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Old 23-08-2021, 08:13   #46
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Re: how to test a chinese part versus name brand

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Originally Posted by Base821 View Post
I agree with the other posters that you can just try them and inspect them after use, which is probably all you really care about. But if you really want to know, there are material analysis labs you can send these into to test.

For example

https://www.emsl.com/Services.aspx?a...ceCategoryID=8
So if I am buying a £25 cutlass bearing, you are suggesting I have the material tested? How about a lithium battery at $400?

Its not going to happen is it. Now tell us about your boat please.

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Old 23-08-2021, 08:17   #47
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Re: how to test a chinese part versus name brand

No Pete. I am not suggesting that. Please apply your critical reading skills.

I said there are options "if you really wanted to know" that would cost more than the parts you are buying and that one really only cares about the functional performance of the parts, not really the materials.
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Old 23-08-2021, 08:33   #48
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Re: how to test a chinese part versus name brand

Back to original question(s)....

Depends on the item(s) you need/want to test.

Some products, a visual inspection, maybe some type of magnification lens required. Compare with the original installed OEM product. Note any differences/tolerances in size/machining/metal hardness. Using a file and magnification can tell you some information about the hardness of the metal.

A simple magnet can provide the metal types or composition of metals used. (if metal) Plastics usually have some sort of markings on composition, lookup the numbers/percent's . https://www.polyvance.com/identify_01.php

Bearings/ball bearings are somewhat easier to notice and spot poor vs premium quality. Are there spaces/gaps in and around the seal/housing? if a sealed bearing. How long does it roll/spin in your hand? Could tell you something about the grease/lubrications inside or lack of. Also is it rough during operation? Could mean poor internal bearings or impurities inside.
Search for some yt videos spotting fake/cheap bearings. (fidget spinners come to mind)

Electronics would need the electrical schematics and multi-meter to test/verify voltage/current. Not all have the schematics available or shipped with the unit.

Most issues are the "knock-offs" that are produced around the world and sold under the premium name brands. Parts are made in China because labor is cheap and can adapt quickly to new MFG specs/process. Not always because they make an inferior product. I would suspect a lot of no name and brand names are made in the same faculties or next door to each other.
Items that fail a QC for premium brands move on to the no name brand MFG and sold cheaper.

Question to ask yourself, how much is your time worth replacing part xyz?
Does it take a few minutes/hours? Replacing it every few weeks might not be ideal. Especially extra wear/tear on other parts being removed during process or the surrounding areas. Do you need sealed bearings to prevent particulate ingress? ie. Saltwater.

Is it critical to the operation if/when failure occurs? can it be broken for a few hours/days?

Cheap parts may be cheap, but factor in some of the above and they may not be that "cheap" in the long run.
YMMV
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Old 23-08-2021, 08:50   #49
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Re: how to test a chinese part versus name brand

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Umm…. You do not need to test to any particular specifications. The true test of serviceability is an operational test. Install the bearings and see if the work. Then continue using and see how long they last.


You could do a quick test before installing. Place both brands on a hard smooth surface. Lightly drop a common hammer head on each.
Inspect for distortion (are they still round?)
Inspect for chipping.
If they both test similar, give it a go!
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Old 23-08-2021, 09:09   #50
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Re: how to test a chinese part versus name brand

China can (and does) produce high quality stuff when demanded.

As mentioned, a reputable company doesn’t just call a Chinese company and order BBs as-is. They’ll usually provide a very detailed specification. The Chinese manufacturer then attempts to meet that spec for the order. Maybe their stuff already meets it, or maybe they have to modify their materials/process. The company then tests for compliance.

But if you order direct as the consumer, you really don’t know what you’re getting. It could be the very same supplier that Harken uses, but they may produce 5% Harken balls, 95% cheap junk—which you may end up buying. No real way to know.

If it’s a critical component that must be right the first time, or something that is a PITA to R&R, spend the extra money for the high quality parts. Otherwise, taking a gamble and doing the operational test as mentioned may save you some coin.
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Old 23-08-2021, 09:35   #51
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Re: how to test a chinese part versus name brand

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Originally Posted by C420sailor View Post
China can (and does) produce high quality stuff when demanded.

As mentioned, a reputable company doesn’t just call a Chinese company and order BBs as-is. They’ll usually provide a very detailed specification. The Chinese manufacturer then attempts to meet that spec for the order. Maybe their stuff already meets it, or maybe they have to modify their materials/process. The company then tests for compliance.

But if you order direct as the consumer, you really don’t know what you’re getting. It could be the very same supplier that Harken uses, but they may produce 5% Harken balls, 95% cheap junk—which you may end up buying. No real way to know.

If it’s a critical component that must be right the first time, or something that is a PITA to R&R, spend the extra money for the high quality parts. Otherwise, taking a gamble and doing the operational test as mentioned may save you some coin.
THIS.^^ I have been involved with this offloading to a small extent. They will build what you want, but you must know what you want and specify it! And make sure nothing is lost in translation. They will also build a piece of crap if you dont "set the expectation". An iPhone is a great example of Chinese quality.
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Old 23-08-2021, 10:26   #52
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Re: how to test a chinese part versus name brand

Plastic welding type tests

Take three old ones and three new ones

Heat - see if they melt / behave same with soldering iron. See if smoke smells same.
Fire - as above with a cigarette lighter
Hardness - Scape them both with a screwdriver, knife and then the square edge of a file.
Brittle - Hit them with a hammer

You'll know fast if it's similar plastic or not.
Sun / age may reduce performance of older material, making it more brittle.
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Old 23-08-2021, 10:30   #53
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Re: how to test a chinese part versus name brand

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What about the computers, phones and tablets you smash out your anti China rhetoric on?
Surely the items you have listed are not your proof the high quality of China products???? If it is, that is very funny. A phone, tablet computer that may last 12 months.That can't be repaired if it fails
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Old 23-08-2021, 11:20   #54
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Re: how to test a chinese part versus name brand

Lewmar and Harken specifiy torlon balls. You are talking about delrin balls. With a bit of scouring the internet, you can find 3/8" torlon balls in quantity for about 0.75 USD per ball, and similar delrin balls for about 0.10 USD per.



The difference? Under high pressure conditions (like in a genoa traveler, particularly when you snap a sheet from loose to tight--flogging, for example) delrin will internally heat and deform (not a lot) and delrin is not as hard and abrasion resistant (think of dried salt on the bearings).


So.... were I sailing an <30' boat in fresh water, would I replace worn torlon with delrin. Yes--because they are easy to replace and I could use up 7 sets of delrin bearings for the cost of torlon. But since I'm sailing a 46' heavy displacement boat in salt water, I have higher stress and higher abrasion, and I'd bet that the difference in price between the two would easily favor torlon if I paid myself minimum wage for lost sailing time (and particularly if I factored in the frustration of harder work at EOL for the delrin)


And would I be willing to bet that the torlon balls available from the sailing manufacturers and those from McMaster Carr, or any other reasonably reputable wholesalers all come from the same three factories? Absolutely. Would I buy 0.15 USD balls from AliBaba. Probably not. Odds of headaches are too high.
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Old 23-08-2021, 12:34   #55
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Re: how to test a chinese part versus name brand

Well that answers it. As far as I can tell Torlon, polyamide-imide, is manufactured only by one company, its inventor, Solvay Specialty Polymers. Torlon is apparently a superplastic, with some properties more similar to metal than plastic.

Since the OP's boat is a Leopard 47, the Delrin balls are best left for lesser duties, maybe bearings in the seat swivels...that's not to say that there may be more economical sources for genuine Torlon balls though.

For instance, there are several different sizes used in Chrysler automatic transmissions...but Mcmaster's probably the simplest solution --- providing Harken hasn't specified some bastard size in a typical proprietary-dick move.
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Old 23-08-2021, 12:59   #56
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Re: how to test a chinese part versus name brand

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The Anerican firm places its order with a Chinese manufacturer. The specification is pages (or more) long, and the bearings get tested as meeting the specification. The American company does not want to have to recall every product it sent out because a supplier sent it defective bearings. In other words the American source is your assurance that the quality is OK; where it was manufactured is not important.

Yeah, testing bearings would take a lab full of equipment. In this case, it wuld include chemical analysis.
You would hope that the American company tested them, in practice they may not, I have come across a lot of failings that were supposed to be high quality products, and failed through cheap or poor manufacturing, and be sure 1000s of companies have been stung with recalls.

Generally in the OP case, it’s not worth the risk or the saving, unless your using huge quantities, the items in question are surely not expensive enough to worry about the costs.
Better save the effort for something that’s going to save lots of coins.
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Old 23-08-2021, 13:02   #57
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Re: how to test a chinese part versus name brand

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I have recently found myself in need of some polyoxymethylene ball bearings. Harkin sells them for about 98 cents per bearing, Lewmar for about 1.25 per bearing. A company in Tennessee sells them for about 15 cents and a Chinese retailer sells them for $3 per thousand.


I would be very surprised if Lewmar or Harkin didn't get their bearings from a Chinese manufacturer but I of course have no proof. For $3 I am thinking of ordering a thousand from China and testing them to see how they compare. If they are crap I can use them as sling shot ammunition.


The question.
How could one go about comparing these items without a bunch of sophisticated equipment?


As always thank you for your thoughts
SP
Acetal/delrin compounds have good mechanical qualities for a plastic.
If you had one or two "good" samples, you could squash a suspect specimen in a vice, counting the vice handle rotation after contact with the jaws: you could grab one in a vicelok and press it over fine emery cloth, to check for the size of the flat, and finally you could check its melting temperature (beware! acetal is flammable)
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Old 23-08-2021, 13:15   #58
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Re: how to test a chinese part versus name brand

You pays your money and you takes your chances.
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Old 23-08-2021, 14:00   #59
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Re: how to test a chinese part versus name brand

If you feel the need to ask, I’d say buy factory original.
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Old 23-08-2021, 14:39   #60
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Re: how to test a chinese part versus name brand

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Originally Posted by Carl-T705 View Post
Surely the items you have listed are not your proof the high quality of China products???? If it is, that is very funny. A phone, tablet computer that may last 12 months. That can't be repaired if it fails
Carl-T705, I have been very impressed with phones and tablet computers made in China. Right now both my wife and I each have a phone and a tablet made in China, and I expect the service life to be excellent. I expect that because we've had previous units from China. Being on a boat we tend to be hard on gadgets. Which brings up another point you make which I'd also like to contest: "can't be repaired". Of course that is total hogwash. We've broken screens, power ports, etc, and our local "Cell Phone Doctor" manages to be able to repair whatever we take to him. Maybe the repair guys in your area are not as good as the Mexican ones in my area.

I also have three laptop computers on board. One, my favorite, from 2010, has been broken (screen, once, and hard drive, once) due to my misuse. Also had a mother board failure and a graphics board connector failure due to overheating. All totally fixable and so I'm still using that computer just because I love the screen even though my other two are newer and made outside of China (yet still in Asia). These are standard consumer products and have been in use continuously in a saltwater environment. So I have no argument with the quality and durability of Chinese goods.

I also have lots of other stuff, some expensive, some very cheap which were made in China. Of course I have stuff made in the US, Germany, and even the UK which I am also quite happy with.

In my view anyone who bashes all Chinese made stuff as junk is ignorant and racist.
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