Drilling through a magnet?

About 2 weeks ago, our team was bored, and while sitting around, we found a really old radio. We proceeded to void the warranty (giggle giggle) and fiddle with it.

We took out some of the things (and it still worked, weird) but when we ran out of things to take out, we went for the speaker.

We got the magnet and its housing out, and then I attempted to drill through it.
Eventually I got the magnet out of the casing, so now I have JUST the magnet itself…

We want to drill a hole through the middle of it, but it is causing us trouble.
Long story short, we now have 2 melted drill bits and a hole-free magnet.

When I use our drill press on the magnet, the bit just spins itself around, but doesn’t actually drill through it. The drill press is set to be around 700 RPM, but to no avail.

I thought that if I can just make a small hole to start with it will be easier, but even when pushing it through the bandsaw, it BARLEY scratches the surface of the magnet…

Any ideas?

EDIT: Forgot to mention, the magnet is a cyclinder, about 1 inch in circumfrence, and about 1 inch in length.

I have many ideas, every last one of them involves finding something more productive to do with your time. Top of my list is that my driveway needs shoveling. My next idea is that instead of trying to destroy said radio you should have figured out how it worked. Destroying something for the sake of education is acceptable (when you have permission) but destroying something for the sake of destroying it is a pointless waste of time.

Maybe the above is just me being a grumpy old man but anytime I see a post about how someone just decided to tear something they found apart I get a little angry. Perhaps I would be a little less irritated if I knew what you hoped to gain by drilling a hole in this magnet? Or what you learned by tearing a radio apart?


PS. If this post sounds too harsh it was meant that way, to me this appears like kids were just let loose. In addition to destroying the radio they wrecked two drill bits and endangered themselves (the drill bits could have shattered or the magnet could have, neither of which would be good). Where were the mentors? If you have access to a drill press and a band saw someone who knows how to use them should be nearby.

Depending on the strength of the magnet you may not be able to drill through it. Your biggest problem is probably the hardness of the magnet compared with the drill you are using but there are other complications.

The reason this is the case is because the chips that normally would be falling away as you drill are actually attracted to each other and stay in the “hole” They won’t leave an empty spot…
So you can’t drill.

The holes you see in Neodymium magnets are actually placed there during the manufacture of the magnet… usually during a compression like activity that forms the magnet… About the only other way a hole could be made is by an enormously hard and strong punch press…and even then it is extremely difficult…

Weak magnets “might” be able to have a hole drilled in them…but strong magnets will only cause you grief.

It would be like digging a hole in the ground but not being able to take any dirt out of the hole…your shovel would continue to try over and over to remove the same dirt… it would overheat… and eventually melt…

Well at least in the case of a drill bit that is what will happen. The heat has to go somewhere and the bit heats…distempers… turns blue and is wasted…

Also remember that the magnet may well be harder than your blades or bits… if its not harder it can’t cut anyway…

Does that make any sense to you?

Have you tried punching the magnet?

Andrew, I would be interested to drill through a magnet for the only reason to see if the drill was able to pull about the magnetic bonds within the ions.

I do want to remind people: Safety glasses, adult supervision and don’t let freshmen touch the robot. ::safety::

Seriously? Condemning experimentation like this as a waste of time? I wouldn’t have expected that from a FIRSTer.

I’m hardly the machining expert, but my guess it that you could set the drill press to an appropriate RPM if you had some guess as to what the magnet is made from. For instance, if you found that the magnet is about as hard as steel, you might want to set up the press as if you were drilling steel. As for the drill bits melting, my first instinct would be to try a bigger drill bit. Still, I realize that this may not be possible because of the size of the magnet. My last idea involves using a punch on the magnet to get the bit started. If all that doesn’t work, you obviously are holding a magnetic diamond. Congrats.

Edit: Darn, rtfgnow beat me to it

You’re right, I didn’t really give any reasons.

To begin with, the radio was already in a very poor condition, could only pick up about 3 channels, all of which were covered with static. Anyway, it wasn’t like we just tore the thing apart. We actually spent around an hour with it, looking through some of the wiring, and trying to figure out what a particular part was. (After we removed it, the radio still worked, which had us really confused)

One of our other members kept the case to use in a future project (he is going to install one of his mini Mac computers I believe inside of it)

As for the magnet, it may be a “silly” reason, but we want to know what the force in the center of a magnet is.
We know that there is a north and south pole, and if the magnet is broken in half, it forms 2 new poles. But what will the force in the center be?

So yes, we didn’t just tear the radio apart for the heck of it.

What is with all of the 2 minute posts?

Have fun with your experiment and be safe!

Hmmmmm I think you guys need to take a good physics course if you are looking for the “force” in the middle of the magnet…
Pick up a physics book and take a look at magnetic fields and how they are generated…and the relationships within the magnetic domains in the magnetic elements you are dealing with…

or ask you physics teacher…

even better

have fun!! and I like your curiosity…!!! Keep it up!!

Bob Steele: I think you are probably right, about the chips becoming attached back to the magnet, and then the blue shavings. (We were wondering what the blue shavings were, haha)

We did try using a bigger drill bit, which did succeed getting through some of it, (I used a 1/2 inch bit) but because that is almost the size of the magnet… heh.

As for the 2 destroyed drill bits: They were NOT new ones, they were several years old, and we have at least 2 more of the same size.

And for the physics course, that’s true, but where is the experimentation with that? :stuck_out_tongue: (Besides, I haven’t taken physics yet, sadly. Not open for me until next year. )

I applaud your curiosity/experimentation… that is how we find out new things…

You should be in my AP Physics class… we actually do some of that experimentation in here…sometimes we even use robots…
Most of the greatest physicists that have ever lived have been great experimenters and observers… You might want to find out more about Michael Faraday… great physicist… great experimenter…even greater observer…

keep up the good work!!


Well, then consider my grumpy old person post removed. I was very concerned this was just a bunch of kids without supervision, it doesn’t sound like this was the case at all.

I’m not anti experimentation, I’ve torn my fair share of things apart. Actually trying to figure out how it still worked with parts removed is a pretty cool reason to pull something apart. Did you ever find out? Radios are actually really cool pieces of technology, especially the old ones.

I would say that it is a pretty good reason, physics may be able to tell you what should happen (and what will happen) but sometimes seeing your calculations verified is just wicked cool.

@JackG Not condemning experimentation, condemning pointless destruction. Take for example, Mythbusters, yeah they destroy stuff but they back it up with why it will or won’t work. If they just destroyed stuff for no reason it wouldn’t be worth much but because they aren’t learning anything. If these guys are learning stuff than great for them!

Andrew’s just mad that he can’t figure out a good method to try, so I’ll cut him some slack.

A way to do it might be to try cutting a circle with a plasma cutter. Then punch the middle out. The do’ers of this method will probably need gas masks for noxious fumes if it’s a rare-earth magnet, as well as alot of other protective gear for the flying molten magnet. There are probably other issues I can’t even imagine as well.

Good luck :cool:

I know what I am asking my physics teacher tomorrow. :smiley: Maybe I can get lucky and she will let us experiment… :yikes:

I’m with everyone else on this. Be safe, by all means experiment. How else would we learn? Just make sure not to hurt yourselves, it tends to slow down progress for some reason… :rolleyes:

It will simply be a donught magnet (which it already was, you just didnt know it). Normally, when we are misinformed that all magnets are bar magnets, we precieve the magnetic field as a 2-D series of lines going from one pole to the other. However, this field also goes linearly through the magnet itself. Realize that for the magnet you have (and all magents) that this a 3-D field that not only goes from one pole to the other outside the magnet, but also THROUGH the magnet. When you remove the center of this magnet, this field will still be going through that void in a similar manner. If you manage to hollow it out, try pushing another magnet through the empty space to illustrate what happens.

And, the drill bit is your problem, its not hard enough. Do you have a set of cobalt bits? Though I would recommend you not ruin them by trying, they would be your best bet. Most of these magnets have been pressure-fired and a very very hard.

Just a thought, but some magnets are formed as a ceramic. Just as metal drill bits don’t do a good job drilling through concrete, they don’t like ceramic either. If you have chips of the magnet and they seem brittle and “rock-like”, you may consider googling to see how to drill ceramic tiles. Of course if you are buying stuff to cut holes in a magnet, perhaps you should just buy one with a hole in it.

seems to be what you are trying to make, and it doesn’t cost as much as a drill bit.

Greg McKaskle

OK, since I didn’t see this yet, I’ll state the obvious: The magnet material is harder than the drill material.

The magnet is most likely Ferrite. Google it for it’s hardness, and compare that to High Speed Steel, which is likely what the drill bits were made of. Hint: Like using butter to drill through glass.

But you knew that.

A “glass” or Masonry bit might get a hole in it, but in all likelihood the magnet will shatter instead. It is very brittle. If you could just get a BB to move at 1/100 the speed of light it’ll make a nice hole for you. :rolleyes:

I, for one, am very pleased that you took the radio apart. Find more stuff to take apart, and let your imagination do stuff. (Just be careful, there’s toxic materials in most things. And TV tubes are not to be trifled with, you can kill yourself with one. I almost did.)::safety::

Like Don, I am sorry I didn’t see this earlier. Speaker magnets can be made out of any of a number of materials. If it looks like steel, i.e. has a nice shiny surface, it is likely a steel alloy using a fair amount of nickel, cobalt, iron or some weird stuff like neodymium, strontium or Alnico. All of these materials are super hard and heat treated during manufacture so that they retain the magnetic field they are required to have. Ceramic magnets are also popular for smaller speakers but are not shiny and usually have a soft texture. More often, ceramic is used in motors with several poles or for straight DC motors like the CIM.
In all cases, drilling of a completed magnet usually results in chipping and cracking. The heat developed and the new hole in the magnet structure will reduce the magnetic field to some extent depending on a variety of factors.
In speakers, remember that the maximum magnetic flux is designed to pass through the gap between the center pole and the support structure. The magnetic field returns to the opposite magnetic pole through that structure. This intense field is what the speaker coil must cut through to become essentially a motor.
Some speakers are designed with very long voice coils so that only a portion of the coil is in the field at any given moment. Other are designed with long magnetic structures so that the entire coil will never leave the field. To produce the least distortion, the coil must ride within a field that has no variation.
If you had taken apart a really old radio, ca. 1930’s, you would have found no magnet in the speaker. In that era before rare earth and super magnetizing machines, manufactures performed a little electronic black magic. Since they needed an inductor to smooth power supply ripple, they simply wound the inductor around a piece of nickel/iron and used it for a speaker magnet. This was the high voltage supply in the radio, usually 300 volts or more. And yes, I tried replacing a speaker of that type that had become damaged with a magnetic one, only to find out the radio didn’t work at all. I learned about LC low pass filters, and speaker design all in one lesson.
I like taking things apart (it is what I am paid to do) and that is where I have learned some of the most valuable lessons. I also tried drilling a magnet once, an Alnico. That’s all it took for me, just the once.

Oh and Andrew who you calling old?!?!

We do this at work, it’s not that hard if you have a significant investment in the right equipment…

The right equipment being diamond tooling for processing ceramics…

As someone has noted, the magnet from a radio is most likely a ferrite type material (blackish), which is a high temp fired ceramic. The stuff is hard.

Also, you need to use liquid cooling, magnets do not like to be heated up. They tend to become ceramic paperweights. Google “Curie Temperature”.

1st - what is your definition of “old radio” ?

I am curious about the ‘old’ definition especially for us ‘old’ radio types like Don and Al and myself.

2nd - a comment. There is potentially a LOT to be learned by your exercise. First of all the history of magenetic devices in radio speakers. And secondly a lot about properties of materials.

A lot of people don’t know it but there are engineering degrees in Material Science Engineering. Those folks spend all their time on making sure engineers have access to “the right stuff”.

I think I saw on 60 minutes or somewhere that in some countries in Europe a part of engineering education involves spending time in a lab with a variety of different metals and substances. Basically they file and file and file and cut and cut and drill and drill and cut and file and file. All by hand. It helps the student really get a hands on feel for material properties.

If you decide to try a drill bit made for ceramic tile I recommend a wet diamond core bit. Using a standard shaft type bit will increase your chances of cracking while a core or hole saw type bit will cut a cleaner hole. Just make sure to get a wet bit and use plenty of water while drilling (the water is a coolant and a lubricant in this case).