Mk 111 restoration project (first post)

[PARCHMENT]

Hi Peter

I have enclosed two pictures, one shows the clamping ring covered in paint and you mentioned that the ring is 'tinned' is this tinned as in solder and polished or another method. the other shows the prism, the spring spring screws are removed but I cannot release it from the case.

[Peter Laidler]

Tinned as in tin plated - or plated in something similar but they're always silvered.

Releasing the spring is by what we call 'manipulation of the parts in question'. But I have never failed yet...........

[Peter Laidler]

As a matter of interest, I note that you are not going to unseat the bowl glass but just empty it, refill and de-gas the liquid. Before you go down this route you ought to tell/ask yourself this. Fluid was lost last time so unless you correct something, fluid will be lost this time. It might take a bit of time but it WILL leak again. Leaks never improve with age. Just my thoughts based on my limited experience since.............. a long time

[PARCHMENT]

Hi Peter

I under stand your concerns and would go along with you.
The reason that I was not going to remove the ring and glass is the possibly of a mess that may be under the glass, and the problem to seal after and of course the Radium has to be considered.
I have found from this sight a picture showing the mess that I might have to clean from the bowl.

Michael

[Peter Laidler]

I can see what you are saying but the mess and crud will still be there when you're finished....., internally too! Spoiling the ship for a hap'orth of tar my mum used to say!

The radium didn't ever cause us any harm. Wrist watches, gun sights, compasses etc etc by the dozen. Mind you we didn't have too much health and safety either. Don't know how we managed!!!!!! We're not talking nuclear fission or plutonium 329 here

[gsimmons]

I'm actually more concerned about all the X-Ray's I've had than all the WW2 watch dials round my shop. I think it was more of a concern when you had warehouses full of the stuff.

[us019255]

While the radium is active and will remain so for the next zillion years you can worry yourself sick about it - or just get on with life

My background is a PhD in Physical Chemistry including course work on radio chemistry. Radium emits Alpha particles which are stopped by anything more substantial than a sheet of paper. The only danger to humans is if it is ingested (eaten) it will deposit in the bones (chemically it is in the same group as Calcium). There it can cause cancer. The screaming and hollering that resulted in stoppage of use in clocks watches etc. was that those who made the items got it on their hands then ate stuff without washing it off. The worst was young women who had a job painting the faces. The lines were fine so they would lick the brushes that had the Radium paint on them. The bottom line: Don't set up a business putting Radium in or on things just use those you have, and don't eat them.

[PARCHMENT]

Hi Peter
I went on line and found more information.from a Collectors sight:
I checked all of my compasses with my radiation detector (Gamma-Scout) and the results you can find on the pages. 5 microSievert/hour sets off an alarm on the detector.
Then went to 'WIKPDEDIA' and found more information. Sievert is the measure of quantity
of Radiation.
Sievert=1
MilliSievert=0.001
Microsievert=0.000001

I believe these figures are correct and shows the small amounts of Radiation, and you will not be working on the Compass for long periods.
Are these assumption in the right Ball Park.
And my thanks to 'us019255' for his excellent explanation on Radium, and 'gsimmons' for his input.

Now this is the question Peter when I remove the fluid, the retaining ring and glass what is the best way to remove the putty/mastic, once all this is completed how do I reseal and with what material.

Thanks again for all your help

Michael

[Peter Laidler]

Just clean it off carefully. It'#ll just break away. When it's done and clean you can rinse it in clean methylated spirit using a fine sable haired paint brush on the lens, swinging card and inside the bowl. Just be VERY careful because inside the bowl, under where the prism looks down is an almost invisible protruding pin that helps eliminate parallax when taking a back-bearing. Find it with a magnifying glass and carefully brush it clean.

The seals. Come back when you have done this. Too much info at one time = info overload

[PARCHMENT]

Hi Peter

I have removed the fluid from the bowl, when the fluid flowed out it looked very much to be oil,as mentioned before lamp oil, the filler screw in the bowl is not flat as I have seen on others posts. The fiber washer may be be like a 'polo' mint.
The ring and the glass are out,one of the 8 bolts sheared off, so I will have to drill out, the rest came with no problem.The sealing material has been cleaned away, it had the appearance of silicon rubber the same elastic material that is used on the bath to seal.The 8 bolts for the sealing will be replaced, as they have moved previously some of the slots are rough.
The next part is to refill the bowl and reseal, remove the old lacquer and will try out 'Humbrol' satin black enamel and spray on and reassemble, that is the cunning plan so far.

Thanks
Michael

PS. what is the best thing to do with the Radium left in the compass remove or leave where it is.