Advise on using rotary file

[ranma]

Hi, I'm building my CP on metal. I used a metal punch tool to make the holes, but then I realized that my sanwa buttons are slightly larger than the happ buttons (and the standard sizes of my punch kit). So I had to enlarge the holes a bit. For this the first tool that came to mind was a rotary file like this: http://www.amazon.com/VERMOUNT-AMERIACAN-16677-ROTARY-FILE/dp/B000GAV33W.

The thing is that either I'm doing something wrong or this tool is extremely hard to use. I'm not sure if I will be able to explain well, but the problem I'm having is that when I engage the file against the metal, sometimes it goes smoothly and I can go around the hole without problems, but sometimes "something" happens and the file gets locked on the metal and I loose all control of the tool. Sometimes I cannot even place the file onto a certain part of the hole because it will not "engage" cleanly. Did I explain correctly?

I'm not sure why this happens, if it's because of vibrations of the metal sheet or what, but any pointers (or a better tool to use) is highly appreciated. Only thing is I might not find every specialized tools on my country, I bought the metal puncher when traveling to the US, but couldn't find anything alike around here. So any suggestion has to be with "simple" tools. 

Thanks

[jasonbar]

I'd recommend a half-round file--you can probably get a clean enough & round enough surface by hand.  The buttons should have a flange to hide any hole imperfections.  A file like this: http://www.etamiya.com/shop/images/tamiya_toolspaints/74062.jpg

Or, a Dremel with a sanding drum: http://www.google.com/images?q=dremel%20sanding%20drum&rls=com.microsoft:en-us:IE-Address&oe=&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1209&bih=906

With either of these tools, you won't get grabbing that's dangerous to you & your panel.


Or maybe you can try a step drill, depending on your current hole size & desired hole size?  http://www.google.com/images?q=step%20drill&rls=com.microsoft:en-us:IE-Address&oe=&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1209&bih=906


-Jason

[BobA]

+1 for a step drill.  Very useful on metal control panels.

[lilshawn]

sometimes it goes smoothly and I can go around the hole without problems, but sometimes "something" happens and the file gets locked on the metal and I loose all control of the tool. Sometimes I cannot even place the file onto a certain part of the hole because it will not "engage" cleanly. Did I explain correctly?

this can happen with these style of tools if they are not driven fast or powerfully enough.

they are designed to be used in a die grinder, which spin in the neighborhood of 20,000 - 30,000 rpm. often with cheap electric die grinders, or air powered die grinders operated at less than optimal flow, you get too much slowdown when you apply the tool. (no high rpm end power) when it slows you get more power, but it's slower and the tool tends to dig in to the work piece.

you will notice if you look close your metal will have a slight oscillation in depth, this is what your tool is catching onto causing a vibration where no work is getting done, since the tool catches and lifts off the workpiece. when you try over and over and you get the same oscillation...

the way to fix it, is to "hit" the area hard and fast, removing the offending material on the work piece. i don't mean gouge it or lay into it, just get your tool up to speed and give it a hard bzzt! just a fraction of a second. you might need to do it 3 or 4 times if the metal of your workpiece is tough.

though very efficient, you can avoid this issue completely by using a different tool. a stone based grinder:

is allot slower, but less prone to issues such as this.
also a sandpaper type grinding wheel:

can be used for metal/wood/plastic whatever... a good all around tool.

[ranma]

Thanks!, that was quick advise... 

I tried a half-round file but progress was REALLY slow, thats when I decided to go to an electric solution. I also though Dremel but I don't have one, and buying one just for this seems overkill (and expensive!)

The step-drill seems the tool for the job, I wish I knew about it when I was traveling more frequently to the US. As I thought, no one ever heard of that around here.

Thanks lilshawn for such detailed explanation, that describes it perfectly. This tool was sold to me as to be used with a drill, and I highly doubt my drill goes so high in RPM.

I guess right now my best bet is a stone or sandpaper based grinder. (or continue using the tool I have with this advise)

Thanks all!