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Yankee Drills


Restoring Boring Tools - Push Drills, Hand Drills, Braces, etc.

  Tuning an Eggbeater Drill by Andy Seaman   1 of 3  

I love eggbeater drills. They work well for poking small holes in most any material. They’re compact and light, don’t have batteries that need to be changed, are quiet, safe and operate smoothly if you know how to tune them.

The other thing that I love about eggbeaters is that they’re mechanically complex relative to planes, spokeshaves and other hand tools, yet the classic makers of these tools have done a terrific job of producing elegant designs.

My dad was kind enough to lend me his Millers Falls #77A eggbeater so I could run you through a tune-up.

Actually, I was hoping he’d say, “Keep it,” since he hasn’t used it for quite some time anyway, but I think he wants it back (nuts!)

As you can see, Dad’s drill is in pretty good shape. It spins fairly smoothly, all of the parts are present (I consider side handles to be an amenity since I’ve yet to find an eggbeater that wasn’t missing its original side handle), and there isn’t very much spindle run out (i.e. it spins with minimal wobble on its axis).

However, Dad’s drill is a bit grimy, the chuck sticks, and it doesn’t operate as smoothly as it can. By addressing these issues this drill will run more smoothly and will be able to drill larger holes with less effort.

The first thing I like to cleanup is the chuck. This takes the most effort so I like to do it first. Unscrew the chuck from the spindle and submerge it or spray all over and inside with WD-40, my favorite solvent, or whatever solvent or penetrating oil you prefer.

While the chuck is basting, disassemble the rest of the drill and clean it up with WD-40, rags and a toothbrush. Personally I don’t really care about the paint spatters and such (especially since this is Dad’s drill!) but you can go to the trouble of removing all of these if you like. 

Clean any grime from the spindle threads as these affect how smoothly the chuck will operate.  Use a stiff nylon or brass brush to clean the smegma from the teeth of the main gear and the pinions. 

Spray and wipe out the bearing in the main gear (the central hole) and inspect the journal that it mates to on the frame of the drill.  Wipe off the journal and smooth any burrs or raised metal with slipstones or whatever fine abrasive you prefer. 

You want this journal to be polished and smooth to reduce friction. I don’t recommend removing the pinions (the little gears).  These are typically pinned in place and can be removed, but it’s usually not worth the effort.  Now that the chuck has soaked for a bit, it’s time to open it up.

I grab the knurled surface of the chuck in my machinists vise. I made up some brass “soft jaws” when I got this vice and they’ve worked well for holding small parts without marring.  Try not to go nuts on the vise and make your chuck egg-shaped.  You can see that the top of the chuck cap is slotted, as if for a giant screwdriver.  I’m fairly certain that Millers Falls used this design for ease of assembly, not disassembly (a common approach amongst American mechanical designs).  Resist the temptation to jam something in the slot and twist!

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Yankee Drills

Boring Tools


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