Drilling aluminium sheet

[BluffChill]

I don't really know how to describe this so I've struggled with googling for answers!

Basically I have an enclosure which is folded aluminium/aluminum. When I drill it (drill press, HSS step drill) I get this piling up of metal on the underside of the hole like it's pushing through rather than actually drilling. How do I stop this? Slower? Faster? Different bits? I've tried using WD40 on the bit to decrease adhesion but still get ugly holes on the underside. Here's a pic:

[Govmnt_Lacky]

Aluminum is a soft metal. The best way to avoid this is to ensure you have a SHARP drill bit/unibit and go SLOW when pressing down onto the metal surface.

I get this all the time as well with true aluminum metal. What I do is go sharp and slow. If I get the "piling up" then I just use a de-burr tool to remove it.

[GGBB]

Clamp a block of wood under it so you are drilling through the aluminum into the wood.

[MetalGuy]

Most common aluminum grade is 1050 which is major PITA for machining. If this is the case most of the time the results are ugly. One trick I know when drilling holes in aluminum sheet is to apply the most common ethyl alcohol. For some reason it works very well. Also as mentioned sharp drill bits and slow speed drilling helps a lot.

[amptramp]

I get this all the time on soft aluminum and I just hit the bottom with a countersink or a larger drill bit.  1050 is 99.50% pure aluminum.  It will smear all over the place with most machining operations.

Stronger grades of aluminum alloy seem to work better - I was just drilling a piece of 2024 - 0 yesterday and I got the same thing but maybe only a few thousandths of an inch below the surface.  2024 is an aluminum-copper alloy and was the first high-strength aluminum alloy but it is not corrosion-resistant like 6061.  But if you want to etch aluminum, 2024, by virtue of being corrodible, will etch very well.  It is common to add a suffix for heat treatment so 2024-T4 (solution heat treated) and 6061-T6 (solution heat treated and artificially aged) are common sheet stock if you are working with flat sheet.  My 2024-0 is not treated at all.

2024 is aluminum with 4.4% Cu, 0.6% Mn and 1.5% Mg

6061 is aluminum with 0.28% Cu, 1.0% Mg, 0.6% Si and 0.20% Cr

These are the most common alloys.

[MetalGuy]

I get good results with 5754 grade.

[italianguy63]

I use one of these-- chucked up in a nut-driver handle... I follow the drilling, top and bottom with a couple twists, and it blows the burrs off the metal.

https://www.harborfreight.com/12-in-six-flute-countersink-61552.html

Won't work if the hole is 1/2" or larger however!

MC

[Mark Hammer]

I also use a countersink, in addition to a step-bit. If the shape of the aluminum permits, I'll drill up to one step less than the needed diameter, then flip the metal over and drill the remaining step from the other direction.  That will usually remove 95% of the burr.  A little finger-twidding of a countersink will remove the remaining 5%.

[anotherjim]

If the rear side is easy to access, I'll sand it all down. Actually, I find an Orbital sander can make a neat scrubbed finish to alumin(complete your own spelling).
Small holes I deburr With a countersink (handy in an electric screwdriver). Larger I use the step drill. Larger still, I use a knife or chisel.
Drilling through to a sacrificial backing can help, but the soft metal will still jump up around the bit and let a burr form. Also, the material you want to use up for the backing can be soft enough for a burr to form into it (drill a lot of holes and the metal can be semi-riveted to the backing by the burrs).
I've never owned or used a proper de-burring tool so I wouldn't know what might be a good one.

[stallik]

If you can get one in the size you need, sheet metal hole punches work well. Small hole for the nut, punch creates a nice bigger hole. Expensive option though

[amptramp]

The Greenlee chassis punches are nice but they may put a slight wrinkle in the finish because two of the sides contact the metal before the rest of it.  If the metal springs back, fine.  If not, you have another problem.  I have a 1" punch that I got cheap at a garage sale - these things are pricey new.

[davent]

Like Govnmt_Lacky suggested, a deburring tool, they look kinda' suspect but do a great job on any size hole you can fit one into, don't cost much.




dave

[tubegeek]

I've had pretty good results using an Xacto knife to slice the burr away.

[davent]

I've had pretty good results using an Xacto knife to slice the burr away.

Yup, that's pretty much what the deburrer does but being carbide it just laughs at the aluminum.
dave

[Rob Strand]

One trick I know when drilling holes in aluminum sheet is to apply the most common ethyl alcohol. For some reason it works very well.

Perhaps evaporative cooling?   I know when I clean temperature probes with alcohol the temperature reading drops quite a bit until the alcohol has evaporated.

[duck_arse]

Like Govnmt_Lacky suggested, a deburring tool, they look kinda' suspect but do a great job on any size hole you can fit one into, don't cost much.




dave

I'm about ta get me one of them, how do they work, how do you apply it?

[stallik]

Pencil like part is the handle. The bent part swivels in the handle. The very end of the bent part has a sharp edge which you press against the edge you want to smooth. Then just drag the handle along the edge and the blade will follow like a drag knife. Works on straight edges, circles and fancy shapes

Use them all the time on aluminium composites and they work like a dream leaving a fantastic finish

[davent]

Like Govnmt_Lacky suggested, a deburring tool, they look kinda' suspect but do a great job on any size hole you can fit one into, don't cost much.

I'm about ta get me one of them, how do they work, how do you apply it?

Pencil like part is the handle. The bent part swivels in the handle. The very end of the bent part has a sharp edge which you press against the edge you want to smooth. Then just drag the handle along the edge and the blade will follow like a drag knife. Works on straight edges, circles and fancy shapes

Use them all the time on aluminium composites and they work like a dream leaving a fantastic finish

Mine the cutter is fixed into the handle screw so if it should ever wear out can be replaced, can't imagine ever having to do that.

Mine i use like a knife to trim away the burr, the crook in the cutter allows you a wide range of angles to attack at, can go very low almost flat to the surface and trim the burr away.
dave

[EBK]

I've always used a tapered reamer as a deburring tool.  Now that I've seen the real deburring tools, I may get one.

[rutabaga bob]

Dave C.
   They do get dull, like any cutting tool.  They last longer on softer metals, though.