Drilling aluminium enclosures without a pillar drill.

[Buriedcode]

Recently I've had several jobs that involved modification of existing equipment, generally very simple stuff like additional LED indicators and switches.  One thing that I dislike about these jobs is having to drill the holes in extruded aluminium enclosures.

If its just plain alu sheet, up to 5mm, I'm fine.  Not using a pillar drill and vice is far from ideal I know, but a mark, centre punch, pilot hole of ~2mm, followed by a 4mm hole, then step drill works for larger holes.  These jobs don't happen often enough to warrant a fixed drill stand with vice.

However, most of these enclosures have PCB guides on the inside, both on the sides, and a few in the centre on the top and bottom.  Where I need to drill is just off-centre of one of these guides.  This means, the pilot drill goes through just fine - both the top and bottom of the sheet is flat, however, when drilling the wider hole, as the bit goes through the sheet it hits one of this guides, so one side of the bit is drilling through 4mm, but the other side is 2mm.   As alu is so soft this tends to just push the bit to the right making a nice oval hole that's a few mm right of where it should be.

Previously I have used a dremel to grind off the guide, but this is messy and makes it look like  shoddy job.  Without using a pillar drill and vice to hole it in place - any ideas on what to do?  It's a relatively simple problem, but I'm stumped, thus a forum post

[Muttley Snickers]

I would probably have a go at it with a centre drill, even with a mill or pedestal drill any normal drill bit around the diameter you mentioned will have a tendency to wander particularly if an obstruction is encountered on the way through so a non-flexible bit may be the answer, I have many of these in various diameters and also a set of small diamond tipped core drills on the way but I don't imagine the core drills being very good for aluminium, might be handy for other stuff though.

It's not easy to drill freehand and expect immaculate results in any material, a single hole is generally not an issue but multiple holes that are to be evenly spaced or aligned can be a big problem, sometimes it is worth the effort to drill out a template of thicker or stronger material with the correct alignment and then clamp that plate to the work piece as a drill guide or jig.

[nmugzy40]

You can also make a simple indexing jig. Draw a strength line on a piece of steel plate. Mark the distance between holes and drill. Mark the first hole and drill  use a second drill bit to index the plate and the work piece. You can now drill the second and subsiquent holes.

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[TerraHertz]

sometimes it is worth the effort to drill out a template of thicker or stronger material with the correct alignment and then clamp that plate to the work piece as a drill guide or jig.

Yes, this. It sounds like you do many of the exact same modification. So make a drill template. Using some tough material (steel, or dense slippery plastic, or high density MDF) with at least 20mm thickness and 40+ mm if possible. Cut a piece so the edges butt up against something as a reference, drill the template hole with the drill bit you will use for the chassis holes, doing this in a drill press so it's perpendicular to the face.
Then clamp this template in your chassis and drill through it into the chassis by hand.

[DaveCooks]

I think you'd get better results if you use a step drill to enlarge the hole.

[IanB]

Firstly, if you are in business, get the right tools for the job. A bench top pillar drill is not that expensive, you can probably obtain one for less than a solder rework station.

Secondly, drilling "half a hole" is always a problem, regardless of your tools. The best solution is to clamp a sacrificial piece of aluminium in the gap where the drill will go, so the drill does not try to float off to the side.

Another possibility is to drill the hole only as deep as the wall thickness, without trying to drill through the PCB guide. Then afterwards, reach through the hole with a long thin side cutter in a rotary tool and cut away the obstruction.

[KL27x]

I would take any excuse to buy a pillar drill.

If you like to mod, make, build anything at all, a drill press is very useful. Drilling, sanding, routing, and even turning small pieces of wood/plastic.

I've a Harbor Freight bench topper, under $100.00. If I needed to buy a larger free-standing version for a job, even better.

[ChunkyPastaSauce]

Depends on length of drill and diameter...you might be able to do what Muttly suggests if the drill is stiff enough (recommend a drill bushing in the fixture plate). However if the drill has flex beyond the drill guide, is still wont be straight. A standard drill press wont help either on its own, both because drill presses usually have some play in the spindle (not designed for side cutting) and because smaller diameter drills aren't stiff.  Normally for this kinda thing, you'd use an endmill in a milling machine.

[Brumby]

... drilling "half a hole" is always a problem, regardless of your tools.

Unless you have a laser or water jet cutter, absolutely.

I'd go for something like this:

The best solution is to clamp a sacrificial piece of aluminium in the gap where the drill will go, so the drill does not try to float off to the side.

[Jeroen3]

Get a drill press. Search on your online second hand market and buy a proper used drill press. Don't get the cheap diy-store one, it will be wobbly and not improve your end result.
Calculate how many times you can screw up an enclosure for the price of a drill.

[Buriedcode]

Firstly, if you are in business, get the right tools for the job. A bench top pillar drill is not that expensive, you can probably obtain one for less than a solder rework station.

I'll admit I would really like a pillar drill, but whilst these jobs are generally the same specs (same size enclosure, same hole locations etc..) almost all my work is electronics, and occasionally wiring. I never had formal training (or informal for that matter) in a machine shop but have always used customers workshop tools.  It isn't so much the price of a pillar drill, its the size/space required compounded by infrequent use.  With that said I have cleared my garage so its an option.

Secondly, drilling "half a hole" is always a problem, regardless of your tools. The best solution is to clamp a sacrificial piece of aluminium in the gap where the drill will go, so the drill does not try to float off to the side.

You know, I was thinking 'make a jig' but the idea of just clamping a block so its right at the edge of where the hole should be is a damn good idea.  The pilot hole should stop it wandering too much in any direction, but the block should stop it wanting to move in the direction it wants.  Using a hand powerdrill is awful for this work, but I am accustomed to slowing down and not using much pressure when it hits that rail which seems to help (letting the bit slowly take curls off it) but its never perfect.  Definately going to try this on the next one. Thanks!

Another possibility is to drill the hole only as deep as the wall thickness, without trying to drill through the PCB guide. Then afterwards, reach through the hole with a long thin side cutter in a rotary tool and cut away the obstruction.

Again... I didn't think of that.  I mean as I said I used to grind off the rail (its like 2x2mm anyway) but at first I would have to remove all of the parts off the plate, then I got tired/impatient (one of several mistakes) of that so used a dremel with a smaller grinding bit to work around the components - whilst this worked, looked chewed up on the inside.  Perhaps I could even use a chisel to tap the rail either side of the hole.

[Buriedcode]

The best solution is to clamp a sacrificial piece of aluminium in the gap where the drill will go, so the drill does not try to float off to the side.

And I didn't read that bit before... so ... for you IanB thats what, 3 out of 3 suggestions you've posted that are better (as in least effort/cost) than I could think of... thanks dude!  I may not have workshop tools but I can fairly precise dremel work (as in, slow) it shouldn't take long to grind out a few channels in aluminium so that it 'slots' on the underside, effectively as you said - making it look like a solid block to the bit.

As for the rest of the replies.. I've actually copied/pasted them in a text file for future reference - often even if someone says 'make a jig' there's always small details in there that experienced people take for granted, but which is really good practice.

These jobs will probably dry up, so I'll hold off on the pillar drill, but it is next on the list especially as my shoddy RVFM drill stand for my dremel (used for PCB's holes < 2mm) has developed serious wobble.

[G7PSK]

If you can get inside the extruded section and often they are made as two half's, remove the bit of guide rail/ slot either side of the area the hole is to be drilled you can do this with a pair of side cutters, a chisel or best would be a burr in a dremmel or die grinder. Then drill the hole from the outside as normal

[KL27x]

These jobs will probably dry up, so I'll hold off on the pillar drill

IMO, the block/guide idea is to be used in conjunction WITH a pillar drill, if you want to even bother doing it. (IMO, if the pillar drill alone doesn't do it, the block is going to add a lot more fuss!)

It's the leverage/control over Z axis as well as the lateral rigidity that make the pillar drill work. A hand drill will just destroy your guide block when the bit breaks thru the sheet metal and grabs, and it shoots down into the offset support.

Depending on how far away your hole needs to be from the edge, a pillar drill might cost you as little as 60.00.

[Brumby]

Depending on how far away your hole needs to be from the edge, a pillar drill might cost you as little as 60.00.

Throat depth.  (Distance from the centre axis of the drill to the nearest obstruction - which is usually the column.)

This becomes a very important distance when drilling in from an edge.  If you need to drill a hole that's 4" from the nearest edge, you need a throat depth that is at least that much or you won't be able to get the drill in the right place.


I bought mine some years ago - and this was the most important factor for my needs.

[Buriedcode]

As the box was indeed in two halves, I ended up doing what I've done previously - using a dremel to take out a section of the PCB guide rail.  A grinder would probably have been best, but as aluminium is so soft it tends to gunk up rather quickly, so... I used a cutoff wheel to break up the marked off section - then a chisel with light tapping to take the bits out.

First I marked out the hole and center-punched, then slowly drilled through the bulk of the panel until it was just about to hit the rail - about 2mm in.  After the rail was removed, finished the drilling.  I had to do 4 of these so making a jig would probably have taken longer.  Whilst I tend to think of the dremel as the 'arduino of the machining world' it really has come in handy for jobs like this - low volume awkward ones.

Given the state of the manufacturing of these units (holes off by several mm, shoddy solder connections or none at all (wire loosely wrapped around switch connections) it looks like I'll end up having to make these from scratch - so a pillar drill is on the way.

[Galenbo]

...These jobs don't happen often enough to warrant a fixed drill stand with vice.
...However, most of these enclosures have PCB guides on the inside,
...As alu is so soft this tends to just push the bit to the right making a nice oval hole that's a few mm right of where it should be.

Even with a pillar drill you risk having this problem, because the column and the drill can bend and go off-centre.
Make a 5mm thick steel plate with all holes you need, and grip it, as a guide, on the plate-to-be-drilled.

No need to pre-drill wit other diameters here.

http://store.workshopsupply.com/catalogue/drillguide-metric-p-4477.html?osCsid=b4b4bbd53a9a06cacab79a0c7d7ff7eb