View Full Version : Drilling Bismuth

11-12-2004, 11:41 PM
Hi Guys - I need to drill 1/4" holes through 1/8" thick pure bismuth metal plates. The plates are being specially caste for me - but I'd like to do the drilling in my own home workshop. Bismuth is soft and brittle, and I want to avoid cracking the plates. I have a drill press, and will keep the RPM very slow, but are there any other tips on drill type, lubricant, procedure, etc?
Thanks for any help, Rod.

11-13-2004, 08:57 AM
Isn't bismuth one of those things that's lethal (or at least not healthy) to breathe the dust of? (Or maybe that's berillium?)

11-13-2004, 09:27 AM
Dbl post. Sorry!

[This message has been edited by tonydacrow (edited 11-13-2004).]

11-13-2004, 09:27 AM
Yeah, SGW. You're thinking of beryllium.

Bismuth is the heaviest and only non-toxic of the heavy metals. They use it now in (very expensive) lead free shot for water-foul hunting because it's heavier than lead and when the geese or ducks dredge the bottom of the wetlands, they don't poison themselves.

So Rod, what are you using the bismuth plate for? Some kind of electromagnetic shielding? I'd love to know!

11-13-2004, 09:27 AM
The stuff gets put in indigestion tablets.
so it must be safe .
all the best.mark

11-13-2004, 09:55 AM
Actually........it is "slightly less" heavy than lead. About 90% of lead's density, but (according to reports) certainly less toxic and non-carcinogenic. It lies next to lead on the periodic table.

Seems to have some rather interesting electrical properties. "SOME PEOPLE" even think that it "MIGHT" have anti-gravity applications, but I think that they might be "smoking the stuff". http://bbs.homeshopmachinist.net//biggrin.gif



reality checker
11-13-2004, 11:11 AM
If I was having plates "specially cast for me" I would have a drafted pin inserted into the mold and all the holes would be the same.

The plates will weigh less as cast, many people charge for castings by weight, more savings when the metal is more dense.

Sometimes the cost reduction of the part can offset the cost of mold work. Consider the lower mass of the part with the hole, put a value on the metal not needed, figure how many parts you need to decide the savings on metal, consider the cost of machining the feature, and you may decide that a cored hole is best.

Net shape casting is an inportant reason to choose casting. I know that material plays a part too.

11-13-2004, 01:56 PM
Why don't you cast it yourself? It melts at 520 F. Easier than casting lead, which is easy. You can use a hardwood form.

[This message has been edited by Evan (edited 11-13-2004).]

11-13-2004, 04:17 PM
Evan's got the right idea. If you don't have a lead casting setup, go to one of the 'marts and get yourself an appropriate size dutch oven(cast iron for long term durability or aluminum for cost)and put it on the gas grill or better yet, a turkey frier...

I'm waiting for the turkey friers to go on sale so I can build a small smelter for lead using a 16 quart dutch oven.


11-13-2004, 04:27 PM
If you use something like white oak for a form it won't even get charred, just a bit scorched. The charring temperature of white oak is around 570°. As said, use a small cast iron pot on an electric hotplate or similar to melt the bismuth. Before using the form bake out any moisture in the oven first.

[This message has been edited by Evan (edited 11-13-2004).]

11-13-2004, 05:57 PM

According to the USGS, "Among the heavy metals, it is the heaviest and the only non-toxic." I'm perfectly willing to admit that the US government screws things up from time to time, but I'm wondering if you're thinking about some common bismuth alloys rather than elemental Bismuth.

11-13-2004, 08:47 PM

I read the USGS statement earlier and forgot to mention it.

I don't really know what they mean when they say "Heavy Metals". Most books refer to Heavy Metals as any metal with a specific gravity over 5, but this can be confusing. The term "Heavy Metals" tend to have more to do with their atomic composition than their densities.

That being the case, I guess you could say that Bismuth is a "Heavier Metal" than Lead and "is" less toxic, but that wasn't my point. My point was that Lead is "heavier" than Bismuth. I guess it really depends on how one defines "weight".

According to "most" Peridic Element Charts, Bismuth has an Atomic Wt of 209.98 and a density (or specific gravity) of 9.8 g/mL. Lead has an Atomic Wt of 207.2 (less than Bismuth) and a density of 11.4 g/mL. Based on the densities, Bismuth "weighs" 0.3532 pounds per cubic inch or 610.3 pounds per cubic foot. Lead "weighs" 0.4096 pounds per cubic inch or 707.7 pounds per cubic foot.

I'm not a nuclear scientist nor a chemist, so I can't precisely define the differences between Atomic Weights, Atomic Masses and Specific Gravities. The whole thing is rather irrelavent, as I can't pick up a cubic foot of either material, but given a choice, I'll take a cubic foot of Platinum. It weighs 1333.5 pounds per cubic foot, but only has an Atomic wt of 195.09.



11-14-2004, 01:47 AM
OK, you now get the nit pick baton... http://bbs.homeshopmachinist.net//biggrin.gif Well done.

Michael Az
11-14-2004, 10:32 AM
I wonder if it needs to be fluxed like lead, just in case you do decide to do your own melt. Lead needs to be fluxed to remix the different stuff that is in it when it is melted.

11-14-2004, 09:49 PM
I doubt it. The melting temp is below most other metals.

11-14-2004, 10:27 PM
We cast some at work for some rupture discs,just made a simple mould by milling the desired profile into a block of steel.

11-15-2004, 10:13 PM
So Rod:

Whatcha building? I'm curious as heck!

11-18-2004, 11:22 AM
Hey, common Rod.

Lots of people tried to help you with your drilling problem. Some of us just want to know what you're using the parts for. If its propriatary, just let us know generally. I'm curious if you're using bismuth for its electromagnetic properties or for some other reason...

11-18-2004, 05:36 PM
Thank you everyone for your suggestions.

I'm using the bismuth for its diamagnetic properties (hopefully) to form an adequate magnetic shield for a project I'm workin on. There is no known proper insulation as such, for magnetic fields - but rather highly magnetically permeable materials that can be used to "divert" the field; and diamagnetic materials which generate very week opposing fields.

Regards, Rod.

11-18-2004, 06:11 PM
Sounds fascinating. Good luck with the work and if it all comes together and you eventually can talk about it let us know! http://bbs.homeshopmachinist.net//smile.gif

11-18-2004, 06:54 PM

Have you heard of mu metal? That is what it is used for.

You probably won't like the price though. Sit down please.


11-18-2004, 08:30 PM
Mumetal (in its various forms) is a highly magnetically permeable nickel alloy. Unfortunately, it is not a pure (or passive) insulator of magnetic fields, but is used to divert or detour the fields away from an area to be protected - the downside being it is itself highly attracted to magnetic fields.

11-18-2004, 08:36 PM
OK, then what about some high temp superconductor and some LN2?

11-20-2004, 07:54 PM
Evan - thanks for the thought.