Category: <span>Terminator T800 Arm Scratchbuild</span>

The final arm in it’s display case home. Several hundred parts in total and almost two years from conception to completion. In addition to the arm, I built and completed my wood and metal shop and gained quite a few new tools. I also restored quite a few as well, and every one was a learning experience. I also wrote quite a bit of custom software for the mill, lathe, and other items for the shop. I’m mighty proud of what I created and learned along the way considering that when I started I had few metal-working tools beyond a hacksaw.

8-Final Work

Originally I planned to make a display case identical to the one that Miles Dyson admires in the vault Terminator 2. It looked as though it had been made from metal and glass, but I was unable to machine a large enough piece of metal to match it for the base, so I decided to go with wood and plexiglass.

Some 1/8″ and 1/4′ plywood would serve as the foundations for the base and lid. Plywood ribs added some structural stability to the cylinder-like top and bottom.

Epoxy was used to glue all the wooded ribs and rings into the rough shape.

Once the top and bottom cores had dried, I wrapped both pieces with 1/64″ plywood bent to the cylindrical shape. Again, epoxy was used to hold this skin onto the ribs.

After some sanding, I used wood filler to fill in any large gaps and seams.

Hardware of blind nuts was epoxied into place and then reinforced with plywood. Then the entire interior was reinforced with fiberglass cloth and epoxy for strength. This gave the once-flimsy 1/64″ outer plywood skin a metal-like solidity.

There were actually four wooden pieces to the case: From left to right the base, the shoulder for the top, the shoulder for the bottom with holes for the arm cabling and the top. The smaller holes in the shoulders are for 10 small LED spotlights that would iluminate the arm from within the case.

I decided to engrave a nameplate for the arm using my mill and some engraving bits. Once again, my MillDroid software provided the layout and CNC control.

I purchased a 10-inch diameter, 36″ length of 1/4″ plexiglass tubing. After a few practice cuts I fire-glazed the edges to get a clean edge. This is when I goofed–I overheated the edge, and caused one end of the tube to shrink by about a 1/4″ in the overall diameter. It affects the outer three inches of the tube, ruining the piece and forcing me to purchase a second tube and start over. I was much more cautious and the second tube came out perfect. It was a $60 mistake that bought me how quickly the heat of a torch can melt expensive plastics.

The two shoulder pieces are now painted and mounted to the top and bottom of the case. The finished wood pieces were finished with several coats of thinned wood filler, sanding sealer, then shellac with lots of fine sanding between each. A couple coats of enamel primer and three coats of nickel satin paint then three coats of satin clear coat. The shoulders where then wrapped with a 1/16″ inch layer of gray hard foam. This brought the shoulder diameter up to just slightly larger than the inner diameter of the plexiglass tube for a snug slip fit.

The case awaiting interior detailing and wiring. On the right you can see the $60 mistake I made on the first tube attempt. Ugh. Hope to find a use for is someday.

I didn’t take any pictures of the interior wiring. It consisted of a couple of 1/8″ power jacks (one for the top and once for the bottom) and some small LED “Projectors” that I machined from styrene and metal to emulate the look of the arm’s mechanics. I alternated blue and white LEDs to get a nice lighting arrangement on the metal of the arm.

7-Display Case

Assembly was hardly a start-to-finish process. I would test fit a group of pieces, say of a single finger, then pull it all apart and make adjustments. Something this was a bit of filing to make an axle a bit smoother. Sometimes it would involve polishing a piece a bit more or removing some burrs that were missing during finishing or tumbling. On average I would guess that everything was assembled at least 3-5 times each before dismantling it all before final assembly. I then literally ‘dunked’ all the pieces into an aluminum protective coating to prevent oxidation. Stainless steel parts were similarly protected by oiling or teflon lubricants. After a couple days hanging and drying final assembly could begin.

I used my Panavise to hold the palm plate and began attaching the skeletally completed fingers to the metacarpals. A bit of finessing for a good fit was necessary for each joint along with proper lubrication and remembering to add all the teflon washers I has made to reduce friction. If I had not been so concerned with matching the original arm construction, I would have probably made a change regarding the joints of all the moving parts. As they were originally made, the tightness of the cap screws of each joint determines how tight the joint actually is for movement–this is fundamentally a bad design and why I had to make certain I didn’t over-tighten the joints and bend the metal pieces and cause too much friction. A better design would have been to make some bronze or brass bearing sleeves for the interior of each joint that would prevent over tightening. As it was, I relied on red loc-tite for hold all the cap screws in their permanent positions and thus remained true to matching the original look.

More fingers being mounted, the thumb and all the interior pulleys awaiting cabling. The thumb pivots around the base of the wrist plate, consisting of a cable (for tightening the thumb joints) and a rotating sleeve around the cable (for rotation of the thumb). The orinal props thumb has some design limitations over a real thumb, but accuracy was everything for this project.

I used some tiny paint brushes to apply teflon lubricant and loc-tite where necessary. The areas for application were too small to get into with the bottles and applicators. I avoided silicone lubrication so I would not have any contamination issues with the aluminum protective finishes. Once you get silicone onto a project, it is almost impossible to clean it off short of scrubbing and soaking the part in acetone. Better to keep it out of the shop entirely unless absolutely necessary.

Muscle cables and sheaths being installed. I spent a good amount of time looking for stainless steel cabling stranded cabling that was strong enough and flexible enough to bend around the joints and pulleys yet look the proper diameter of that in the film. It turned out to be an impossible task for a couple of reasons. Cable that looked thick enough in the closeups of the arm could not have been flexible enough to use in the ‘moving arm’ that flexes at the end of Arnold’s arm in some scenes. The conclusion was that the two different scenes had two different props. Since I wanted visual accuracy over movability, I chose the thicker of the cabling choices. The joints could still be pulled and released somewhat, but it would never be as ‘animatable’ as the motion prop that was used in that scene. The sheathes for the cable tool nearly as long to locate. I found a company that made the sheaths for mountain bike brake cables that were encased in rubber. Underneath, they were a nice stainless steel (to help avoid rust) and looked perfect. Some interior lube and threading of the cables and I had my “muscles” ready to be threaded in and around all the pulleys’.

Ajusting the tension on the cables against the springs that were in all the pistons to achieve a nice ‘balanced’ look and feel took some tweaking, but it was really satisfying to be able to pull a cable from in the base of the forearm and finally see a finger flex and pivot. At this point it was starting to feel like a completed project.

A closeup of the fingertips

Here you can see the dual sheaths for controlling each finger at their bases. In this photo the cables are not yet threaded through the sheaths and pulleys, nor are the ‘palmer pistons’ installed on the empty lugs that would pull each finger down.

A closeup of the wrist plate, showing the three smaller ball joints at the end of the forearm pistons. The palmer piston are in place here, pushing against the palm to straighten each finger. All the finger cable sheaths continue down through the wrist plate and through the forearm to the elbow region. As the cable sheaths began to multiple I worried that the amount of parts in the forearm would be too dense to be contained in the allotted space and still allow movement and ‘good looks’. In the end it all fit. Barely.

Trying to crawl away towards Sarah Conner, methinks.

Here you can see some of the detail on the back of the hand and the side pistons for each finger. These spring-loaded pistons, along with a counter cable/sheath on the opposite side, cause the lateral side-to-side movement of each finger, similar to you you cam spread your singers apart.

Details of the base of each finger. The lateral cabling is not attached in this shot and one of the sheaths is not attached.

Details of the palmer pistons mounted to the lugs on each finger to push them into their straight positions. Cabling is present in this image.

Closeup of all the cable sheaths in place. You can see where, along with all the pistons, the area at the base of the wrist plate becomes quite congested with moving parts.

Forearm showing the three large pistons and ball joints for pivoting wrist movement. Lots of tiny set screws visible for adjusting and locking the springs and ball joint pieces in place.


As I generated more parts, the sheer number of pieces became difficult to track. While I could stamp some larger piece with alphanumeric stamps and a hammer for later identification, tiny pieces were more difficult to identify. Combined with the fact that some tiny parts existed as ten to twenty pieces that might look identical but have slightly different measurements each. Many times I would set something down, then need to come back and re-measure fifteen or twenty pieces to find the one I had misplaced. I started a ‘bagging’ system of tiny kitchen zip-lock bags, labeling them similarly until I had enough parts to group entire sections such as “index finger” or “thumb. After that I reorganized everything be group for final assembly.

The first ‘pass’ of organization into similar parts. The labels read like the table of contents of “Gray’s Anatomy” Volume 1.

As all the parts for individual fingers were completed, those associated parts could be unbaked and placed together.

At this point, smaller threaded parts could be made and cut to final lengths during test fittings. The tiny little pieces as set screws, as small as #2-64 size, which were quite the challenge to cut to length and then correct any threads that were ‘spoiled’ in the cutting process. I used a tiny set of jeweler’s files under a microscope for that work and made my own set of tiny hex drivers (because I was practicing knurling at the time) to work them. Springs could now be cut to size, having been made long in case of mistakes.

Forearm parts all being inventoried with the larger piston springs being adjusted for size. Small set screws for these would let me lock springs into proper position and allow for adjustment for proper tension.

Wrist, forearm and ‘elbow plate’ and associated parts after cleanup and organization.

A couple of fingers and their pulley, pins, end caps, teflon washers and phalanges.

From a distance it I sometimes can’t believe I kept it all straight for the duration of the project.

5-Part Layouts

So at this point I basically started over, having learned from my mistakes. I had finished assembly a complete finger as a prototype and felt confident I could machine all the rest of the parts. over the course of the next several months I did just that, refining my ‘MillDroid’ CNC software and building new tools along the way. Here are some of the highlights along the journey….

Without the ability to weld aluminum, sometimes I wasted a lot of metal. The carpals and metacarpals of the hand would have probably been more efficient to machine from separate pieces, but I pushed everything through as a single pice of metal whenever possible for strength and ease of assembly later.

Pieces such as this, while difficult to machine, were much stronger that if they have been separate pieces held together with a screw. Plus, being true to the original arm prop, if I didn’t see a screw holding it, that meant I tried my best to machine it as the original was, no matter how difficult.

I did do a very small amount of aluminum soldering. I was never happy about the strength of these joints, but again, wanted to stay true to the original.

The ‘palm plate’ or metacarpal plate served as the base of the hand like a wrist.

This plate was to have a very ‘organic’ shape with all curves. I probably could have written some CNC code for arcs, but being able to cut complex curves began to interest me and I was immediately sidetracked by the concept.

I detoured from the project for a few weeks to design and write some custom software that would allow me to draw bezier curves and output them directly to my MillDroid CNC application. This gave me yet another custom piece of software that I could enhance over the years whenever I felt the need. Of course, I could only blame myself if I found any bugs, but I can live with that. The curve editing application I wrote became almost a full fledges CAD/CAM app over time and I named it Pathfinder. You can find details on it on this blog under the Software/Pathfinder section.

Pathfinder’s first cuts. All you curve are belong to us.

A few dozen precise holes for all the metacarpals, cables and pulleys and we’re good to go!

As I made more pieces, a nightly ritual became filling my compound tumbler with media and lubricant, letting it run overnight, then a day or so later refining the tumbler media to finer and finer compounds to soften and polish the pieces. Tumbing metal is as much a science as an art, and a few times my tumbler ‘shook itself to pieces’ overnight, surprising me in the morning with a pile of media and timber parts on the floor of my shop. It’ a very time consuming operation (and messy) but interesting to try to master. Unfortunately I didn’t take many pictures during the tumbling process.

My grandfather used to say “experience is in the finger and the head” He nailed this project!

I set up a few jigs for holding pieces during ‘aluminum welding’ (closer to silver soldering, actually) to maintain the critical angles for pieces.

A LOT of work went into getting the ‘aluminum welding’ correct, maintaining the shape of the molten metal and keeping the shape proper. I was very pleased it worked out, because going into this part of the process I was very nervous about keeping everything accurate.

Hold still, damn you. Another of my crazy jigs made to hold things in place.

I would sometimes get hung up on ‘order of operations’, that is, should I drill certain holes first, risking them being off, or wait until something was in place. This was one of those times. I couldn’t drill the cabling holes until the pieces were in place in case the move a bit, so that meant doing all the drilling while working around all the already mounted metacarpals. It became quite the jigsaw puzzle of operations but always stayed interesting.

Some of the smaller parts to be made. This shows the progression from raw aluminum stock to a finished ‘lug’. This was one of several that would sever as mounting points for various ‘muscle cables’ or ‘muscle pistons’ on each of the fingers. It also involve learning about threading to make the mounting of the pieces nice and strong.

Ah, the pulleys. There were over a dozen tiny pulley required, around which all the ‘muscle cables’ would pull and flex. Since almost every one of these was a different size, I learned how to grind custom lathe tooling (the high-speed steel tool below the pencil). Another learning adventure that helped along the way.

These tiny little buggers are, for lack of a better term, joint washers. Again, they each had unique shapes and dimensions so were made individually. There were around 30 on the hand and were a lot of fun getting correct on the lathe.

These little servo horns were a challenger to make. Getting the curves to all line up and deciding on the order of operations took a bit of trial and error. I’m sure an experienced machinist would had taken one look and decided on the proper course of actions but I think I wasted a few pieces after discovering I should have done things in a different order. I learn more from my mistakes than from my successes.

I owned a 30 year old Craftsman drill press. Nothing really wrong with it, but to show it some love I made a large aluminum tooling table with lots of threaded holes for jigs. I also built a digital caliper into it and mounted the table on a large X/Y Vise that I cleaned up and made more accurate. Now the drill press was a more precise tool for larger drilling projects (see the blog entry for more details). That sidetracked me for a few days, but allowed me to use my small Sherline Vise to hold some of the smaller parts. These piston shafts were about an inch and a half long. Along the way I also invested in some sets of numbered, lettered and fractional drills and reamers. Every tool I’ve bought along the way makes me think how much easier things are with the proper tools and “why did I wait so long to buy this?”. Hindsight is a powerful thing.

A bunch of axels, all drilled out and ready to be internally threaded on the lathe and cut to length for each of the various knuckle joints. I made all of these from stainless steel since they would be fit into the aluminum finger bones and might bend under too much stress. The steel being about three times stronger than the same size aluminum would have been. At about 3/16″ in diameter, they would be pretty weak if made of aluminum with the centers drilled out as they were.

Each of the joints of the fingers relies on to things to move it. Looking at your hand, a finger can move laterally (left and right) by several degrees as well as curling up or extending. In the T800 hand, pistons loaded with springs are used to ‘push’ those movements in one direction, while ‘muscle cables’ are used to pull them in the opposite directions. Bu tightening or loosening two cables against the opposing two pistons, a finger gains a full two-axis of motion in four directions. I did a lot of searching to find stainless steel aircraft cable that was very thin, but flexible enough to go into sheathings and be ‘weaved’ around the various pulleys and joints in the fingers and hand. In the end, I purchases about six different diameters of stranded and solid cable and experimented until I like its operation. Then I made stainless steel end caps for the cables to prevent them from pulling from their lugs and cemented then with steel shavings in epoxy. I remember my grandfather used to file nails into dust then mix it into epoxy. It didn’t dawn on my what he was doing until decades later when I learned about JB Weld Epoxies.

I started to realize that it was difficult to find springs in the various diameters that I would need for the insides of the custom pistons I was making. I checked with a lot of hardware stores and someone online suggested I make my own. It had never occurred to me to make springs so I did some research into the metallurgy and heat treating process required. Turns out that many hardware stores already sell the proper steel wire (if you know exactly what you are after) and the wire is relatively cheap. That’s good because it takes some practice and trial and error. a couple hours to make a jig for my lathe so that I could wind the wires to the proper diameters.

Winding your own springs is a fascinating process to learn about. Figuring out the proper diameters and winding ‘ratios’ so that, when released, the springs are the correct size takes a lot of practice (and record keeping so you can remember how the heck you got it right once you do). It can also be an extremely dangerous endeavor, which isn’t obvious when you start. When you are winding steel cables (as in the picture above) it is easy to overlook exactly how much kinetic energy you are ‘storing’ into the metal coil. That energy is absolutely DYING to be released, and all it takes is a slip of the wire off the jig, or winding a bit too much, or forgetting tighten something properly. If that happens, that tiny piece of wire releases all the energy in an instant–causing it to rip or tear through anything nearby work that Indiana Jone’s bullwhip. Fortunately an online acquaintence with some experience with making springs warned me in advanced about this possibility. There are plenty of videos online showing how much damage a spring can do, and a lot of stories about 1/4″ springs slipping lose during creating and ripping someone’s throat out before they even knew it had happened. Armed with a healthy dose of caution, I only had a few minor mishaps for which I was a safe distance away and shielded by protective gear, but my equipment has some deep gouges from those incidents that will always be reminders for proper safety precautions.

Wrapping the springs in foil to prevent oxidation and then heat treating them in the oven at the proper temperatures and durations, then gradually cooling them for tempering took some trial and error as well but those processes are well documented in metallurgy books if you are willing to read up on it. Once removed from the oven and cooled keeping the spring oxygen free before oiling them up prevent quick flash rusting. It’s amazing how fast the steel spring would begin to turn reddish once out in the open air humidity. I learned this when lapping some of my steel pieced on wet sandpaper that they would flash rust during the summer months within minutes, so much so that I build a powered lapping table that allowed me to sand/polish metal underwater (see another blog entry on my shop pages for details). This had two benefits: The water continuously running over the parts as I lapped them washed away the grit and particles, preventing scratching an ‘lubricating’ the lapping, and the water kept the oxygen in our humid air from flash rusting the part in less than a minute. Once I removed items from the water I would immediately dry and clean them in acetone to remove any contaminents and apply one of either oil or wax depending on the part and its use. Camilia Oil is a favorite of mine for preventing was on steel tools that are exposed to air.

All those aluminum knucke joints rubbing against each other would scratch my finely polished pieces over time. I was thinking of making some thin bronze or brass washers but that would add up to visible gaps between the pieces that would differ from the original arm’s design too much for me to tolerate. So I came up with the idea of using very thin sheets of Teflon. Hey, if it is friction and stick resistant enough for your pots and pans, it’s good enough for the Terminator, right? After learning how difficult it is to hand-cut tine circles by hand I soldered up a small ‘punch’ from some brass tubing and block and sharpened the edges. Now I could would wack the press through the teflon sheet into a soft pice of pine and crank out several dozen tiny Teflon washers in a few minutes.

The wrist ball being turned on the lathe. Not having a true ball turning jig, I cut incremental notches to get the ball close to shape, then used files followed by progressively finer grits of wet sandpaper with aluminum cutting fluid. A final polish wrapped it up nicely.

Transferring the chuck with the ball joint over to my mill, I used a slotting end mill to carve out the slots for the pin that would align and allow a full range of motion.

Three smaller ball joints would be needed for the three main forearm pistons. These were bolted to the bottom of the wrist plate. Movement of those three spring loaded pistons cause the motion of the ball joint in the wrist allowing it to be quite flexible. These, like most of the pieces in the wrist were made from aluminum.

The final pieces of the wrist joint freshly cut and awaiting tumbling and polish. At the top of the image is the ‘head’ of the wrist ‘bone’. The original was most likely make from a small unidentified piston so I duplicated the measurements I took from various photos to get the scale of all the details. The curves were cut similarly to the forearm casing using my Pathfinder application to generate the final code for the rotary table on my mill.

The final wrist ball joint. The stainless steel pin allow movement laterally while the ball allows full rotation. A turned bronze center socket piece holds everything together and reduces any friction.

An thick aluminum tube would server and the foundation of the forearm and main ‘load-bearing’ element.

The forearm ‘ulna/radius’ bone was originally made from what appeared to be a hollow piston, cut and machined into the final shapes. I duplicated this from some aluminum tubing and machined it to shape on my mill and lathe. The wrist joint, a kind of combined two-axis joint mimicking the Scaphoid and Lunate bones of you wrist, was a couplex ball joint. I machined it from a two inch cylinder of aluminum, machining the ball and hollowing out the center for a bronze ‘axle’ for the fore/aft movement of the wrist. The ball action allowed for full rotation and lateral movement very similar to a real human wrist. This was a challenging piece to get accurate within it’s socket.

Having had a background in graphic commercial arts and spent a lot of time drawing the human figure, I had learned a lot of human anatomy. So keeping all the parts straight by their ‘human counterpart’ names became second nature. These muscle piston bases are a mix of your forearm flexors and extensors, controlling the movements of the wrist more then the elbow in the case of the Terminator’s arm. These would have large springs inside as ‘pushers’ against the pistons that they would contain, holding the wrist in a default position, but allowing it to be move about in any direction.

More tiny lugs awaiting cleanup and polishing before being attached to pistons.

Big parts pushing my tools to their limit. Or as Judd Nelson would say, “I can see you’re really pushing maximum density”

The forearm ‘shell’ was one of the largest pieces of the arm and really forced me to be creative when working within the smaller size envelope of my precision machining tools. Cutting up the large aluminum tube that would be used required a large wooden jib for my newly restored metal cutting bandsaw.

The forearm casing has a lot of precise detailing carved into the surfaces and a curved profile shape. It was too large for my lathe, so after the initial cutting and polishing of the tube, I held it in place with my rotary table’s chuck with the jaws reversed as to hold it from the inside of the tube.

The only piece large enough to fit your entire hand into
The jaws of the lathe chuck holding it from the inside

This would be a little precarious. Since the part was nearly four inches in diameter and several inches long, common sense told me that it really should be held tightly at both ends. Unfortunately I couldn’t come up with a good method with the tooling I possessed. Instead I decided to proceed very slowly and with very shallow depth of cut for all the operations on this piece as to not dislodge it from the chuck on the one end, nor make it displace and ruin all the work as it drifted off course.

I used some aluminum cutting lubricant and lots of compressed air to keep the chips clean. That, combines with nice a slow, shallow cuts worked very well. The complex curves were calculated with the Pathfinder curve cutting application I had written and I nailed it on the first try using a 1/8″ two fluted end mill on my mill. Mounting the rotary table with the chuck and workpiece at the very end of the mill’s X-axis gave me just barely enough room. If the piece had been an inch longer I wouldn’t have been able to do it.

I designed the rest of the etched details in my Milldroid application and again, used slow, shallow depth of cuts to machine out the rest of the slotted details into the surface of the forearm shell.

The final result. I was very pleased with it, not to mention a bit surprised that I only had to make one. I because of the large nature of the part I feel certain it would take two or three before I got it perfect.

The final shell, after some minor demurring, was polished with various reducing grits of aluminum wet and paper and aluminum polishing compounds to achieve a nice shine.

Here are some of the forearm pieces being test fitted to some of the hand elements. Better to know it is all going to fit together BEFORE I complete all the other parts, right?

Now that I have the processes down pat for fingers I could go back and start cranking out all the different phalanges. Almost every one of the bones in the hand is different enough to require individual machining. As I started losing track of which was which I had to come up with a labeling system for the parts, hence the tape labels and some of the dykem dye choice on the parts. The dyes helped me keep track of which surface still needed flycutting for maximum accuracy.

This give a good indication of the complexity involved in a single finger. These are all the parts, each custom made from washers to axels, in the index finger. Still missing from this photo are the custom springs, pistons and cabling. Approximately 30-35 parts per finger total.

It’s starting to look like a hand now. The main phalanges and metacarpals, lugs and fingertips ready for tumbling and polishing.

The first finger test assembled. The single Phillips screw and Cap Screws are the only parts that weren’t custom made. I used an off the shelf stainless screw for those of the same exact part used in the original arm. If it hadn’t been off the shelf on the original, you can bet I would have made them from scratch too. The fingertip on this one ended up being remade, as the surface finish was a little rough for my approval.

Some phalanges after coming out of the tumbling process. I used some small tumbler media of pyramids, just large enough to not get into the holes and damage the precise diameters I has drilled and reamed for the axels. After the pyramid media, I went with a finer media of ‘lizard bedding” from a pet store. This is a duplicate of tumbler media that you find for 1/10th the cost and is the same exact material. Thanks to some online experts who informed me about cheaper sources for tumbler media–that save a lot of money. The final tumbling was mixed with some red rough polishing compound that gave me this final rich luster. The final pieces transformed form an aluminum luster to an almost nickel-like sheen.

4-Part Builds

The closest I’d ever come to working metal was owning a vise and a hacksaw. So I had a lot to learn.

I spent a few months reading everything I could about it metal fabrication, milling, lathes, saws. While I owned a nice woodshop and had done a lot of woodworking, this required an entire different set of tools and discipline. Where most woodworking accuracies were around 1/32 of an inch, metalworking relied on accuracies of at least .001″, and in many cases for this project .0001″.

I decided to work in aluminum and steel for the majority of the arm construction. I started trying to cut pieces with crazily-rigged saber saw in a linear jig I fashioned to cut 1″ aluminum bars. What a waste of time that turned out to be, causing no end of frustration. More research told me that I needed a metal capable bandsaw. It turned out that someone I knew owned an old, 1950’s era saw that was perfect, but needed a ton of restoration. I took on the project and the details of that can be found in my blog section titled “Bandsaw Restoration”. Just like that, BOOM-a couple months went in that project!

I came back to the arm able to cut metal much more efficiently.

What used to take and hour now took minutes with a proper bandsaw. My hacksaw arm has never forgiven me.

My next purchase as a mill. I bought a Sherline 5400 manual mill and spent a few weeks learning and practicing, then started converting it to be CNC capable. I was using some off-the-shelf software (Mach 3) to control it with my own hardware circuitry and a Gecko G540 Controller/driver. I found myself frustrated with the antiquity of the Mach 3 Software and fell down a rabbit hole.

I’m certain that when it was written, Mach3 was at 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 programmatically. 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 saw a lot of Mach3 crashes. The company that now owns the ancient Mach3 code base has been claiming (as of this writing) 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, instead using LUA as it’s new script language. I have nothing against alternative scripting languages, but LUA?? In forty-some 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 end users. What to they say about having to eat your own dog food….?

Over the course of the next few months I abandoned the Mach 3 software and decided to write my own CNC software to control the Mill. For the details of THAT adventure, see my blog entry “MillDroid”. Once again, BANG!-a few months go by as I get that project off the ground.

By now I was getting anxious to start making chips….

A crazy attempt at using a mill to simulate a lathe. I don’t recommend it. I was trying to avoid having to spend the money on a lathe.

I could now do some simple machining, both manually and via CNC as the software I was writing began to take shape and become more robust.

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 its 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.

Let the chips fall where they may. A lot of cranking went into manually milling the first pieces.

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 picked up a Harbor Freight Tumbler to do some of the finishing of the 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 (a few 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.

A first metal knuckle attempt.

Without a lathe, I tried to be creative with my new mill, and succeeded at some things. Using a rotary table mounted 90 degrees to the spindle, I was able to write CNC code to mill the round finger bones. It was slow, but it worked!

Another hare-brained scheme to avoid buying a lathe

I can’t believe it worked as well as it did, but it was slow, taking hours in some cases. Not to mention how much time was lost if I screwed up a part. I called these finger bones ‘barbells’.

I started getting more productive once I made several jigs from aluminum to hold all these custom shapes, irregular parts. Even a single finger barbell may have looked symmetric, but all the sides and thickness of each side were different and offset from the center ‘pole’. I was determined to get the measurements perfect if for nothing else, the learning experience.

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. Gradually as I wrote my MillDroid application and added features I moved away from Mach 3. Slowly….

Now we’re getting somewhere

The tips of the fingers had some interesting geometry with which to deal.

With a first finger prototype nearly done, I came to the conclusion that, if I wanted to be more productive and get this thing finished within the next twenty years, I would need to invest in a Lathe.

So I splurged and bought a Sherline 4400 manual lathe and (you guessed it) BANG! several weeks are now spent learning to use the lathe, converting it to CNC, and adding code to my MillDroid CNC application (which by now was becoming AWESOME). My metal shop was now becoming a serious threat to humanity as I built up cabinets of the standards, micrometers, saws, windmills, grinders and all the other terrific things that suck up hobby money and time like a black hole. But now I was getting very productive….

3-First Metal parts

With the completion of my research, I decided that I would build the arm based upon the following info:

  • The foundation would be the arm used for the closeups in T2
  • The drawing I had found based upon that arm would be used for accuracy
  • I would only modify measurements if necessary to maintain movements, but visual accuracy would be paramount.

I have previously done a lot of resin casting for some shop tooling and my Iron Man Arc Reactor prop build. I played with doing this for some prototyping, thinking I could work with a resin hard enough to work. I started by casting some tubular shapes, making half rounds and corners for the bones of a finger prototype.

Some AAA batteries, by coincidence, were the exact diameter, so I cast silicone molds of some (and other objects of the correct size). These half-round modes were then filled with resin and other two-part plastics.

Once hardened, it was a quick method of making many duplicated for testing. One downside was that, without a proper vacuum chamber, my castings tended to have some small bubbles, which I had to manually fill with putty along the way. Another problem with casting small items is that you tend to mix small quantities of plastic, and the smaller the quantity, the more difficult it is to get the ratios of chemicals correct. Many castings came out ‘soft’, or too brittle because of this. Even tiny discrepancies in volume of resin vs. hardeners made it very difficult to cast single or small number of parts like this.

I used styrene for the more ‘sheet-like’ components, cutting and carving and gluing to get more complex shapes.

Knuckles for a finger

A completed finger length from knuckle to knuckle. So, what did I learn?

  • Resin is too finicky to work with in very small quantities.
  • Casting in resin requires a vacuum chamber unless you want to spend significant amounts of time patching hole left from bubbles that gradually rise in the resin while it hardens.
  • Styrene is easy to work, shape and glue.
  • Overall, the plastic/resin just wasn’t strong enough; it could be bent, and was still brittle enough to snap.
  • The styrene glue joints, since styrene is ‘welded’ with solvent, are very strong. But epoxy joints between resin and styrene didn’t have enough surface area to be strong enough to trust. CA glue proved handy along the way.

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 rubbing against each other. 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 upon a Sherline Mill. 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 measurements before I make it CNC compatible. Therefore the T800 arm would be on hold for a bit as I tool up for metalworking.

2-Beginning plastic prototype

“Now listen to me vewy carefulwy….”

I had dreamed of building a Terminator T-800 arm ever since I saw this scene in Terminator 2 decades ago. If I was going to do it, I didn’t want to build a kit–I wanted to create the entire thing from scratch and as visually accurate as possible to allow it to still move, yet match the movie prop. The two were sometimes in conflict with other.

Having done a lot of resin work in the past, I considered machining the parts from machinable wax then casting in resin. Since there are no duplicate parts anywhere in the arm using castings 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 (a finger bone) 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 access to the original Terminator props and precisely measured them, transferring it all into some precise drawings. In all there were nearly 60 pages of sketches.

I started the research and development for the project in October of 2012 and discovered a lot of information about the various props used in the Terminator movies. The actual choice of which arm I would build was a bit vaque until the research was completed. It took around 3 months to gather all my sources, learning what was incorrect information on the web and what was accurate.

I’ve broken the project blog into several categories based upon my attempted approaches and final builds. Hopefully it will prove entertaining if not educational. Several people have built arms since mine based upon discussions they have had with me that spurred them to their own projects. Children of the Arm, as it were.

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.

This shot from Terminator 2 revealed many differences from arm in the first Terminator film. This spurred me to serious research into the various props. Here is a summary of what I learned. The very nature of the web being that ‘everyone with a keyboard and opinion is an expert’ must be remembered, and I did my best to sift through to as many facts as seemed verifiable.

What I can tell is that there were several skeletons and/or arms made for each film so it will always be debatable as to ‘which was which”.

The original terminator arm was created for the first movie. For the most part this arm was made from what looks like steel and aluminum and many parts were ‘pressed’ or ‘bent’ into their final shapes. A few select pieces were cut from existing devices such as engine pistons.

You can see much of the damage inflicted on the original props during shooting and afterwards. ‘Blobs’ where pieces were welded quickly in order to get through a scene are apparent in the knuckes that are now permanently fused together. The first film’s prop is much less detailed than that of the second film. Interestingly, the wrist joint and three forearm piston muscles are very similiar between films. According to sources, the original arm was not tripled chrome plated. Some parts where steel, and you can see many of the ‘smaller muscle pistions’ of the fingers were actually stainless steel control rods used in radio control model airplanes. Most of the steel parts have a reddish tint to them in these photos as they have begun to rust.

Once the Terminator 2 film began production, entirely new props were made. This arm was not triple-chrome plated either, and also contained a fair amount of aluminum. This prop was than vacuum metalized later.

Much more detailed work went into the machining of the bones of this arm. There is also a lot of cabling through pistons and pulley, allowing some movement. Most of the axels consist of steel pins thread with stainless steel hex screws and custom made ‘washer caps’ on both sides of every joint.

During shooting a LOT of damage was done to the props. This happens during a shoot, and no one thinks twice about damaging a prop in order to get the day’s shooting completed. So if a finger breaks, someone will weld it, solder it, glue it, whatever it takes to quickly get the shot completed. By the time production is completed, props hardly be recognizable from what they once were, as evident by these photos….brace yourself, these are painful to see…..

Ugh. It’s like looking at the results of mechanical arthritis.

Not only is all motion now rendered impossible, some of the pieces can barely be identified. Aluminum melted by welds, giant blobs of melted metal or solder, and large pieces ground away. It get worse….

This is the palm plate of the hand, probably crushed in a vise during work.
This looks like it may have been a metacarpal bone. Somewhere under there is art.

As near as I have been able to tell, after T2 finished filming, the endoarm was sold to a company called Profiles in History along with an endoskeleton that they cobbled together as a prop for the magician Chris Angel’s stage show. The endoskeleton was composed of replica and original parts including this once fully animatronic arm. By this time it was very damaged form the heavily welded, sodered and deformed parts. Much of the detail was lost.

At this point, Lucasfilm Limited was hired to restore the arm, possible for their part in the Terminator Amusement Park Ride, but this is unconfirmed.

I don’t know who he is, but he gave it his best shot.

The arm was then broken down into individual components, cut apart and ground down in an attempt to restore detail. According to accounts, over 100 hours of grinding and sanding went into this. A lot of damage was done to the once sharp, details edges of the corners, as all later pictures show edges with a more ’rounded’ profile. This was probably unavoidable at this point. A lot of filing was also done into once filleted joint corners, and the entire thing was then smoothed (probably by tumbling in media).

At this point the pieces were then chromed and reassembled.

Although now quite silvery, the arm’s original glory is as close to it was before shooting as possible.

1-Project Origin and History