Introduction: Make This Cheap and Easy Mini Power Tool

About: Old timer ... Still learning

I had shown a picture of my homemade mini power tool in one of my Instructables and mentioned how easy it was to make. I had also, immediately following, started this Instructable featuring it, but for some reason, it got side-tracked.

Just yesterday I received a message from a member who saw that Instructable and asked me if I could make one featuring the mini power drill (picture above), so here I am, writing again!

It's very easy to make yourself a mini power tool that can do drilling, buffing, cutting, grinding etc. All you need is a motor, a drill chuck, all the various attachments and (of course) a DC power source and you're off.

Step 1: Your Options

We have four options here:

1. The Easy Option

2. The "Environmentally Concerned" Option

3. The Alternative Chuck Option

4. The Green Option

Step 2: The Easy Option

A complete kit (see the picture) is available from Ebay, but I prefer buying from the AliExpress website because their specifications are more detailed and they include lots of pictures of the product. Also, they have many alternatives to choose from.

The kit is available from this link.

It will contain the following:

  • 1x 12V 500mA Motor
  • 1x Axis (or Motor Shaft Coupler)
  • 1x Brass Cap
  • 1x Allen wrench
  • 1x 0.5mm drill collet
  • 1x 1.0mm drill collet
  • 1x 1.5mm drill collet
  • 1x 2.5mm drill collet
  • 1x 3.0mm drill collet

It will take 15 to 20 days to arrive.

All you need to do is put it together, connect a 12V 1A power supply and you are good to go.

The drill collet size (in mm) is the diameter of the drill shaft or the shaft of the rotary tool that the collet will take.

Step 3: The "Environmentally Concerned" Option

This is for people who like to go green, but also like the easy way out :)

Going Green ... The Motor

We will start with the green part of the option first. This has to do with recycling old products.

I have a big collection of all kinds of motors. All stripped from old products. These motors are, surprisingly, built to last very much longer than the product. For high quality, high torque motors, I'm talking about printers.

A huge number of printers are discarded every year for various reasons e.g. not Wi-Fi enabled, no longer supported by the manufacturer, cheaper to buy a new one than repair the old one, the ink is more expensive than for the later model, repeated failure (quite possibly a user issue), etc. I haven't seen a single failed motor yet.

The short of it is, take a walk round your block, pick that printer out of the dumpster, take it home and dismantle it. You should get at least three motors including at least one 12V high torque motor and possibly a couple of stepper motors (which you can use for your next CNC project :)). In my experience, the older the printer, the better the motor quality.

Note: It's a good idea to keep the motor mounting screws as well (screw them back to the motor screw holes). They will be useful when you want to upgrade to a drill press.

The Chuck

Now that we have done our bit for the environment, we can reward ourselves by ordering the chuck of our choice. My preference again is AliExpress for their wide choice. Just do a search for "drill chuck"

There are a couple of things you have to note when ordering the chuck:

1. there are two types of these brass chucks available. One is with a fixed collet (see the first picture above) ... you don't want this. What you want is the one with interchangeable collets, same as our previous option. This is where the pictures are important. Make sure that the picture shows all the individual parts of the chuck separately. You will find an example here of the type you should order (also see the second picture above), but before you go ahead and order please read the next item.

2. After surfing around AliExpress a bit, I found that the holes at the bottom of these chucks are made to match three common motor shaft diameters. I have shown the sizes in the first picture above as a guide i.e. 2.0mm, 2.3mm & 3.17mm.

Before ordering I suggest using a Vernier Calliper to check the diameter of the shaft of the motor you have.

I tried to make a list of links of suppliers for each of the sizes mentioned above, but it seems that the motor shaft diameter size is no longer mentioned. I was only able to find one chuck model that I could confirm was for a 2.3mm diameter motor shaft. The link is here. Unfortunately it doesn't come along with the Allen Key, but that shouldn't be a problem for most members here.

If you have a motor with one of the other shaft diameters, please contact a few of the supplier using the link on their product page and check if they have the size you need. See the third picture above for an example of where you will find the supplier's ("Seller") link. They are very helpful. Attaching a picture (taken from their page) showing what you want helps.

Step 4: The Alternative Chuck Option

I haven't done this, but if you managed to salvage a more powerful motor in the previous section and you prefer a 0.3mm to 4mm chuck with a key as shown in the picture (more expensive), the links for chucks with the motor shaft coupler for 2.3mm and 3.17mm shafts are below:

Chuck with:

Motor Shaft Coupling for 2.3mm diameter motor shaft

Motor Shaft Coupling for 3.17mm diameter motor shaft

I could only find the 3.17mm version with the Allen key locking screw. The 2.3mm shaft version is push-fit for the chuck side as well as the motor shaft side.

You can also get a chuck with a coupling for a motor with a 5mm diameter shaft. The price is much higher.

Step 5: The Green Option

This is where we use all recycled materials.

Assuming that we already have the motor that we salvaged from that printer, all we now need is a chuck.

The Chuck

The chuck of my first mini drill (which I used for PCB drilling) was made using a sawed-off hand twist-drill. We got these in a toolkit. Nobody ever used them, so I collected a few.

Check out the pictures for the details.

The biggest problem was fitting the sawed off handle of the hand-drill centrally over the motor shaft so that there was no wobble.

I resolved the wobble problem by using PVC sleeving over the motor shaft. I was lucky it was a perfect fit.

A better option would have been heat shrink sleeving. I didn't have access to it at the time. In this case you would add one piece of sleeving over the other, shrinking each piece and checking the fit with the sawed-off drill holder until it was perfect (i.e. just sliding in smoothly with no side-ways play).

When you are happy with the fit, you apply epoxy to the motor shaft before finally sliding the chuck in. Be careful not to get the epoxy anywhere near the motor bearing.

If you have access to machine tools or a 3D printer, you can, of course make a more accurate coupler to eliminate the wobbling.

Note: The collets that I got in my "Environmentally Concerned" option (see the picture above) fit quite nicely on this chuck, so I still have the option of using rotary attachments with different shaft diameters and drill-bits from 0.5mm to 3.0mm.

The Motor

In case you are wondering about the motor in the picture, I got it from a discarded tape loading mechanism of a professional video tape player. There were, in fact, two of them on the same mechanism along with some solid-looking brass gears. You can see this one has taken some battering. 20 years later, it is still running!

Step 6: Wiring Up the Motor

Powering the Motor

The power requirements of most motors of this kind are 12V and 500mA. I checked the current drawn by some of my motors under high load e.g. Stopping the motor by hand while it was running, and I found that the maximum current drawn is around 800mA. Therefore, to be on the safe side and also for smooth running of the motor, a regulated 12V supply capable of a current of 1A or more is recommended.

This is easily handled by a 3-terminal 12V regulator (LM7812) on a heatsink. An example of the Power Supply circuit is attached. The components are not critical except for the transformer and the voltage regulator. The capacitor voltages should not be lower than indicated.

The Motor Wiring

I have attached a wiring diagram for powering the motor. It is recommended to have a capacitor (as shown in the diagram) directly across the motor lugs. This is mainly for spark suppression, to reduce RF noise and to protect the power supply from surges.

The micro-switch is also recommended. They take a much higher current than other switches of the same size (the one shown is rated at 3A) and they are spring loaded, which means fast switching, less sparking and therefore longer life. The wires go to the C and NO tags. You can easily remove the lever if you don't want it.

As you can see in the picture in the previous section, I mounted both, the DC Jack and the micro-switch on the motor lugs. This is because there was already a PCB there so I modified it to take both. If you prefer, you can hot-glue the switch to the side of the motor or wire it to a foot-switch.

Motor Polarity

Some salvaged motors have a red mark on one of the lugs. You immediately assume that this goes to the positive of the power supply. This may be true for the equipment in which the motor was used, but wired this way, the motor may not turn in the right direction e.g. for drilling. It is best, therefore, before starting the wiring, to check the direction of the motor by connecting it to your power supply and confirming which lug goes to positive.

Step 7: Additional Notes and Improvement Ideas

Enclosing the Motor Wiring

I had an idea of making a hole in a half egg-shaped plastic dome (half the shell of the enclosure that holds the toys in a toy vending machine), mounting the DC Jack through the hole and then mounting the whole assembly at the back of the motor, so that you have your wiring neatly enclosed, but the arrangement I have works fine, so I never got down to it.

Rotary Tools You Can Use

Since I work mainly on plastic boxes and sheets for electronic hobby projects, cutting round and square holes, a mini power tool is ideal for me. I have attached a picture of some of the tools I use:

Rotary Saw Blade: The blade is very thin (around 0.1mm thick x 21.5 mm diameter) so It is ideal for cutting small square or rectangular holes for panel meters and displays.

Diamond Cutting Blade: This is a diamond granule coated blade. Ideal for cutting and grinding harder materials

Grinding/Cutting Wheel: Great for cutting down unwanted pillars in a plastic box and flattening them

Fine Grinding Wheel: Helps in smoothing the edge of a plastic sheet or rounding corners.


I hope I have covered everything you need

I am sure you will enjoy making and using your Mini Power Tool as much as I do :)

Note: All the product pictures are taken from the AliExpress website. Considering the free advertising they are getting, I don't think they will mind.