Biocompatibility of 302 SS

A while ago I built a new manufacturing facility for these guys:

http://www.micro100.com/

At that time, they would also manufacture micro tools to specification. It looks like they still will. They should be able to speak directly to your question, and make the drills to your spec.

Hi Doorman, thanks for your comment. As a matter of fact we can make the tool at our facility at a very low cost (rougly calculated 3.8$ a piece + the cost of the SS rod). Despite nothing wrong should happen by using this type of SS, I was wondering if there was a source to confirm my thoughts or if someone had had a negative experience using it for the same purpose. Best regards! BTW: I always wear boxers!

Ah.. Sorry, I misunderstood your question.

lynlynch has given more correct info, and has also called the name of one of the material science masters around here. I am sure you will get some more very good advice.

The advice in my signature line is that of my grandmother. She would be happy to hear you are following her advice.

Milo will know.

302 has 3% Cu.

Below came from: Stainless Steel Information

18-8 is a term used interchangeably when referring to 300 series stainless steel having approximately 18% chromium and 8% nickel. It can include stainless made from 302, 302HQ, 303, 304, 305, 384, and XM7, among others. There is little overall difference in corrosion resistance among these types, but slight differences in chemical composition can make certain grades more resistant than others against particular chemicals or atmospheres. 18-8 bolts are commonly 304 stainless, while screws are typically 302HQ.

There must be some regulatory commission that would have a list of accepted materials.

Where would you go to get approval for a new/non-conforming material?

I thought this web site was a good one.

R&DDoc, given that the device is in short term contact with body tissues and is disposable you really only need something corrsion resistant enough to withstand sterilization and storage. The 300 series stainlesses have two drawbacks I can see in this application. first off, they aren't terribly strong or hard. This means they'll dull quickly, possibly damaging healthy bone through overheating. Secondly they have nickel in them which means that any nickel residue that would remain embedded in the bone may eventually lead to the body forming a nickel contact allergy and start an inflammatory process in the bone (I presume the drilled hole is either for an implant or a bone screw or some other Orthopedic appliance. ) this would not bode well for the long term stability/viability of the implant it would seem to me.

A better option may be a straight chromium steel 400 series heat treatable (martensitic) stainless such as 420 or 440C. These would give you a stainless material that does not have nickel in them and would allow you to heat treat the part for longer wear. The problem of Chloride cracking is not likely to be an issue in the short time frame that the part would be in contact with blood, etc. and there would be very little chance of causing an allergic reaction. 440C MIGHT start showing some cracking by the time you are done drilling, but I doubt it.

Rorschach! In the first place I would have chosen a 300 or 400 series SS, probably 420 or 304 as they are the most widely available / low cost (at least here). The problem is that I am looking for a diameter of 3,7 to 3,9 mm[b/], and (until now) I only found it in .5 increases: 3mm, 3.5 mm, 4mm and so on. One of our regular suppliers of SS offered 3.9 mm rods to me, and sent me a sample ... but as you say: it is too soft for the intended use. You guessed right: it is to drill a 30 mm long hole in soft bone (by hand)

I understood that there were issues of supply geometry, my point was that by expanding your scope of supply, you might find it supplied in the diameter you need in a different material.

Some other CRS materials that might be suitable as well:

17-4PH

17-7PH

Beta titanium (6Al4V, or one of it's sisters)

All three of these materials are commonly used to manufacture corrosion resistant springs and as such are available in a wide range of wire sizes. They are also all three heat treatable using Instead of trying to specify it in mm, consider specifying it in AWG gauge or even Inches, you might be surprised to find it specified in a different UoM. #7 AWG wire is 3.66522mm #9 Steel Wire Gauge is 3.76682mm #9 Imperial Wire Gauge is 3.6576mm.

Stubb's Steel wire gauge seems most promising, #23 is 3.8862mm, #26 is 3.7084, so anything in between would fit the bill.

Talk to some spring manufacturers, you might get lucky.

Which brings me to a question about something you mentioned earlier, Why is a medical grade required for this short term contact application? what is different about medical grade that an equivalent industrial grade would not be suitable?

Hi Rorschach, for some uses, I buy wires and tubes from manufacturers in the US. whos standard is AWG. As most products sold here are metric, I went that way first, at this moment I have an assistant searching locally for imperial diameters and AWG. If not found in my country I will have to import it from the US (the issue here is that most companies have rather long delivery times). "" Which brings me to a question about something you mentioned earlier, Why is a medical grade required for this short term contact application? what is different about medical grade that an equivalent industrial grade would not be suitable?"" When it comes to Titanium, the seller of the product must certifie the medical grade of the material, cause you may loose your FDA or CE marks if caught using industrial stuff. I suppose the medical grade Titanium is made using raw materials, while the industrial one has a % of scrap or recycled stuff. (A time ago I red that a company bought bars of Russian Titanium, which made the Geiger counters go mad upon inspection: after some research, they found out some Rusian mills had been using material that came from scrapped nuclear November Class submarines!)

heh, yes, I wrote that. It's a true story too, I've met the metallurgical tech that analyzed the scrap.

My point being if the spectrographic analysis is the same (or rather, good enough, and the Geiger counters aren't ringing off the wall...) who cares where the raw materials came from? especially a cutting tool that is used once and thrown away? now if it was left in the body, that would be a whole different matter

(shakes head and walks off while contemplating the stupidity of government bureaucrats...)

" (shakes head and walks off while contemplating the stupidity of government bureaucrats...) " Bureucrats and Lawyers make medicine so expensive!!!!

Have you considered using a coating such as Titanium Nitride or Tungsten Carbide in a Chrome binder to build up on the o.d. of the smaller material?, it would be harder and cut better to boot.

r&ddoc is this device classified as a medical device and if so which class (FDA classiifies slightly different to European)? If you can answer this then I maybe able to provide you with some more information.

Hi Guest, despite the drill will be used BY HAND (meaning no mechanical effort, due to RPM´s) and will be removed from the body immediately after use, it´s a FDA Class II (European IIa) device.

i've found this article on material selection for surgical equip

http://www.asminternational.org/images2/surgical04.pdf

http://cartech.ides.com/datasheet.aspx?i=103&e=245&c=TechArt

http://www.cartech.com/techarticles.aspx?id=1670

hope this can help

Vitt

corrosion control

Consider using titanium as a drill bit material. It will make a better drill than 300 series stainless steel and its bio-compatibility is legendary.

Hi welderman! you are right, but medical grade titanium is quite more expensive than industrial grade. There are a lot of excellent SS types available, but my problem is more referred to get the diameter I need rather the material to be chosen.

The majority of this conversation ( wire type, sources, bio compatibility,) is beyond me but I have a couple questions I'd like to ask anyway.

If you have the capacity to manufacture the drills then Why are you worried about the wire size. (in American units) 4.0mm is .007874" larger than 3.8mm Why not centerless grind it to the desired diameter?

Surely either product would still need to go through the same or similar cleaning and inspection processes.

Could this option open up opportunities of wire selection and process changes that could aid overall savings?

Please excuse my naivete. I'm only curious.

Why are you worried about the wire ... Hi crimich13, your option is valid too, but this wire diameter is a stock product: I just have to find the supplier in Argentina (where I live), or to import it from another country. We are customers of Wytech, a US company in California that can supply this material, but when I requested a quote, they told me their delivery time would be of about 2 weeks, and I need it for YESTERDAY! :-) On the other hand, I do have the machinery for manufacturing the drills, but not for centerless grinding it...

Best regards

Contact Information

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Company Name:	CRGO COIL LTD
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City:	Buenos Aires
Province/State:	DISTRITO FEDERAL
Country/Region:	Argentina
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Send your message to this supplier Mr. COLLINS WILSON
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Does this help? This is all I found so far.

Hi crimich, the coordinates are weird: Street Address 15 Comunidad Valenciana seems to be a Zip code in Spain. Distrito Federal is a nomenclature we do not use. We say Capital Federal. Zip QWE RTY does not exist, we use a combination of letters an numbers. Mine es B1644GDC. Might Mr. Collins Wilson´s address be in the Bermudas Triangle? :-) Have a great weekend.

"qwerty" are the first six keys on a US style keyboard, methinks I smell a rat as well.

My keyboard is qwerty as well, but as the letters were separated in 2 groups of 4 + 2 letters, I missed it!

As I'm Not in or from Argentina I had No Idea. Sorry about that. My wife (the alien) agrees with you. She's from Uruguay. Perhaps I should have consulted with her first? She also confirms that there is no such address in the Bermuda triangle either.

Hi crimich, Thanks for your help anyway! Send my best regards to the "Charrua" from this side of the River Plate! You are a lucky man!

You all have a lot of good ideas here.

My wife has a sensitivity to Nickel. If she has common stainless against her forearm for more than a few seconds, she gets a 10 day rash. Her fingertips are a bit more resistant. There are others out there with similar weirdness. You would not want any Nickel alloy in such patients. Plating would have to be fairly thick to protect them.

Just one more thing to worry about.

Hi dh, to be honest, besides something like perhaps plasma coating, there are not many surface treatments that can be done on a medical device, as most are potentially harmful