• From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Topic: Watch out for imitation grade 8 bolts!

I was working on the Jaggernaut last night and ran across a new problem. When we first got the car we noticed one of our ball joints was bad enough to give 1/4" play at the top of the wheel, so of course we set replacing it as one of our priorities. Jaguar ball joints are really pricey - $70 a piece. After searching the entire damn web we found a "URO Parts" ball joint considerably cheaper. When I went to install the ball joint I noticed the old bolts were grade 8 hardened standard bolts - 5/16" fine thread. The new bolts are marked "8.8" which is a metric hardness rating that's comparable to grade 8. I held the thread of the two bolts together and they matched up perfectly!

I started threading the new bolts in place. Man, they were fitting more snug than the old bolts, but the old bolts did have a lot of corrosion on them. Maybe it's the threads. They look a little rough. Aren't grade 8 bolts usually black or anodized?

SNAP! @#$%ing thing broke off!

Clue #1 - Looks the same size as a standard bolt but has a metric marking.
Clue #2 - Difficult to thread in.
Clue #3 - Poor machine work - not deburred.
Clue #4 - Shiny

Consider yourself warned. Replace the bolts.

BTW, Neither Lowe's nor Home Depot stock fine thread grade 8 bolts.

  • Spank
  • Utter Madman
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  • From: Escondido, CA
  • Registered: 2009-06-10
  • Posts: 5,864

Re: Watch out for imitation grade 8 bolts!

8.8 metric bolts are a different size and thread pitch than 5/16" bolts. Not much, but if you're trying to thread a metric bolt into a non-metric hole, it ain't gonna work.

Sorry if I'm stating the obvious and you know this already.

Spank's Website

  • From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Re: Watch out for imitation grade 8 bolts!

You are stating the obvious and I already know that, but I appreciate your response. The threads match up perfectly. I don't mean they mostly match up, I mean they matched up perfectly. After comparing the old and new bolts some more, the replacement bolts seem a hair larger at the threads. Perhaps if they'd been deburred they'd fit better, but they're still not grade 8 - it drilled out way too easily.

I did get the bolt out finally. The extractor wouldn't budge it, so I drilled it out bigger and then broke a tap trying to clean the remains out of the threads.

  • JThw8
  • JThw8
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  • From: Mullica Hill, NJ
  • Registered: 2009-06-10
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Re: Watch out for imitation grade 8 bolts!

Another point which I was corrected on when I made the same mistake as you by a metallurgy and fastener specialist.  Metric 8.8 is NOT the metric equivalent to grade 8.  Metric 10.9 is the grade 8 equivalent.

So indeed you are correct they were not grade 8, but they were also not imitation.

http://wartburg.misfittoysracing.com
OTTER: "I think that this situation absolutely requires a really futile and stupid gesture be done on somebody's part."
BLUTO: "We're just the guys to do it."

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  • Serj
  • Serj
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  • From: Cincinnati, OH
  • Registered: 2009-05-02
  • Posts: 1,601

Re: Watch out for imitation grade 8 bolts!

funny how i just look for the highest damn grade bolt i can get for the application. i don't like taking chances. i actually think all the hardware i got for my submarine harness is 10.9, plus some place i found high-strength washers. I'll have to find the box for those.

6 Reply by EriktheAwful (edited by EriktheAwful 2010-04-22 03:43 AM)

  • From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Re: Watch out for imitation grade 8 bolts!

but they were also not imitation

When the bolt is a standard size, but it's marked with a metric hardness rating, I think it's a pretty good indicator that the rating's been faked. Especially when it's not black or bronze but very shiny and it's not stainless steel.

I might be wrong. I do know it wasn't up to the standard of the original bolt. Jaguar may not have had a reputation for reliability, but everything on the car is built like a brick outhouse.

  • JThw8
  • JThw8
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  • From: Mullica Hill, NJ
  • Registered: 2009-06-10
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Re: Watch out for imitation grade 8 bolts!

EriktheAwful wrote:

Especially when it's not black or bronze but very shiny and it's not stainless steel.

Not trying to dispute you as much of this is what I thought as well.  Again coming from the discussion I had with the expert on another forum, the coatings are actually not a required or standard item on grade 8 and in fact he recommends against them as usually the coating process can actually alter the strenght properties.

http://wartburg.misfittoysracing.com
OTTER: "I think that this situation absolutely requires a really futile and stupid gesture be done on somebody's part."
BLUTO: "We're just the guys to do it."

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  • From: Des Moines IA
  • Registered: 2009-06-08
  • Posts: 135

Re: Watch out for imitation grade 8 bolts!

You tried to thread a metric 8.8 bolt into a standard hole if you eyeballed the bolts they would look identical the only way to tell the difference is to go at them with calipers and a thread gauge.  Metric 8.8 is grade 5 not grade 8.  It has nothing to do with fake bolts you got the wrong hardware for the job.

Formerly an asshole driving an Infinity
Now just another cock with a Porsche
Chief bad decision maker of Team Lowbrau

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  • From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Re: Watch out for imitation grade 8 bolts!

I know that metric and standard threads are different. I know how to use a thread gauge. I have two decades of experience putting bolts into equipment. The threads were absolutely f***ing identical. The original bolt was a 3/4" long 5/16"- 24 thread bolt, and the one that replaced it was a 3/4" long 5/16" - 24 bolt. You can thread gauge it all day. The fact is the threads were a hair taller and the bolt was not the proper hardness. The threads were just big enough to bind up, and the bolt was too soft for the job.

I drilled the bolt out and the remains of the threads that came out were not cross threaded and neither (thankfully) was the spindle.

The bolt was a piece of $#!+.

  • From: Knoxville, TN
  • Registered: 2009-12-04
  • Posts: 145

Re: Watch out for imitation grade 8 bolts!

http://www.unified-eng.com/scitech/bolt/boltmarks.html

8.8 are low strength, equal to grade 5.

Rich DeFrancisco
Chump Change Racing aka "The Bridesmaids"
1986 BMW 535im
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  • From: Elgin, IL
  • Registered: 2009-05-01
  • Posts: 136

Re: Watch out for imitation grade 8 bolts!

EriktheAwful wrote:

I have two decades of experience putting bolts into equipment.

Experience fail.  If it says 8.8 it's metric, the threads are not identical.  If you have more of these "fake" bolts take them and the 5/16 bolts to a hardware store and see what size nuts thread onto them.  Or just admit now that you screwed up.  It's OK, I'm sure a lot of us have made the metric/SAE error.  I've done it.

Aaron

1999 Astro (Green the Daily Driver) - 2WD, 4.3L, 3.23, 200k+ miles, FE2 steering
1997 Astro (Grumpy the $250 Rally Van) - AWD, 4.3L, 3.42, 330k+ miles on the orig eng and trans, $30 eBay fuel pump
  • From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Re: Watch out for imitation grade 8 bolts!

You're ignoring what I'm saying. The bolt was MARKED as a metric, but it was a STANDARD SIZE BOLT! I can put the two bolts together, threads to threads and they line up for the entire length! Will it help if I tell you when I gauge it it's between 1.0 and 1.25 metric threads? Do you want me to mail one to you?

Should I have trusted this bolt in the first place? No. That was my experience fail. I thought to myself "It's what came with the part. The threads line up good and it threads into the hole decently well. I'll go ahead and use it." I should have paid more attention to the warning signs of 1) standard bolt marked as metric, 2) tight fit, 3) unfinished threads, and 4) not as hard as the originals.

I knew that 8.8 wasn't as hard as grade 8, but I thought it was relatively close. I guess that's why I'm not a metallurgist.

I'm sorry if you think I'm tilting at windmills. I thought I was doing a service by reminding you that there is crap like this out there.

  • From: Dallas Tejas
  • Registered: 2009-05-01
  • Posts: 527

Re: Watch out for imitation grade 8 bolts!

EriktheAwful wrote:

I know that metric and standard threads are different. I know how to use a thread gauge. I have two decades of experience putting bolts into equipment. The threads were absolutely f***ing identical. The original bolt was a 3/4" long 5/16"- 24 thread bolt, and the one that replaced it was a 3/4" long 5/16" - 24 bolt. You can thread gauge it all day. The fact is the threads were a hair taller and the bolt was not the proper hardness. The threads were just big enough to bind up, and the bolt was too soft for the job.

I drilled the bolt out and the remains of the threads that came out were not cross threaded and neither (thankfully) was the spindle.

The bolt was a piece of $#!+.

As for diameter, 5/16 is 0.3125" 8mm is (8/24.5) = 3.1496"  enough to make for a tight fit, a hair taller as you describe.

As far as thread pitch goes 5/16-24 and 8mmx1 are so close that without a longer bolt you cant tell that the thread pitch is off.   0.9% difference or 1 thread in 101.

As for thread form, there are trivial differences.

So yes, with a small thin nut they are interchangeable.  With a full depth nut or threaded hole it will seize.  Softer material might thread in but you are deforming one or the other.

YMWV

El Capitan de los Bastardos De Lemons
1993 Linco Mark Ate
1957 Renault Dauphine
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  • From: Elgin, IL
  • Registered: 2009-05-01
  • Posts: 136

Re: Watch out for imitation grade 8 bolts!

EriktheAwful wrote:

You're ignoring what I'm saying. The bolt was MARKED as a metric, but it was a STANDARD SIZE BOLT!

You can keep going till you type your finger down to nubs and I still don't think anyone will go along with that it is a Metric marked SAE bolt.

Time to head to the hardware store with a video camera, try to prove yourself right and post the results on YT.

Aaron

1999 Astro (Green the Daily Driver) - 2WD, 4.3L, 3.23, 200k+ miles, FE2 steering
1997 Astro (Grumpy the $250 Rally Van) - AWD, 4.3L, 3.42, 330k+ miles on the orig eng and trans, $30 eBay fuel pump

15 Reply by EriktheAwful (edited by EriktheAwful 2010-04-23 11:03 AM)

  • From: Choctaw, Oklahoma
  • Registered: 2009-11-12
  • Posts: 2,145

Re: Watch out for imitation grade 8 bolts!

If it's one thread in a hundred, then that might be why the seven other bolts went in and there were no stripped threads. I've never seen a metric bolt go in a standard hole that easy though.

I will say that I was wrong.