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Author: Subject: oh my god! 2900$ for a mortar???
pneumatician
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[*] posted on 12-4-2021 at 16:29
oh my god! 2900$ for a mortar???


I need a mortar for grind some rocks of around 7 in mohs scale and a mortar of iron is destrolled with this material! so I check to buy a mortar of Titanium and... wft!! 2900$ for this toy??? a bit expensive, no?

someone used one of titanium?? the area of impact in pestle is smooth after use with really hard rocks?? or lose some bits, is full of scraches...??

Tungsten Carbide is no good for heavy metals?

so others options "a bit" more cheap??

https://axel-search-e.as-1.co.jp/asone/global/g/NC3-7613-01/

https://www.samaterials.com/tungsten-carbide/2750-tungsten-c...
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violet sin
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[*] posted on 12-4-2021 at 18:07


That looks like a fancy lill thing ... PRICEY though.

On a more reasonable note, could you not throw a facing sheet in the bottom of something durable? A thin sheet bent up or tube sleeve for the bore length.

Kinda feel like you could beat the piss outta some hard rocks in an improvised device: section of galvie pipe nipple and end cap with a titanium disk 1/4" thick and a thin sheet sleeve. Really depends on how much material, will it be often used and such. But for a short run you may be able to cheat.

I've got two slabs of Ti( 6Al4V ) that would definitely crush stuff.. finding it would be the trick, hahahhaha.
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[*] posted on 12-4-2021 at 19:17


oh yeah, good redneck idea! :-) but titanium can be welded with steel?
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[*] posted on 12-4-2021 at 20:15


I can only see paying that much for a mortar if it's the artillary kind.



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[*] posted on 12-4-2021 at 23:46


Titanium is challenging to machine and somewhat expensive as an alloy, and it also comes with huge premium being a specialty product.

You might wanna look into materials that are unreactive. Second to that, acceptable impurities should be considered, if the material is not for analytical purpose. Also, if the impurities are inert, like glass, it doesn't matter. Using too soft or unsuitable materials for small amounts and short time is usually not a problem. For example, I just pumped HCl gas through PU tube - it corrodes and is already nasty yellowish-green, but it still lasts several hours and doesn't affect the process. PU tube costs 50c per m, while PTFE cost 10€.
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rockyit98
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[*] posted on 13-4-2021 at 00:55


try alumina mortar s .



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zed
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[*] posted on 13-4-2021 at 06:52


Ball Milling? Let the rocks, beat-up on the other rocks. That, is how time, made our beaches.

Your milling jar, can be ABS plastic. It's kinda soft, and durable. While stones are hard and brittle.

It's like a game of Rock, Paper, Scissors. The container endures, while the rocks are reduced to dust.

At some point, the addition of some Ball Bearings, might be helpful. Same principle as a Rock Tumbler.

https://www.samaterials.com/tungsten-carbide/2749-tungsten-c...

You just set things up. Pour yourself a beer, and go watch a soccer match on TV. If your rocks aren't powder when yer done, just leave things running, and go to sleep. Check again in the morning.

https://en.wikipedia.org/wiki/Ball_mill

[Edited on 13-4-2021 by zed]

[Edited on 13-4-2021 by zed]

[Edited on 13-4-2021 by zed]
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Fulmen
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[*] posted on 13-4-2021 at 07:12


Titanium would be a poor choice for a mortar. Contrary to common belief titanium isn't particularly hard. It has excellent strength-to-weight-ratio, but it's not stronger or harder than tool steel. If hardened steel won't cut it I would start looking at ceramics.



We're not banging rocks together here. We know how to put a man back together.
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violet sin
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[*] posted on 13-4-2021 at 10:23


@Fulmen
What about it's work hardening property. From my LIMITED experience and fair amount of reading, it gets really pissy about heat and pressure.

Look at the YouTube vids on cutting it with cold temps and single pass w/ tons of lubricant. It's said if you forge forward with too high a feed rate, it will start eating blades left and right. You can drill it as long as there's not too much dwell time. But might as well pick a new spot to drill if it f's up there (normal drill bits). Metal forums said it's hard to deal with and thick sections are ideally cut by water jet. Last time I inquired it was 30$/in to do that in california.

My stiletto hammer will beat the piss outta steel brackets and has done so for years. It's just too light to proper F them things. Really annoying when every joist hanger is low and in the way for drywall.

Perhaps the internet lies or exaggerates the facts, but it sure becomes less than profitable to blow through a whole bunch of cutting tools for something small. So maybe it's just from metal fabricators love of profits, rightfully so, that gives it such a bad name.

I've included no references, sorry. No time for that presently.
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Morgan
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[*] posted on 13-4-2021 at 10:43


That brought to mind some "pestle shapes" I bought at some industrial supply store for cheap. They were large titanium ball joints for hip replacements still in the package. The finish of course was mirror smooth and they had a long angled spike on them. They were probably an alloy though?
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[*] posted on 13-4-2021 at 10:58


Morgan, those are expensive. Very expensive. Sellable.

When my Aunt Died, they recycled her Titanium Hip transplant.
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[*] posted on 13-4-2021 at 11:37


Steels can work harden too you know. The workhorse of the industry, Ti6Al4V, has an ultimate tensile strength of 950MPa. That's nothing, I can buy fasteners that are 1200Mpa at the hardware store. And tool steel can reach twice of that.

But titanium machines like crap, that's for sure. It work hardens like nothing else, and I suspect the low Youngs Modulus makes everything just that much worse.
Steels can work harden as well, 316L is somewhat infamous in that respect. Not as bad as Ti though.




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[*] posted on 13-4-2021 at 11:46


Umm, yeah, about that hardness..

Titanium doesn't exactly cut it. Pun intended. It is PITA to work with, as it work hardens like nothing, and there are those who work with titanium, and then the rest of us who don't. Only inconels are comparable to the unmanageability of titanium.

But titanium isn't hard. It's very good structural material, as it's light and strong. But the HRC of it lacks, and even if it gets higher with some alloys, it's pretty much like using gold nuggets as shotgun pellets instead of lead or steel. Titanium isn't that expensive as material, as it's one of the most common elements on earth, but whatever's made of it, costs a lot because of it's difficulty in machining it, hence it's preserved for purposes it's most suitable, and that is aerospace and transplants due to biocompatibility.

If you need HARD mortar, get ceramic or hardened tool steel one. The ceramics do not have upper limit in hardness, but tool steels easily cross way over 60HRC and you will need some effort to put a dent in that. If what you are grinding is so hard that tungsten carbide, diamond and cubic boron nitride get scratched by it, then you will need to consider some other working methods, like laser cutting.

And, like I said, many times it's better to use expendable materials for some purposes. I've even discarded pots after boiling lead or some other nasty stuff because they were cheap and I didn't bother going through the trouble of cleaning them.
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Fulmen
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[*] posted on 13-4-2021 at 12:02


Titanium might be abundant, but the refining process (Kroll) is exceedingly inefficient and therefore costly.



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[*] posted on 13-4-2021 at 14:30


I think you could make this pretty easily if you found a machine shop that will turn down a Titanium rod(s) for you.


https://www.ebay.com/itm/3-5-X-2-TI6-4-titanium-round-stock-...

This seller has tons of good Ti cheap. I think he even has up to 6" diameter round's and you can get it by the inch.
https://www.ebay.com/itm/Titanium-Round-Bar-6AL4V-1-375-x-12...



All you need for the pestel is various diameters turned down to a 1/2 sphere and tapered up maybe 1/2 inch. Then drill a hole, tap it, and make a steel handle with a screw coming out of it, so you could change the pestle head when you want or need to. You could make small ones to larger ones and vary the curve.
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[*] posted on 13-4-2021 at 23:43


Quote: Originally posted by Fulmen  
Titanium might be abundant, but the refining process (Kroll) is exceedingly inefficient and therefore costly.


Yes, compared to other metals, it's quite expensive. At cheapest, you can prepare to pay 10-50€/kg of the stuff, depending on form, alloy, quantity and other factors, like location. The mere materials cost for such mortar can be in order of 100-300€ depending on size, and as true socialists we do not count any added value for the work needed to turn that ingot into a mortar and a pestle. ;)
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[*] posted on 14-4-2021 at 04:53


well, thinking a bit about this subject after reading all this opinions... no matter if a mortar-pestle is mega hard, the problem arise when the material to crush is near or very near as hard like the combo mortar-pestle. So with a iron mortar can reduce to dust egg shell without any scrache or fear of losing shattered bits that contaminate the thing you want to crush, but with rocks... near hard as mortar the contamination by erosion and small chipped pieces is inevitable.

well to try this "theorie" I need to spend a lot of money buying a lot of mortars of every material on sale and inclusive making my own!!! :-(

redneck tech here do not work because too much contaminants and I want only the material crushed

https://www.youtube.com/watch?v=Rg6WrRzknWY
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Morgan
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[*] posted on 14-4-2021 at 07:16


I wonder if you could press/stamp form a bowl or mortar shape if you bought a round sheet or plate of titanium, maybe heating the metal to prevent cracking.
There're a lot of inexpensive camping titanium bowl shapes for sale if you could form a support mold or cladding underneath the titanium for strength.

Here's an expensive rice bowl however that has a somewhat appealing design.
https://www.eatingtools.com/home/80-ti-rice-bowl-titanium-by...

Speaking of insane pricing, it occurs to me my brother bought a pair of Van Staal titanium pliers/corrosion proof for fishing offshore in the gulf.
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Fulmen
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[*] posted on 14-4-2021 at 10:44


First off: Forget about titanium, it's not the solution even if the cost isn't an issue.

And it's not like you need something harder than the material you're grinding. I've crushed and milled a lot of quartz with steel jaw crushers and disk mills. Of course there is some wear, but it's not as bad as you might think. The reason is that steel is ductile while rock is brittle.




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[*] posted on 14-4-2021 at 21:11


Ummm. I'm thinking shock. Sledge hammer impact.

Thermal Shock, is a possibility too.

Or, lapidary equipment. Grind it up via Carbide (or Diamond) Grinding wheel.

You don't like tumbling/ball milling?

[Edited on 15-4-2021 by zed]
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[*] posted on 15-4-2021 at 05:28


As Fyndium mentioned: titanium is falsely portrayed as some kind of miracle material; the truth is that steel beats the pants off it any day of the week in almost all applications.

Typical grades are on par with only mild steel (50-70ksi), and a well-selected grade of steel wins in all aspects - toughness, hardness, yield strength, and fatigue resistance. High strength titanium involves expensive alloys and typically requires forging; that is not what you'll get buying a bowl or a bar from eBay. You'll find that consumer products are made from the worst play-dough-grade Ti to keep manufacturing costs low and are more of a gimmick than anything.

Something as simple as off the shelf AISI 4140 steel bar stock with a little heat treatment is FAR tougher - the core somewhere around 130ksi and the surface HRC 63-65 - and everyone and their brother can machine it for you. (I'm a development engineer in the bearing industry, by the way - this is my wheelhouse)

Titanium shines in aerospace and defense because it is about 56% as dense as steel and stronger than most grades of aluminum (especially at higher temperatures), which makes it attractive for aircraft use. This unfortunately earns it the moniker of a "Military Grade" material, and salespeople will eagerly ram that down the throat of anyone who doesn't know much about why titanium is a terrible choice in any situation where weight is not of maximum importance.

To weigh in on the crushing issue, just wrap the rocks in a newspaper packet and go to town with a good hammer until you get the size you want. Otherwise, a ball mill is the obvious choice - very hard ceramic media is widely available should you need rock flour for some reason.
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[*] posted on 15-4-2021 at 09:24


if you can do this, epoxy bonded alumina or silicon carbide sand layer inside in a normal mortar (even wood) will give best of both world.as it's hard and not brittle, even when you hit it. just think of composite abrasive grinding wheels .I think the best way to do this is by applying medium viscosity take long time to harden epoxy and coating the inside of the mortar and out side of the pestle and filling and pressings the mortar with said sand and pushing the pestle in it. then let it cure and pure the excess sand and washing to clean it thoroughly. if you feeling adventures you can also now coat with low viscosity clear epoxy to make sand more secure.



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unionised
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[*] posted on 15-4-2021 at 10:05


Buy or make a percussion mortar.
https://www.ascscientific.com/geology-laboratory-equipment/j...

Steel is just fine.

[Edited on 15-4-21 by unionised]
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Morgan
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[*] posted on 15-4-2021 at 12:23


I remember telling a pulsejet enthusiast titanium wouldn't be a good choice for making a pulsejet. He went ahead and made one out of grade 2 titanium anyway but found it started flaking badly from reacting with the air.

"Testing out R/C control of a new 6" titanium valveless pulse jet. This Ti jet is about half the weight of an equivalent stainless jet at 2.4lbs. Too bad titanium can't take the heat. The combustion chamber began to ablate as soon as the jet got up to temp. Oh well. Back to stainless I guess :) " https://www.youtube.com/watch?v=y8sxbw8u3e8

Grade 2 or chemically pure titanium forms cracks in automotive exhaust systems and the oxidation resistance is insufficient a Porsche article says at around 700 C or 1292 F.
Maybe because the SR-71 uses it people think it's good for "high" heat in air or that it excels in all areas or the best choice for strength or hardness.

Tidbit
https://www.amt-advanced-materials-technology.com/materials/...



[Edited on 15-4-2021 by Morgan]
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[*] posted on 15-4-2021 at 14:08


Quote: Originally posted by Fulmen  
First off: Forget about titanium, it's not the solution even if the cost isn't an issue.

And it's not like you need something harder than the material you're grinding. I've crushed and milled a lot of quartz with steel jaw crushers and disk mills. Of course there is some wear, but it's not as bad as you might think. The reason is that steel is ductile while rock is brittle.


Yuo are right but I search "pharma purity", ok I use steel, and with a magnet separate the pieces of mortar-pestle chipped... ha ha ha, the problem here?? ha ha ha, the rocks I want to reduce to dust are ferro-magnetic!!! :-)
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