Tight Fitting Miters

[bffulgham]

Here's a collection of basic frames I've built over the last 6 or 7 years to display our travel photos at home. All of these, with one exception are what I call gallery frames....kind of a reversed shadow box type construction. While not every corner is perfect.......

All of the prints in these are 8x10s (kinda give an idea of overall size)
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The center one is a 16x20 print
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This is a more 'traditional' frame with outside dimensions of about 33x43"
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Here is my collection of critical frame building tools. The MOST important tool of the bunch is my ancient Starrett combination square.
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I guess the length stop on the far end of my miter saw would have to rank right up there with the Starrett. If the opposing pieces ain't IDENTICAL lenghts....it ain't gonna be square. Not shown is my 510 with the jointer attached to get the straight edges required, and my lunchbox planer to get all the stock to the same thickness.

One thing I've learned about getting identical lengths using the stop is to try to use the same force on each piece when butting the first mitered end against the stop. The softer the wood, the easier it is to smush the soft point of the outside edge and get a longer piece. I'll also do a test frame from scrap stock as described by pennview:

.... I use a scrap frame and make test cuts until the angle is exactly 45 degrees. This means trimming the end of each piece in the frame for a total of eight cuts. If the angle isn't right, tweak the miter gauge and then make eight additional cuts until the angle is perfect.

The band clamp is also a wonderful invention. I make sure I use the corner supports to keep from smushing the outside corners and try to not over tighten to avoid springing the frame pieces out of square. Another thing to check after tightening the band clamp is to make sure all sides of the frame are flat on the bench surface.

I used my Porter Cable biscuit joiner with #20 biscuits on each corner of the frame in the last picture I posted. This should help to prevent corners from gapping over the long run. The glass made this sucker pretty darned heavy, and a glue-only joint is not the strongest joint in the world as a mitered corner is mostly end grain to end grain.

For me, set up is the most critical step in the whole process. Using the miter saw works best for me, but the same concepts will apply using whatever version of a miter gauge on a table saw, a radial arm saw, or a miter box with a back saw......I've used em all thru the years.

One other thing I might mention is that I also try to assemble my frames as soon as I can after cutting the last corner. Even a slight change in humidity can make some of the pieces crawl around a bit....don't care how dry the wood is....and even a tiny bit can screw up the fit of the corners.

One more 'one other thing'...... If you mount glass in the frame, make sure there is a slight gap between the glass and the frame....exactly like doing raised panels. Let the wood do it's changes with temperature and humidity without putting anything in a bind.

[Gene Howe]

That's a nice looking accessory. Do you find that you can get as cleans cut with a table saw as with the Lion Miter? In my experience, even when used in conjunction with a zero clearance insert and backer, I couldn't get as cleans cut as with a well honed Lion Miter.

Not quite as smooth, I'm sure. Although, to the touch it appears so. I use a 60 tooth full kerf Tenryu blade for mitering. In hardwoods like mesquite, white oak and maple, the cut is pretty darned slick. On Walnut and some other softer woods, it's still certainly smooth enough to glue up. I always use a backer, too and my shop made zero clearance inserts. In addition, The front of my miter gauge has a strip of sand paper to hold the piece more securely. Of course the stop holds it well for the 2nd cut. I really believe that the blade makes the difference in the cut quality, though.
I haven't mitered any fir or pine with that blade, so I'm not sure what it would do, there.

[charlese]

Special tools and jigs are fun to use and do the job well, but have you ever thought of how old timers - before these tools were invented made their accurate miters?

My self? I use a Shopsmith MiterPro http://www.shopsmith.com/ownersite/catalog/swd_miterpro.htm and saw the right side of each angle with the long leg and the left side of the joint with the short side. Result is a perfect 45.
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For more than 8 sides I love the MiterSet! Here is an example of a trial to make an 11 sided frame using the MS.

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[Ed in Tampa]

I guess my method is not really what Dusty is looking for but I will post it anyhow. I use a power miter saw with a miter saw blade. Since I got the miter saw I haven't had a problem with miters at all.

One secret I learned back when I was cutting miters on the Shopsmith. I would undercut the bevel so that just the visible edge would meet. Any small needed adjustment could then be easily corrected because of the flex in the thin wood.

Someone asked how did they cut miters back before all these gadgets. They undercut the miter and used the edge of a screw driver to roll an edge.

If the joint was open closer to the inside the undercut would allow the Craftsman to push the joint closed. If the joint was open on the outside running the shaft of the screw driver up and down the joint would close it.

[mrhart]

Special tools and jigs are fun to use and do the job well, but have you ever thought of how old timers - before these tools were invented made their accurate miters?

My self? I use a Shopsmith MiterPro http://www.shopsmith.com/ownersite/catalog/swd_miterpro.htm and saw the right side of each angle with the long leg and the left side of the joint with the short side. Result is a perfect 45.
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For more than 8 sides I love the MiterSet! Here is an example of a trial to make an 11 sided frame using the MS.

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I don't understand the process here, try me one more time, I have the miter pro, have not used it yet.

[dusty]

Dusty did not have any preconceived idea of what he was looking for.

Dusty was just looking for tips and tricks so that someday Dusty's efforts might result in some outstanding frames (and moldings).

I have built a few but have never gotten any to brag about. I have all the right equipment (Lion Miter excepted) but lack the experience and patience to turn out GOOD frames.

I really like Charlese' recommendation of doing the right side with one leg of the miter and the left side with the other leg. That way, mating pieces will match the Miterpro . Great idea and probably great results so long as the MiterPro is square.

Gotta go check my MiterPro (which I think is disassembled).

[bffulgham]

Here's yet another couple of ways from Doug Stowe, the box making guru that writes for FWW at times....
http://www.finewoodworking.com/Workshop/WorkshopArticle.aspx?id=30357

The second sled he shows is an adaptation of the Miter Pro concept. As Charlese and Dusty mentioned, if you properly alternate left and right cuts from the respective faces of the fence, you will get perfect 90* angles. But ONLY if the fences are at an exact 90* to each other. I've seen a different adaptation somewhere of this, where they used an inexpensive plastic drafting square mounted to the sled and cut thru the plastic square on the first cut.

Both of these sleds should work equally well on traditional table saws or the SS. Be careful of unsupported off-cuts on the up hill side using the SS and the first sled. The blade can, and will, launch those when they slide down into the spinning blade. Not that I've ever experienced anything like that....

Another of the pre-power tool methods was to use a miter box for the initial cut and a hand plane with a 45* shooting board to tweak the joints.

[robinson46176]

Another old time trick was to carve a leaf or something like that and attach it over the joint. It might have had a huge gap in the joint.


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[charlese]

I don't understand the process here, try me one more time, I have the miter pro, have not used it yet.

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The photo is from the Shopsmith page - The user is using the long leg. The short leg is near the operator. If the mating cut has been sawn from the short leg, the miter will be exact 45 deg. (sorry I had referred to right and left sides of a joint. I should have said mating joint surfaces)

Since the short leg has no stop block it should be used for the first cut. Then that miter can be placed in the angle of the stop block (as shown in the photo) before sawing the miter on the other end of a board. Continuing this process on 4 boards will produce a square frame. Adjusting the stop block for two of the boards will give a rectangle.

Note: the sandpaper faces of the MiterPro are used to prevent slipping.

[dusty]

I was curious about what degree of precision is required to get really good fitting miter joints. Since I did not have enough cutoff in the shop, I decided to play with sketchup and to build a couple picture frames there.

It was interesting and a bit informative. I suggest that everyone should give it a try. Create four pieces with perfect (45°) miters and four pieces with 44.9° miters.

The conclusion is obvious. A perfect frame cannot be constructed with anything less than perfect miters (and perfectly dimensioned sides - meaning opposite sides must be of equal length).

Side note: In sketchup, make each frame piece a component. If you do not, once they are joined, the union is permanent. Just like real shop work. You can dry fit and still make corrections but once you glue the joint you have no further opportunity to make correction.