The Yankee screwdriver, as it is most commonly known, is my favorite tool. I wanted to write this because instructions on how to clean or even disassemble one of these are hard to find in anything other than bits and pieces online. In books? Maybe, but... it's more fun to figure it out yourself!
A brief history:
The spiral-rachet screwdriver has been around since at least 1860. The North Bros. Manufacturing company patented their design on December 11, 1923 and marketed it under their "Yankee" line of screwdrivers. Despite the fact that North Bros.' "Yankee" line included racheting and even regular screwdrivers, the name became synonymous with the spiral-rachet design. After WW2, Stanley bought North Bros. Stanley continued to produce "Yankee" spiral-rachet screwdrivers in the USA, then later in the UK until production finally stopped a few years ago. (I don't know the exact date, but I assume it to be >2000.) Later, a German tool company by the name of Schroeder purchased the design from Stanley (I think) and is currently producing "Yankee" spiral-rachet screwdrivers with both standard chucks or built-in hex chucks.
Why a Yankee? This and the hand drill are pretty much the original hand-held power tools. But they don't require electricity, last pretty much forever (as evidenced by these antiques from the 1920s, 30s and 40s) and cost a fraction of what modern power tools do (if bought used). They're also really versitle: Put a standard hex chuck adapter on it and it can fasten/unfasten any screw you can find. Plus, there are hex drill bits, too! Or you can put a 1/4" socket drive adaptor in the hex chuck and now all your sockets will work, too! So head out to your local flea market or antique mall and find one today!
Note: This article is based on a North Bros. model 130A "Yankee" spiral-rachet screwdriver. It should, however, be largely trasferrable to other models from North Bros., Stanley and Schroeder.
Note2: This article is unfortunately, NOT based on a complete tear-down, because I haven't figured out how to remove that one washer. More on that later.
Step 1: Safety
Step 2: Materials
Step 3: Parts Explosion
Step 4: Step 1 - Remove the Bit and Spring
If you were lucky enough to get a bit with your Yankee, remove it now. If you don't know how, just pull down on the chuck and lift the bit out.
On the opposite end of the screwdriver is, ironically, the clutch screw. Behind this, lies the return spring. Note that model 30 and its variants do not have a spring. Before you take the screw out, rotate the lock collar to release the spindle and extend the spring.
Now, carefully use your 8mm slotted screwdriver to remove the clutch screw.
Step 5: Step 2 - Remove the Handle
Step 6: Step 3 - Remove the Sleeve Screw
Step 7: Step 4 - Remove the Sleeve
The short version of this step is to rotate the sleve to the right, then pull down to expose the inner workings. Before you can move the sleeve at all, you will need to press the shifter straight down. You almost need three hands for this. The shifter will need to go under the sleeve when you rotate it.
If you look at the back of the Yankee (opposite the shifter), you will see a tab and a slot. When you rotate the sleeve, that tab will fit into that slot, then you can pull it down. Be careful to hold the Yankee with the shifter-side up, because the shifter will want to fall out when the sleeve comes off.
Step 8: Step 5 - Removing (some Of) the Internals
First to come out will be the shifter. Set it aside.
Next, the pawls, which provide the racheting action will be removed. These may adhere to the other parts by the old grease, so you may need to lift them out with a bent paper clip or something. Remember which way they go back in!
Now you can see what's beneith the pawls: the drive and draw nuts. If you move the spindle up and down, you'll see that these rotate opposite of each other.
Step 9: Step 6 - Cleaning!
To clean the internals that we're not going to take out, apply your cleaner of choice and move the spindle in and out to rotate the nuts. Here you see my Yankee soaking in Simple Green foam. To flush the cleaner out, hold the Yankee at an angle, so that the spindle side is pointing down. Pour a little water over the nuts and move the spindle to rotate them. Repeat as necessary.
The more stubborn grease can be wiped away. I used cotton swabs. A cloth would also be acceptable. Place the swab on the nut and rotate them. Be careful not to let it get pulled in or you'll be picking out cotton before you can move on.
Use your cleaner on, then wipe the remaining grease off of the pawls and shifter. Some things to note in this picture. First, make sure the copper strip on the bottom of the shifter has a good curve to it, like in the picture, maybe more even. Second, take not of the condition of the pawls. The underside of the thin part (which contacts the draw/drive nuts and provides the rachet) can wear down and become unusable. Because the pawls are the same shape and size, you can do a Scot's Staircase on them. (That is, you can turn them over and they'll work like new. Big note here: If you need to do that, you have to switch them so they go in the correct way! If you don't, your Yankee won't ratchet right and you'll have to re-disassemble it. Look at the picture in step 5b for the correct way.) These pawls are upside-down, but notice the way the thin part shines as if it has an edge. That's the wear.
Step 10: Step 7 - Grease It Back Up
Step 11: Step 8 - Reassembly
Remember to put the pawls in the right way!
Remember that the sleeve has to fit that notch in to go back on correctly.
Put the spring and screws back in and wipe everything off.
Step 12: Optional Step - Painting
Step 13: Step Penultimate - Notes on a Full Tear-down
Here are some notes on a full tear-down, if it were to happen.
After you've removed the handle in step 2, there's a hole where you can access the spindle washer. Remove that and the spindle will come out the top.
With the spindle removed, use a quarter or something to remove the shell screw at the top. When removing this, keep in mind that just below is the lock collar, which houses the two ball bearings that lock the spindle. Set them aisde.
After you remove the sleeve, look at the back of the Yankee and you'll see the three stops. Pry them out somehow, maybe by sticking a screwdriver into the top of the Yankee and pressing down. With these out, the drive and draw nuts will come out. Remember which one is which!
Clean everything and put it back together.
Step 14: Step the Last - Resources