Defective hardware (bolts)

[GoceKU]

Over the years i've seen lots of defective hardware, under sized, over sized, cross threaded, but this is a first for me, how come the whole batch passed QC, around 500 pcs almost all split in half, has anyone come across this with stainless steel bolts.

 

[extropic]

Over the years i've seen lots of defective hardware, under sized, over sized, cross threaded, but this is a first for me, how come the whole batch passed QC, around 500 pcs almost all split in half, has anyone come across this with stainless steel bolts.

I don't come across many examples of manufacturing defects in fasteners, certainly not enough to be considered significant.
What you pictured is new to me.
Rather than asking "how come the whole batch passed QC", I'd just return them and look for a more reliable supplier.

Are those metric fasteners, supposed to conform to some DIN or other standard?

 

[GoceKU]

I don't come across many examples of manufacturing defects in fasteners, certainly not enough to be considered significant.
What you pictured is new to me.
Rather than asking "how come the whole batch passed QC", I'd just return them and look for a more reliable supplier.

Are those metric fasteners, supposed to conform to some DIN or other standard?

I did exchanged them, but the thought of what can happen if i did not catch them is bothering me, the supplier is not at fault is the manufacturer. Yeah they are M8x25mm, everything here is metric.

 

[RJSakowski]

With large manufacturing lots, quality control is exercised by random sampling. The frequency of sampling is determined in part by previous history. As the number of incidents of bad parts decreases, the sampling becomes more lax. Modern quality control relies heavily on statistics.

My guess is that the defect arose because of a bad stretch in the stainless steel coil used to make the bolts. Most likely, this was caused by a cold shut in the rod forming process which could go unnoticed by the rod manufacturer. When the rod was converted into bolts, the bad section resulted in a number of bolts in the batch with the defect. These could easily be missed by the quality control sampling.

Bringing this up to the vendor should result in the filing of a non-conformance report to the bolt manufacture who, in theory, will take up correctove actions including increased sampling rates and determining the root cause of the problem.

If it points to the rod manufacturer, they will go through the same process..

 

[extropic]

I did exchanged them, but the thought of what can happen if i did not catch them is bothering me, the supplier is not at fault is the manufacturer. Yeah they are M8x25mm, everything here is metric.

I don't know how your supply chain works in Macedonia but, assuming that you didn't specify the manufacturer, I would certainly consider the supplier (seller) responsible for dealing exclusively with reputable manufacturers and buying fasteners that conform to applicable standards.

If the fasteners are used in a product for resale (so failure would be a problem), maybe you should be specifying the applicable standard, as well as the size, on you purchase order. The fasteners don't conform to the standard = supplier problem = find a more reliable supplier who does a better job of selecting manufacturers.

 

[P. Waller]

What makes you think that the manufacturer has QC at all?

I should imagine that it would be difficult to do that during the fastener making process, the fault almost certainly lies with the wire manufacturer that made the stock coils of material.
Whomever was running the header and roller was not present at the time (-:

Screws at that size are a 1000 part or more per hour process, it would be quite easy to make thousands of bad parts if the raw material is flawed.

 

[hman]

Shoula considered hanging on to a couple of them .... they'd be "just the thing" for oversized holes

 

[pstemari]

Harrumpf. Even at 1,000 pieces/hour, that's still a half-hour's worth of 100% bad parts. It's pretty poor manufacturing to not notice that.

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[GoceKU]

With large manufacturing lots, quality control is exercised by random sampling. The frequency of sampling is determined in part by previous history. As the number of incidents of bad parts decreases, the sampling becomes more lax. Modern quality control relies heavily on statistics.

My guess is that the defect arose because of a bad stretch in the stainless steel coil used to make the bolts. Most likely, this was caused by a cold shut in the rod forming process which could go unnoticed by the rod manufacturer. When the rod was converted into bolts, the bad section resulted in a number of bolts in the batch with the defect. These could easily be missed by the quality control sampling.

Bringing this up to the vendor should result in the filing of a non-conformance report to the bolt manufacture who, in theory, will take up correctove actions including increased sampling rates and determining the root cause of the problem.

If it points to the rod manufacturer, they will go through the same process..

RJ, i think you're are right, this must be cold shutdown or double feed.

 

[GoceKU]

When i got the bolts exchanged the guy over the counter said, with plated fasteners they go to multiple QC's as they go thru the processes, stainless bolts get packed right out of the machine never the less it opened my eyes to be more careful even when using new hardware.

 

[pontiac428]

And don't leave your hardware out in the cold!

 

[P. Waller]

Harrumpf. Even at 1,000 pieces/hour, that's still a half-hour's worth of 100% bad parts. It's pretty poor manufacturing to not notice that.

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Indeed it is, however a majority of consumers will not pay more for increased inspection intervals or very expensive in-process inspection technology.

The remedy is to just take the bad ones back and give the consumer 500 more no questions asked. Exactly how much money per screw did they cost?

 

[sailor1845]

Those bolts probably came from China and there is no quality control over there. There are no junk yards in China, they send all of it here!
I refuse to buy China made and will go out of my way and pay more for American made products.

 

[GoceKU]

Exactly how much money per screw did they cost?

Individually they are 0.35 euro each, when buying in bulk on a box price is 0,15 euro a piece, they are not made in china, i think the box said made in Belgium.

 

[GoceKU]

It happened again, but this time on zinc plated M6x25mm steel bolts, different store different manufacturer, the same problem, the bolts had a part of them pulling away, but this time i check them in the store and asked for a different box, they exchanged them right there but i did not take a picture to share, talking about no QC.

 

[Tozguy]

This thread is a reminder for me to do QC on everything I buy from anywhere. It is too easy to believe that things are the way they should be but in reality they are not ALWAYS especially when humans with smart phones are involved. Thanks for sharing GoceKU

 

[john.k]

If the bolts wernt made in China,Ill bet the stainless coil was............recent case I witnessed a EWP was rebuilt for 10 yr inspection,all new 11.8 bolts in the turntable mount to frame...........bolts all tensioned by a hydraulic unit............worked a few hours ,when the machine was moved ,painters noticed a lot of new nuts and bits on the ground...........around 2/3 of the bolts had cracked around the thread in a spiral as they were tensioned,and broken off completely when put to work.....all the bolts were OEM supplied certified.......but the machine was Chinese,so the bolts were too.