Does anyone know something about drilling into aluminum? DIY tonearm fail!!

[Doctorhugo]

Hey Guys -

Does anyone know anything about drilling into aluminum please? I have a depressing failure on my hands......

The back story: I'm trying to build an ultra-low (no) budget tonearm base for an incomplete Mission 774LC that I've had forever. The arm is only missing the base. So I found an aluminum block in my spares box, and measured the pillar of the tonearm and bought a drill bit to match.

However: when I tried to drill into the aluminum, the bit vibrated so badly that it actually shook the chuck assembly off the shaft on my drill press......and the result is in the photos. I don't know what to do, can anyone advise? I've not had a problem like this before and it's completely killed the project.

Any advice appreciated, thanks!!

 

[peerson]

Sharp bit, Cutting Oil, Low speed, hold part firmly in place

 

[peerson]

From the Picture, it appears that the piece is jumping around while you are drilling. Remember: Drill Presses need to run at slow speed.

 

[analoge4ever]

Why don't you just take it to a machine shop.

 

[jbrainey]

You're trying to remove too much material at once. Start with a pilot hole and work your way up in smaller steps. Use some type of lubricant like WD40. I prefere Alumitap or Tap Magic.

 

[Retrovert]

Cutting speed should be higher for aluminum, not slower. It may be cut at two to four times the speed of steel. (Look it up if you don't believe me.)

The problem with drilling aluminum is that it is very soft and sticky, and will jam the bit. The long curls also are a problem. Aluminum sticks to certain drillbit coatings, particularly carbides and titanium nitride (gold color). The bit geometry also matters. Many common bits optimize twist and flute geometry for harder metals, typically steel, not softer ones like aluminum. I've learned this the hard, errr, soft way having machined softer metals like aluminum for many projects.

WD-40 is not a lubricant and is not a cutting oil. It is a Water-Displacement formula which consists of a heavy petroleum oil and lighter-weight solvent. WD-40 is flammable, and this is generally to be avoided where substantial heat is being generated.

A cutting oil is the proper lubricant for this job.

The preferred cutting oil—inexpensive and readily available—is neatsfoot oil, which is a saturated, rendered animal fat, much like clarified butter. (Yes, the same conditioning oil used for leather.) Whatever oil is selected must have a very high smoke point; unsaturated vegetable oils are consequently unsuitable. I've used those when nothing else was available, but not recommended.

I've used motor oil when nothing else was available, but because of the additives and thickeners it's really not the best. I've also used hydrogenated vegetable oils and lard, again because it was handy, but not the best. Old-school machinists who worked on ships during WWII and Korea, suggested I use lard combined with a lighter oil or solvent to tailor the viscosity, but talk about messy and it goes rancid. Bleh.

So the solution is to purchase from your local hardware store or possibly big-box store, or order online, (a) cutting oil, and (b) a large bit designed for aluminum.

Both will help prevent the chattering. If you get desperate, you can polish the hole with emery paper wrapped around a dowel or cone abrasive for shape. The pores will rapidly clog with soft aluminum, so regularly clean it.

 

[Retrovert]

Why don't you just take it to a machine shop.

Because any adult unable to drill holes in aluminum will be among the first eaten by zombies.

Machine shop skills will be valuable in the apocalypse. So, for that matter, will be leather pants, studded accouterments, and an ample supply of hair product. (I refer you to the excellent documentaries produced by George Miller.) Accordingly equip your go bag.

 

[Tronk]

Check the bit, Is it sharp or possibly bent? Once the hole becomes the diameter of the bit, the vibration and walking around will most likely go away.

 

[Grenadeslio]

Drilled a lot of aluminum in my time as a machinist, no special bits were used. Now when turning on a lathe and making my own cutting tools the angle of the chip breaker was typically steeper, and as already mentioned higher speeds usually work best.

Also as already mentioned this should be done in stages. From the looks of the chatter you're getting I hope you weren't using a carbide tipped masonry bit. For cutting aluminum a nice sharp bit should go through like butter.

 

[Binkman]

*********And a vice. Small machine shops are suseptible to cash donuts.

 

[toxcrusadr]

200-300 rpm seems to be the recommended speed for drilling aluminum.

 

[bluestime]

Clamp the part securely and use a paddle bit. You can lube with water. The pilot hole should be a little smaller than pilot on the paddle bit. The speed will depend on the diameter of the bit used.

 

[Binkman]

Under Mag.. It's also the wrong drill bit. Fluted metal cutting grade is much better for size 1/2" (and a vice) You could stagger drill bits sizes up to 1/2" but a vice is so much easier to hold a small piece.

 

[gadget73]

What they all said, clamp it solid and go in steps. WD40 is a fairly lousy lube for most things, but surprisingly does well on aluminum. Kerosene works well for that too, but WD40 is easier to meter out. If you have actual cutting oil, use that. My usual oil of choice on aluminum is Tap Magic, mostly because there is a large container at work that occasionally has surplus, or the dark thread cutting oil sold in the plumbing section of the hardware store. I've also used whatever spray can or bottle of oil-like substance was on hand in a pinch. ATF has an interesting smell when you get it good and hot, and it looks like blood spraying around if you use too much.

 

[Guest159]

I always got good results using short insert drills.

 

[ConradH]

Do this 'bout every other day and most suggestions here are good. I'd add that mass solves a huge number of other problems- a heavy vise will help prevent chatter. IMO, WD-40 is a near useless product save for two things- removing gum and stickers, and as a cutting fluid for aluminum when you don't have anything better. Lots of machinists use it with great success. I prefer a veggie oil based product like Cool Tool II, if you can get it. Work your way up, but watch out for grabbing. Fasten the vise down. Also, don't be too gentle. If it wants to chatter, increase the cutting pressure a bit. Also, use decent drills. If it came from HF, you're probably in trouble before you even start.

 

[dosmalo]

One post says drill bit speed should be high and another says use a lower speed.
That's your signal to take it to a shop.

 

[toxcrusadr]

I'd like to hear from the experienced machinists on speed. Retrovert recommended high speed. I have a variable speed drill press that has a chart on it for various materials and cutting diameters, so I'd look at that if I was at my shop. The 200-300 rpm I posted came from two different websites, one that makes and sells drill bits.

 

[Retrovert]

One post says drill bit speed should be high and another says use a lower speed.
That's your signal to take it to a shop.

With that defeatist attitude you, sir, will be ignominiously eaten by zombies when your poorly-armored vehicle is overrun.

The truth or falsity of a particular speed recommendation for a drillbit in aluminum, as well as the type of bit and coating, may be trivially verified using the internet.

Less easy to verify the best way to make pulled pork.

 

[UncleBingo]

Small diameter pilot hole to start and then a Unibit/stepped drill to get it close. Finish boring to exact size.