I am fairly new to routers, and am building some new shop cabinets using a 3/4 bit to cut dados for the shelves. I have all the main stuff cut and fitted, but have decided I need some internal partitions. This will require me to figure out how to cut the dados on the partitians so that the shelves and baffles all line up properly and don’t slant off in odd directions.
The answer, obviously, is to measure properly, and set the straightedge guide “fence” in the right place. I have had a heck of a time doing this. The cuts seem always off by an eighth or so — just enough to bother the eye.
Unlike a saw, I can’t seem to accurately eyeball the placement of the router bit, and therefore to set the guide properly. Surely other people face this all the time.
What should I do?
Replies
Joe, If you are using a 3/4" bit, and your router's base is six inches wide, you have to place your guide (Straight edge) exactly 2-5/8"away from the edge of the dado. If you run TWO parallel strips six inches apart, the router will follow through the guides and create a perfectly straight dado Be sure your original work piece has been cut straight,square and parallel on opposing sides sides and square and parallel
As for the divider dadoes, use a good square to lay out the 90° intersecting dadoes.
If you must make each division equal, make the first two grooves at the left, then, make a template that drops into the groove and is exactly wide enough to present an edge to ride against for the third pass. Repeat from left to right for any additional dividers .
Steinmetz.
Very useful, thanks.
The round base plates on many routers are not consistent. If you don't hold the router in the same place against the fence, you can get variations. I don't use round plates when going against a guide fence, I make some square bases and mark one side that always goes against the guide. Set up and cut on a scrap so you know exactly how far the edge of the bit is from the fence. Once you know the difference in measurement, do all the measuring from one end of the cabinet parts.
You can also make a router fence jig that has two guide rails. Folks often use a template guide with these type of fixtures. You can almost set them right over your location marks and don't have to allow for the width of the router base. There is still a discrepancy due to the template guides relation to the actual edge of the bit.
Router bits don't always match the thickness of the material you want to fit in the dado. With a double guide rail, you can set one side off to make the return cut against. This will take off that little bit of extra to make the fit. I just make my square bases different on each side, + 1/64", + 1/32". etc. . I do the plus side first than make a second pass on the zero (starting) side. It's a matter of bit rotation in the cut. You normally want to go with the rotation of the bit, not in a climb fashion.
Beat it to fit / Paint it to match
That makes sense, too. Thanks for the explanation. I read The Router Book pretty carefully before getting into this, and it does touch on this, but as with all physical skills, the words don't really click until you try to do it. Now after bungling around and then with your explanation, it is at least starting to click.
My router is a Triton 2 1/4 plunge, BTW. I know I will probably need more someday, but would like to master this one first.
Edited 1/20/2007 11:31 am ET by Joe Sullivan
I don't own a Triton, but it seems to me you have made a good choice of router.
Suggestion--Consider getting Bill Hylton's book "Router Magic" or Carol Reed's book, "Router Joinery Workshop" (I think have the book title right. Don't want to go out to shop and check).
I have several jigs made (very simple). Consists of 4 parts. two side-fences, with end-pieces to hold them parallel. Make sure the side-pieces (fences) are longer than the width of material you will be dadoing. The side-pieces are spaced exactly the distance of the diameter of your router base. Make sure the sides-pieces are square to the end-pieces. When the jig is finished, place it on a scrap piece of plywood with one of the end pieces tight against the edge and clamp to the work piece. Place router with bit in between the fences and route a groove. Start your groove outside the end-piece so the groove goes through it before contacting the plywood.
Now you have a pattern (where groove goes through end-piece). Line up the groove with the groove location you wish to cut. You will need one of these jigs for each size bit you use.
As someone else said earlier, dadoes cut with standard dimension bits will not match the thickness of most plywood. So you may have to use a smaller dia. bit and move from one side of the planned dado to the with you want. Also, always hold the router in the same position while passing through the dado cut.
Hope this helps. Best Wishes.
Billy B.
Add "Woodworking with the Router", by Hylton. It has plans for the best dado jig I've seen. Plus it covers everything to do the basics and then some with a router, discusses router table design, and I think has plans for three different router tables.
It would have been money well spent, if I had read it before I bought anything. And, I had actually been "trained", in how to use a router in shop class, so it wasn't all new to me.
Right--I have that book also. You made a good point, router novices would be well ahead if they were to purchase books such as we suggested here. It would even make it easier to follow suggestions made by others here on the forum.
Billy B.
can't eyeball setup and expect to have consistant results.
subtract half of the width of the bit (half of a 3/4" bit is 3/8")from the distance between the edge of your baseplate and the center of the bit (if a 6" round baseplate that would be 3"). so 3" (-) 3/8"= 2-5/8"
decide where you want the dado and mark the near side of the dado on both pieces you intend to route.
measure 2-5/8" (or whatever that number turns out to be) from that mark. that is where you put your edge guide
Joe, "The answer, obviously, is to measure properly, and set the straightedge guide "fence" in the right place. I have had a heck of a time doing this. The cuts seem always off by an eighth or so -- just enough to bother the eye." Welcome to woodworking! Learning to accurately measure, prepare stock and cut where we want the cut to be is basically evrything we do prior to finishing. Off by an eighth is enough to bother the eye? I should say so! Off by 1/32" is enough to make the parts impossible to fit together. Not related specifically to how you are trying to control your router, but vital to the whole job, are you certain your cabinet parts are absolutely square and cut to the tolerances needed? Without that, your router cuts may be off, simply because your stock is not allowing you the accuracy you need to position the router guide. Rich
Edited 1/20/2007 2:49 pm ET by Rich14
Joe, I am attaching a pdf of plans for the jig set I use. It is pretty straight forward, but if you have questions let me know.
IMHO: The best basic book on the router, that everybody who owns a router needs to read, is "Woodworking with the Router", by Bill Hylton. Check with your library to see if they have it, if you want to put off buying it. But, once you read it you will want it handy as a reference. And, the cost of buying plans for the router tables and jigs he shows how to make, would be far more than the cost of the book.
I recommend the use of a 3/8-in bit if you have one. That way the jigs work for both 3/4, and 1/2-in plywood.
Edited 1/20/2007 4:26 pm ET by Jigs-n-fixtures
I saw and used the simplest and most accurate jug for this, but I can't remember where I saw it. I made a T form with the long leg longer than any dado I might want to cut. Be sure to make the jig a perfect right angle. Put the jig against a piece of scrap board and run the router through the T. Now all you have to do is slide the T to where the slot you cut is exactly where you want the dado and clamp the T in place. I my case I did one side of the T with a 3/4" bit and the other with a 1/2" which were the most commons ones I used.
THanks to all for the wonderful helpful information. I will head to the bookstore (on line, of course and get myself a course of reading. meanwhile, the 3/4 bit works well, because I am using dimensional lumber and not plywood.Again, thanks.j
This forum post is now archived. Commenting has been disabled