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Discussion Starter · #1 ·
Was just reading about this cast stainless frame that was recalled! If u got one send it back unless u like eating cast . Off topic but I bought some cast horse shoes one time and the shoes busted hitting the pole some cast not that good guys.
 

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If anyone has more Info on this please share. I have a GZK HH+ and wonder if there is a way to be sure if it is cast or not and whom to contact about the recall if there is a problem etc, thanks.
 

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You have to be so careful with Chinese slings. There's even a new stainless sling out of the uk coming soon that is cast, and only 10mm thick. I would be very cautious of it.

The way I would check is to put the forks in a vice and give the handle a blow with a rubber mallet. If it breaks its cast, and shouldn't have been used anyway. If it's good stainless. You'll never break it with a 12 pound sledge. And stainless will bend right around without breaking.
 

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The scales on the above HH frame look right but the metal looks different than what is shown on the GZK web page. The screw on the above frame is larger, black in color and has a raised area around it. The GZK HH has a smaller, polished stainless screw that sits flush to the fork.

http://gzkchina.onloon.net/detail?itemId=91b1ff59319148059b8857fa3cecfeeb

I'm far from knowledgeable about steels but I thought properly cast 304 stainless steel was strong. I have all my steel frames tested for metal content to be sure they are not zinc or some strange alloy. The cast stainless frames come out dark and are polished to bring the shiny finish. I remember reading somewhere that a true 440 stainless is very hard but can be brittle and should be inspected for cracks if dropped on concrete or other hard surface.
 

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This is rather worrying to say the least. I would assume that the slingshots concerned were possibly made of "pot metal" i.e. ZAMAK:

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

Quote from Wikipedia: "The name zamak is an acronym of the German names for the metals of which the alloys are composed: Zink (zinc), Aluminium, Magnesium and Kupfer (copper).[2] The New Jersey Zinc Company developed zamak alloys in 1929. Zinc alloys are popularly referred to as pot metal or white metal. While zamak is held to higher industrial standards, it is still considered a pot metal." (end quote).

It's commonly used for injection molded parts, including certain firearms (think of the German "Arminius" revolvers). To be avoided like the plague for slingshots of any kind because of the danger of sudden breakage under force.

304 stainless steel consists of the following (quote from this specialist site: https://www.reliance-foundry.com/blog/304-vs-316-stainless-steel#gref)

"304 stainless steel is the most common form of stainless steel used around the world, largely due to its excellent corrosion resistance and value. It contains between 16 and 24 percent chromium and up to 35 percent nickel, as well as small amounts of carbon and manganese.

The most common form of 304 stainless steel is 18-8, or 18/8, stainless steel, which contains 18 percent chromium and 8 percent nickel.

304 can withstand corrosion from most oxidizing acids. That durability makes 304 easy to sanitize, and therefore ideal for kitchen and food applications. It is also common in buildings, décor, and site furnishings."

From what I have read, 440 stainless steel appears somewhat harder, and can be subject to sudden breakage, as opposed to gradual bending under excessive force like 304 steel because of the nickel content. Here is a relevant comparison of 304 and 440 stainless steel.

https://www.makeitfrom.com/compare/AISI-304-S30400-Stainless-Steel/AISI-440C-S44004-Stainless-Steel

All the 304 steel slingshots I have purchased via Aliexpress (Piao Yu) are slightly magnetic. Technically, they should be safe. :hmm:
 

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Seems like the material quality is always in question when it comes to Chinese slingshots. I don't know why they are always weakening the forks with all the clever and gimmicky clamps and such. I'd be more likely to buy if they had beefy solid forks that I wouldn't need to worry about...
 
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A closer look at cast Iron, in case the slingshots concerned were made of this material - which seems unlikely after reading this:

https://www.reliance-foundry.com/blog/cast-iron#gref

(Quote): "Cast iron is produced by smelting iron-carbon alloys that have a carbon content greater than 2%. After smelting, the metal is poured into a mold. The primary difference in production between wrought iron and cast iron is that cast iron is not worked with hammers and tools. There are also differences in composition-cast iron contains 2-4% carbon and other alloys, and 1-3% of silicon, which improves the casting performance of the molten metal. Small amounts of manganese and some impurities like sulfur and phosphorous may also be present. Differences between wrought iron and cast iron can also be found in the details of chemical structure and physical properties.

  • Although both steel and cast iron contain traces of carbon and appear similar, there are significant differences between the two metals. Steel contains less than 2% carbon, which enables the final product to solidify in a single microcrystalline structure. The higher carbon content of cast iron means that it solidifies as a heterogeneous alloy, and therefore has more than one microcrystalline structure present in the material."

Interesting! Comparing cast iron to Zamak (zink alloy), cast iron is much stronger in general:

https://www.makeitfrom.com/compare/ASTM-Grade-40-or-275-F12801-Grey-Cast-Iron/Zamak-7-ASTM-AG40B-Z33523-Mazak-7-Zinc-Alloy

Cast stainless steel (quote from Google) :"Commonly Cast Stainless Steel Alloys:

400 series steels are high strength and very machinable. They will tend to break rather than bend under intense pressure. 17-4 is the strongest of the stainless steel family and is used on parts that cannot bend".(end quote)

Thus, I am pretty certain that the slingshots with broken forks must have been made of zink alloy. The relevant question here would to know where this shoddy product was purchased to avoid nasty surprises for others.
 

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I know I have mentioned this many times but maybe someone here hasn't read the old postings.

Look for a local "gold buyer" outlet and take a few slingshots on your visit. It takes about one minute for them to test metal content. Over the last several years I had 15 slingshot frames tested and none contained zinc (12 Dankung & 3 AliExpress frames). The iron content is typically 70-85% and chromium 15-20%. Many contained nickel, manganese and sometimes a trace amount of copper (<1%). I have not found titanium in any frames, although at least one advertised as containing the element.
 

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It would be great if you could have the metal of that broken fork tip tested to know what it actually is. Some slingshots from China are also made of magnesium alloy:

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

"Magnesium alloys are mixtures of magnesium with other metals (called an alloy), often aluminum, zinc, manganese, silicon, copper, rare earths and zirconium. Magnesium is the lightest structural metal."

If your slingshot is magnetic in any way, you'll know it's not either zinc or magnesium alloy. Either way, it's some form of cast metal in view of the surface where the breakage occurred (I'm certainly not a specialist, just speaking from past experience).
 

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Discussion Starter · #13 ·
i have seen a lot of busted metal in trade that’s not good metal for sure . A stainless sling shot should take fork hits or drops .I have made frames 3 mm 300 stainless would not bat a eye at a fork hit . At 10 mm it should be indestructible even if the bolt hole was modified .Metal always cracks from sharp corners or bolt hole that frame looks like it just snapped off strange the way it busted
 

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There is so much to learn about metals. I came across this interesting site: the "Stainless Steel Directory" while looking up info about 304 stainless steel, which is what most Chinese slingshots appear to be made of - check it out:

https://askzn.co.za/stainless-steel/tech-grade-304.htm

Something that caught my eye is the following:

"Cold Working

CS 304 / 304L being extremely tough and ductile, are readily fabricated by old working.Typical operations include bending, forming, deep drawing and upsetting.

Note "bending". Thus, I would assume that 304 stainless steel would bend under excessive stress, as opposed to suddenly cracking - which is what makes it safe for slingshot frames.
 

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The broken zinc alloy slingshot fork photos shown at Dankung reveal a lesser material density (more porosity) than the ones shown above by Port boy, where the metal appears to be very fine grained: if Port boy's slingshot was not made of zinc alloy, then it's all the more important to find out what metal it actually is - particularly because of the very similar surface appearance :hmm: of the non-broken sections when compared to proper 304 stainless steel slingshots.

Cast iron objects do break when they fall on a hard surface, or when they are subjected to excessive torsion, and the broken edges I have seen in the past after such incidents look fairly similar to the photos from Port boy, but possibly not as fine-grained: specialist assessment is needed here, both in terms of color and material density.

The bottom line is to buy from a reliable seller: Dankung is indeed very reliable, but so is for instance Piao Yu at Aliexpress. I've ordered various slingshots from Piao Yu that are made of stainless steel as stated. If uncertain of what one has ordered, it's probably a good idea to have the metal tested. This would clearly apply to slingshots sold at a bargain price e.g. a slingshot sold as made of stainless steel for US$ 5 is rather questionable, whereas one selling in the US$ 15 to 25 range is generally the real deal. El cheapo always turns out to be more expensive at the end of the day.

Moreover, I would assume that serious sellers present at Aliexpress know full well that their business would come to crashing end if they knowingly sell slingshots made of brittle materials such as zinc alloy (Zamak, or "pot metal"), but advertised as being made of sturdy materials. It seems as though many of the dodgy products one hears about seem to show up on Ebay, where there may be fewer background checks of the sellers concerned.
 
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