don't forget a miter knife...
Did you mean "trimmer"? Miter knives googled show a branch grafting tool. There are a number of trimmers out there beside the Lion style. Our local framing shop has a trimmer mounted on a steel post with 6 foot long arms to position stock on. I can't imagine a shop without a high quality trimmer. But the local shop purchases most of its stock in bundles.
I have used the router to cut shallow grooves in which I glue trim pieces, such as the decorative molding strips in the picture below. You can use a table saw or router to shape the wood and the router to soften those shapes. If you shape the top side, leave the bottom and sides flat until the last, which is when you cut any angle you want on the outside of the frame, and then the rabbet for the canvas stretcher or art to sit in. Keeping three sides flat will give you a base for your final cuts and refining.
I would also suggest making a highly waxed assembly table with perfectly square L shaped pieces to brace the frame for fitting and glue up. The open shape will make it easier to use different size frames.
Length of raw stock is an issue as well. The length of a frame is determined by the length of each dimension of the art, plus a quarter inch to allow for fitting and trimming, plus double the width of the frame stock. The mitered section is equal to the width of the stock. The width, lenght of the art or frame stretcher for a painting (plus a quarter inch) is the inside dimension of the frame. The outside is that, plus twice the width of the frame material. Measure the frame stretcher (canvas) carefully, and measure to include the fold over at the corners of the canvas. This can add an eighth inch. The quarter inch spare will be eaten up by the trimming of 1/32nd to 1/16 th inch on the miter trimmer.
This means that 3 inch wide stock on a 24x36 painting will be
2 ft inside dimentions
Inside length 24 1/4"
Add width x 2 6"
TOTAL 30 1/4"
3 ft inside dimensions
Inside length 36 1/4"
Add width x 2 6'
TOTAL 42 1/4"
Total minimum length of stock including 6 inches of waste.
30 1/4 x 2 = 60 1/2
42 1/4 x 2 = 84 1/2
TOTAL + 6" = 151"
That's about 13 ft of stock, which can be hard to find, particularly if you're careful to not get checked or twisted stock. So that likely means buying two pieces and jointing and planing a bit oversized material. If you're using a high quality hardwood, that can be extremely expensive, and if there's a twist, knot or other imperfection, you'll have to buy 50 to 100% more. Pre finished frame stock of hard woods are made from imperfection free wood, we're talking high-priced premium material.
That process and cost is why frames for oversized art costs hundreds of dollars. And that cost, plus profit for a LOT of hand work, is why market must aim for the well to do who deal in art work. Many artists can't afford such luxuries. Serious galleries (who can afford such services) would be one of the targets of my marketing. I'd plan to go to every exhibition and artist's showing in your region for starters.
Finishing is also a big issue. Your stain and finish work must support the tone of the painting or artwork, which is another reason why commercial stock comes pre-finished as well as raw. Pre finished material is the choice of many frame shops, which means keeping an inventory on hand of the most popular materials. Count on several thousand bucks to keep that inventory up to a workable minimum.
Most of the time, I use unfinished, shaped material (mostly pine) to make my frames. The picture of 9 strips are examples, and are available easily at Lowes or HD This is normally pretty thin stuff, so I use straight 7/8th pine on the back to form the rabbet. This stock must be perfectly flat, so it gets jointed and planed, then cut to width, then usually has the outside edge cut at a slight angle for appearance sake (I want the decorative frame to be prominent). This is cut square, not mitered and is really a rail and style. This piece can have small knots, and I'd cover the exposed ends with iron on or glued on strips.. It also serves to flatten slightly warped frame front material.
Pine needs to be finished carefully, and I generally use sanding to do this. Another picture below shows the shaped sanding blocks I use for this--the make sanding pretty easy. I use a sanding sealer to raise the grain and before sanding, which with 220 grit gives a wonderfully smooth finish. I don't use paper backed sandpaper anymore. I find the new flex backed 3M sanding medium is much better, faster, lasts a long time and conforms to the shape nicely. A scraper would be a possible choice depending on the shape.
If I had a frame business, I'd offer the pine alternative, but would also show samples of my construction method I described above.
Hopefully this will be helpful to others who are making picture frames. They are a lot more difficult to produce than you might think, particularly if they are for sale.