Welcome to the Grumble, Jose.
I can't help you with #1 as I have never owned a guillotine chopper.
#2 and #3 depend on the profile of the float frame. I use floaters from 7 different companies and they range from simple "L" shaped float frames to 2 step frames and wide contemporary float frames and each one of them require different methods of joining and mounting the canvas in them. You can use V-nails, 5mm, 7mm, or 10mm depending on the profile and thickness of the moulding, you can even stack nails on some of them and that is a plus if you can't nail into the thin "back" of the float frame, that portion that is behind the stretcher bars. I have never nailed through the face of the float frame moulding. I feel that the clean lines of a float frame are destroyed with nail holes in the face of the frame even if you fill them with putty afterward.
Mounting again depends on how the float frame is designed. Some of them have long "backs" to them and can be drilled and screwed directly into the back of the stretcher bars, others have to be helped with other attaching hardware. I have used mending plates both flat and bent to the angles needed to attach the canvas, offsets can be used sometimes and can also be bent to apply pressure to the back of the float frame and hold the canvas securely in the frame. I would not use this method with the simple "L" shaped floater as there is a good chance that the canvas could slip unless you drill the other end of the offset and screw both ends to the appropriate wood. This works well on a stepped floater if the canvas is fairly snug in the frame groove to begin with.
You can use screw eyes (yeah, I know you don't like to hear this) turned into the inside of the floater and a wood screw inserted into the screw eye and turned into the stretcher bar. If you use a light touch when inserting the screw you will have no problem with anything pulling out or bending. You only need to tighten the screw enough to snug up the canvas against the frame. You can also do a similar mount with Multipoints and #6 screws on small canvases. I position the multipoints about 4" apart to ensure that the canvas is supported evenly along each side. You have to be very careful how you tighten these screws as the multipoints will pull loose if you overtighten the screws. Tighten just enough to snug the canvas into the frame.
As was mentioned, the trick sometimes is to line up the canvas evenly around the float frame when everything is laying face down on your workbench. I built some risers out of 6" square scrap foamboard glued together. I made 4 of these and, if you glue 10 of these together, you have just under 2" of support under your canvas. I position them so that they support the canvas at the 4 corners of the canvas. I center the canvas in the frame face up and carefully hold the canvas in position while turning the frame upside down and placing it on the 4 corner risers. Once the frame/canvas is laid down face down you can install hardware. Try not to bump the frame or the canvas out of position. If you do, simply pick it up and center it again.
I sometimes lay the canvas in the float frame and wedge lengths of foamcore around the canvas in the slot in the floater. If you use the same number of foamcore strips on each side, you should have a canvas that is automatically centered in the frame. This works well on simple "L" shaped floaters and sometimes is easier than the above method. You can flip the canvas and frame over onto your risers and apply the hardware without the worry of the canvas moving out of center..
The larger the canvas and the frame, the more you need to pay attention to proper support for the canvas in the float frame. I have seen framers air nail canvases into a float frame from the back and also use staples to fasten them together again from the back. I personally prefer the screw fastening techniques mentioned here as a threaded rod (screw) will always give more holding power than a smooth rod (nail). Plus I don't trust my aim nor the air power of an air nailer if it decides to launch a brad or staple through the stretcher bar AND the canvas!! And if all else fails, use your creative imagination and come up with a new method of holding the canvases in the float frame. And be sure to post your method here as I would be interested in learning new ways to mount these pesky paintings myself.
Good luck.
Framerguy
