Any tips on getting these miters "perfect"?

[Dave Squires]

I'm building a console shelf that has mitered corners, it's made from 8/4 hard maple, each board is 1 3/4 x 10", I'll use hidden splines in final glue up. But I'm having a hell of a time getting these miters to match up nicely.

I originally cut the miters on a miter saw because they were too cumbersome for the table saw. This left pretty rough miters, so I used a low angle block plane to try and clean them up. This helped, but some were real bad. So I sort of rigged it up on the table saw and clamped it down real good and shaved a little off - this was an improvement, but still.. not perfect. You can see I made a little sled to ride my plane against at a 45... this is OK, but the wood is thick it's difficult - probably a jack plane would be better, but I don't have one (yet).

Any suggestions on what process you would take to get these perfect? Would you just keep at it w/ the planes, fitting it often? I have a Japanese combination square I'm using to check the angles, but with the edge being so big, any tiny variation on the inside and the miters are off.. Really appreciate any tips!

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[Prashun Patel]

There are a couple ways.

If you are comfortable using a shooting board, you can make a 45 deg ramp for it (Donkey's ear) and clean it up that way.

The second way is to make a dedicated sled on the table saw.

[Jacques Gagnon]

Dave:

Prashun provided two good approaches. Another option is to use an "L-shaped" auxiliary fence and run your board with a strip of wood, attached with double-sided tape, that will act as a straight edge. The blade on the table saw will be set at 45 degrees. Please refer to the article in Fine Woodworking (link below) July 30, 2014.

http://www.finewoodworking.com/2014/07/30/versatile-tablesaw-l-fence

Good luck,

Jacques

[Andrew Hughes]

Getting perfect Miters is not going to happen. Shoot for excellence.A block plane and a accurate combination square would be my choice. But work fast maple can move enough in a day to throw things off.good luck

[Prashun Patel]

Oh yeah... and try to use a better blade. At the very least you can eliminate the tearout you are getting.

[David Eisenhauer]

I agree with P Patel on using a better blade. I have had luck using one of those "super cutoff" 60-80 t ATB carbide blades and making a series of minutely adjusted fence setups to end up with a decent/excellent miter joint, but, in the end, moved to using hand tools for a quicker result. To me, a hand plane and a shooting board or donkey ear is faster/more satisfying than the endless adjustments on a fence for a single or very few cuts.

[Dave Squires]

Thanks for all the suggestions, so I made a shooting board, you can kind of see it in one of the pics on the bottom, it does work.. but the block plane isn't wide enough to cover the full board, probably if I use a low angle jack plane, that would be more ideal? (been itching to justify the the LN low angle jack)

[Brian Holcombe]

First thing is first. Is the stock flat and uniform thickness? Have you verified this with winding sticks. If you have not, or if you are assuming it perfect off the machine, it is not perfect and likely causing you grief.

After you verify that it is imperfect the next step is to joint the inside "reference" surface, then thickness plane the outside surface to size.

You are then referencing off of your sides to cut your miter square to the board, are the sides straight and square to the edge of the board? Verify this with an accurate straight edge and square. Do not assume that coming off the machine means it's true.

Mark one side as your reference and do all of your cuts off that side if possible (not likely possible with your table saw) if now, then do all of your checking off the reference side.

Saw them again.

Tune them with a plane, can be a block plane. You need the blade to be sharp, very sharp. Make one side the reference side, make certain that it is 45 degrees all the way across then true and square to the reference (it must be flat). Fit the opposing side to it, you can fit it up and slip in a .001" feeler gauge, mark the high spots and plane them down until this board lines up well.

Next time....cut dovetails on the corner and just miter the edges.

You might think that machines are accurate from their manufacturers. I find that not to be the case very often at all, in fact I have enough time in my Festool Kapex to suggest never to trust a machine to cut square from the manufacture....but it does now....

[Von Bickley]

If you will not see the "back-side", cut the miters at 44 - 44.5 degrees and the front side will look great. The gap or crack will not be seen.

[lowell holmes]

If you will not see the "back-side", cut the miters at 44 - 44.5 degrees and the front side will look great. The gap or crack will not be seen.


Bingo! :)

[andy bessette]

BH--good post.

OP--I have had good luck with re-fitting large, ill-fitting miters by slightly hollowing out the "insides" of the miter faces using a shoulder plane, and then adjusting the final fit of what shows.

[Doug Garson]

A trick I'm sure I saw on Stumpy Nubs website by Mustache Mike (although I just looked and can't find it now), is after you have done the best you can and glued up the joint and the glue has dried is to run the shaft of a round screwdriver along one edge to effectively bend the wood over and close any gap. He didn't add any glue which I would be inclined to do if I tried this trick. Won't make a terrible joint perfect but might make a marginal joint acceptable. I haven't tried it myself. I have used a little glue in the open joint gaps and sanded it close up the joint. Again won't make a terrible joint perfect but can make a fair joint better.

[Prashun Patel]

I agree that (like dovetails) the joint will look better once glued. Even if you don't burnish the edge with a screwdriver, sanding will help.

Due deference to Von and Lowell, I'd be leery about undercutting the miters. While this may result in a cleaner outer edge, it will cause a gap along the side that doesn't hide so easily.

Also, when you are clamping, an undercut miter - if it's not a box - can cause the sides to be pulled out of square. I've made this very mistake (and continue to do it unintentionally...)

[Art Moore]

I wouldn't say it's the best way, but I've sometimes used a 45 degree chamfer bit on the router table.

[Mark Gibney]

I use an L-fence like in the link Jacques posted, mostly for plywood work but on occasion for solid wood, such as making a waterfall table.

If you use an L-fence to cut a 45* miter the blade will need to eat into the edge of the fence.
And I also find it works best to leave at least 1/32" of material remaining on the cut edge. If I don't, and aim for a knife edge, the board will swivel slightly as it's coming out of the cut and the miters won't kiss perfectly. After glue-up this edge is sanded smooth.

The key here is getting your material perfectly flat and square before cutting the 45* miter, which of course you know, but I never tire of reminding myself before a poor joint reminds me...

[Robert Engel]

First thing is first. Is the stock flat and uniform thickness? Have you verified this with winding sticks. If you have not, or if you are assuming it perfect off the machine, it is not perfect and likely causing you grief.


The key here is getting your material perfectly flat and square before cutting the 45* miter

No, I don't do this 5x a week but me sense is this your issue. Tablesaw w/ high quality blade should get it close enough. Personally I would use a panel cutting sled.

You're using splines, right?