If you are having trouble filing blades, here's a Templot idea for a filing aid which might help.
For "B" blades, print a straight template for a strange-size turnout having a 12ft straight switch and 1:32 crossing angle. The turnout road will then be straight. You need to print only this part of it. Make it up on some scrap copper-clad with the stock rails only (blue rails). Make sure the set bend is accurate and correctly positioned by measuring the stock gauge at 2 in the diagram. There are no curved sections:
The yellow rail is the blade being worked on. Mark it all over with waterproof felt-tip marker, so that you can see where you are filing. Make sure you have it the right way up (thick edge at the top). File the back of it, just going down to the web at the tip, and running out in a length of 29mm (29.33mm to be precise) at the end of the planing. Don't go far into the web, otherwise the blade will be too flexible at the tip, and it will be difficult to get a clear flangeway all along behind the open blade.
Clip it to the stock rail all along the planing (bent-up paper-clips are ideal), at 1 in the diagram. Adjust the filing until it sits nicely flush against the stock rail all along the planing, and the rails diverge at the end of the planing, at 2 in the diagram. At this stage the rail at 3 will be wrong (too close to the stock rail).
Remove it and make a small bend at the end of the planing (2 in the diagram), so that when clipped back in place, the rail at 3 is correctly aligned. You can check this using track gauges from the opposite stock rail. Repeat trial and error as necessary.
When you are happy with the fit, you can start filing the front of the bade. Getting this right is not as important as the back of it. Remove the bulk of the metal first, then for the final filing you could perhaps do it in place on the filing aid if you clamp the rail down at 3. To that end it would be good to make the filing aid on a piece of board which can be held vertically in the vice.
Use the file at an angle, with the safe edge at the bottom to leave the rail foot intact, and file until the the blade tip is a knife edge at the top, with the running edge dead straight all through the filing aid. The filed length is the same as for the back of the blade, running out to nothing at 2. Some more ink on the rail may help to see it.
Finally fettle it with abrasive paper to make a smooth top edge against the stock rail for the wheel flanges. This will cause the knife edge at the end to be reduced a little below the top of the stock rail in the prototype manner.
That makes a left-hand point blade. Now print a right-hand version and repeat the whole process to make a right-hand blade.
For "A" blades make the template a 9ft straight switch and 1:24 crossing angle. The planing length is 22mm.
If you are careful these filing aids should be good for several blades. But cost next to nothing if you need to replace them.
More about planing lengths and the stock gauge here: http://www.templot.com/martweb/gs_realt ... lit_switch