engages fully.

The rotation will tighten it, and the Dado outer blade is thick enough and small enough that the washer is not needed.

However, for those very few machines that have electronic braking on the motor - - a dado can pitch forward under braking and loosen the nut.

My machine has breaking. It'll stop in 6 seconds. It has two anti rotation shafts ( about 3/8" dia) on either side of the arbor that must engage a set of complimentary holes in all my tooling. I've never seen any evidence that they were of any use - the nut has never loosened - but one never knows.

[Kevin Godshall]

One thing I haven't seen asked or addressed in this thread....... How big is your TS? What make and model is it?

Normally, in my limited experience, shaft arbors are kind of sized to the limits of the saw. That is, if your saw really doesn't have the horses to turn a 1" or 3/4" stacked dado cutter, the arbor is intentionally limited to keep you from doing it. (Takes a lot to hog that much material).

My rule of thumb (both to my kids and people I have supervised in a previous life) has been: If you have to ask if something is safe or not, it isn't. Don't do it.

That doubt in the back of your mind will only nag and persist and nothing good ever comes from it. Just because it may be right or safe for others, doesn't necessarily do the same for you. Only do what you are truly comfortable and knowledgable with.

My 2 cents.

[Mike Hess]

As another alternative, you could plane down the shelves that will fit into those dados to, say 5/8" if that would work for your design. You can then cut the dados in a single pass, with the arbor nut fully engaged on your dado stack.

I'd probably not be comfortable using the setup pictured.