I needed an 8x1.25mm bolt for removing stuck brake drums.
I asked the hardware store for the strongest bolts they had.
They had a grade 8.8 (zinc) in SAE sizes but class 10.9 (black) in metric
The guy was helpful and apologized that the class 10.9 was the hardest he
had in metric, and he was sure it was weaker than grade 8.8 - but he
wasn't sure 'what' it really meant.
The metric bolt, at $1.25 each, has a 10.9 stamped on the hex head.
Any idea what 'class 10.9' means in a black metric 8x125mm two-inch bolt?
Same as SAE Class 8. 8.8 is Class 5
I don't know what the numbers represent other than they correlate w/ SAE
grades. I'll leave that as "exercise for the student"... :)
In this nick of the woods (So Cal), brake drum's usually come off
without much trouble. I have a couple of garden variety, unknown grade
M8 X 1.25 bolts in my box dedicated to drum rotor pulling that now have
35 plus years of use on them. Never recall needing to use more than 5
ft/lbs or so.
Then again, I don't do a 'lot' of brakes, but even so, I bet they've
seen use over 100 times through the years, and still look new.
YMMV if you live/work in rust country.
On Monday, September 17, 2012 10:50:23 PM UTC-4, Bob Stevens wrote:
I'm not sure if this is correct, but it could just so you know what grade they
Most grade 8 bolts and washers I've purchased are gold-ish in color, but it's
just a coating. For example, if you extend the threads of a grade 8 bolt up onto
the neck, you'll exposed the silver below the gold-ish coating.
Could the colors just be "coding" so you know what grade you are using by sight?
The black is probably black oxide, as someone else mentioned. The
gold-ish is yellow zinc plating. Zinc is a hell of lot better than black
oxide for corrosion protection, but people like the look of the black
for some applications.
Someone else linked to a table of head-stampings for different grades.
So, the color is a coating, not a coding.
On Mon, 17 Sep 2012 19:46:24 -0400, Ed Pawlowski wrote:
That's good it's strong on tensile strength because I want to use it to
remove brake drums.
Based on the charts, it seems that the word "Class" is merely the metric
(i.e., ISO) set of standards while the SAE uses "Grade" and the ASTM uses
"Type" and "Grade" - but it seems they all connotate the same thing.
In this appication you will be /compressing/ the bolt, not tensioning it.
In any case, the holes in the drum will split /long/ before the bolt ever
10.9 is overkill for brake-drum removal. You can get away with the cheapest
bolts from any big box store. If they fit the threads in the drum, they are
good to use.
Two things to bear in mind:
1) possible rust ridge behind the shoes, and
2) the center hole rusted to the hub.
Do NOT simply keep screwing down on the bolts to overcome either of those
You need to shock it with impacts. An 8oz ball-peen hammer tapped
repeatedly around the lugs should do it. You want to tap as hard as if you
were knocking loudly on a door. You need many, many impacts to break up the
rust. Do this BEFORE applying any penetrant.
Do not neglect the rust-ridge at the open end of the drum! If present, this
will require you to back the shoes off using the access hole usually found
at the rear of the drums.
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