Just how square does a router table fence need to be?

[Wayne Jolly]

I am rebuilding the router table fence I built for my homebuilt router table. I had to do this because I found out the hard way that the base platform for the fence had warped just a little and some frame-and-panel doors didn't come out quite right. When dry fitting all of the pieces and clamping them together, they would not lay flat. I checked the "squareness" of the fence face to the table and it was off by . . . well . . . quite a bit. somewhere in the rage of .025"-.035". I should have known better than to use a cheap piece of crappy plywood for the base. Lesson Learned.

So this time I am using some Baltic birch plywood with a red oak face, and maple corner blocks to keep them square to each other. But there is square and there is square. When using my engineers square to check for square, the fence is back about .002"-.003", MUCH better than before. Now this would be a fairly easy to shim and get it "perfectly" square, but this IS a wooden fence using three different kinds of wood, so is a couple of thou really worth all the effort to eliminate, and just how long would it last anyway?


Thanks,

Wayne

P.S. Here are some pictures of what I am working on. Both the fence and the table are still a WIP. The table needs a door on the front, a safety power switch, and dust collection. The fence just needs to be finished. Oh, I didn't quite leave enough space between each of the drawer fronts so in very humid weather, open one drawer and you are likely to open them all. So they need some finish applied to them to help with that.

[Mike Heidrick]

Your wood fibers in your work will vary the piece that much. Enjoy your new fence.

[Brian Henderson]

That's a nice looking set up you have there. As to your question, the answer is "as square as you care to make it". How much "error" can you tolerate? I'm sure there are woodworkers out there who would look at 0.025" and not care because they're not working with extreme precision. There are others who would be horrified to find 0.002" out of square. How anal do you want to be about it? That's something only you can answer. Can you make something out of square at 0.002" and be satisfied? Or is it going to bug you? Like you said, shimming it is easy. Are you going to check it every day to see if it's moved a thou or two and readjust?

[pat warner]

Ordinary decorative cuttings? Then not to worry.

Joinery is another matter (your doors being a good example).
For openers there are these variables:

1) Work: square, equal thickness, flat and straight.
If not, the straightest, squarest fence will not produce perfect/great cuts.
But, to be sure, if the fence is misshapen and not square (to the table) you'll have double trouble.

2) Your router table surface has to be flat, ideally ~+/-.003 max, like cast iron.
If it's pretzeled, your work will squirm as it passes the cutter.
And
3) Your fence needs to straight, flat and square (<.5° max) to the table. Wood is not great for the contact surface. >2-3" wide and it will change shape; especially with all those x-grain pieces fastened to it.

So bottomline: A lot of stuff needs to be accounted for, for consistent, repeatable cuttings.
And joinery cuts will be the least enjoy-able if this stuff is ignored..

[Jerry Miner]

I'm having a hard time understanding why you think your fence kept your doors from being flat. Are you using a standard cope-and-stick set-up? Milling the parts lying flat on the table (or coping sled)? If so, then the fence serves mostly to establish the depth of the cut, not the flatness of the joint.

More likely the stock (or possibly a sled) was not flat, or did not remain flat.

Or the door got pulled out of flat at the clamping stage (did you check for flat at that stage?)

By all means make a nice flat, square fence, but I question whether that will resolve your out-of-flat door issue. My .02