I have some alluminium boxes that I want to drill holes into for specific item, ie. Switches, fuse holders etc etc.
Is it best to use a cone drill or a step drill ?
When using a step drill, how is it able to go to next size hole etc
Jim (very confused)
Cone drill will drill any size hole, with a slight slant. Step drill will only drill discrete sizes of holes without any slant, BUT to a certain depth only before they start enlarging the front of the hole due to the next step size beginning to cut. So a step drill can only be used up to a certain enclosure wall thickness - I think polyester tend to be very thick wall on large sizes (=A345+) due to their crumbly nature. A solution on very thickwall is to drill with a step-drill to the depth limit and then file larger.
Cheap fleabay step drills work well on alloy & polyester enclosures, but are very sharp so any mind wandering and you will end up drilling beyond the size you want. The sizes tend not to be engraved so beware "think I will try the next one up" to save a bit of filing. You do not need the high end german drill bits unless working in production with tough (or highly abrasive gf reinforced) materials.
You just continue drilling and it "steps up" onto the next one. The edge of each step does the cutting, the rest of the step is parallel to the shaft. Again, check the wall thickness of your enclosures against the step distance on a step drill - or it can lead to tears (generally only polyester are that thickwall due to the crumbly nature of the material, although I suppose ABS PVC etc could be if a large enough enclosure).
If the aluminium boxes are of a poor alloy (ie, not Bopla or Rose) then drill carefully. Some of the cheap ones seem to have the sand mould buried inside them and drill bits can wander quite a bit (even bizarrely a centre drill).
IMHO, soft plastic gets a step drill every time. It's an easier cut and you get accurately round and sized holes.
For sheet metal, it depends. The cone drill is easier, but has a tendency to drill oval and size control is hard. It's very prone to catching and digging a "snail shell" hole if used freehand. Sometimes I start with a cone, but finish with a step. With a drill press, both are much easier.
Just like a normal drill. You can't drill a huge hole in one bite, but you can easily enlarge an existing hole by a couple of mm.
You can reduce this by turning the material over and just touching the hole from the other side (but note this makes the hole slightly bigger). Usually it doesn't matter though.
I use them in a pillar drill/drill press. I would guess they're harder to use freehand.
In message , Andrew Gabriel writes
I've always used and much preferred hand powered tapered reamers. Much easier to make an accurate hole.
The ones I've used (from RS, I think) seem to have been "improved" so that instead of fitting a brace and bit or having a cross piece of metal rod to apply some welly, they now have a rather delicate handle.
A step drill is best since it gives parallel sides to the hole. Assuming you get one with the correct sizes. They come in both imperial and metric.
Each 'step' is preceded by a taper so you can easily go up from a smaller to larger one.
It's worth mentioning that a step drill can be used from both sides of the material if the thickness of the material is an issue.
I dont use these bits on ali at all if I can help it. Its far less work and less hole errors to use a punch. The downside of punches is you need one for each size.
You can get cone & step bit sets from screwfix, toolsatan etc, but I dont remember seeing punches there.
NT
Depends on the thickness of the ally. On thin sheet, a Q-Max etc is best.
Trouble is they are very expensive. Stepped cutters - I got a set from Lidl which are just fine - cheap. Got a set of imperial ones at my local Sunday market too. For most things they're just fine and so much faster than a Q-Max.
Good ones are a bit, long time since I acquired any so I'd forgotten. Carbon steel sets are cheap though, and you dont need quality metal for soft materials like ali & plastic, just dont use them on steel.
FWIW punches look quite diyable with a basic lathe.
NT
You'd need to be a heavy user to keep one set for non ferrous and one for steel. And I've never seen 'cheap' ones on sale - only Q-Max.
re metal hole punches
The op wants to cut ali, why would he want to buy a 2nd highly priced set.
NT
They are not difficult, if you have the right tool steel and know how to harden them.
Colin Bignell
Well thank you to all who took part in this thread. I am much wiser now. A step drill it will be. The alli box is less than an 1/8 probably about 3/32 thick so should be ok. Cheers everyone. Jim
You clipped the bit about not being able to buy 'cheap' ones easily. Most decent toolshops stock Q-max. And like any tool, does it make sense to buy a light duty version anyway? Unless you're going to throw it away after use.
I found cheap carbon steel ones by googling, but couldnt remember the price
on soft non-ferrous metals, a carbon steel tool should last ages.
NT
I got most of my Q-Max cutters from autojumbles. Wouldn't be without them.
But for other than very thin sheet normally use a stepped cutter as it's quicker and good enough. ;-)
Unless you want one for a D-type connector!
That is fairly simple, compared to some I've made, but you certainly couldn't make it on a basic lathe.
Colin Bignell
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