Square holes

[grumpydoc]

What's the best way to cut a neat square hole 4mmx9mm in 2-3mm thick ABS. It's for this slider switch, or possibly this one - up to 5x10mm would probably be OK but I'm not sure I'd want to get much larger than that.

I found some 1/4" square punches with which I'm sure I could do 6.35mm x 10mm but that's slightly large, I can't find any that are smaller.

Bear in mind that I'm mostly thumbs where this sort of thing is concerned and want something neat - drill plus file is probably not going to cut it (sorry - just realised the pun there ). I also want it to be quick enough to do small runs of perhaps 10 or 20 without taking too long.

[aroby]

A scroll saw would do the job.  Something like this http://www.micromark.com/microlux-jigsaw-and-scroll-saw,6673.html would probably be ideal.

Anthony

[djacobow]

After directions from this forum, I've become a huge fan of files for working plastic.

I usually drill out a whole large enough to get the file in, or sometimes a series of holes to perforate a section I can remove. Then lots of careful filing to widen and shape the hole.


http://www.harborfreight.com/8-inch-square-file-96630.html

[StrangeloveMD]

An alternative method would be a jeweler's (small hack) saw.  Obviously, you'll still need to drill a hole.

If you really want to kill some time, I'd recommend routing a line, then squaring the corners w/ a file.  Tedious, but should be clean.  If you are lucky enough to have a Dremel, perhaps this is a chance to justify that nifty little plunge router attachment they have.  As with a lot of things, the set up will take longer than the operations, but a good jig will eliminate some of the "all thumbs" rough edges that may occur with the jewelers saw.

P.S.:  A scroll saw comment swooped in on me.   It's like a jeweler's saw that does the work for you.  Use that if you have access to one.

[IanB]

A good technique to make accurate holes is to print the outline of the hole on paper and then glue the paper onto the surface where the hole is to be made (use a temporary tack glue so the paper is easily removed later). Carefully drill/file/saw the hole to the outline on the paper and then remove the paper.

[StrangeloveMD]

Sorry to off-topic,  but IanB has prompted me to wonder if anybody knows of a plastics/ABS marking fluid.  (Either professional or hobbyist-hack type)  A uselessly-quick google search didn't show anything.

[mazurov]

Nibbler tool works well is your hole is not too small (mine requires 1/4"-ish drilled hole to start). There are several nibblers on the market, most are crap so choose wisely.

[grumpydoc]

Nibbler tool works well is your hole is not too small

That's the trouble, all the nibblers that I've found need at  least a 1/4" hole to start with.

Looks like the only viable option in the short term is drill+file.

[Psi]

With a hole that size i would just make a 4mm drill hole and then use a small file to enlarge it up to the needed size.

Carefully make some scratch marks using a ruler that outline the exact area to be removed so you have a guide for filing up to.

Or, for a super exact cut, repeatedly drill+file the required hole into a random piece of sheet metal until you get a perfect hole.
Then clamp that to the ABS and drill+file it out through both. (you can hear the sound change when your file hits the metal vs plastic.

[tjb1]

Sorry to off-topic,  but IanB has prompted me to wonder if anybody knows of a plastics/ABS marking fluid.  (Either professional or hobbyist-hack type)  A uselessly-quick google search didn't show anything.

You could try Dykem but I'm not sure if it would have any impact on the plastic or if the remover would.

[rob77]

i usually drill many small holes along the sides of the square, then punch out the centre and then either file it to flat (longer, but nice finish) or just atach a small grinding stone to my proxxon and grind the walls to flat (fast, but not so nice finish). if the walls of the square are not visible (under the switch for example) then proxxon with grinding stone wins if it's a square hole for display , then manual filing is the winner

[Richard Crowley]

If you are worried about getting a clean and accurate rectangular hole. you could try "sacrificing" one switch to use as a "template".  Drill the two end holes first, and then secure the frame of a disassembled switch and that will limit the file to the desired hole size and shape.  This assumes that the frame of the switch is metal and not plastic, of course.

[SL4P]

Can you cut out a slightly larger hole, then make a bezel to carry the switch?
Or perhaps this is the excuse you needed to buy a laser cutter (!)

[G7PSK]

Contact these people they make punch and die sets.  http://www.candwengineering.co.uk/  Not all that expensive to have a set made to size and if you have it made with a hole through the 2 halves all you need is to drill a hole in the center of where the switch is going and thread a bolt through the die work and punch and wind a nut down on it to get a neat hole otherwise get a cheap arbor press.

[KJDS]

Take a shotgun cartridge and replace the pellets with a square slug.

[N2IXK]

Well, the "best" way would be a custom-made punch and die setup. This is how that hole would be done in production quantities.

For one-off quantities, the nicest method is a milling machine, a tiny end mill, and a bit of math.  You will need to square up the corners to remove the radius the end mill will leave.

Without access to a mill, drill as large a hole as you can, then file the rest using a square needle file. Easier yet, avoid components that need square or rectangular openings whenever possible.

[grumpydoc]

Take a shotgun cartridge and replace the pellets with a square slug.

That seems a little excessive

Well, the "best" way would be a custom-made punch and die setup. This is how that hole would be done in production quantities.

Yes, if I had 1000's to do I would go down that route but it will be 10's at most.

[VK5RC]

My pet hate is making a large rectangular neat hole for LCD displays in front panels (that my mild OCD states) HAVE to be really neat.
I pencil out the outline, use a fresh sharp drill and drill out close to the outline, fret saw away the waste then with a sharp file, SLOWLY file to edge .
Measure/look twice, cut/file once.
The dedicated punch and die set looks promising, does it bend the panel much?

[robrenz]

If I had a bunch to do I would make a broach like the quick design I did in Solidworks shown here. Just drill a 4mm start hole and push this through using your drill press as a broach press. Not running obviously

[nctnico]

I second the laser cutting. It is not expensive nowadays. A punch is just as expensive. OTOH I did buy a punch+die on Ebay for use in an automatic press. With some care you can use these in a drill press as well.

[grumpydoc]

Some good suggestions.

I quite like the idea of using the switch shell as a template - might see how well that works.

If it winds up being more than a few 10's then I could justify £40-60 which looks like it would cover a custom punch+die, though 5x9mm is a lot smaller than I've seen any "off the shelf" ones.

I'd love an excuse to get something like the Proxxon MF70 (with the ultimate aim of a CNC conversion) but this isn't it.

As I said my level of skill is not great - somehow no matter how carefully I measure and try to position a hole or cut it always seems to go somewhere else.

An old school report for metalwork and woodwork might shed some light on my practical abilities "....is always enthusiastic and tackles projects with gusto, unfortunately some of the results can only be said to be a little `unusual'...."

I border on dyspraxic, it does get in the way of stuff like this

[dexters_lab]

i have used a number of options over the years, for small holes i would draw up the hole and print onto paper, tape the paper down where you want the hole, then using something with a very sharp point poke a marker into the plastic through the paper in each of the corners, you can then remove the paper and  then using a scalpel and a steel ruler mark out the straight lines. You can then work to these when your using your file.

If you have multiple holes etc to be made they can be placed on the original printed paper so all the corners and hole centres are marked in one go

not something you want to keep doing though, its for one-offs

if i was making 20 of something, i would seriously be eyeing up a 3d printer!

[jamesglanville]

I'd second the 3d printer, I quite often print small plates with the correct cutout, so I can just mount it over a roughly drilled hole:



Obviously not applicable to every situation, but it's handy.

[Richard Crowley]

There are online/mail-order places that make panels much like vendors of custom PC boards.  Like "Front Panel Express" et.al.

One of these days very soon, I will get my CNC kit and I will be able to custom-cut things like this. I'm looking forward to never having to file out square holes or use one of those dodgy "nibblers" again!

[Richard Crowley]

I'd second the 3d printer, I quite often print small plates with the correct cutout, so I can just mount it over a roughly drilled hole:
Obviously not applicable to every situation, but it's handy.

That looks like a nice connector. What is it?