I published the Micro Drill Press in June 2012. The tool has performed very well for me except...that cheap rotary tool started getting so sloppy with run-out it became unacceptable.
So, in honor of the tinkers of the world, I decided to spend the time and energy to make a good tool better.
See the original build: https://www.instructables.com/id/Micro-Drill-Press/
This revision is fairly straightforward so I will try to make it short and sweet.
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Step 1: The Motor
The DC motor came from my usual source: a cordless drill I found at goodwill. This one turns at 30,000 RPM. Wheeee!!! I run it with the same 18v/5a power supply with a PWM speed controller.
The chuck I found on EBay. Search for 'micro drill chuck'. A set with three collets was less than $10. Also search 'brass drill chuck' for more results.
I used a piece of 3/16" brass tubing to mount the chuck. The tubing ID is a slip fit for both the motor shaft and the chuck shaft. How lucky is that?
After soldering the chuck into the tubing, I staked the tube onto the shaft with a center punch. It took a small bit of bumping the chuck to get the assembly running true. You know...tap it, run it, stop it, tap it again, run it, stop it, again and again till the bit doesn't wobble.
Step 2: Motor Mount
I wanted the motor mount to be stiff with little side play. I made one out of various pieces of brass strap soldered together. Use the picture of the mount as an example. Everyone will have their own design.
I needed to extend the control knob after installing the motor mount. For that I used a short piece of 5/32" brass tubing.
The pinion shaft and brass tubing are drilled thru, then a piece of 1/16" brass wire is hammered in as a shear pin. Another piece of brass is pressed into the knob, then soldered into the tubing end.
I wanted to mount the motor directly to the bottom plate, but the chuck was too close to the work surface, I used standoffs and longer screws to change the height.
And here is Revision A.
The speed and torque have been increased (a lot). The run-out has been eliminated. My new drill press works much better than that old worn out one.
I plan on getting many more hours of use out of this great tool.