# Drilling aluminium



## RobinBHM (21 Aug 2016)

Im making some jigs which will require some holes drilled. It would be nice if I could drill clean, round holes rather than wood butchered ones I usually end up with  

16mm diameter holes in 6mm thick aluminium.

Would a 16mm starrett work?

http://www.ebay.co.uk/itm/252089593019? ... EBIDX%3AIT

Also 6mm countersunk holes for M6 allen socket screws. Will a normal hss drill be best followed by a csk?

Can I use a piloted csk or centre drill in a pillar drill? I hate when countersinks go off centre and chatter badly leaving a dog chewed mess!

TIA 
Robin


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## porker (21 Aug 2016)

Aluminium can be quite easily drilled with HSS or cabon steel bits. easiest in a drill press if you have one. you can get 16mm drill bits with a reduced shank or you could use a holesaw like you link to. Use paraffin or WD40 as a cutting lubricant. HTH.

Sent from my SM-G920F using Tapatalk


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## LancsRick (21 Aug 2016)

A few drops of white spirit will also stop it sticking quite as badly .


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## woodpig (21 Aug 2016)

I wouldn't use a hole saw, it's likely to make a mess in aluminium alloy that thick. I'd drill it in stages with at least three or four drills. Something like 6, 10, 13, 16mm. My largest plain shank drill bit is 16mm but if your chuck doesn't take a bit that big then as said reduced shank blacksmiths drills are available or you could use Morse taper bits. I normally drill alloy dry but paraffin is a good lubricant if needed. I use plain counter sinks and don't have any problems. The fewer the teeth the more cleanly they seem to cut. "Snail" counter sinks work quite well although I think they're really designed more for deburing. To avoid chatter run the drill as slow as you can.


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## MusicMan (21 Aug 2016)

For metal, you need a different countersink from wood. Wood c/s have many cutting edges, like a star, metal just one. This helps prevent chatter and corrugated holes.

Keith


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## RobinBHM (21 Aug 2016)

Many thanks for all the advise.

I think I shall try a 16mm blacksmiths drill in the pillar drill, starting with smaller sizes and working up. A bit of white spirit for lubrication as well.

Ive got a csk bit with 4 cutting points, so will have a go with that.

Cheers Robin


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## woodpig (21 Aug 2016)

I have a couple of these which work very well in Alloy.

http://www.axminster.co.uk/fisch-premiu ... s-ax890786


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## oakmitre (21 Aug 2016)

If you have access to a pillar drill and you have clearance under the metal, then a step drill is a very good option.

They will drill and shallow countersink at the same time, and cut very clean and fast. All they require is baby oil and because of the large mass they resist overheating.

I have just drilled a hole in 1/4" 6.35mm aluminium to demonstrate - pictures attached.

The bit is an imperial version that cost less than £2 off ebay. 

My pillar drill has shocking run out front to back, it rocks 0.5-0.75mm but with this bit, it still works. Also the break out on the other side is very slight, much less that with a normal bit probably due to the side cutting action of the bit.


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## RobinBHM (21 Aug 2016)

oakmitre":1mgqrwkz said:


> If you have access to a pillar drill and you have clearance under the metal, then a step drill is a very good option.
> 
> They will drill and shallow countersink at the same time, and cut very clean and fast. All they require is baby oil and because of the large mass they resist overheating.
> 
> ...



Many thanks for that oakmitre, Ive always thought step drills were a bit of a gimmick, but the image certainly shows a very clean hole to my eyes.

Cheers Robin


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## chaoticbob (21 Aug 2016)

RobinBHM":2zc49vxl said:


> Many thanks for all the advise.
> 
> 
> Ive got a csk bit with 4 cutting points, so will have a go with that.
> ...



For some reason which I don't understand the recommendation for metalcutting countersinks is to go with an odd number of flutes. This has been borne out by experience for me - I have three, four and five flute cutters and the three-flutes are the easiest, followed by the fives. The four flute is fine in wood, but chatters like mad in metal. Another thing that no-one has mentioned is workholding. You will increase your chance of getting a clean csk if you can clamp your workpiece securely to the drill table. What seems to happen if you don't is that one tooth (inevitably) hits first, the workpiece moves slightly and from then on its a fight between the teeth.
Rob.


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