--- Sterling Silver Caliper Ring --- Prototype

I am designing a pair functional rings from non-ferrous metals. I plan to execute this ring twice, once using a CNC - machining it from 7075 aluminum - and once by hand -using sterling silver -on a milling machine and hand shaping techniques.

This ring is meant to function as a caliper which measures imperial thicknesses to the 32nds.

I went to Myron Tobak , in the diamond district, planning on purchasing silver stock (about a half hour of time??). I ended up being assisted by Zachary, Mr. Tobak's grandson, who ended up advising me for over an hour and a half, helping me refine my plans. I cannot recommend more emphatically, Myron Tobak. (also, lesson confirmed- bring your CAD with you everywhere!)

So I purchased some silver stock ==

Now I had some stock to design around! I also had some wonderful notes from Zachary.

not pictured are caliper nibs and measurement etching

So I designed down the cad to a 2-D blueprint in order to have a transfer to the stock.

To get machining- I have to face my metal.

The silver is not "true" - not flush/flat.

(This should be checked on a machined true surface)

So I started filing and sanding.

I felt that this process would be a slower process, yes, and would remove the same amount in the end as using the mill to face the silver.

So I started trying to face the silver on the vertical mill. Because of the precious nature of the material and that I will be using almost all of the material, and I will be using a rotary table on the mill with only large strap clamps, I need to make some jigs to hold the material down and flush - basically making my own vise and parallels.

So facing the sides of the ring proved a wasted venture. Because silver is so soft, making it tightly fit into any jaw with enough tension to be secure and yet not obstruct machining, was a fun problem. (I preemptively Sprayed the silver stock black, in prep for laser etching the blueprints on).

I began machining some 6061 aluminum to press fit the silver into - leaving enough room to to then press the two sides overhanging on the silver to secure the entire jig - with strap clamps-on the rotary table.

I was wary of press-fitting the silver into the jig. I wanted to do this right before machining, but I felt that the blueprint etching might warp when pressed in, therefore, my silver and went to laser - warped and all--

So there is some curvature to the silver in the 6061 parallels - i.e. the metal is certainly NOT flush/flat/parallel. I'm ok with this.... I will do some cutting operations and then work it out. It might be like polishing a turd - getting the metal trued- at any stage- but as long as the measuring channels and face are not manipulated, it should be fine.

I ran the 2-D blueprint file. NOTE: the laser cutter is not made for seriously tight tolerances (hence the subtler etchings).

I decided to redesign the ring. There were components of the above design that just did not feel super flushed out:

Having two caliper nibs moving on two distinct channels means that they will always be flapping about - no way to hold them, clasp them, making the ring potentially annoying to wear.

Making one ring the moving ring and providing the other a post.

I am currently considering the mechanism to hold the caliper nib to the post on the right.

I will likely change this design again, but I believe I have enough to begin machining.

In considering how to machine this ring - and how to go about the most secure methodology for holding the work, cutting the inside parts etc - I decided that the aluminum jig should be flush to the silver (keeping the tiny bits safe).

I faced the silver and aluminum.

To machine circular operations, I needed to use the rotary table.

to get set up- I needed to make the center of the rotary table center to the spindle.

I set a live center in the center and a center drill in the spindle and mated them. tip-to-tip.

As this was my first rotary table operation, I tested tolerances and true-ness with a bit of ren-shape.

It looked acceptable, so I started to machine the ring- following suite from the ren-shape process.

It worked fairly well. However, I milled out a large portion of the first ring. In doing so, I lost a lot of control (holding, for milling). Therefore, There were some errors in the first ring. Therefore, the second ring, I milled out without completely removing the entire sections, by using the concept of tabs. I was able to achieve much more precision. (the milled sections in the center were prep work for the nibs etc.)

I know that I want to inlay metal (marry metals) to represent the measurements on the ring. I did a test of inlay today- soldering some brass and silver to some notches on the copper:

Having futzed with doing this by hand- I am finding it not only massively prohibitive in both time and money. Instead, I have decided to CNC some machineable wax on a Roland MD 40-A - which is a fine detail milling machine with a rotary axis.

This will then be cast in a silicone mold and sent to a foundry for casting.

I made some adaptations to the design-

Including -adding slots every 32" of an inch with a 1/64" of an inch end mill (see the vertical slats on the top ring).

Secondly, as the ring is intended to be aesthetically interesting, I have included a "shelf" on the bottom ring to house a billet of different metal alloys which show the physical with of -

1/64" / 1/32" / 1/16" / 1/8" / 1/4"

So I duplicated the components and modeled them with tabs, set them inside the material I plan to use.

I cnc milled the file on a Roland MDX-40A with a rotary axis.

I made a few technical changes to the file to accommodate the milling process.

Because the wax is so very fragile, (I have broken/snapped/disfigured so many of these), I feel I might need to get these cast, and then buff and file the metal.

https://davidneat.wordpress.com/materials/modelling/modelling-wax/

So, in asking around, in NYC, there is this company in the diamond district which produces molds and does the casting called Taba.

http://www.tabacast.com/

hannah mishin

Caliper Ring

--- Sterling Silver Caliper Ring --- Prototype