Bofors 40mm gun in brass

janos · Apr 30, 2026

I need some change from working soooo much in timber, so here is a different project. I bought a 1:16 kit of a 40mm Bofors gun on eBay - part CNC turned and etched brass, part white plastic (I assume 3D print, but they might be just simple molds). The idea is to make it all brass, so I am re-building the plastic parts from brass and going to use the originally brass parts too. For turning I am using my Unimat 3 lathe, the mill is a Proxxon Mf70 (I can't find it listed now, so it might have been discontinued), for cutting I use my Proxxon band saw, and the disk sander is also Proxxon - and obviously different hand tools too. The photos show an intermittent phase, some parts are already done, they just need to be assembled, some are still to be made. Some parts are made of solid brass (flat, rod, plate), turned, milled and filed, some just as sheet metal parts. For assembly I tried and failed hard soldering (either the paste I recently bought was off or the heating was not right) so, strangely enough, I am using superglue and/or epoxy. Turning was fun as the material I had was partially H59 quality, which has good machinability, but partially something else which was quite difficult to turn. At milling I managed to brake a few 1mm bits so at the end I also used a 15mm dia 1mm thick saw blade in my Proxxon hand drill.
The situation is as shown on the pictures - the first one shows the original parts, the second the brass pieces already made, but not assembled yet. In some cases I managed to achieve nice tight tolerances, in others there are nasty patches.
So far so good (the hours aren't counted). Some problems are successfully solved (with some errors which I will not show of course ):= ), but there are still some challenging parts ahead, ie. the chairs for which I have ideas, but not proven yet.
Some more pictures will come later as I am proceeding.
Janos

RichardG · Apr 30, 2026

They look like quality parts.

Roger Pellett · Apr 30, 2026

Were your 1mm milling cutters carbide? If so see if you can buy some HSS (high speed steel ones). They will easily cut any nonferrous material. The carbide ones shatter if you breathe on them.

Roger

Bryian · Apr 30, 2026

That’s an interesting project Janos. I’m thinking about something like this myself.

Woodpecker · Apr 30, 2026

I used the same kit on my 1/16 scale PT boat. It's a nice setup

janos · Wednesday at 11:47 PM

Just showing the current state, with 3 'subassemblies', and their original equivalent in plastic and CNC aluminium.
This was the 'easy' part, what comes now will be more challenging for me, having done no similar etched metal projects. Still contemplating whether glueing will do in this case or I have to try something else, ie. soft soldering.
More pictures will follow.
János

Bryian · Wednesday at 11:50 PM

You have motivated me into purchasing a similar gun kit.

janos · Wednesday at 11:56 PM

I realised that I unintentionally mixed up a few pictures, so here are a few more.
János

janos · Thursday at 12:43 AM

Bryian said:
You have motivated me into purchasing a similar gun kit.

Hi Bryian,
You will need a few types of brass - round, flat, plate - and a number of milling bits! It is not a cheap project - the brass, what I had to buy additionally (having a few rounds and plates already) cost about the same price as the kit itself. Just saying.
Before I purchased the kit (a good year ago) I contacted the seller whether he can send me a kit with brass cannon barrel. He answered 'yes, of course' - and sent me the original kit content anyhow. But I am beyond this point already.
János