Drilling clean holes in sheet aluminum?

Frank O

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Feb 14, 2017
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Normally if I'm drilling holes where exact placement isn't critical, I'll use a hand drill or drill press and put the workpiece on sacrificial scrap wood, which helps prevent hole tearout on the exit side.

Currently I have to drill a number of holes in .050" 5052 aluminum sheet where placement is more important, so I'm thinking about doing it on the mill. The diameters are common (most are 1/4"), so I could go with either drill bits or end mills.

For working on the mill, any suggestions on the best approach to ensure clean holes?
 
I find that an end mill leaves a cleaner exit in aluminum. You might want to drill pilot holes first. Use a lubricant like WD40. A backing board will help too.
 
I grind drill for sheet metal similar to the spear point drills used for woodwork; I grind the drill point lake a flat bottom drill but more hollow in the middle and with a square tapered point to center and stabilize the drill until the outer cutting edges cut through.
 
A backing board will help too.


Thanks. I guess instead of using parallels in a vise like I would for most workpieces, I could just place it on an appropriately sized block of sacrificial wood, still using the vise to hold position.
 
I grind drill for sheet metal similar to the spear point drills used for woodwork; I grind the drill point lake a flat bottom drill but more hollow in the middle and with a square tapered point to center and stabilize the drill until the outer cutting edges cut through.


Sounds like a good approach. However, I don't think I have enough of these holes I need to make to justify the drill mods.
 
Carbide circuit board drills work great also . :encourage:
 
The step drills with a single flute also work great for sheet metal. I drill a small starter hole, then the step drill will follow through. The single flute leaves the rest of the body to keep the bit centered as the hole gets bigger.
 
The step drills with a single flute also work great for sheet metal. I drill a small starter hole, then the step drill will follow through. The single flute leaves the rest of the body to keep the bit centered as the hole gets bigger.


What @Superburban said ^^^^^^^^^^^^
 
The step drills with a single flute also work great for sheet metal.


Is there something that would be good to have as a starting point? I see a lot of options, ranging from McMaster to Amazon, but have no idea how to narrow down something to try out.
 
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