Square peg, round hole.

[Zilla]

Hi all,

I am trying to figure out a way to mount this slid switch:

http://www.taydaelectronics.com/electromechanical/switches-key-pad/slide-switch/slide-switch-1p2t-solder-lug-0-5a-50vdc.html#

The mounting holes for the switch aren't a problem.  What is the problem is making a rectangular hole for the switch. I do have access to a 4-axis manual milling machine at work and I can see milling out an elliptical hole and using a file to get the square corners, but is there an easier way for me to do this at home without a drill press?

Thanks

[PRR]

Small flat file into a round hole?



They also come square; but the triangle is easier to find (it sharpens wood-saws) and can do the job neatly.

If you are allergic to mechanical effort, maybe not. But in most chassis materials I can whack out the corners of a circle quicker than I can post on a forum.

This is done with a drill, rough-saw, and then files:



Yes, that's plastic, but fairly tough stuff and much bigger openings than a slide-switch. (This did take a while to get not-ugly.)

You can also just over-size the round hole so the slide works freely. Who is going to get that close to see a square peg in a round hole?

Those mounting holes look very odd for simple construction, but you say it's fine.

4-axis chip-maker sure sounds like over-kill; and as you note the corners still have to be filed out.

[Zilla]

Yeah I thought about that. The only challenge is that the is a mini switch, so the switch itself is less than a quarter inch tall.. Not sure if they make files that small?

[R.G.]

Jeweler's saw or "Zona saw", which is one brand name.

[davent]

Small drillbits, needle files and an accurate layout to stick onto the enclosure.



dave

[Jdansti]

An example of needle files from Harbor Freight.

[Zilla]

Awesome! Thanks for the tips!

[PRR]

> Not sure if they make files that small?

They make files to notch watch-teeth, too small for ordinary people.

I'm sure a saw-file is a fine size and stocked locally.

[amptramp]

Square drill fixture:

There is a floating drill that cuts randomly constrained only by an external guide:

[R.G.]

There is a variation of that process that drills triangular and pentagonal holes. The hole precision is usually not as good as punching or broaching, though.

[alanp]

I did the one on my ?Flange by drilling out a LOT of holes with a small bit (way smaller than the square hole), knocking out the bridges with a hammer and punch, then using a needle file.

And those Tayda switches are rubbish, get a Smallbear DPDT one, much sturdier. As in London Bridge compared to a rope bridge.

[anotherjim]

The next step up from the needle file is very useful. I know them as Warding Files...

Needle files are worth having, but they're really too fine for Ali. The Warding are more coarse and make quicker work of it.

Don't be tempted to drill the exact width of the hole. A worn or imperfect drill bit will make a larger hole than it's size if its point is off centre. Leave a mm from each side for the file.

As Paul said, the triangular file is most useful. Do corners one side at a time. It's very hard to file a corner evenly if you're attacking both sides at once with a square file. If the flat file will fit in, note it should have one smooth "safe" edge and keep that edge facing the corner you're cutting towards.

[Brisance]

Files are also great for getting your PCBs/Veros smooth and sexy, with round corners

[greaser_au]

Starting to stray off-topic a bit - and it isn't going to help, but there were series of slide switches with a round actuator some time back. These would need the 2 drilled mounting holes and a simple rotary milled slot (or 2 well-drilled holes and a couple of file strokes) for the 'handle'. e.g. :  something like this. 20-odd years back DSE and tandy would have had several types on the shelf both in black and silver.   Aaaaaah... the good old days!   

david