Category: <span>T800 Arm</span>

Well, I got so engrossed in completing this project that I didn’t update the blog for quite some time. I’m now going back and “filling in the gaps” with the build info. I’ll start by wrapping it up with the final summary and pictures.

I’m very proud of how everything turned out, especially since when I started I had little more than some metal and a saber saw. A lot of things were built along the way and every one of them was worth it since I learned so much. This project was one long education.

The final arm is fully articulated and I finished a acrylic display for it with some custom lighting. It took approximately two years of spare time from start to finish. In hindsight that seems extraordinarily fast when I include everything else that was built to help the process, not the least of which was my custom written CNC software & software (see the my blog section on MillDroid).


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4: Terminator T800 Hand - Metal Build

Now we’re getting serious. I have spent about two years tooling up for this build and now I’m making real parts.

I’ll start with the three middle fingers bones. These are similar enough to be machines together and should save some time on tool changes and holding.

I started by rough cutting three bars of 3/4 6061 Aluminum on the bandsaw then truing them up on the mill with a carbide facemill.IMG_0008

One side of each of these phalanges gets milled down a bit. This makes it a bit of a chore to hold in a chuck because they are more difficult to center….so i use a four-jaw independent chuck.


I don’t have a lathe so I planned to mount my rotary table as a fourth axis and (slowly) mill out the center of the stock to create the “bar-bell” shape of the phalanges. I wrote a custom tool for my MillDroid code that makes setup simple and mills each one in about 40 minutes. A Lathe would undoubtedly be faster, but I don’t think i would want to subject a small mill to the interrupted cutting of taking a square piece of stock down to a cylinder….that’s a lot of abuse to the hardware.


The pieces moves past the 1/2″ end mill left and right, rotating the A axis every pass by several degrees.



Three barbells later! Good finish on the cylindrical parts is achieved with a quick pass of wet sandpaper grades 360-500-1000-1500-2000 in increasing order before I remove them from the rotary table chuck.

I wrote a Slotting custom tool for MillDroid to cut the slots that run through the core of the cylinder in the barbells.

Holding these odd-shaped parts securely for the next cutting operation required a bit of R&D. I built a jig for my tooling plate to keep the parts centered between two aluminum plates then clamped them down with an aluminum bar. The offset side it lifter with a metal shim to keep the whole thing square.


Now I could use a carbide flycutter to cut away the ends into the required L-shapes.


4: Terminator T800 Hand - Metal Build

After doing my research on the Terminator T800 hand I started building some of the “bones” in plastic and resin. If this all worked out well I would proceed with the complete hand.

All the “bones” in the T800 arm are rod stock in diameters that are impossible to purchase. I then went looking for items that were the proper diameter from which I would then cast resin duplicates. AAA batteries, and X-Acto handle, a mechanical pencil and a few others were all tubes in the diameters I needed. I cast silicone rubber molds from these and resin casts were struck. I then sanded down the resin casts to make half and quarter round versions and made rubber molds from these for new casts. After about two weeks I had several quarter, half and full round stocks in the various diameters for the bones.

I then laminated various thicknesses of styrene stock together to build sheet stock in the sizes I would need for the “knuckles”. I laminated a bit thicker than the actual piece then wet sanded down to the true sizes. Several sanding passes to round off corners to the proper radii resulted in some very accurate knuckles.

At this point I experimented with CA glue and epoxies to cement and fillet the bones to the knuckles and test a prototype. No pulleys or non-structural details at this point.

Although it was very cool to see the structure and shape coming together I felt that the resin/glue was a bit flimsy. I had experimented a bit with adding glass fiber to the resin casts but it didn’t help much. I was also concerned that painting the hand in metallic would be even more difficult because of the moving parts. I began reconsidering the medium and started thinking about metal.

I already own a full compliment of woodworking tools but metalworking would require an entirely different setup. I spent about two months researching and talking online to people and came to the conclusion that I would need (at minimum) a lathe and a mill. I looked into Chinese mini-mills and several others and settled on a Sherline. Small enough for what I’m working on and expandable to within reason it seemed like a good setup for this and other projects. I’m also planning on designing my own encoder readers and software for measurement before I make it CNC compatible. Therefore the T800 arm will be on hold for a bit as I tool up for metalworking.

2: Terminator T800 Hand - Resin & Plastic Attempt

I’ve wanted to build a Terminator T-800 arm for some time but couldn’t decide on the medium.

Machining the entire thing from Aluminum stock would be very cool but metalworking is not my specialty. A metal mill and lathe would be required.

I considered machining the parts from machinable wax then casting in resin. Since there are no duplicates anywhere in the arm casting wouldn’t be efficient. Casting is ideal for multiple parts that are identical so it seemed like overkill in this case.

I decided to approach the project as a buildup in styrene and resin. First I’d do a prototype of one phalanx of the index finger of the hand. This would allow me to test the strength of the build and the epoxy & glues I’d be using.

Since the project required some drilling into very small pieces I would need a new xy-table/vise for my drill press to accurately position parts. I did a lot of research and the general consensus was that almost all those available are from China and they suck. Online discussions led me to believe that the only way to get a decent xy-table/vise was to take one of these and fix it. I found one at Harbor Freight that had the basic capabilities. See my blog posting about getting the vise up to caliber.

New drill press centering jig, check. Fresh orders of silicone rubber, resins, sheet styrene, epoxies on the way.

I found some decent blueprints on the internet that someone had made from the actual movies prop and some very good reference photos.

T800 Arm

I’ve wanted to build a Terminator T-800 arm for some time but couldn’t decide on the medium.

I considered machining the parts from machinable wax then casting in resin. Since there are no duplicates anywhere in the arm casting wouldn’t be efficient. Casting is ideal for multiple parts that are identical so it seemed like overkill in this case.

I originally decided to approach the project as a buildup in styrene and resin. First I’d do a prototype of one phalanx of the index finger of the hand. This would allow me to test the strength of the build and the epoxy & glues I’d be using.

I found someone on the internet that had had access to the original Terminator props and precisely measured them, transferring it all into very accurate blueprints. Nearly 60 pages of them.

I started the research and development for the plastic version in October of 2012.

I’ve broken the project blog into several categories based upon my attempted approaches.

Attempt One-T800 in Plastics was in plastics, which I abandoned after about a month of work. It wasn’t giving me the strength or heavy metallic feel I was after. I though metalworking would be much better but had no metalworking experience.

I decided to learn metalworking. That single sentence contains a LOT of work and about a year and a half of R&D learning and tooling up to be able to do it.

Attempt Two-T800 Hand Metal Prototype was practice–I learned CNC machining and wrote my own CNC Milling application….mainly because I though that what was commercially available was buggy and sucked. For details on that adventure, see my blog entry on MillDroid.

Most of the Shop projects on this blog are a result of the learning experience I spent on the T800 hand. Learning techniques, building my own tooling, restoring old metal tools that I could use. An expert metal worker could probable have done the hand in a week; I had to learn and build everything along the way. These distractions, while time consuming, helped me with the techniques I would need as I built the hand. I’m nothing if not very patient.

Attempt Three-T800 Metal Hand is my true build of the hand using all the tools and techniques I’ve learned over the last year and a half. Now I have to complete it without any new distractions or new tools 🙂


1: Terminator T800 Hand - Introduction

After purchasing my Sherline Mill and customizing it to stepper motors and full CNC I spent a few months playing with scraps and learning some metal working techniques. What a different world from woodworking!

I used the ‘standard’ Mach3 software to control the mill, but have continuously found myself despising the software. I’m certain that when it was written it was the top of the heap.

However, this software is buggy as hell. It crashes a LOT. Many of the ‘features’ are either beta and never finished, or assumed to work and never tests. It handles the basics fine–give it G-code and it will run–but I really wanted to use it’s Visual Basic capabilities to program my parts manually. The VB interface (which isn’t really VB but is actually something called Cypress Basic) is also very buggy. I think it was patched into the code to claim VB capability but never truly debugged entirely. When I inquired only of Mach3 experts about some issues I was told I “wasn’t using Mach3 the way it was intended”. That may be so, but I was only doing things the software claimed it could do. If it crashed with just a little pushing what good was it?

It took a LOT of time to make the code work and I still see a lot of Mach3 crashes. The company that now owns the ancient Mach3 code base has been claiming a new version will be out any day for the last few years….I’m thinking they had no idea what they were getting into with that project. They’ve also said that the new code will no longer support VB scripting, chosing LUA as it’s new script language. I have nothing against alternative scripting languages, but LUA?? In twenty-five years of programming I’ve only seen one other application that used LUA and even they switched to Python after a few years. This is what happens when programmers make decisions that should be made by users. What to they say about eating your own dog food….?

I’ve been giving serious consideration to writing my own Mill controller. I don’t think I’d even use G-code as a base. It seems like something that could use an entirely new approach and it would be an interesting project. Right now I’m putting it off until I get some more chips made……

A few practice pieces from 6061 aluminum…..I have a local metal working supply shop that has a large selection of end mills in bins for a couple bucks each. It’s a great local resource and let’s me avoid shipping costs every time I need a simple tool. Need a 3/8″ double-sided 2 fluted high speed steel end mill? They’ve got 50 in stock for $3.00 each. At those prices you don’t feel bad experimenting and breaking a few end mills.

I’ve been making some parallels from hot rolled steel but doing most of my cutting with 6061 aluminum. I really like the aluminum better and think it will be a better material for the T800 hand. The Sherline Mill is a very nice piece of hardware. The main thing it is missing are covers for it’s ways, but that isn’t fatal. I figure that by the time I wear them out I’ll want to build a larger mill from scratch.

First T800 phalanges for a single finger. Lots of metal removal and some operations that would probably have been faster on a lathe but I figured out a way to do them on my CNC rotary table on the mill. Takes longer but worked very well once I figured out the math and code.

I purchases a vibratory tumbler with the intention of polishing the finished pieces. Through some trial and error I found that Ceramic media left the Aluminum with a black coating (Aluminum Oxide, perhaps?) After some experimenting I found that tumbling in Plastic Pyramid media for 2 days, then walnut shells embedded with red rough for 8 hours produced a nice polished chrome-like appearance. Too long in the pyramids caused the edges of the metal to “round” more than I wanted.

The quest for walnut media was interesting. Online suppliers wanted $50 for small quantities (several pounds) of crushed walnut shell media. An online metalworker suggested to me looking in a pet store for Amphibian/Lizard Litter used to line the cages of pets. Sure enough, they had twenty pound bags of the stuff (pure ground walnut shells) for $8.00!

The Red Rough I added to the walnut media was suggested online…..that stuff is messy. It sticks to everything including your hands. I’m going to try some tests without it and see if the difference is noticeable.

First programming lines, then block removal, then arcs, then slots….I practiced some of the basics. I wrote everything in VB/Cypress Basic and it generated the G-Code that ran in Mach3. I put a lot of error correction into the VB to catch Mach3 Exceptions.

Through the combination of the rotary table and the mill I’ve managed to avoid purchasing a lathe. It would definitely be faster to do some of these cuts but I really like the fact that I can do all the setups on the mill.

After a few weeks of practice I’ve started milling actual parts. I’m actually starting to get the hang of this metal stuff…..

Now I’m ready to begin doing finish parts.

3: Terminator T800 - Metal Prototype Attempt