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Mk3 ZuS40 Attachment


Well-Known Member
Im told that this one is a zinc version of the deadly booby-trap employed in some of the german bombs.
Attached to a 17 or a 38,please correct me if im wrong(as usual!)This example is missing its wire spring im told but its not bad for my first one.
Its currently undergoing a `silkopen` oil bath at the moment to free up those catches.
You can see the stamps on the casing though after its had a good clean up.



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Hi Waff how's this project going. I have been reading up on Bomb fuze's and these look an interesting piece, even better with a 17 clockwork fuze added. Are these ZuS40s rare and what do they go for.
Hi Chris,The catches dont seem to budge even after 6 weeks in pen-oil.
I think certain ones are rare due to what they are made from?.
I think Fuzeman will be able to add to this one?
As for price,ive hopefully got a better one of this from the US if the seller gets back in touch with me?
My one cost around 50 if i remember rightly??



Try soaking this is some automatic trans fluid (dextron) and add a wee bit of heat.

I work on rusty old Vespa scooters all day long and I find this works great. The ATF realy works its way in once you put some gentle heat on the work. I will also soften up any rust/corrosion that may be jamming the works....also the heat will draw the oil into place that just a soak can get to.

What I do is soak the work for a week or so then heat it and resoak. Then I hit it with some heat and gently start working the part that is seized once it starts to move I use compressed air to blow out any loose rust etc. Then resoak and heat 9 times out of 10 this works but it a patient mans game as it can take some time.

Let me know how it goes

They say that Kroil is the best stuff, it comes from the US. Anyone used it.
Hi paul
Thats the correct information thats the 3 rd version of the zus40 , the mark 2 was in plastic , but often failed , in operation due to the plastic being damaged, those recently been offered were all cracked.
Version 1 which differed in design , in only having two knife edges as against the other two versions , that had 3.
Thanks for the information chaps.
Im not really set up in the garage properly for the heat treatment yet but i will take the idea onboard for when i get sorted in there.


They say that Kroil is the best stuff, it comes from the US. Anyone used it.


I stumbled across your site while looking for a ZUS40 picture.

I know almost nothing of ordinance; but far more than I wish I did about dealing with rusty parts, mostly on cars. I grew up in the "Salt Belt" around the Great Lakes.

Kroll, from Kano Labs is the best penetrating oil I have ever found. I was introduced to it by a now-deceased machinist friend, who was in McArthur's Occupation Forces in Tokyo. [Ah ha, a tie-in to your world.]

If you can get it in the UK; I highly recommend it. It stinks, but it's worth it.
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Be exceptionally carefull when using heat on it as it is made of MAZAK. Most of the Mazak alloys have a sub 400 deg/c melting point and due to its small size and shape you could easily exceed that. Try boiling it in water, olive oil (or something not too flammable).

"A wise man learns from other peoples mistakes"



luk!!!! ElAZ-17 A mit ZusZ. 40


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Thanks boys for the tips.
yes,i could imagine these melting under heat and that`s why they are still in soak oil!


lovely fuze pictured there Harry!


Hi Waff

Both my zus40s were locked solid and managed to work them all free
just using plus gas and a pair of model makers thin nose pliers.

so long as you can grip just the claw itself and gently work it in the direction that it pivots on then i think you might be in luck.

There are also sprung loaded pins which sit under the claw on the inside of the body where the gaine slides into,and those proved to be prety tricky
to get springing again with only partial success.

I did mine without heat knowing those springs were there so that if i did get them free the heat would not have knocked the temper out of them.

Best Phil
Another tip I was taught. If you have an ultrasonic cleaner available; take a beaker, put your part into it, pour in enough Kroil to immerse it, and set the beaker in the cleaner's bath. [Obviously, use a tall enough beaker so that the beaker is not flooded.]

This will clean and free up many stuck parts...

I do have a Zus40 question: What did the German munitions troops do if they needed to disarm one? Was there some secret revealed after the war?
Good question with the dis-arming a ZuS40.
As far as im aware,the whole bomb was blown by BD staff?
I assume any of these in `captivity` are examples found in stores/dumps or even the factories after the war?