Aluminum build-up on drills

[Erik S]

Was chatting with @giovanni about enclosure drilling over on the workbench thread, and I mentioned how I like to drill with a little alcohol in order to try and reduce the heat at the cutting edge, and try and reduce the amount of aluminum the builds up on the cutting edge of the drill.

I just finished drilling 258 holes all with the same step drill then took a look at the cutting edges.

Getting a phone shot through the microscope is tough, but here's one with a little aluminum booger on the edge, and then after I scraped it back off.

If your step bit seems like it's dull, it might just have aluminum built up on the cutting edges. If you can get it off without messing up the edge it should cut like new again.

Regarding the efficacy of the alcohol, I had no build up on the tip of the tool, and really only significant boogers on the steps where I pause to chamfer the common hole sizes. At that point I think the alcohol at the edge has largely evaporated or gone down the hole, so it's less effective at that point. Not totally scientific, but I'm going to keep doing it.

Looking close I realize my before/ after shots may not be the exact same edge, but you get the idea.

 

[pricklyrobot]

I keep a utility or x-acto knife handy when I have a bunch of holes to drill. Those thin steel blades will scrape the aluminum gunk off of your stepped bit pretty easily most of the time.
* Just keep your safety glasses on while you’re doing it. X-acto blades don’t snap that easily, but when they do, they somehow always fly straight at your face

Interesting idea about the alcohol. I always try to drill on as slow a speed as I can manage, but things do still warm up if you’ve got enough holes…
I wonder if acetone might not work even better than alcohol, for some evap cooling action? Or would it disappear too quickly to do any good?

 

[Erik S]

I wonder if acetone might not work even better than alcohol, for some evap cooling action?

I’d rather not be huffing acetone all evening. I have few enough brain cells left as it is.

WD40 works great, but these enclosures are all going to get clear coated, and any little speck of wd40 that doesn’t get stripped off would screw with the paint.

I did my scraping with a chisel, but an exacto sounds like a good option.

Speeds and feeds are like a dark art of machining. I’m not a machinist but I do watch a lot of YouTube videos about it… I think sometimes slow will run cooler, but depending on your feed pressure, you might end up with higher chip load, more heat blah blah blah.

I’ll try and figure out what I was running that step drill at for rpms…

Edit - somewhere around 1500 rpm’s and pretty gentle feed is what felt right to me.

For reference my 2 speed 1/2 inch dewalt drill says it does 1750 on high.

I have a wall chart that says target for cutting aluminum is 200-300 surface feet per minute. For a 1/4 inch hole that would be between 3,055 and 4,583 rpms. Take that with a grain of salt since those are probably based on production manufacturing numbers, but you certainly CAN run very fast in aluminum.

I cranked the mill up to 4400 just to get a feel for it, but it gets loud going that fast. I think I’ll stick with slow and steady.

 

[rwl]

Well, I'll be damned. I thought I had just bought cheap bits and abused them, rather than thinking they'd built up aluminum scraps...


No microscope necessary! It looked like the edge of the steps was "smearing" out (this was after 40 pedals). I assumed because the temperature was causing the bit to melt slightly.

But raking down the channel with the claw of a hammer and voila!


Not that you should trust my judgment on this (clearly!), but just going from drilling dry to dipping the bit in water before each drill made a huge difference for me.

 

[Erik S]

Well, I'll be damned. I thought I had just bought cheap bits and abused them, rather than thinking they'd built up aluminum scraps...

View attachment 83854
No microscope necessary! It looked like the edge of the steps was "smearing" out (this was after 40 pedals). I assumed because the temperature was causing the bit to melt slightly.

But raking down the channel with the claw of a hammer and voila!
View attachment 83855

Not that you should trust my judgment on this (clearly!), but just going from drilling dry to dipping the bit in water before each drill made a huge difference for me.

Wow! Yeah, that should cut much better now!

 

[pricklyrobot]

Don’t have anything so fancy that I can set the RPMs. My speed control is just easing up on the trigger

But my day job is electrician, so I’ve probably hand-drilled I don’t know how many hundreds, or thousands, of holes in panels and j-boxes.

You definitely get a feel for that slow-ish speed and gentle pressure where it’s just eating up the metal, but not so slow that it’s in danger of binding up…

 

[Stickman393]

Lube helps. Aluminum has a tendency of gumming up and welding itself to the surface of your cutting tools.

Its particularly annoying on end mills. Dulls em up real quick and causes all kinds of chaos and vibrations. And don't even get me started on tapping aluminum...woof. Its a PITA.

Alcohol will absorb some of the heat, but it'll evaporate quickly. The only potential issue I see with using alcohol is that it kinda primes the bit you're using for the aluminum to weld itself to your tool: clean, degreased surfaces are what you want when joining metal pieces together.

Cutting fluid will reduce friction, absorb heat, and won't clean the surfaces of what you're working on. Generally, you don't need much. Tap magic is great but stinks to hell. I like A-9 for aluminum. There's a bunch out there though.

What degreasers like ISO and WD-40 have over cutting fluid though is ease of cleanup. ISO will in fact just evaporate, and it'll absorb heat well enough to protect the tip of your drill bit.

One can also take a *small* and *fine-toothed* file to a straight-fluted step bit. Just use light passes parallel to the flat until you knock off the build up. Xactos work too, but I'd recommend scraping outwards to avoid dinging up the cutting edge.

 

[mdc]

Dish soap work well in a pinch, you can cut it with water and iso alcohol.

 

[Alan W]

There are specific cutting fluids for aluminum. Over the years, I began to drift more towards cutting waxes, especially when tapping threads. Very easy to use, you just stab the cutting end into the tub, and it migrates less than most liquids.

With aluminum, almost any lubricant will also work; the fear of getting all the oil off before painting is valid though. We pretty much banned dry film aerosols (basically Teflon in a can) from my shop because of how near impossible it was to fully clean off parts. Before painting aluminum, I’d always put it through a soap and water wash, and at least one solvent rinse—usually lacquer thinner or alcohol, unless it had been really dirty, when I’d get out the acetone. (Acetone is really nasty on your body.)

 

[Erik S]

There are specific cutting fluids for aluminum. Over the years, I began to drift more towards cutting waxes, especially when tapping threads. Very easy to use, you just stab the cutting end into the tub, and it migrates less than most liquids.

With aluminum, almost any lubricant will also work; the fear of getting all the oil off before painting is valid though. We pretty much banned dry film aerosols (basically Teflon in a can) from my shop because of how near impossible it was to fully clean off parts. Before painting aluminum, I’d always put it through a soap and water wash, and at least one solvent rinse—usually lacquer thinner or alcohol, unless it had been really dirty, when I’d get out the acetone. (Acetone is really nasty on your body.)

In my little home shop I don’t get too specialized with the cutting fluids. Other than the alcohol on my enclosures, it’s usually wd40, smelly dark cutting oil, or anchor lube. I like the anchor lube if I’ve got a lot of tapping to do it stays put okay, and doesn’t smell too bad.

What’s your recommendation for a wax to try? I used to work in a shop that had some kinda cutting wax at the big vertical metal cutting bandsaw, but I’ve never tried any at home.

 

[Alan W]

This is one familiar brand. Probably a life time supply for a home shop…
No odor, doesn’t get all over everything.