Instructables

Your First Lathe Project: The M40 Grenade from "Aliens"

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This is an excellent starter project for the metal lathe; it requires several different operations, requires a minimal set of tooling, it can be done in lightweight 'free machining" aluminium, and aside from a couple of key places accuracy to within a thousandth of an inch is not required.



Materials needed;

1" Aluminium round bar (2011 T3 is a good choice for this)
3/8" Aluminium round bar
1/4" Brass round bar (I used C360 free machining brass)

You only need a foot or two of each of these (get enough for errors!) I bought mine at OnlineMetals.com, which I have found cheap and fast to order from. Since you are turning all of this stock down anyways, you can make do with anything that is of at least the above dimensions.

5/16" x 1" compression spring.  (I used a Servalite #135U bought at Orchard Supply Hardware.)



Tools needed:

Right-hand turning tool, medium straight knurl, parting tool -- I'll discuss the tooling more within the Instructable.

Oh, yes; and a lathe.
 
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Step 1: Don't Worry, I Have a Plan

The first step for any replica prop is to do the research, and draw up accurate plans.

The M41A Pulse Rifle, as created for the James Cameron classic action/SF film Aliens, is one of the top ten recognizable and emblematic weapons of the genre. Canonically, it fires 10x24 caseless armor-piercing bullets and 30mm rifle grenades in an over-and-under configuration. Only the M40 HEDP grenade is seen in the film, both as fired from the Pulse Rifle, and in a secondary role as a classic "push button, wait four seconds" hand grenade.

(Actually, it is hard to tell in the lighting of the scene, but at least one green-cap variant shows up in the Operations Room scene. "Don't touch that, honey; it's dangerous.")

According to the movie's armorer Simon Atherton, speaking in the DVD commentary, the original grenade props were manufactured from 12-gauge snap caps; soft aluminium or plastic dummy rounds used for training.

After some poking around at the Aliens Legacy forum and similar, I chose to make my own plans more-or-less from scratch. Which is a subject for another Instructable! The plans I made, I freely give back to the community.
blue-ice3 months ago

Nice job. I love your attention to detail, and I hope to try out this project someday. Your descriptions are easy to follow and precise, so I think I will have no issues when I try to make this.

I thought the coolest part was how the aluminum insert blended in perfectly after it was faced on the lathe. That was very neat- I expected some sort of line or gap, but there was none. Very, very cool :)

nomuse (author)  blue-ice3 months ago
MOST of the time!

I did have one where my drill bit wanted to wander. It chewed up the hole a bit, and I ended up with a visible gap. Could have probably taken more of a bite with the face but I was doing a set of four at once I wanted to be as close to identical as possible.

Getting the plug sized right is a huge pain. My average is three plugs cut for every finished grenade. Only one so far was so loose I had to drill it out, at least.

Gelfling64 months ago

Sorry, when I saw this picture on the EMAIL feed, with the cap, All I could think of right then was...... Nitro-9... (The Only can of deodorant that registers 9 on the Richter scale!) (--Doctor Who, Ace)

NPTT134 months ago

That was absolutely awesome brother. And I was thinking man this guy talks like he has previous military experience. If its safe to be presumptuous here I would say you are prior services, maybe even more specifically army. If not you are definatly talented enough to get in on the GOV work crew with this kind of attention to detail.

nomuse (author)  NPTT134 months ago

Yup. That was twenty years ago, but I was Army, twelve boom-boom to be precise, plus got to wear the red beanie and jump out of perfectly good airplanes while they was still in the air.

smj564 months ago

Wow. Awesome Project. I am a high school 'shop' teacher. I am always looking for machine lathe projects. Might have to make this first before I turn my students loose on it. That 45deg. knurling looks tricky. Thanks

nomuse (author)  smj564 months ago
Thanks!

That knurl was scary all right, and with two tries I still haven't gotten it quite right. Might be safer to flip first and knurl towards the headstock, at that...
Honus4 months ago

Outstanding work!

KEUrban4 months ago

Nicely written and documented.