Thanks for visiting my vintage Hamilton watch blog. I like to restore US-made Hamilton wrist watches back to their original glory and share my experiences with other enthusiasts. Use the "Search" space below if you know what model you're looking for. Feel free to leave polite comments or questions in the spaces provided. Also check out my "watches for sale" on my Etsy site - the link is on the right, just below.

Saturday, February 27, 2016

1959 Thinomatic T-401

Once more unto the breach, dear friends, once more... Now set the teeth and stretch the nostril wide, hold hard the breath and bend up every spirit to his full height...

What does William Shakespeare's "The Life of King Henry the Fifth" have to do with Hamilton watches, you say?

Sometimes taking on a project requires a little courage, or at least a firm resolve.

The last time I tried to tackle a micro-rotor automatic it was a complete disaster, a total write off, a miserable failure.  Actually, it was worse than that.  It was so bad that I swore off ever attempting another one.

How's that for bad?

Well, it's been probably four years since my last attempt and I bet I have 600+ additional watches under my belt.  So I decided I might give it another go.

Once more unto the breach, dear friends.

There are 57 different Thin-o-matic models and not all of them use micro-rotor movements but the majority of them do.  Micro-rotor movements were made by Buren.  In the 1960's Hamilton partnered with Buren and eventually acquired them.  But the master became the servant in 1969 when Hamilton's US production was shut down and production moved to Buren's factory in Switzerland.

One of the more interesting Thin-o-matics is the 1959 Thin-o-matic T-401.  It was produced for four years.  It's one of only two square automatics... the other is the 1956 Automatic K-405.

The T-401 came in a 10K yellow gold filled case.  The white-finished dial featured solid 14K gold numerals and markers with an engraved pearled track.

Inside the T-401 is a 17 jewel Hamilton 663 movement.  There are a number of very similar micro rotor grades and I don't know precisely what makes them different.  My experience with them is very limited.  One of the grades is 666... the number of the beast.  That's a fitting number, I think.

My T-401 project watch arrived in fair shape.  The crystal was beat and the waterproof crown isn't correct.  It should have dress crown, as this is not a waterproof model.  The crown also has a long tube so it sticks out the side of the case.

The T-401 case is substantial. Although this one is pretty dirty, it doesn't show a lot of excessive wear to so it should shine up nicely.

What makes micro-rotors interesting is all of the parts are on one plane.  Half the watch surface is for winding and the other half is the gear train.  A small rotor spins around as the watch is moved and it transmits energy through a series of wheels to the mainspring.  You can also wind the watch manually, which is good since a lot of people feel the small rotor isn't powerful enough to really keep the watch energized.

Flipping the watch over, you can see the dial-side of the main plate looks like pretty much every other watch.  However, there are a number of bushings from about 1:00 to 7:00 that hold the pivots of all the winding parts.  The large pink jewel to the upper left of center supports a wheel that has no arbor at all - it's just sandwiched between two parts - it allows the rotor to wind the watch, regardless of which direction it turns.

And so it begins...  I learned from my last attempt that energy from the mainspring goes two directions... one toward the balance and the other back up stream to the rotor.  One way to release the mainspring energy is to remove the balance assembly and then remove the pallet fork.  Without the pallet fork, the gear train is free to move and the mainspring unwinds unconstrained.

In the shot below, the balance is removed and the pallet fork can come off next.

The pallet fork is now gone and the wheels spun to a complete stop.  I can safely start taking the rest of the movement apart without risking accidentally releasing energy at the wrong time.

Micro-rotors have two ratchet wheels.  One is driven by the crown mechanism and the other by the rotor assembly.  The two wheels can move independently but a small spline connects them so the crown can turn the wheel the rotor also turns.  In the shot below, the top wheel is removed and the second wheel below it is now visible.

There's a small bridge than covers all the winding pinions and it's been removed below to expose the winding wheel.  You can see the winding wheel doesn't engage the ratchet wheel - there's a series of gears that connect the winding wheel to the ratchet wheel and they have been removed.

Now I can turn my attention to the rotor.  A large screw holds the rotor to it's arbor.  I can unscrew it and lift the rotor up and off.

With the rotor removed, you can now see the bridge that covers all of the gears that convey the rotor's energy to the large golden wheel that drives the ratchet wheel.  Did I mention there are a gazillion parts in a micro rotor?

Here's a shot of the backside of the rotor's bridge.  The silver gear is what the rotor turns when it rotates.

There is a very long and delicate spring inside that operates as a click and keeps the energy from the mainspring from coming back through to the rotor.

Here's what that spring looks like relative to my wedding ring.  Can you say tiny?  It makes me wonder if this part is really necessary?  (it is)

Some more of the bridges are removed to show you how the gear train is organized.

There, all of the winding parts have been removed.  Now for the other half of the movement.

One piece of spring wire serves two purposes with the "click" of the watch.  It's very small and you probably wouldn't even notice it unless you stab your finger with it, like I did.

You can see the spring wire a little better in this shot of the other side of the barrel bridge.

All that is left now is the gear train... but there are a lot of parts there too.  Two screws hold the train bridge on.

If you look at the movement from this angle you can see there are two wheels nested together.  Also, the center wheel is held in place with it's own bridge and a pinion goes through the center of the center wheel to drive the second hand.

The train bridge is removed to reveal the third wheel, fourth wheel, escape wheel and what ever the wheel nestled on top of the third wheel is called.

Here you can see that the two stacked wheels can move independently.

Finally!  I'm down to the last wheel to come off.

The last parts to come off are the balance jewels.  They're held in with spring loaded "shock springs". that are easy to open so you can get the jewels out for cleaning.

The balance jewels are actually two jewels... one has a hole and the other is a cap that covers the end of the balance staff.

I reinstalled the balance so that I could remove the jewels from the balance cock too.

While everything is being cleaned I will prep a new crystal for installation.

How's this for a daunting sight... look at all these tiny parts.  There is easily twice as many parts in a micro rotor than your typical manual winding movement.  They all need to be cleaned and dried before being reassembled with fresh lubrication.

The first challenge is to get the train bridge back on.  It took a little finessing but I was able to get it into place fairly quickly.

The barrel goes in next.  Now I can install the pallet fork and balance and be left with a manual-winding watch.

Reinstalling the balance means I have to reinstall the balance jewels.  That's easy as long as I don't squeeze them too hard with the tweezers and shoot them off into oblivion.

Now I can work my way back to the rotor by just doing the opposite of what I had to do to take it apart.

Here's another very tricky part... getting the bridge to cover all the auto-winding wheels.  The little silver circles are bushings for the various arbors.  Even the little spring has to be lined up just right in order for the bridge to seat properly.

Now the rotor goes on and the watch is back into running order.

Well, it's running fairly well.  Good amplitude and a beat error on the high side of acceptable.  I'll leave it like this for a while and see if it settles down.

Getting the dial and hands back on is a piece of cake compared to what I had to go through for the rest of it.  I think the watch turned out great.  The dial is a bit dirty but it's not bad enough to risk goofing up the pearled track with a refinish.  I replaced the crown with a slightly better crown but I need a longer stem to fit a proper dress crown.  It doesn't look too bad as it is though.

If you're curious about the Shakespeare text I referenced above, here's the full version.

Once more unto the breach, dear friends, once more;
Or close the wall up with our English dead.
In peace there's nothing so becomes a man
As modest stillness and humility:
But when the blast of war blows in our ears,
Then imitate the action of the tiger;
Stiffen the sinews, summon up the blood,
Disguise fair nature with hard-favour'd rage;
Then lend the eye a terrible aspect;
Let pry through the portage of the head
Like the brass cannon; let the brow o'erwhelm it
As fearfully as doth a galled rock
O'erhang and jutty his confounded base,
Swill'd with the wild and wasteful ocean.
Now set the teeth and stretch the nostril wide,
Hold hard the breath and bend up every spirit
To his full height. On, on, you noblest English.
Whose blood is fet from fathers of war-proof!
Fathers that, like so many Alexanders,
Have in these parts from morn till even fought
And sheathed their swords for lack of argument:
Dishonour not your mothers; now attest
That those whom you call'd fathers did beget you.
Be copy now to men of grosser blood,
And teach them how to war. And you, good yeoman,
Whose limbs were made in England, show us here
The mettle of your pasture; let us swear
That you are worth your breeding; which I doubt not;
For there is none of you so mean and base,
That hath not noble lustre in your eyes.
I see you stand like greyhounds in the slips,
Straining upon the start. The game's afoot:
Follow your spirit, and upon this charge
Cry 'God for Harry, England, and Saint George!'


  1. Nice one man. I just picked up a Buren micro rotor with 30 jewels. Thanks for the info as always. And yes your project turned out very nice.

  2. Do you happen to know the lift angle?

    1. I don't tend to worry about lift angles to be honest. I just assume it's 52 degrees since the vast majority of time that is the case.