HP-01 Back Cover Tool


I'm considering having my machine shop make one of these for my own use.

Is anyone else interested? I will likely make it out of aluminum with brass pins to engage the cover.


Interesting. And what will be the price?


The more people there are, the lower.

I would guess at this point $30-40


If it were made of metal, could it not damage the back plate and/or strip the threads? The original ones were made of hard plastic, if I recall.. cheap to manufacture and would likely break before shearing any of the metal watch parts.


I don't think what I am proposing would damage the back. Both Aluminum and Brass have a lower hardness than the Stainless Steel back.

What I was thinking of producing was something like this one

Except make it in aluminum with brass pins. I suppose it could be made with plastic (Delrin or CPVC) and the pins pressed into it.


I'd suggest to grab a cheap watch and do some tests. I could imagine, that brass and aluminium will leave traces on brushed steel, and it's probably hard to remove these traces.


Hello AJ....

I think that it is a great idea (and I would order at least one), and if manufactured correctly then marking the case back would not be a problem.

I have restored over 150 watches, including 10 hp-01's and some of the main case markings are done by over-zealous rough watch repairers scoring the case backs. Mainly due to the incorrect use of the wrench. However a wrench of this style would be unlikely to slip and score the case back.

Another type of case wrench I use is an old India rubber ball (super ball). This of course does not scratch a case back but will also not remove a 'stuck' case either.

The HP-01 'Cricket' comes with (if you are lucky enough) a plastic wrench which contains 5 357 spare batteries, two back case gaskets and of course the prongs which mesh with the grooves in the case back. So the caveat would be that the prongs are not too long!

The problem with standard watch wrenches(figure 1 and 2) is that the prongs are too deep and will ruin the piezo transducer (figure 3 "A") which is attached to the inside case back:

figure 1:

figure 2:

figrue 3 (A: piezo transducer which is visible from the top side of the back case in the deeper part of the recess.)

Of course what posting would be complete without some gratuitous eye candy. For the full posting of this restoration see the following

link: HP 01 RESTORATION. This is an older post and the book contains a much more refined series of photos and labels sans humor! This one actually made it on the BBC series "Antiques Roadshow", albiet, in the background on a display table surrounded by other LED watches.

This is all covered in chapter six of the book!

Edited: 4 Apr 2011, 2:41 p.m.



I am going to make from UMHW (Delrin) with some metal pins.


Delrin is excellent.

Actually Omega and Lemania use it in their 861 Speedmaster movements due to its self hardness and 'slipperiness' as part of the cam system for stopping and starting the chronograph.

Good choice and sign me up for one!


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