Cutting dados in 3/4" plywood

[rdewinter]

I needed to make several dados in the plywood sides of three cabinets for locating and securing shelves. I installed my dado blade set up to cut 3/4"wide dados. I needed 3/8" deep dados. Because the cabinet sides were about 24" wide, I couldn't use my crosscut sled so I installed my rip fence and cut the dados. Not the best choice because it did bind sometimes, but I got through it. Any suggestons for cutting dados in wide sides?

I also cut my first dado full bore, that is the entire 3/8" all at once. I had to feed really slow and the ss seemed to labor. So I cut the rest of the 11 dados by only taking a pass at 1/8" at a time. Took a while but I think it was a wise decision. Any suggestions about depth of cut when making dados?

Lastly, my stacked dado blades seem to be getting dull. Any suggestions other than steel ss dado blades? Does someone make cardide tipped dado blades with a 5/8" arbor?

[paulmcohen]

There is another thread on dado blades you might want to check it gives lots of different opinions. In my opinion if you can afford them I found nothing beats the DADONATOR™ DADO SET. They run just under $200 unless you get them on sale or in a kit. They are extremely heavy and once they get up to speed little will slow them down.

[dusty]

In my opinion, it is time to use the router and a home made router fence.

[scottss]

I too was cutting dado's yesterday and had some problems. I was cutting 1/4" slots in elm for rails and styles and the blade is vibrating and moving either the table carriage or itself and my cuts are not the same. I have a systematic stacked dado that I have had no problem with before upgrading to a 510, that makes me think its the carriage.

[Ed in Tampa]

I fought with enough Dado setups to know a Router is the only way to go.
Today's routers and bits specially made for the undersize plywood cutting a dado is a one step process, safe and easy.

Interestingly in Europe because of safety concerns you can't buy a tablesaw with an arbor long enough to mount a dado set on it.

Scottss
Get yourself a slot cutting bit or even better a rail and stile setup and your work will have a professional look.

I don't think your problem is the 510/520 carriage I think the problem is in whatever is causing the vibration. NO job or task should cause sufficient vibration to effect your work, something is wrong. You need to find out what and fix it quick.
Ed

[berry]

I think Ed's right on this one. Until recently I use a Freud stacked dado set on my SS with ok results and not too much hassle but recently I decided to make adjustable jig (I can change the width to fit the stock I'm using for shelving) to cut dados with a router. I'd say set up is much easier and the quanlity is better too. Mine were though dados but I'm certain that cutting a stopped dado will be much simpler compared to using a stacked dado set.

I think the jig itself is ackward but I searched for a longtime and finally went with Wood Magazines version.

[charlese]

I needed to make several dados in the plywood sides of three cabinets for locating and securing shelves. I installed my dado blade set up to cut 3/4"wide dados. I needed 3/8" deep dados. Because the cabinet sides were about 24" wide, I couldn't use my crosscut sled....

Because you want to make dados 24" long - the most reasonable way is with a router. However you don't need to buy a special plywood router bit to get the job done. Just set up a simple jig and use a smaller 1/2" bit. Here is a link to the fancier (but nice) jig from "Shopnotes" magazine. http://www.shopnotes.com/issues/076/vid ... -dado-jig/ There is even a video attached!!

You can see that the jig is set up to first rout one side of the dado and then the second side. You can do this by making up two very simple jigs that are identical. and resemble the (one) jig in the referenced link. They will consist of a base (hardboard) and a fence (straight board). Leave enough of the hardboard stick out of the other side of the board to accommodate clamps. After fixing the board to the hardboard - with the 1/2" router bit in the router, trim (rout) off the long side of the hardboard. Do this with both pieces. Now you have a perfect jig to make your 29/32" dadoes.

Simply lay the jig (both pieces) on the workpiece and stand a cutoff of the plywood on end in the place desired for the dado. (This gives you the width you want) Secure the two sides of the jig firm to the cutoff and clamp the jig. Now you can rout the plywood dado one side at a time and have it perfectly situated. Direction of routing is shown in the reverenced link.

P.S. Don't throw away your dado blade(s) The are sometimes very useful and give good results on shorter cuts and longer grooves and rabits. Here's an example of dados and a joint made with a wobble dado. Flat bottoms and no tear out on pine plywood.

Best Wishes

[a1gutterman]

Short and sweet: Got router? Use it:D . Don't got router? Get one:) . Can't get one? Suffer:mad: .

[rdewinter]

Thanks guys, I value your input and suggestions. I think the router with a clamped guide would be the way to go. A router mounted in a table would also be good, if I could come up with a fence that I could set several inches from the bit to rout repetitive cuts. I made a portable router table that I mount in a workmate with the router mounted underneath. But the table of only 20"x20". I thought the dado set in the ss would make for shorter work of the dados.

The router solution raised a question. I've been told that plywood is death on router bits and special bits are necessary for routing plywood. Is that true? Can someone suggest what kind of bit is good for plywood. I don't want to replace the bit after minimal use in plywood.

Thanks

[Ed in Tampa]

Thanks guys, I value your input and suggestions. I think the router with a clamped guide would be the way to go. A router mounted in a table would also be good, if I could come up with a fence that I could set several inches from the bit to rout repetitive cuts. I made a portable router table that I mount in a workmate with the router mounted underneath. But the table of only 20"x20". I thought the dado set in the ss would make for shorter work of the dados.

The router solution raised a question. I've been told that plywood is death on router bits and special bits are necessary for routing plywood. Is that true? Can someone suggest what kind of bit is good for plywood. I don't want to replace the bit after minimal use in plywood.

Thanks

Rdewinter
This question is almost like the one on Woodworking tool review, and the answer is going to be real close to the same. You get what you pay for. I have a router bit that plowed through 736 linear feet of MDF (a real bit killer) cutting flutes and it is still cutting fine. Then I have seen bits destroyed cutting nothing but wood.

Here is what I do. I buy a basic set one of those 33 pieces for $99 and use them on nearly everything. Then when I'm working with hardwood and want/demand a super cut I go buy a good bit of the same profile.

The set gives me enough choice that I can pick the bit I want, most of the bits in set are excellent and work just fine, but I look at them as disposable so if I ruin one I can buy another for less than $5. These cut all my MDF and or ply.

My other bits the ones costing $20+ never see anything but real wood. But even then I have had problems. Back a couple months ago I was having a real problem with some maple. I used a cheap bit, an expensive bit and a real expensive bit and all produced the same results. I then visited Infinity Router bits and Dave the owner sold me a bit that cut the maple like butter producing an cut that was baby bottom smooth. He explained it was the nature of the wood and further explained why his bit would cut it perfectly and it did!

Again buy according to the job, if the material is known to wear out the cutting edge real quick buy a cheaper bit. If your after a baby smooth cut then buy a name brand. Always buy where you can return the bit should it not cut the way you want.

Incidently the bit that cut all the MDF was a excellent bit made by a company no longer in business. When I bought it I figured it would quickly wear out so I bought three. However the other two were never used and I returned them.
Ed