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Tungsten needles

 
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Beatsy



Joined: 05 Jul 2013
Posts: 1598
Location: Malvern, UK

PostPosted: Fri Apr 10, 2020 4:32 pm    Post subject: Tungsten needles Reply with quote

I've started this topic in answer to Rik's question over in Tech and Studio Photography ( https://www.photomacrography.net/forum/viewtopic.php?t=41452 )
rjlittlefield wrote:

...I am clueless about tungsten needles. Do you know a reference that can teach me about them?

Glad it's not just me. They've been around for absolutely yonks. Preferred dissection needle material by the looks. Anything from dissecting (down to cell level), counting and sorting (e.g. spores!!), probing ICs, the list is endless. And I only spotted 'em a month or so ago...

I started with fed-up-ness. Glass needle making drives me nuts and I looked for an alternative (again). This time, I stumbled on the IC probes - and it all went from there. Quick summary on how to get/make 'em to start with...

You can buy 'em
https://surgicaltools.co.uk/fst-products/pins-holders/pins/
https://www.lambdaphoto.co.uk/everbeing-t20-series-tungsten-probe-tips.html
I bought the second type - pack of ten each of 1 micron and 0.3 micron tips. Totally rigid - tip eventually bends if pressed continually into glass (diatom arranging), but the end can be lapped steeper for an indestructible, but still dead-sharp point.

Or make 'em with tungsten wire. 0.25mm sweet spot for manipulating and small dissecting IMO. I certainly won't be buying any more. Pennies vs pounds per needle cost by making - and I can customise each one as needed.

1. Grind and lap a point on it with a Dremel or two. Eats lapping paper and grinding wheels/disks like crazy. Expensive and slow for thick wire. Fiddly (and therefore slow) for thin wire too. Good for finishing a point to strengthen it or or for starting the tip shape in rubbish wire though.

2. NaNO2 - Spall tungsten off red hot wire on near-melted stick of sodium nitrite. https://www.youtube.com/watch?v=WvepYAwiKU8
Takes a bit of practice and really good for thick, low-grade wire. Bullies the shape onto it. Not good for thin wire (for me). Better than grinding for starting a thick wire point.

3. Electrolysis - the best. Loads and loads of nuances, but principle is super straightforward. I use this now. Less than 30 seconds from cutting wire off the spool to having a finished and polished, fine point. This is a good starting point, there are other similar articles.

http://www.mccroneinstitute.org/uploads/Tricks-Bowen_58-3_p131-134_2010-1476996273.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2555190/

Pic here is one of my first "working" needles done by electrolysis, but I hadn't learnt (any) nuances then. Bit rough, but makes a prettier picture Smile


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Macro_Cosmos



Joined: 15 Jan 2018
Posts: 634
Location: Sydney

PostPosted: Sat Apr 11, 2020 5:25 am    Post subject: Reply with quote

It's quite amazing how much these needles cost, they are for sure expensive. Great results, I'll try making some when I can legally muck around outside to get stuff. Shocked
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 20650
Location: Richland, Washington State, USA

PostPosted: Sat Apr 11, 2020 8:09 am    Post subject: Reply with quote

Is some special chemical characteristic of tungsten needed to make this work?

Or is tungsten used only for its high physical strength (109000 psi yield)?

Could I make a really soft one out of, say, annealed copper (4830 psi yield)?

--Rik
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Beatsy



Joined: 05 Jul 2013
Posts: 1598
Location: Malvern, UK

PostPosted: Sat Apr 11, 2020 8:14 am    Post subject: Reply with quote

rjlittlefield wrote:
Is some special chemical characteristic of tungsten needed to make this work?

Or is tungsten used only for its high physical strength (109000 psi yield)?

Could I make a really soft one out of, say, annealed copper (4830 psi yield)?

--Rik

Pretty sure tungsten isn't special in the way it's converted to a salt and pulled off the wire by electrolysis. No reason other metals wouldn't work too - given the right electrolyte. But I've not tried it and can therefore only assume that the physical properties are reason for choosing it.
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Smokedaddy



Joined: 07 Oct 2006
Posts: 1685
Location: Phoenix, Arizona

PostPosted: Sat Apr 11, 2020 10:32 am    Post subject: Reply with quote

You always have interesting ideas. Idea I just finished a project using rust removal by electrolysis. The .PDF you linked is very similar to what I did. Looks like that's definitely the best route. I was amazed how well it worked, like magic. Thanks.

Once upon a time I was a certified welder (still am). Years ago I used Chem Sharp to sharpen tungsten. I assume it's similar to what you've mentioned, heat the tungsten and dip. I didn't care for it but it worked fine. Not that it matters, they make a tungsten sharpener too, that's what I use when TIG welding. They're expensive but do the trick. Most welder chuck up a piece of tungsten in a cordless drill then sharpen it on a grinding wheel (usually a diamond wheel on more critical work). Trouble is, in your application the smallest diameter I've ever used is 1.57mm (hand weld not compurtized). If that wasn't a typo you said 0.25mm.

-JW:

Updated: corrected tungsten size to 1.57mm.


Last edited by Smokedaddy on Sun Apr 12, 2020 3:58 pm; edited 2 times in total
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Smokedaddy



Joined: 07 Oct 2006
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PostPosted: Sat Apr 11, 2020 10:35 am    Post subject: Reply with quote

So what was the diameter of the tungsten wire in the image you posted?
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Beatsy



Joined: 05 Jul 2013
Posts: 1598
Location: Malvern, UK

PostPosted: Sat Apr 11, 2020 11:17 am    Post subject: Reply with quote

Smokedaddy wrote:
So what was the diameter of the tungsten wire in the image you posted?

Thanks for your comments. The pic over on the other thread was a needle made from 0.25mm wire. No typo. This one was 0.1mm (also no typo Smile ).

Thicker 0.5mm wire makes better dissecting needles (much stiffer) but I only got some sub-standard rough wire at that size (From Ukraine). Splits and grooves all over - and the electrolysis follows those so you can't get a decent tip shape. It was 10x more expensive than other wire I got from a Chinese vendor and that was superb - bright shiny and smooth. Makes excellent points first go.

I don't think I could envisage manhandling needles made from "38mm" rod though Very Happy
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Smokedaddy



Joined: 07 Oct 2006
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Location: Phoenix, Arizona

PostPosted: Sat Apr 11, 2020 11:22 am    Post subject: Reply with quote

So Steve, do you meaning something like this?



-JW:
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Beatsy



Joined: 05 Jul 2013
Posts: 1598
Location: Malvern, UK

PostPosted: Sat Apr 11, 2020 11:27 am    Post subject: Reply with quote

Yes, but check purity if you can (the good one I got claimed 99.5%). I bought the last that seller. had I guess you won't know the state of the dies used to pull the wire until you get it. Bur not much fun (or use) to work with if it's all grooved. Perhaps you can ask about that before buying.
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Smokedaddy



Joined: 07 Oct 2006
Posts: 1685
Location: Phoenix, Arizona

PostPosted: Sat Apr 11, 2020 2:36 pm    Post subject: Reply with quote

Since I never thought about looking at the point of my TIG tungsten under a microscope. here is what my tungsten sharpener does to my welding tungsten. I probably could have gotten a little finer point. It has a 30um flat on the end now. I realized it's OOF. Hopefully you see the small horizontal red line just below the tip where Imagej measured its width.



-JW:


Last edited by Smokedaddy on Sun Apr 12, 2020 12:40 pm; edited 1 time in total
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NikonUser



Joined: 04 Sep 2008
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Location: southern New Brunswick, Canada

PostPosted: Sun Apr 12, 2020 4:35 am    Post subject: Reply with quote

I looked at the ref. for the needles you bought: 1 pound for 10 ??
FST in America is asking $95.75 for 10 with 1 micron tips

Are yours really just about $1.50 for 10, even for 1 that would be cheaper than over here
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Beatsy



Joined: 05 Jul 2013
Posts: 1598
Location: Malvern, UK

PostPosted: Sun Apr 12, 2020 4:57 am    Post subject: Reply with quote

NikonUser wrote:
I looked at the ref. for the needles you bought: 1 pound for 10 ??
FST in America is asking $95.75 for 10 with 1 micron tips

Are yours really just about $1.50 for 10, even for 1 that would be cheaper than over here


No. First link have them for over £100 + VAT for ten. Second are £72-ish plus VAT (20%). I got those. I don't regret buying them as they proved a very useful reference point in a sea of "know nothing" at the start. I wouldn't buy more though - ever!
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