# Drilling 1" hole in 1/8" thick aluminum



## Duglite (Jul 1, 2007)

I need a 1" hole in a plate of approx. 1/8" anodized aluminum. This aluminum is kind of hard - it's a rack-mount cover panel. I've drilled some smaller holes in it successfully with a step bit, but I don't have one that goes to 1", and it will cost a bundle to buy one. Could I use one of those bi-metal hole saw bits? Would it be ragged? (I do have a drill press.) I'm willing to buy a bigger step bit if that will give the best results.

I know this belongs on the Materials/Machining forum, but there are more frequent readers here, and you guys have done it all anyway, and I kinda hope to work on it today.

Thanks!
Doug


----------



## Anglepoise (Jul 1, 2007)

A bi-metal hole saw bit will get the job done but the hole will be a bit rough and a little over size. Best bet is to get a 1" drill bit with a thinned down shank to fit the chuck of your drill press. These are called 'Prentiss' drills.

Also for your safety, when using such a large bit on thin material, clamp the workpiece very thoroughly.


----------



## McGizmo (Jul 1, 2007)

I have used both hole saws and step drills with reasonable success with both. If the Al is hard like you say, it may machine easier than if it were soft and prone to galling. Cutting wax or other cutting lubes and coolants will help as well. The step drill should give you a much better finish I would expect. If you bite the bullet and get one, you will have it for later jobs and the ability to do other hole sizes. WHat I really like about step drills in addition to clean holes is the fact you can kiss both sides with the next step for clean deburring and edge breaking. You won't be able to get that in this particular case since 1" is likely the max diameter hole from the bit. :shrug:


----------



## will (Jul 1, 2007)

If you are concerned about the finish on the side that is on the drill press table ( bottom) put some paper down. Also - clamp the work to the table. And, once you have the plate in position, put a piece of wood behind the plate and clamp that securely in place. I can't tell you you how many times I have had something catch and then spin in the drill press.


----------



## 65535 (Jul 1, 2007)

A good trick to make holes (you will need a high speed rotary tool with sanding drums, or some files and a large amount of time) is use a 1" circle and trace it or use a compass, then drill holes closely spaced (3/16" bit) around the circumference and use your files or rotary tool to removed the scrap inside the hole and clean up the edges.


----------



## griff (Jul 1, 2007)

Try a plasma cutter with non-splatter spray


----------



## griff (Jul 1, 2007)

Hehe


----------



## senorcosas (Jul 1, 2007)

Many years ago I used one of these to fabricate a stage box for an audio snake for a sound reinforcement system. Kinda expensive but works great. You may be able to find one cheaper if you google. Best of luck!
http://www.westlake-electronic.com/store/search/1/detail/1/item_no/GREE10049/


----------



## McGizmo (Jul 1, 2007)

senorcosas,

I was going to mention one of these knock out tools as well but I realized that they are more expensive than the step drill and if I am not mistaken their size refers to conduit size and not actual dimension. I have a set of these back in Berkeley so I can't measure them for certain. I do believe though that 1" refers to 1" conduit and not an actual 1" in measure. :thinking: :shrug: I was first exposed to them and used them as an electrician's apprentice and we used them for conduit access ports.


----------



## X_Marine (Jul 1, 2007)

I would opt for a panel punch, 2 piece with bolt through center.
Much cheaper that a bit and cuts cleaner that a hole saw. I want to say Greenlee makes them, if you need more info be happy to look at some of mine.

GL
X..


----------



## will (Jul 1, 2007)

Knock out punches work great in sheet metal up to 16 guage. I don't think they will punch through 1/8 inch aluminum.


----------



## blahblahblah (Jul 1, 2007)

will said:


> Knock out punches work great in sheet metal up to 16 guage. I don't think they will punch through 1/8 inch aluminum.


 
FYI: Greenlee makes different models which are rated for up to 14-10 gauge mild steel or 12-10 gauge STAINLESS. I'm sure some models will have no trouble going through 1/8" (approx 11 gauge) aluminum.


----------



## will (Jul 1, 2007)

blahblahblah said:


> FYI: Greenlee makes different models which are rated for up to 14-10 gauge mild steel or 12-10 gauge STAINLESS. I'm sure some models will have no trouble going through 1/8" (approx 11 gauge) aluminum.



I stand corrected, the only ones I had seen were for sheet metal.


----------



## Data (Jul 1, 2007)

A good way to cut the hole on a drill press is with a fly cutter. See this fly cutter at Enco. Firmly clamp the part backed with a nice flat piece of plywood to the drill press table. Cut the hole undersized first and then you can sneak up on the final size. You need to run the drill press at under 400 rpm. No coolant is needed. Cutting through anodize will not be a problem. It is a thin hard coating and once it is penetrated it is out of the picture. When cutting you need to use enough force to create a nice thin chip. Go too deep and the drill will stall.

This kind of cutter will cut any size hole you want, you just slide the cutter through the holder to the diameter you need.

Try practicing with the cutter. Never wear gloves of any kind around a drill press or lathe.


Cheers
Dave


----------



## sawlight (Jul 1, 2007)

On the cheap?? Laugh all you want, go buy a spade bit ( for wood doors etc., at Lowes) pad you're table, and clamp it well. No pilot bit etc. and run it slow, it will make a nice hole with burrs. File the burrs off, and enjoy!


----------



## X_Marine (Jul 2, 2007)

sawlight said:


> On the cheap?? Laugh all you want, go buy a spade bit ( for wood doors etc., at Lowes) pad you're table, and clamp it well. No pilot bit etc. and run it slow, it will make a nice hole with burrs. File the burrs off, and enjoy!


I call emm butter fly bits, but you are correct and I have use them to cut alum before. There is a preferred lubrication for alum can't remember what it is now.
Also the butter-fly bits are easy to sharpen also when needed.

X..


----------



## sawlight (Jul 2, 2007)

X_Marine said:


> I call emm butter fly bits, but you are correct and I have use them to cut alum before. There is a preferred lubrication for alum can't remember what it is now.
> Also the butter-fly bits are easy to sharpen also when needed.
> 
> X..


 

Alum-a-cut, made by lubriplate I believe.


----------



## LED Zeppelin (Jul 2, 2007)

I've always used Tap Magic cutting fluid with good success. They make one in a silver can specifically for alum, and another in a red can for steels.

Kerosene works well as an alum cutting fluid also.

I think the least expensive route is to go with a good hole saw, use cutting fluid, and clamp the part in your drill press. Properly clamped, you won't even need the centering drill which is handy if for some reason you need the removed disk in tact. Feed slowly with not too much tool speed, and clear out the chips frequently. You should get a decent finish and a swipe with a deburring tool is all you should need to yield a presentable hole.


----------



## Duglite (Jul 2, 2007)

Well, as expected, I got a lot of great responses and valuable ideas. I decided to use a step bit since I had already had some experience with one, but finding one that goes up to 1" on a Sunday was not easy. Finally, an Ace Hardware had one made by Irwin lying at the bottom of their lock-up case. I don't think they normally even carry it, since there was no hanger hook and price tag for it - just the smaller sizes. But it was new in the package, and it was in their SKU system - probably an unclaimed special order. $39.95. Ouch. But my GF had a $5-off coupon.

I needed a good 1/2" hole to start, since the new bit started at that size. I have smaller step bits, so I was in business. I wanted to go in through the brushed surface for best de-burring, but it was dragging the shavings around and scratching the finish. Luckily I noticed in time and was able to turn the piece over to finish. Even at that, the exit burr was very slight and I was able to smooth it with a little 600 grit. I used Tap Magic aluminum.

If anyone wants to see it, I'll post a pic as soon as imageshack sends me a new user login.

Thanks to all for your great suggestions!


----------

