If you have a lot of locomotives to work on and can justify the cost, Micro-Mark sells the MicroLux miniature milling machine for $499.95. I think Harbor Freight Tools has a larger one for less money that will do just as good a job, too.
When I needed to grind out space for a decoder from two Kato NW-2 frames several years ago, I used an electric grinder, but a milling machine does a much neater and faster job of it.
I tried a Dremel, but the motor overheats from trying to do something like this, and the blades tend to bind and cause it to kick back.
You can use a Dremel. Be prepared to go through a lot of cutting wheels, though. I got a bulk-pack of cheap wheels (not Dremel brand) at Lowes. When one breaks, well, who cares? Take it easy, and when the tool itself starts to feel warm, give it a break and let it cool down.
Think about where you're cutting. It may be that if you move over a quarter-inch, you can take advantage of an existing notch or groove and save yourself some effort.
It takes an iron man to play with a toy iron horse.
Cisco,
For controlled metal cutting, milling is the way to go. You can hold and support the frame in a vise and control the depth (or Z-axis) of cut down to a .001". A good quality endmill (i.e. cutting bit) is also important and will be an additional expensive.
If you know pretty much what needs to be done, perhaps the cheapest and easiest way for now would be to have a machinist do it for you. They are usually paid by the hour and cutting frame metal would be fairly quick work.
Find a shop that does low volume and tell him what you want done. A working drawing (with the loosest tolerances possible) for each different locomotive frame is both helpful and will ensure that the job is done right. The looser the tolerances, the faster (faster=cheaper) the work gets done.
Do you know how much of the frame you need to remove on each locomotive? Is it the same for all of your locomotives?
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
What is a good method for cutting down the weight in something like the narrow body locos? I have several to do next..a GP18 first. For my first two or three I have just hacksawed out chunks by hand. Is there a good/better hand-held tool, power or otherwise to do the job?
or....
I'm not sure how expensive something like a hobby sized metal-cutting floor or table bandsaw or jig saw would be, or if they would even work better. But now I am moving to a bigger location and so may even consider a more permanent cutting/milling tool for all these conversions.
Thanks.