How to Use a Pencil Grinder for Grinding Metal
The Voice: You going to rob a bank?
Kevin Caron: No. I'm getting ready to do some grinding on a piece of metal art.
This is a little sculpture I've been working on here in the studio. This is kind of my master's thesis for using a mill. I've taught myself how to work the mill on this piece right here.
It started out as just a big block of aluminum, and I've carved all of this away using just the mill. Now I'm getting into the detail portion of it, so I need the equivalent of a little baby mill.
This tool is called a pencil grinder, because, well, you hold it like a pencil and use it just like a pencil. It looks like a big, fat pencil, but it's air-powered and runs little eighth-inch bits, either burrs or end mills or whatever you can find. This is a little aluminum end mill, so it's a lot faster than a burr.
It's a lot safer than trying to use this tiny burr, or tiny bit, in the mill, because this little grinding machine allows you a lot more control. If you put this into the big mill and put this on the mill and try to crank the table around and work it that way - I don't know about you, but I haven't had good luck with it. I break these things all the time, so I'll use it this way.
Let me put my stuff on and I'll show you how it works.
The Voice: What's your stuff? The safety equipment?
Kevin Caron: Yes, safety stuff. Glasses. Dust mask. Incidentally, aluminum dust is a lot finer. It can get airborne and you can get a little cloud going as you work. It's not good for your lungs, guys. Dust mask, respirator, something; anything. Holding your breath: that's not an option.
Here's how I've handled the aluminum dust. This is a little sanding box that I made. This big hose on it runs over to a big dust collector system. Well, I cheated a little. This is actually for wood, but because I'm just using soft aluminum and the chips are really small, I'm not hurting it any. It works just fine.
I just made this box and ducted to it. So now I have a platform to work on that has a positive downdraft; anytime I'm sitting here working and grinding and shaping and playing, all the chips (well, most of the chips) go down. A few of the chips get stuck on the edges. You can brush those in and clean them up later on. But without using this dust collector, it's an aluminum snowstorm in here, so it definitely helps a lot.
You might want to turn your volume down just a little. (using pencil grinder)
Kevin Caron: Sounds about like the dentist, doesn't it?
The Voice: Where do you get a pencil grinder from, Kev?
Kevin Caron: I bought this one over at Grainger. It's a Speedaire. You can go online and search for them that way.
There are several different varieties out there, different makes and models. Look for one that has a fairly high RPM - 20,000, 30,000, 40,000. You really want to be able to spin some of these little bits to get a nice, smooth cut out of it.
One of the cool things about this piece of equipment is it's got an exhaust tube where you have your incoming air. It goes right up inside this hollow tube into the pencil grinder and then exhausts right back out to this outer sleeve. So, the exhaust is actually way back here.
When you're using this tool, the exhaust is down here, not in your face, or in your ear. You're not getting the oil or water or whatever happens to come out of there on you. It's going to stay down here out of the way. Nice little feature; I like it.
Do you want to see some bits? Come on. I'll show you something else.
Here are some of the different bits that I've got. These are all the eighth-inch shafts for the pencil grinder. These are quarter-inch shafts for one of the bigger grinders.
Notice the difference between some of these bits, the way they're shaped, and why some of them are for aluminum and some of them are for steel. Can you see how big the teeth are on this one?
The Voice: Yeah.
Kevin Caron: Big, deep, very few teeth, lots of grab. This is for aluminum. See how fine these are? This is a cross-cut for harder metals, such as steels or stainless. Where this works great in aluminum, it won't work on hard metals. This one works on hard metals but will clog up in just a few seconds if you put it to soft metals like aluminum or copper.
This is kind of in between the two. The teeth are shallow, so it’s a little less aggressive than this big guy is, but it won't clog up quite as fast as this. And then this little tiny guy is just a smaller version of this one - nice, deep teeth on it, but it works in the pencil grinder for that little detail work.
There are lots of different bits and lots of different burrs and mills. Different sizes, different shapes used for different materials.
You know what tool you have. You know what you're working on. Do your research. Get online. Call your welding store. Figure out which one you need for what job you're trying to do. Get the right one. It makes the job a lot easier.
Speaking of jobs, I've got to go back to mine. See you next time.
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