Titanium Grinding vs. Tumbling

May 1, 2008

Harbor Freight bench shear

I’ve tried a few different methods over the the years to reduce my hands-on time in getting rid of those razor-sharp fresh-cut titanium edges. I started doing this with essentially no tools or money to buy any. I first bought tin snips, and then a small bench shear something like the one pictured.

Polishing MotorThe merciless edges on fresh cut titanium encouraged me to buy leather gloves. To remove those edges, I first used emery paper (wet/dry sand paper) to smooth them. But the tedium soon urged me to learn that a motor, a couple of taper spindles, and Cratex wheels (rubberized carbide) were much faster and spit few sparks. I put my grinder/polisher together from a salvaged ¼ horse motor and parts from a mail-order catalog (this was around 1980). Now there is website: www.RioGrande.com and you can get everything there. But grinding small parts ended up using up finger tips; both gloves and my own.

Harbor Freight Cheap Rock TumblerOn a whim, I tried out my childhood rock tumbler. I just cut up a bunch of pieces, and threw them in with some rocks, and let them go for a week, then three weeks. There was some rounding of the sharp edges, but not much nor fast. I then ordered abrasive ceramic media from RioGrande, and tried that in place of the rocks. After a couple of weeks, nice, smooth edges. The ceramic media lasts for many uses (I have yet to reorder). You can also get it cheaply from HarborFreight, here or at your local Harbor Freight shop. You can also try rock shops, craft stores, or online.

Lightweight vibratory cleaner/polisherBut, c’mon! Weeks? So (many years later) I went to eBay to find a vibratory polisher. I wasn’t ready to spend $500 on a name-brand one at RioGrande. So I found one specified to clean shotgun shell casings for about $60 delivered. It has a clear top, so I could watch the pieces and media do their thing. It reduced the time to about 4 days. I ran it with a dry load, with no water or agents. Amusingly, the dust that grinds off from the media is hydophobic! Water runs right off of it, like mercury on glass. I found that adding tap water at the end and vibrating for another hour suspended the dust in the water and didn’t darken the titanium too much. Anyway, I etch after I tumble.

But I never did manage to get a shine with this machine. I tried ceramic media and porcelain media, I used polishing compounds, ran it wet, ran it dry, and still my best was a matte finish. My worst was that the titanium turns almost black in water with porcelain.

Harbor Freight Vibratory PolisherSo I thought I’d try another type of vibrator. I got it from eBay, and then found that I could have driven across town to HarborFreight and gotten the exact same unit for about $25 less. I first tried running it wet with porcelain. Blackish titanium, eww. I etched the titanium clean, and then tried dry with ceramic media: Shine! Trumpets and doves and a beam of light from above. The gray ceramic media turned dark and shiny in 24 hours, as the titanium deburred and gleamed.

Had this not worked, I would have finally bought a professional (expensive) circulating fluid vibrator assembly (Raytech). But I’ll hold off on those.


Fusion Welding

March 28, 2008
I’ve been interested in learning how to fusion weld, for a long time, but the Sparkie is so expensive. Does anyone know of a fusion welder that would be less expensive, or even an experienced fusion welder who would provide welding services for a fee?Also, would it be possible to create a “nib” of our own for welding purposes, or do the dimensions (etc.) of the nib have to be exact to get a good solid weld?

Thanks for any help.

-Maggie


How can I get consistent colors?

March 26, 2008

This frustrated email arrived today:

I live in Belgium (Europe) and have been making titanium jewellery for 4 or 5 years now. Sometimes I colour the pieces. I have a machine from Wieland, a German company. All this time I did not have any problems because the pieces I made had always the same size. Now lately we are doing titanium leaves in various sizes; Grade 2 thickness 0.5 mm. The problem with coloring these pieces is that I do not seem to have any control over the colours due to the variable sizes of the pieces. Is there a way to make a formula that gives me control (more or less) by taking the weight of the piece? Because of the irregular shape it is impossible to know the amount of surface I am working with.

At the moment I am really taking what comes out of the machine. I did make several colour charts using various shapes but with pieces 6 to7 times as big as my trials I have no control .

I would be very grateful if you have some advise on this, or maybe even a solution.

Thanks in advance.

Peter

My reply: I can’t know exactly what the problem is, for I encounter the same difficulties.
The color you end up with is a function of the electrical current density, the total time, the surface finish, and the grade/alloy (which also affects finish and current flow).

The weight is not as good an indicator as the surface area. If all the pieces are always the same thickness, then the two are functionally interchangeable. But the risk is that if you calibrate on weight, and then start working with other thicknesses, the calibration will not stand.

I passed the question on to Bill Seeley.


How can I build an anodizer for UK Current?

March 22, 2008

Another reader question:

I am thinking of making an anodizer based on your anodizer digram. I live in the UK but was thinking that the volts for your electricity is different from the UK’s 240 volts?
If so do you know any diagrams that can help me with this, what I need to change?
My first thought is: In the UK, you can use the same Variac circuit. I wouldn’t trust the dimmer circuit because of the instability at lower voltages.
The U.S. uses 110 vac (150 volt peak), so we use about 3/4 of the range of the variable transformer (less if it is wired to provide over-voltage).
In the U.K, you would just just use 3/8 or even half of the available range.

If you really want to use the inferior dimmer-switch design, you can probably find a simple step-down transformer to cut your voltage in half upstream of the rest of the circuit.

Then came a follow-up:

Thank you for your reply; it was a big help. I am going to be doing the variable transformer one. I have been looking for stuff, but wow its hard to find anything that is needed.

I didn’t like the idea of using light bulbs, so I wanted to get Power resistor 200w 100 ohm but no one sells them, any idea of other Power resistors that I could use?

Try eBay.

I found several by a simple search for 200 watt resistors on eBay. You could vary the search for whatever power and resistance values you want, or use a search to find a good seller, and then ask them if they have what you need.

There are also a wide variety of variable transformers on eBay. But these heavy items cost more to ship, especially internationally.

Before the internet, I always shopped an electronics salvage store in my county. Many cities have at least one of those. Some junk yards and metal salvage yards also have a room full of gizmos that seem too nice to melt down. Call around.

Note: If you are not comfortable rewiring a lamp or replacing an electrical outlet, then you are probably not qualified to build your own anodizer. Buy a read-made regulated 0-150 vdc power supply.


How can I make some of those Fancy Titanium Colors?

March 21, 2008

Another question from a visitor to my regular site:

I’m starting to anodize on my own. How do they create that color “oil slick” in the picture or the “rainbow”?


The many simple colors are all based on voltage, as described in my anodizing page.

The stripes are made by masking off areas with something waterproof, like automotive striping tape. Then anodize to a high voltage color. Then remove the tape, and anodize to a lower color. The high voltage color blocks the lower voltage colors. Voila, stripes!

The rainbow can be made in several ways. The fastest is to turn the voltage up and the contacts off, immerse the piece,  then turn the contacts on and draw the piece out of the electrolyte. The color is now dependent on the immersion time rather than the voltage setting.

The oil slick is trickier. This is probably done by sponge or brush anodizing (clip the positive lead to the piece, and the negative to something absorbent soaked in electrolyte. Then very carefully apply the high voltage wet thing to the charged piece. Rubber gloves and goggles are required. If metal touches metal, then you are practicing welding. Bright sparks, damaged pieces, and possibly damaged electronics.


Can you make red anodized titanium Jewelry?

March 20, 2008

The short answer is: “No.”

In detail, the colors are caused by a particular trick of physics: Optical Interference. As is described in detail on this page, the colors are limited by the behavior of photons. There is no dye or coloring agent to give us precise control.

Red, in particular, cannot be produced because it’s wavelength is twice as long as blue. So if the interference allows red, it also allows the shorter blue through. This creates the secondary color called Magenta, red-violet, or purple.


Uneven results from dimmer switch anodizer

March 18, 2008

Here’s another question I frequently get:

I followed your instructions on building an anodizer and I would like to say that you have made a great job illustrating it. My anodizer is the dimmer and light bulb type it delivers a maximum of 160 Volts.I prepared a solution of TSP in distilled water placed the cathode (aluminum foil) and the Ti at the anode ran the circuit. The voltage keeps rising slowly and I get shades instead of definite colors (mostly violet, golden and pale blue). I can’t hold the voltage at a definite value. What should I do to get smooth colors? I tried adjusting the voltage first then immersing the piece but the voltage after immersing is lower than what I’ve just set it to. Please help me out here and thanks in advance.
David S.

First of all, the dimmer based voltage control is going to be a bit temperamental and unstable. But I used one myself for years before replacing the dimmer with a Variac.

Aluminum should work for a cathode, but should be lightly sanded to remove the invisible insulating oxide layer that spontaneously forms. I usually use titanium, but have been told by many that stainless steel works well.

When you have a large capacitor smoothing a the choppy dimmer voltage, the top end will be a bit mushy. The lower voltages are the worst for this effect. The tan, violet and blues are at the low end of the voltage scale.

Another issue in getting smooth colors is getting the voltage everywhere simultaneously. You should have the piece to be anodized immersed in the solution before completing the circuit to the leads. That is, you need a switch to turn the leads on and off, while the anodizer is running at the voltage you want.

Cleaning and chemically etching the metal before anodizing also helps assure a uniform color, and is generally considered necessary for getting the higher voltage colors.

The voltage measured on the leads or capacitor will drop when you start anodizing, and should rise back to your preset voltage in a minute or so. The time depends on how big a piece you are anodizing, how big your cathode is, and on the efficiency of your electrolyte.

Another possible problem might be the material of your attachment to the anode piece. Only titanium or niobium should touch the electrolyte at the positive side. Never use copper wire or regular (galvanized or tinned) alligator clips to immerse your piece. The current will just go though that, and little will be applied to your piece.