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May 31, 2006

planning a steel armature

by sven at 8:00 am

I'm in the process of collecting the materials necessary to build a steel armature. There are so many things to consider... Ack! Gotta write some of this down, just to clear my head.

OK, so take a look at this brass armature that I made:

close-up of torso

My new armature is going to be very similar -- only made out of steel. There are six elements in this armature design that need consideration:


A) Type 302 stainless steel balls

Within the amateur stopmo community, most of us have learned how to make steel armatures from Lionel Ivan Orozco ("LIO"). He has three key tutorials on his site: making an open hole double ball joint, drilling metal balls, and brazing balls to rod. LIO also authored a section of Marc Spess' e-book, Secrets of Clay Animation Revealed!, which covers the same material.

LIO recommends type 302 stainless steel balls from I can get a 100 count box of 1/4" balls from for $10.75. Their flat rate for ground mail is $8.95. That's $19.70 total. [Note: shipping goes up if the order weighs more than 10 lbs.]

I could also just buy a box of 25 balls for $3.25. My brass armature used 28 balls... I suspect the steel armature will only use 20 -- but there need to spares in case I make mistakes. Particularly given that these balls need to be drilled, which is an error-prone part of the construction process.

I wanted to know if I could get steel balls for less by buying locally. After checking the yellow pages listing for "bearings", I called Applied Industrial Technologies, Kaman Industrial Technologies Corporation, McGuire Bearing Co, and Motion Industries Inc. Only McGuire was able to help. They have seven type 302 stainless steel balls at their Salem store -- but not in the 1/4" size. If I wanted 100 of the 1/4" type 302 stainless steel balls, they could have some shipped from Illinois. The price would be 35ยข each -- thus $35 for 100 -- plus shipping, which would be $6 - $10.

Lesson learned: type 302 stainless steel balls are a fairly exotic item. Even when shipping costs are included, is the best place to purchase; it's $19.70 versus $40+ -- so ordering through a local store costs more than twice as much!

[Another interesting thing I learned in the process: bearings are rated for "grade". The smaller the number, the more perfectly smooth the balls. Grade 100 is typical. Grade 10 and grade 1 are also available -- though not through I was advised that the difference between these grades is not visible to the naked eye, and that grade 100 should work perfectly well for my applications.]

B) An alternative method: using beads instead of bearings

On my brass armature, I used hollow brass beads for balls in the "open hole double ball" joints. To the best of my knowledge, I'm the only person who's come up with this solution.

...It worked remarkably well, and has two big advantages. First, because the beads have holes in them, drilling is much simplified -- you've already got pilot holes, and just need to enlarge the openings. Second, because the beads are hollow, there's space on the inside where you can put little snippets of solder -- all you have to do is heat the exterior of the bead with a micro-torch. The thing that you'd expect to be a problem -- the end of the rod extending through the opposite side of the ball -- turns out to not be a problem at all. The lip of the sandwich plates prevents the ball-rod piece from rotating to a point where the rod would begin to impede rotation.

I purchased my 8mm brass beads from A Bead Source (15831 SE Division St.). The largest hollow stainless steel beads that they sell are only 6mm. I've asked for the 8mm size to be ordered; an employee wrote a note for the owner -- but I'll have to call back periodically to see if the beads are actually in stock yet. This makes me want to see if I can't find an online bead seller, so I can just order the item myself...

I've also looked in Beads Forever (3522 SE Hawthorne) and Beads at Dusti Creek (4848 SE Division); A Bead Source is the best stocked of the three. Checking the yellow pages, I see that there are a few other bead stores that might be worth calling. Dava Bead And Trade (1815 NE Broadway) looks like a decent possibility.

A Bead Source carried what appeared to be 8mm carbon steel beads; however these were simply drilled -- not hollow. Drilled beads would not work. When you drill bearings yourself, you essentially create a little cup for the liquid solder to sit in. When you use a hollow bead, there's a space inside the bead where the solder can rest. If there's a hole that's drilled all the way through the sphere, then there's nowhere for the solder to rest.

A Bead Source also carried 8mm hollow silver-plated beads. Given that some solders contain silver, it seemed likely that these could work as an alternative to stainless steel. I picked up a bag of 25 for $2.95 for testing.


For sandwich plates, LIO recommends "cold roll steel flats" that are 1/8" thick and 1/4" wide, which can be purchased online from either or I believe the proper material from is "STEEL, COLD ROLLED - Rectangular Bar Type C1018", which costs $2.60 for a 36" length (longest available). I believe at "Mild Steel Rectangle 1018 CF" is the same thing; a 36" length only costs $1, and lengths up to 8' are available. Both companies charge a basic fee of $8.95 for shipping. Note that while is cheaper, it does not seem to carry bearings of any sort -- so it probably makes more sense to purchase both balls and sandwich plates from, at the same time.

A little galled at how much shipping costs, I decided to research local metal suppliers. It seems the best place to start for this research is in the yellow pages, looking under "Steel Distributors & Warehouses". In Portland, the four suppliers that look to be worth visiting are: Eastside Steel, Metal Supermarkets, The Steel Yard, and Pacific Machinery & Tool Steel.

some stock at Metal Supermarkets

Eastide Steel and The Steel Yard keep their materials outdoors, and deal only in steel stock. They seem adequately friendly towards artist-types, but the premises felt "rough" in a way that made me a little uncomfortable nonetheless. ... Metal Supermarkets was excellent. They carry aluminum, brass, and steel; their stock is all indoors; and the staff were remarkably courteous and helpful. This is a national chain, and from what I've seen at this one branch, I recommend it highly. ... Pacific is on the other side of town from me; I haven't had a chance to visit it yet. I get the impression that it is another indoors multi-metal supplier.

I purchased a 6' length of 1/8" x 1/4" "cold-finished" 1018 carbon steel at Metal Supermarkets for $8.42. Compare that with $1.62 for a 6' strip from, or $5.20 for two 36" strips from I'm really surprised to find it's costing less to buy metals online than in-person. Of course, and there's also shipping costs to consider -- and it's quicker to buy stuff in person.

Something interesting that I learned about buying metals: when you're buying in-person locally, the prices change daily. The price of metals at any point in time is linked to the stock market. With Metal Supermarkets, what you can do is check their website (which is organized very nicely) for what item you want, and then call the store to ask for a quote. Pretty easy. [I don't know why online metal suppliers are able to sell their products at fixed-prices.]


Screws are easy: I've got an Ace Hardware less than a mile from me -- just buy 4-40 socket cap set screws from their little bins, however many you need for the project. One interesting discovery... They offer both black "course" 4-40 screws, and stainless steel. I don't understand what "course" refers to... Generally a "course" screw has fewer threads per inch -- but both of these have 40 threads per inch. I know that I like the stainless steel, though -- so it's a moot issue.

4. ROD

LIO recommends "type 01 carbon steel rod, or cold roll steel rod". There are a great many types of steel, and I haven't figured out what "type 01" is yet. I found and purchased something a while back that I think I'm going to try to use... It's 5/32" music wire from the K&S Tube & Wire center at Bridgetown Hobbies & Games (3350 NE Sandy Blvd).

What is music wire? It's not what you think of as "wire" -- it looks like rod. I checked and found "Straightened Spring Steel Music Wire", which appears to be the same thing. When I search Wikipedia for "music wire", I get the entry on "piano wire", which says:

Piano wire is a specialized type of wire made for use in piano and other musical instrument strings, as well as many other purposes. It is made from tempered high-carbon steel, also known as "spring steel". Music wire is another name for piano wire: it is used for the cores of strings, which may be wound with other materials.

...Since this passage says "high-carbon steel", I'm going to guess that it's roughly equivalent to what LIO describes.


On my brass armature, I used standard 60%-tin / 40%-lead wire with a rosin core. I want to get lead out of the equation. Solders also sometimes contain Cadmium or Antimony -- I want to avoid these as well.

LIO recommends 1/32" diameter Safety-Silv 56 from Harris. I found and purchased a kit of 1/16" Safety-Silv 45 at Irontech (6417 SE Powell) that contains 1 oz of silver brazing alloy and 2 oz of Stay-Silv white flux. I'm very pleased with the MSDS, which clearly states what metals and chemicals are contained in the package. However, the price is steep: $24. Youch! ...I guess you're paying for the silver: the "45" in the name refers to 45% silver content.

About a week later I found some 1/32" Safety-Silv 56 at what looks like a mom-and-pop shop, Jones Welding Supply (11230 NE Sandy Blvd). It cost $12.50 for 1 troy ounce, but didn't include the flux (which I already have). Having looked around a little in welding supply stores now, my sense is that Harris brand Safety-Silv is very common. The particular store you visit may not have the exact silver-percentage or diameter you're looking for, but they should be able to order it pretty easily. The Harris website shows that they have an enormous selection of products -- but they don't sell to individual consumers online.

Looking closely at Ace Hardware, I found some more options for lead- and cadmium-free silver solder. Ace carries Alpha Fry brand soldering wire. Product #53982 is 1/16" wire that's 98%-tin / 2 %-silver and comes with a separate tube of flux. Product #62963 is 1/32" wire that's 96%-tin / 4%-silver and has a rosin flux core. Product #62964 is 1/16" wire that's 96%-tin / 4%-silver and has a rosin flux core. These last two products cost $3.49 and $3.79 (I forget which is which).

The Harris brand soldering wires cost about six times what the Alpha Fry stuff costs. Harris has a much higher silver content -- which makes for a stronger bond. An advantage of the Alpha Fry wire, though, is that it has a rosin core -- making it easier to work with, especially when using the "hollow bead" technique I described earlier. One more significant difference: the melting point for Alpha Fry is 430 degrees Fahrenheit; Harris has a melting range between 1250 and 1370 degrees Fahrenheit. The Welder's Handbook by Richard Finch says that butane burns at 3900 degrees, so my micro-torch ought to be fine. (Still, a note of concern is raised in my mind.)

In addition to welding supply stores, one can find silver solder at jewelry supply stores. A quick trip to Ed's House of Gems (7712 NE Sandy Blvd) confirmed what I've read online: jeweler's have a different language for soldering. They sell silver solder in three categories -- "soft", "medium", and "hard" -- and they don't seem to include MSDS info. I decided that I'm just going to avoid buying soldering materials from the jewelry-making world.


I had hoped that I could just purchase some 1" wide cold-finish 1018 carbon steel at Ace Hardware. What they stock, though, is "weld steel" and "plated steel" (which looks galvanized to me) from Steel Works. Neither of these looks right -- so I expect I'll wind up making a quick trip back to Metal Supermarkets.

I'm also curious to take another look at the K&S Stainless Steel Center at Ace Pearl Hardware (1621 NW Glisan St). ...I don't know how well this shiny stainless steel stock would mesh with the carbon steels I've purchased; I'd like to purchase a snippet for testing.

posted by sven | May 31, 2006 8:00 AM | categories: stopmo