Just got my MkIII Compass back from Trademark London

[RyMoeller]

Please accept my apologies for resurrecting an such an old thread (especially for the most selfish of reasons) but being as this is the most comprehensive knowledge base for British Mk III compasses it would be foolish to start anywhere but here!

I'm in the process of breaking down a 1943 CKC MkIII prismatic compass for the purpose of restoring it to factory specifications. I've not done a compass restoration before but have tried my hand at many Swiss watches over the past year and a half and have confidence I'm up for the task provided a little guidance is in the offering.



I've broken down the above compass to most of it's constituent parts but am a bit flummoxed as to how the slide for the prism lens comes apart. The slide is secured behind a small sheet metal square with two small screws. When the screws are removed the square can move up and down a small amount but cannot be removed from the slide bracket as it's engaged in a track and cannot be moved either up or down enough to exit the track before it collides with the prism hinge or the bottom of the slide assembly.



I certainly don't want to force things and break an unreplaceable part so anyone who might have an interest in this thread and perhaps some previous experience working with MkIII compasses, I could sure use the help!

Thanks in advance for any assistance you may have to offer. I've read through every page of this thread before begining my work due to the knowledge the membership has on offer.

Also, if you are interested in reviewing the images of the restoration I've uploaded them to my public Dropbox folder here. I appreciate any feedback positive, negative, or otherwise (but hopefully constructive) as I progress.

[Badger]

With thanks to Advisory Panel member Peter Laidler, a new article has been added to the Technical Articles for Milsurp Collectors and Re-loaders (click here).

COMPASS, PRISMATIC, Mk3 (by Peter Laidler) (click here)

Article Extract .....

There has been a bit of interest on this forum about these prismatic compasses and the variations that have emerged since they were introduced in……….., well, whenever it was, they seem to have been around since, well, forever! Certainly since my time in the Army, first learning to read a map and compass as a Cadet at school in the early 60’s. They’re of some significance to the Lee Enfield story because the compass was a supplementary issue alongside the equally important binoculars and wristwatch for the snipers. While they’ve all changed slightly, they’re still very similar …... article continues in link shown above .....

(Click PIC to Enlarge)(Click PIC to Enlarge)

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Peter has added a personal request in regards to this article.

Note: If you have any questions or don’t understand something or my instructions are ambiguous then please ask on the forum and NOT by PM (Private Message). That way everyone will get the benefit of the question and answer.

Regards,
Doug

[Peter Laidler]

If you bend that small sprung plate - the plate you speak of, held with 2x screws - a slight amount it will rotate out of the slots. Don't worry about it because it';s sprung material and it'll go back to shape. It will also have to be sprung away to replace it. The screws will hold it all back together afterwards. If you really need another sprung plate for the cost of the postage, let me know.

What are you going to use as the liquid damping medium?

[RyMoeller]

If you bend that small sprung plate - the plate you speak of, held with 2x screws - a slight amount it will rotate out of the slots. Don't worry about it because it';s sprung material and it'll go back to shape. It will also have to be sprung away to replace it. The screws will hold it all back together afterwards. If you really need another sprung plate for the cost of the postage, let me know.

What are you going to use as the liquid damping medium?

Thanks for the follow-up guys! I did manage to get the spring plate removed after biting the bullet and giving it a little bit of a bend. It's just a bit of copper and when it came out, it did so without any damage whatsoever.

I'm going to use purified kerosene as the dampening fluid. The kerosene seems to agree with the printing on the compass card as I used it as the medium for cleaning the card without any damage occurring. The card had some rust staining on it which was removed fairly easily with a soft artist's paintbrush. This work was performed while the card was submerged in kerosene though as I didn't want to get any radium dust floating around the workspace.

Please accept my apologies for the broken image links in my earlier post. Image hosting always seems to be a struggle (for me) when it comes to posting in an new forum. You should be able to follow the progress via the link to my public DropBox folder though (see earlier post).

Thanks again for the help. The project is coming along nicely and much of the credit goes to data found in this forum.

[Gedrog]

Apologies wrong heading it should read Spares for MKIII

Hi Guys new to this forum I registered here to be able to read all the guides and watched the vidoe and several other forums on these MKIII compass and now I have a questions questions that I don't see mentioned anywhere.

Before I disassemble it and attempt the accuracy of what Paul is mentioning

The bowl sealing ring or gasket does anyone know of a replacement supply that has these readily available or a part number of an B-profile o'ring gasket?

What dimensions are the fibre washer?

Paul mentions tritium lights but these seems to stick on what have other people been using to restore the lights on the compass?

I have been looking at restoring an interesting MKIII, it was manufactured in 1939 and it has three names scratched into the lid so I can only assume that these were issued to various troops. I looking to trace its history and restore it. Anyone know how I can find out from MOD records who were issued the compass. From there it will be a case of tracing the troops service records.

[RyMoeller]

Apologies wrong heading it should read Spares for MKIII

Hi Guys new to this forum I registered here to be able to read all the guides and watched the vidoe and several other forums on these MKIII compass and now I have a questions questions that I don't see mentioned anywhere.

Before I disassemble it and attempt the accuracy of what Paul is mentioning

The bowl sealing ring or gasket does anyone know of a replacement supply that has these readily available or a part number of an B-profile o'ring gasket?

What dimensions are the fibre washer?

Paul mentions tritium lights but these seems to stick on what have other people been using to restore the lights on the compass?

I have been looking at restoring an interesting MKIII, it was manufactured in 1939 and it has three names scratched into the lid so I can only assume that these were issued to various troops. I looking to trace its history and restore it. Anyone know how I can find out from MOD records who were issued the compass. From there it will be a case of tracing the troops service records.

I'm sure Peter will be able to supply better answers to your question but here's my stab at them:

Regarding the o-ring, I've not found the profile Paul refers to in his post but I'm sure they are out there somewhere. You can try contacting Paul via his website but after reading through his disclaimers it seemed he might not be too receptive to such inquiries. I've decided to go my own route and have sourced some Fluorosilicone o-rings which have a diameter of 39mm. I haven't filled the bowl yet as I discovered one of the holes for the retaining screws was stripped out and will need to be tapped so I cannot yet say whether a regular o-ring will work.

I measured up the fiber washer that came from the bowl and it's 5mm OD, 3mm ID, and .75mm thickness.

Tritium seems to be the way to go since the tritium lights will glow without recharging. I've used both luminous powder and tritium tubes in my repair but I think you can go either way.

Unfortunately I cannot help with MOD inquiries as I'm a Yank(ee) and have no idea how one gets such information from the MOD. Perhaps this is another question that Peter can help with though.

Good luck with your project!

[Peter Laidler]

Use a standard neoprene O ring as the seal but due to some different tolerances between the bowls you MIGHJT have to use an O ring below the glass and one ABOVE the glass. THEN bring the ring down using the 8 screws. We were taught a special sequence of tightening. Here goes. 12o'clock/1st screw down to finger tight, miss two screws, then 4th screw, miss two then 7th screw, miss two next screw and so on slowly tightening down as you go around. Like tightening up a cylinder head the CORRECT way. I've never done i and we certainly wouldn't be allowed to do it in the workshops, but you could try a small suitable O ring for the sealing screw.

Pass no comment on the illuminating but tritium is the way to go. You will never find out who used your compass unless you had an Army number to match

[Gedrog]

Thanks Peter and RayMeoller

Thanks for the information guys really appreciate it, so a few more questions
What thickness O-Ring do you guys use?
I managed to locate a source for D-Ring seals, which I saw mentioned on another site although they are not really commercially readily available. D-ring Seals | Rubber D Rings | Precision Polymer Engineering any thoughts?
I have tried to locate tritium lights, readily available for instruments for commercial purchase, however I have had no success, this company sells them but it isn't like a shopping cart situation I haven't ordered any as I suspect they only deal in bulk orders. Light Source | BETA Light Anyone else have a better source? Otherwise I was thinking of just using this mixed with a decent lacquer
SFXC® Glow in the Dark Photoluminescent Pigments 100g - 10 Hour Glow Time - High Grade Strontium Aluminate: Amazon.co.uk: Kitchen Home
I found this and and thought bargain but after I got it its stipulates that direct sunlight contact will cause it to go yellow so testing a few samples at the moment
2 x Pratley Kraftex Pratligo Adhesive Epoxy Craft Seal 200ml 96102 New Lacquer Varnish Sealer: Amazon.co.uk: Kitchen Home
I mixed the two together to make a thick paste and applied to a couple of corks and will then test them in Isopropyl and kerosene to evaluate the effects plus long term exposure to the sun.
But if anyone has a better solution I am all ears

[Gedrog]

I have been trying to optically align the compass by using some technology
I have a DSLR Nikon D3200 a £16 copy stand (not very stable but I try to align everything as level as I can ) and a £6 Macro lens adapter I use a free app called DSLR Dashboard so you get the picture.
I align the needle that points in from the case part with the glass
This is a decommissioned Stanley G150 I just received so I can see the issue of getting it aligned the one with the bubble is one I have now used this alignment method on but I am not sure if I am doing it correct maybe the experts can advise if I am doing it right. ( THis is after spending overnight in the fridge, fridge before there was no bubble so will refill and overnight again.
Attachment 86484

[Peter Laidler]

I really don't know what you're trying to do but one thing I can tell you is that it's no use doing or trying to do anything with a bubbled compass. Stop faffing about trying to find the D seals. Just use neoprene O rings. One below and if necessary, 1 above the glass then tighten the bezel down equally over 4 or 5 rotations of the bowl. That's what we've been doing ever since I remember