Greetings to All,
I will be helping a friend build an entertainment center in the coming weeks. We will be cutting some dadoes and grooves for the fixed shelves and partition. The plan is to use 3/4” plywood from a local supplier (Lowe’s, HD). I’d like to hear from you your thoughts on using a stacked dado blade vs. a router bit to make the cuts I described. It’s my understanding that 3/4″ plywood isn’t always this exact thickness. If that is the case, is there a router bit made specifically for this application that takes into account that the plywood may actually be 11/16″+/-?
Also, which of the two (blade/bit) is less likely to cause chipout in the plywood veneer? For those who prefer the blade, how do you shim the blade to be “right on the money”?
Thanks in advance for your help and suggestions. Happy holidays!
Cheers,
T2
Replies
The size router bit you'd be after is most likely a 23/32nds bit. Made for undersized plywood.
I make all my dadoes with a router table or hand held router but that's because I don't have a dado in my aresnal of equipment yet. I find that a good sharp router bit leaves nice clean edges and a flat bottomed dado which suits my purposes just fine.
In the end either will probably do the job just fine, though you may have to spend alot of time setting up the dado with shims to be just right.
JD
Either or its all personal preferance. I usually use my router but if the piece is to big then I use the dado set. Again its personal preferance
Darkworksite4:
Estamos ganando detrás el estado de Calif. Derrotando a un #### a la vez. DESEA VIVO LA REVOLUCIÓN
I've seen dovetail bits used well for shelving. It allows for slight chipout on the surface of the carcase covering with the shelf. As far as shimming the dado to the right size use thin peices of cardboard between the chippers.
Tony
We already have enough youth, how about a fountain of smarts.
For stock under 15" wide, I use a RAS.
For wider stock, I think I would feel more comfortable with a router, and it would be easier than fooling with shims and a stack dado.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
I would 2nd the router bit. Even tho I have a high quality stack dado and do use it frequently, you will have IMHO less chance of tearout. I know there will be contradicting opinions on this, there are many tricks to dado without ANY chipout. For a person who is not prepared to fiddle around trying for an exact fit (which is not necessary anyway) the router bit wins hands down.
If you do chose a dado consider a SMALLER dado and then shouldering the shelf. This eliminates any concern of chipping on the carcase side, and gives adequate glue surfaces. score the shoulder cuts on the shelf prior to rabbeting them. For 3/4 +/- ply plow a 1/2 dado..FIRST then fit the shelf tongue..much easier than shimming.'
But by all means have safe fun..
Yes there are router bits made for the undersized plywood. The choice is really which you feel most comfortable and safe using.
I do most dados on my TS with a CMT stacked dado. I have a 50" fence and an outfeed roller table so it's not to tough to do them for facing panels at once and then rip it in half. CMT and others make precision shims for dado sets and include 1/16" and 3/32" chippers. Using a dial caliper I can get pretty close on the first test cut.
FWIW I like magic wires for the adjustable shelves and the vertical dividers for the pocket doors. Where I have a face frame that would block removal of the pocket door dividers, I've attached the face frame w/ cam and post KD hardware making it removable with no exposed hdwr.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
Sounds like a fun project for both of you.
I use both. The better stacked dado sets include various thicknesses of shims to permit micro adjustments. As others have cited, you can also purchased router bits for the modern-sized sheet products. Several things to consider: If the piece will be ackward to reach accross it's width with a router, the chance for the router to wander is great. If you dado cut is of a depth to require two passes, the chances for a mistake is intensified. To avoid both of these problems, build a jig with parallel fenses to keep the router from wandering. Don't cut too much in a single pass since ply core contains glue and you can really burn the bit. The one advantage with the router is that you are passing the machine over the work and the consitency of the cut should be more uniform. If you stock is flat and your work surfaces are flush and true, you should be able achieve the same results with a dado
Using a TS is also difficult for long pieces and/or very deep pieces. You need to be able to position the fense for all of the cuts you will need to make as well as having an outtable to maintain a smooth consistent feed while passing the work over the dado. One consideration, depending on wood and the depth of the cut, a TS with less than a 2hp motor will have a problem turning an 8" stacked dado for 3/4" cut and you may have to drop down to a 6' dado set.
My personal experience is that you should have minimal tearout with either approach provided your cutting tools are sharp and not pushed past their useful limts.
Good cutting.
Doug
As with all projects, test your dados and router plows on some scrap material. This could be costly if you are going to be working with large sheets of plywood. The larger the pieces, the more difficulty there is in making uniform dados or plows. This is also a good way to test your setup for accuracy and workability.
I like to use blue masking tape on my x-grain dados, it helps reduce tearout, but proper feed speed is also important.
"is there a router bit made specifically for this application that takes into account that the plywood may actually be 11/16"+/-?"
As sphere mentioned earlier, there is another approach, and a router bit that easily accomodates a 3/4"± shelf is a 1/2"± bit. After routing the 1/2" wide housing (US dado) in the carcass sides using the 1/2" bit in conjunction with a typical T square and router arrangement, you simply cut the shelves to length and form a rebated tongue on the end of each one using a router, a suitable bit, and a side fence so that the tongue formed fits the already cut housing.
If you get smart you can cut housings in multiple sides in one go, and then the tongue in multiple widths of shelves also in one go, finally ripping both to an appropriate width later. A solid lipping can be used to hide both the ends of the housing in the sides, and the tongue that would otherwise show at the front of the shelves.
If you use a plunge router you can stop and start the housing or even tongue wherever you like, and an added bonus is that the resultant joint is significantly stronger than a full housing due to the increased gluing area and additional returns resulting in better mechanical locking properties.
Secondly, it's probably significantly safer to pass a lightweight router over a wide and heavy board than it is to pass a wide and heavy board over a table saw rigged up with a dado blade.
Oh, by the way, I've never yet found a use for a dado blade in my range of woodworking techniques, so I could really be only blowing wind out of my backside, ha, ha. Slainte.
Edited 12/18/2003 6:38:31 PM ET by Sgian Dubh
T2,
Router all the way. But you need to do it in multiple passes like I suggest if you want perfect dadoes (which are easily attainable).
Get an undersized router bit and the right sized router bit. The undersized bit should probably be 1/2" but you could also use 5/8" if you wanted. Also, I like to use 4 flute, solid carbide machine tool end mills. They rough much better. Now plow out your dado to near depth. Do not go all the way down. Plow also down the middle of where you want your dado to be. After roughing, put in your right sized router bit (you could also use a 4 flute end mill.... they finish nice too.... and if you find the right supplier, they will be cheaper than a "router" bit). Now, dial in your depth and speed. Depth on final pass... yes this is the final pass... should be no more than a smidgen or less than .030" and speed should be fairly fast. Feed your tool or stock in one pass at a controlled rate. Your dado will now be so close to actual size that you wouldn't be able to measure the inaccuracy and perfect for gluing up.
Good luck
Rob Kress
I am in the process of building an entertainment center with fixed shelves. I used an undersized router bit and there was no tearout but......the fit of the shelves into the dadoes was so tight that it was a ##### to fit the shelves into the dadoes and assemble the carcas as the glue is skinning over and I'm making up my own swears because I've already used all the rest. While setting up a dado blade in the TS can be fussy (dado sets usually come with their own metal shims to fine tune the size), you can make the fit as tight or loose as you are comfortable with. Good luck.
Darren
Hello,
In my opinion, you would be better off using the router bit. You will get a cleaner cut, and a far better dado depth consistency. You might try the first pass at one-half the depth, then run a second pass at full depth - this will reduce strain on the router bit. Router bits are far safer than stacked or adjustable dado blades on a table saw. PS - don't get too wrapped up in measurement increments of 16ths or 32nds. This is woodworking, not machinery.
For those who prefer the blade, how do you shim the blade to be "right on the money"?
In the spirit of full disclosure I have used dado's exactly one time buuuuttt.....I read in a magazine somewhere and worked perfectly well is use the appropriate chippers and blades then use ALL of the shims on a scrap piece. When that is done, test fit it. The joint should be loose. Then use the shims and keep adding them until it's tight. Once it's tight, leave those shims off and you should be d.o.b accurate!
Derek,
I'm probably closer to your skill level than many of the posters to your query. I've built about one or two dozen cabinets that required dado's....used the router for about 2/3rds and the TS with dado blades for the rest. I've had excellent results with both...and disasters with both. I like using the shouldered shelf approach (especially for a large piece)as was mentioned by Sphere and Sgain...however, when cutting the rabbit on the shelf the router destroyed the shelf with tear out..but that was just once. I use the undersized bit in the router...but the stock is not that uniform and getting it in the dado either requires a second cut or sanding and pounding...which can bend the sides of the case.
The TS with the dado blades is the fastest especially when working alone. You just set your dado blades up and set your rip fence and go to it. I usually set the blades tight....and if needed either move the fence or add a sheet of paper to the end of the stock between the fence and run it through again...
On large cabinets (6-7') I'll clamp on a straight edge and use the router. I don't like having to reset the straight edge for the router...but with two of you that may be less of an issue. I guess I could put a piece of tape on the router edge and widen the dado that way...but have not tried it.. With large pieces I prefer to use the shoulder approach which makes dealing with the varying thickness issue of the plywood easier....good luck
I use my dado (Frued 8" stack) for the majority of my dadoes in plywood. I have found the the thickness of veneer plywood can not only differ from sheet to sheet but also on the same sheet. I never have a problem with tearout on the face of the ply and any tearout on the end or beginning of the cut will more than like be covered with whatever treatment you use to cover the edge. For unwildly and large pieces I will use a router, which is safer than trying to do it on a tablesaw. Just my opinion and the way I do things. Just remember that whatever works for you and does not compromise your safety is the right way to do it, regardless of what we say. JP.
I use a router to do mine, Size well if it's over 1/2" use spacers to make up the correct size....Or Buy one (router bit) at any good supplier...But I Use 1/2 bit..then add the width to make it the size I want...the cuts are Perfect and flat...
If nothing sticks to Teflon,how does Teflon Stick to metal. Huh
No dado's BISQUITS!!!! They are the bestest, stongest joint known to mankind..NOTHING is even close. <G>..HA aha ha.
Shims for a stacker set..playing cards. and old CD's and sandpaper..
I have used both the stacked dado and the router bit approach. I have had problems with both methods that I think may be worth your consideration.
First, variations in ply thickness have resulted in very tight and very loose dado joints in both methods. Verify the uniformity of the thickness of each piece of wood you are using for a shelf before choosing the method. If the shelf wood is uniform either method will work for the WIDTH of the dado
Second, If the dado is to be cut in a board that is cupped or bowed the stacked dado approach can result in a variation in dado depth. As the board moves over the saw table, cupping or bowing may cause the board to "lift" off the table resulting in a shallower cut. I have seen variations in depth of a tenth of an inch in wide boards due to this cause. The smaller footprint of the router technique will minimize the variation in depth but the router method can still have problems due to the variations in board or ply thickness.
If I have some bow or cupping and or a variation in shelf thickness I use the following technique. Cut two equal thickness straight edge boards about 3/4" to 1" thick, place the actual piece of wood that will be the shelf on the board to be dadoed in the position (and orthogonal to it) it will take on completion of the dado. Sandwich this shelf with the two straight boards shimming each end on one side with a playing card or folded dollar bill. Clamp the two straight edges to the board to be dadoed very firmly in order to remove any cupping or bowing. Using a pattern bit (bearing at the top of the cutter, and with a cutter diameter greater than half the thickness of your shelf, but less than the thinnest shelf) set the router cutting depth and route out along one straightedge and back along the second.
Although not the the most efficient method for making dadoes I have found that I can get excellent fit with just the right amount of clearance (set by the shim thickness) every time by using this method
I use those plastic shims from veritas with a lot of scrap wood. But once I get it right I write the formula down on the lid of the box I store my dado blade in.
Darkworksite4:
Estamos ganando detrás el estado de Calif. Derrotando a un #### a la vez. DESEA VIVO LA REVOLUCIÓN
Check sommerfeld's tools for wood he sells CMT which I think are pretty good and on the cover of his latest catalog he has a new item for making cabinets that looks interesting , it's a router bit set that uses tongres and groves. You can see him online at http://www.sommerfeldtools.com What ever you do have fun
TRUSCHE2
I have used both, but use the router pretty much exclusively now. A Tru-Grip fence assist. Probably the best way is the approach metioned by Sgain. It's the same as cutting a tenon over-size and then trimming down to a perfect fit. It gives more glue surface also.
If you use the dado, davidh hit on a problem you could encounter with bowed ply. Uneven depth. When I used to use the dado, I simply use a medium shoulder plane to clean out the bottom and get the depth even.
Good Luck...
sarge..jt
Proud member of the : "I Rocked With ToolDoc Club" .... :>)
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