Roll Your Own Rotary Tool

Rotary tools are great little handheld powerhouses that fill the void between manual tools and larger shop machines. They’re also kind of expensive for what they are, which is essentially a power circuit, a switch, and a high-RPM motor with a tool coupling on the shaft. If your tooling needs are few and you have the resources, why not make your own?

[DIY King 00] built himself a cordless rotary tool for less than $10 out of commonly-available parts. It doesn’t run nearly as fast as commercial rotary tools, but that’s not necessarily a bad thing. He made the body out of 2″ diameter PVC and mounted a 12 V, 400 RPM DC motor directly to one of the fiberglass end caps. Tools are chucked into a collet that screws into a coupler on the motor shaft.

For power, [DIY King 00] built a 7.4 V battery pack by wiring two 18650 cells from an old laptop battery in series. It isn’t the full 12 V, but it’s enough power for light-duty work. These 2200 mAh cells should last a while and are rechargeable through the port mounted in the other end cap.

Drill down past the break to see the build video and watch the tool power through plywood, fiberglass, and inch-thick lumber. Once you’ve made your own rotary tool, try your hand at a DIY cordless soldering iron.

37 thoughts on “Roll Your Own Rotary Tool

  1. okaz, let’s see…no low discharge / overcharging protection on the LiPo batteries, Motor wired with wrong polarity (doesn’t really matter), no bearing to take the load of the motor…
    yes, I can see why this is $10 and a dremel is $60…

    At least my dremel is less likely to explode due to overcharged / discharged LiPo cells…

    1. I’d say a lot of, rather than most, general purpose motors aren’t really timed/tuned for particular rotation. But high performance hobby motors are. Back in the day before all this outrunner and lipo stuffs, you’d take your generic “Mabuchi 540” and rotate the backplate a bit to give it a tad more.

  2. How different is that compared to this other “hack”?
    The drill on today’s article looks a bit better (it even features a case and some paint and a Li-ion battery we have no idea how it’s protected, how impressive!), but I’m afraid that most HaD readers won’t be impressed at all by this kind of “Aliexpress/Amazon bolt-on”, even though there is some reused stuff.

      1. Actually, it’s more this kind of hacks I’m looking for on Hackaday. Even if it does not looks fully completed, there is some engineering and thinking behind that. Getting the most you can out of cheap stuff is not as easy as ordering stuff from the usual suspects.

        1. Well, it’s definitely a hack in the other sense.

          1) no thrust bearing – motor will seize up
          2) no cooling – motor will burn up
          3) no battery cell management – batteries will burn up

          This rotary drill is just ordering parts online and hammering them together without barely a thought about how they’ll perform the intended function. This would be a nice hack if you were in a log cabin in the middle of nowhere with just a pile of rubbish and broken parts to work with, but going through the bother to order the motor coupler and the motor online, it just shows a lack of understanding and foresight.

        1. I would like to when I can get back to finishing it. It’s on

          I am struggling with complex health issues including neurological impairment at the moment and these issues may or may not resolve. Fingers crossed, I might get back to it one day. I have been a passive visitor here lately and my projects are not getting any attention or progress.

    1. It’s more back to the basics, because that i entiely a hack. Not a build, not made by “maker”, it’s definitely a hack. And this site is “Hack a day”. Yep, maybe there are blog entries about things with better finishing, but this IS a hack and it belongs here.

  3. I had a light duty motor tool (Wahl) that ran off an 18volt wall wart. It went to being run off of a variable bench supply so it can just purr along and not stall for using little brushes in cleaning delicate organ contacts. The power switch went out. Then the plastic case fell apart. So I shoved it into a piece of rubber hose (oil spots now accessible) that was a snug fit and a good grip. By then the bearings were worn out, so I pulled the chuck off and pressed it onto a motor from a VCR or some such device out of the junk drawer. Same range of RPM up to 10,000. Same hose piece same chuck, the 3 jaw type not collet. It gets used for tiny drill bits as well the 1/8 INCH standard for most of the service bits.
    Depending on the speed and torque that you need there is a motor in just about any thrift shop or junk collection.
    I have the end of the shaft of a real Dremel that died. I need to center drill and press it onto another DC motor.

    1. Still seems better than some designs (the one in the article included) as the bearings are at least reasonably sized. Taking a standard cheap motor with little balancing and using it without external bearings is what some cheap designs do and is even worse.

      IIRC Proxxon designs are pretty good even in their cheapest versions with the more expensive ones tolerating (relatively) high axial and radial loads. OTOH Proxxon aren’t among the cheapest.

      1. I’ll never buy another dremel after their crappy column stand disaster. and no, dremel is not cheaper, just crapier. I’ve switched to proxxon and love their addons. no cheap plastics but metal. :-)

  4. Dremel is a durable and reliable tool with wonderfull ergonomy and set of high quality bearings, which ensure very low wobbling during long lifetime. For God’s sake please dont call this piece a Dremel! And one more thing: STOP soldering to the 18650 an similar battery terminals: you are killing them, there is a spot weld for this kind of work!!! My engineering eyes are bleeding of this sh*t!!

    1. Dremels are not long-lived, high quality tools. I wore out four of them before I switched to the much cheaper Black and Decker rotary tool which is compatible with Dremel brand accessories.

      I wear out the Black and Deckers at the same rate I was wearing out the much more expensive Dremel branded tools.

      The B&D is sold as a “three speed” tool, but it is actually a continuously variable speed control with three detent positions.

    2. What? Dremel being durable and reliable? LOL! Really…

      I bought a low-temperature solder (alloy really – no flux and not in wire form) for soldering battey terminals and it works well.

      Another way to do it is taking into account heat conduction of the terminals and solder small balls with enough time for the temperature to drop before doing the next ball. Solder have less cnductive heat transfer properties than the nickel coated copper commonly used on the terminals -> it is (theoretically) possible to solder a wire to the balls without destroying the battery.

      But I’ve only done it not verified if it’s true.

  5. Dremel is a durable and reliable tool with wonderfull ergonomy and set of high quality bearings, which ensure very low wobbling during long lifetime. For God’s sake please dont call this piece a Dremel! And one more thing: STOP soldering to the 18650 an similar battery terminals: you are killing them, there is a spot weld for this kind of work!!! My engineering eyes are bleeding of this.

  6. I bought similar cheap drill from eBay and it’s total crap. It looks fine, aluminium casing, nice motor, but head that holds bit is absolutely terrible. It’s very asymmetrical and vibrates a lot, even on relative slow speeds 5V power supply provides. Practically unusable. So rolling your own drill might be a good idea, if you can make bit holder symmetrical and balanced so it doesn’t vibrate. It definitely can’t be compared with Proxxon FBS230, but neither can weight and price.

  7. For Canadians, if you don’t have a rotary tool, I recommend the JobMate one when it goes on sale for $12 or so at Crappy Tire, it takes a licking… kinda useless on less than speed 4 (Goes to 6). I ported a cylinder head with mine, which is the kind of job a die grinder is the “right” tool for, but despite thoroughly abusing it in terms of pressure I put on it and long run times, I just made the bearings a bit noisy, and it still works. I actually expected to destroy it and bought a backup, but the first one is still functioning well enough for general use. It’s possible I was careless with grit and dust control and it may not have got as noisy if I was taking more care. Anyway, I believe you gets your moneys worth for the amount of abuse it will stand for $12.

  8. The video looks like it was made in India / Pakistan or one of those countries. Having lived there – i know how difficult it can be for hackers to get their hands on decent equipment and the insanity of converting Rupees to Dollars is way more than what most people can justify spending on their projects. Its a tool to get a a job done, even if it isn’t perfect.

    Well done DiyKing :-)

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