Mk 111 restoration project (first post)

[PARCHMENT]

Hi
Happy New Year to one and all.
This my first post and some information about myself.
Draughtsman, Petro chem ,Mechanical engineering Apprenticeship.Retired

I have a project with a MK111 Compass with a view to bring back to good condition.
I have looked through all previous post and they are very good but if possible I would like some more information .I have enclosed a Photograph of my Compass with a few problem areas.(I hope)
Attachment 68405
1.These are the Radium 226, can these be removed and replaced with a safer item, I have read one
One article stated that for education purposes to obtain Radium 226 they take a old clock face , Compass needles etc, and dissolve the Radium with Acetone into a suitable container, are the components still Radio Active even though the Radium has been removed.
When you refill the Bowl with new fluid I have read that Rubber gloves and a respirator are to be used, would the Respirator be a Military Surplus Gas mask or what is used in the industry.My Brothers have taught to be cautious some I am looking for a Safe project.
2.The lid flops up and down, the pin is tapered and has worn over the years, can this be replaced and which side do you knock out the pin.( are the pins available).
3.The index ring clamp screw spins round, I am not sure if the screw is stripped or the thread in the case is stripped can these be repaired?.
4.To seal in the glass into the Bowl it appears that putty/mastic has been used,I believe there should be a ‘O’ ring to seal off the damping fluid, can I find a ‘O’ and replace the putt/mastic ?.
5.The area around the clamping ring and the 8 screws have been painted white, is this another type of finish used?
6.On one side of the outer case one of the screws that hold in the Bowl is made of steel no good, are new brass screws available, I presume that the thread would be B.A.
Is the bowl safe to take out of the casing so that I can paint the casing and the lid, I have painted brass before but the paint always comes off, do I require Etch primer or Lacquer finish.
On the base of the Compass there is a worn rubber ring in black, I have seen red rings can they be obtained or make your own?.

This quite a list and I thank you for you time.
Regards
Michael

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Peter Laidler]

I was taught to be cautious too but soooooooooo many Q's and so little time:

2The lid is indeed hinmged on a tapered axis pin. But you just need to punch it in a tad more so that it tightens up on the taper. That's what we used to do. You could renew it but only if tightening up the taper fails. What side it is tapered from.......... er...... you'll have to identify it from the pin as I forget
3 Index ring clamp screw. The little nut on the other side has probably come loose/unsoldered.

Will answer some more tomorrow..........

[Peter Laidler]

5: This area is left 'tinned'
6: Yep, brass 8 or 10BA screws. I suppose you could use non magnetic stainless steel......I forget the name of the process now but non magnetic, yes.

It is quite safe to take the bowl out of the casing. Strip the paint. We used to lightly bead blast and paint using either 'PAINT, brushing, instrument Black' or better stillo, send them through the Armourers shop who would paint them with small-arms black paint called sunkorite and low bake.

There were both rusty red and black base rings. All of these parts are available from a supplier on Ebay who breaks them for spares.

There is a person who rebuilds these called Trade Mark London but he has a cosy little private business that thinks anyone else who overhauls these - or who has ever overhauled hundreds of them are not worthy of life on earth.

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. To cut a long story short, Prof Mike Hxxxxxxx from AERE Harwell - who know a bit about the nuclear industry suggested to me that people who live in Aberdeen have more radium in them that you'll collect from being careful with your Compass. In fact my Omega wristwatch gives off more ronchens than the compass! On that basis, get started.

If you want to strip the bowl next, get some isoprophyl alcohol, or clear paraffin or methylated spirit. It all simply acts as a damping agent. Get the sealing rings and a new filler plug washer

[PARCHMENT]

Hi
In my first post I forgot to ask about the Index ring 'GLASS' I thought it was Glass but it is plastic, can the marks and scratches be polished out to give a new look finish?.
Can someone tell me the size of the 'o' ring seal for the Bowl.

Thanks again
Regards

MICHAEL

[CINDERS]

See if I can find the thread where I did the absolute cheap /cheats way of doing my MkIII's which I may add a few months down the track there is no air bubble in either of the bowls, in regards to the bloke who breaks them up I brought an index glass from him only to find it did not fit the index ring, any help on an easy way to grind down the diameter of the glass to get fit into the ring. Also I am one who likes patina on an item within reason and honestly fail to see the point in scrubbing away an items history from the past 70+ years just me I guess with 5 cents worth.

May be of some use to you Pchmnt...MkIII re-visited

[Peter Laidler]

There are 3 glasses (or lenses if you exclude the prism)) on the compass. The bowl glass, the rotating bezel glass and the cover glass - and in my very limited experience with them, they're all glass! What one concerns you?

The EBay man is PSKettlewell.

To remove the bowl glass from yours, this is what we used to do. Empty the Iso Alc through the filler plug. Unscrew 8x cover screws, put hand over the top/glass and bottom diaphragm and put low pressure air line into filler hole. Glass should pop off into your hand. Once you have this off. PUT IT BACK ON AS I WANT TO TELL YOU SOMETHING ELSE IMPORTANT BEFORE YOU START GETTING INSIDE.......

[PARCHMENT]

Hi Peter
Thanks for the Reply

The glass/plastic is the rotating bezel glass, is the glass in question,it has quite a lot of scratches, which made me think it was plastic.Also the glass has to be thin to keep down the weight, this also made me think that it was plastic.The cover glass is in better condition.
(on the bezel glass are the figures etched on or painter)

Regarding the the index ring clamp, 'The little nut on the other side has probably come loose/unsoldered' the nut does not exist, the thread has a small hole drilled through and a piece of brass rod through the hole and bent over to stop the screw falling out, this is from a previous repair.I will make a nut and place in the inside as it should be.

---------- Post added at 05:31 PM ---------- Previous post was at 05:23 PM ----------

Hi CINDERS

Thanks for the information.
I understand your view on the patina, I agree to a certain extent but this Compass has had a hard life much of the paint on the outside is down to the brass and other item need looking at.
I will have a good read on .MkIII re-visited.

[Peter Laidler]

The nut for the bbezel clamp will have to be VERY small. If not it will prevent you replacing the bowl. I suppose you could try polishing out the scratches in the glass using jewellers rouge but what for? The glass is thin optical glass with a minimal refractive index. I think that the compass markings are 'fired' into the glass, like an etched reticle then varnished over - depending on maker of course.

Got the bowl window off yet? Not going to tell you how to suck eggs but there is a distinct method of screwing the circumferential clamp ring down. As for the seals, we didn't use the standard 'D' seal as that sort proved to leak when the liquid was under pressure in the heat, but....... I'll tell you when we get there

[PARCHMENT]

Hi Peter

I will polish with jewellers rouge. in the past I have used cigarette ash made into a paste, it works well on a watch face.

The bowl glass look ok and this I will polish, I will fill the bowl with new damping fluid and hope to stop any bubbles forming.What I propose to do is mask the bowl glass repaint the ring with white paint, then remove the 8 screw one by one clean the heads and replace, this will minimum disturbance to the inside of the bowl and keep the putty/mastic in place and still sealing I hope.

I have removed the screws prism slide and the bolts for the ring but it has not come out of the mounting, do I have to knock out the two long pins in the assembly.

Thanks

[Peter Laidler]

The spring that holds the prism assembly bars in place is slotted into the block. Remove 2x vertical screws and slide spring up or down to remove. Best not paint the retaining ring but clean with T-cut to retain the silvered appearance