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Having taken a break from trying to learn woodworking, I'm hoping to learn some new skills over the holidays, weather permitting. My interest in woodworking was inspired by Norm. This video is one of the best introductions to routers I've seen, so I highly recommend it to other beginners. What frustrates me about it, though, is the dado jig. He cuts the dado, and the shelf fits perfectly. In my limited experience, it's next to impossible to get a bit to fit the thickness of a shelf perfectly. I can only assume that he either milled the shelf to match the bit, or he got lucky. My guess is that for most people using this jig, it would be better to use a 1/2" bit and to cut the dado in two operations, shifting the jig from one side of the 3/4" dado to the other. Your comments and suggestions are welcome.

 

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Mike, plywood bits are sized to work with the 1/32" reduced sizes. Solid wood is still on 1/4" sizes.
 
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Also remember that what we saw on the video is not necessarily all that happened. If I remember right, Norm did say that the show was edited for time, and that you didn't always see everything that went into making his projects. Even with that said, I agree...Norm was great to watch.


Gary
 

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Never assume anything..


nominal Thickness Actual Thickness
1/4” 1/4”
3/8” 11/32”
1/2” 15/32”
5/8” 19/32”
3/4” 23/32”
1-1/8” 1-1/8”

Thickness in Millimeters

Thickness (inch) Thickness (milimeter)
1/8” 3.2mm
1/4” 6.4mm
5/16” 8mm
3/8” 9.5mm
7/16” 11.1mm
1/2” 12.7mm
5/8” 15.9mm
3/4” 19mm
1-1/8” 28.6mm
1-1/4” 31.75mm

Baltic Birch produced to metric equivalents.

Source: Plywood Thickness | ThePlywood.com

comment from Norm A. himself on plywood:
Norm Abram replies: I come up against this problem all the time, and there's no simple answer. For starters, plywood is not like lumber; it's made to the thickness actually stamped on its face. The problem is, the manufacturing tolerances vary depending on the kind of plywood being made. For instance, sanded grades of softwood plywood that are ¾ inch thick or less — the type you'd probably use for utility shelves — are manufactured to tolerances of plus/minus 0.4 mm (1/64 inch). Most other softwood plywood, including the unsanded grades, is manufactured to a tolerance of plus/minus 0.8 mm (1/32 inch).

Hardwood plywood, which is used to build higher-quality cabinets and shelves, is a slightly different story. Panels ¼ inch thick or more are made to a tolerance of plus 0.0 mm/minus 1.2 mm (3/64 inch). A plus-zero tolerance is dictated by the cabinet and furniture manufacturers, the biggest users of this material, who can live with a panel that's slightly too thin but not one that's too thick, because of the assembly problems it causes.

http://www.thisoldhouse.com/toh/asktoh/question/0,,459293,00.html
 

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I'll toss in that dimensional lumber often isn't of a consistent thickness, either. I've gotten boards that are sold as 3/4" thick but are often 1/64" to 1/32" less. Your best bet is an exact width dado jig so you make a dado based on the actual thickness of the board you are going to use. This is sometimes hard when you are making a dado for the bottom of a drawer or such but for shelves and carcases it makes a lot of sense. You certainly can tune a dado blade to the correct thickness but for the router approach you are stuck with the existing bit widths.

By the way, router bits aren't all that consistent either. When you combine bit runout and collet runout you can get a wider slot. Usually not terrible but it can lead to a looser fit than you would think. It happened to me with a freud bit and PC collet (not talking about low end stuff here). I got loose box joints. A quarter turn of the bit in the collet and I got tight ones. The difference was a little less than 1/64".
 

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Discussion Starter #8
I'll toss in that dimensional lumber often isn't of a consistent thickness, either. I've gotten boards that are sold as 3/4" thick but are often 1/64" to 1/32" less. Your best bet is an exact width dado jig so you make a dado based on the actual thickness of the board you are going to use. This is sometimes hard when you are making a dado for the bottom of a drawer or such but for shelves and carcases it makes a lot of sense. You certainly can tune a dado blade to the correct thickness but for the router approach you are stuck with the existing bit widths.

By the way, router bits aren't all that consistent either. When you combine bit runout and collet runout you can get a wider slot. Usually not terrible but it can lead to a looser fit than you would think. It happened to me with a freud bit and PC collet (not talking about low end stuff here). I got loose box joints. A quarter turn of the bit in the collet and I got tight ones. The difference was a little less than 1/64".
And there you go. I get my confidence up, and then I realize that I'm probably just getting ready to make another mess.
 

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Hi there. I have only just taken up the hobby and have just bought a router and table.
The first project that was undertaken was a dado jig that didn't need a bush. The only real stipulation is that you use the same bit with the jig every time.
I used wing nuts instead of the ones that need a spanner to make it easier.
I hope I have been able to help as this is my first post apart from my introduction.
Oh dear:frown: I have just realised that I cannot use URL's yet but the guide I followed can be found by googling ukworkshop videos Adjustable dado / housing joint jig.
Hope I havn't broken any rules by doing that.

 

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No rules broken Ken. You'll be able to post urls as soon as you get to 10 posts. It's an anti-spam measure. You can post pictures from your own hard drive now and if you need help to do that just ask. There vhave been a few designs posted on the forum before and may be found using the Community Search function. I made a circular saw cutting guide the same as what I think you are referring to.
 

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I had every episode of The NYW save on VHS tape >:) and was disappointed when Norm stopped doing the show.

During one episode, Norm made a display ladder and put his routers on it. I used to think Norm had the largest collection of routers I had ever seen (until I came to this forum)

I second Charley's recommendation to build the exact-width Dado jig - then you're not dealing with the thickness of the panel or the size of the bit.

And, as Gary said - the show was edited for time, so we didn't see everything else that went on in the background or between takes.

my .02 cents, Canadian
 

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Just for point of information, Norm has all (most?) of his shows available for viewing here:new yankee workshop There is usually a different one every week or so.
 

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I used to spend my Saturday afternoons watching Norm, This Old House, and the Router Workshop. I still miss that. One think I noticed watching this video is Norm's total lack of obsession about accuracy. We see many new members with their calipers, micrometers, and dial gauges out trying for that last 10,000th of an inch. Norm applied a little glue , a few brad nails, and then it was off to get the job done.
 
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