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Replace cheap 4.8 bolt with What markings indicate a stainless or strength bolt?
- Thread starter Jacobson
- Start date
metlmunchr
Well-known member
- Joined
- Sep 10, 2011
- Messages
- 1,281
Metric 4.8 is roughly the equivalent of Grade 2 in SAE bolts. Run of the mill 18-8 SS bolts have about the same strength as Grade 2 bolts. Standard SS bolts are used for corrosion resistance, not for high strength. The same applies to metric ss bolts as well. For high strength ss bolts you have to go to a specialty manufacturer like ARP. They make SS bolts with strength equal to Grade 8 heat treated alloy bolts.
bob15
Well-known member
What is the application?
Stainless bolts aren't always the end-all greatest bolt out there. Besides Grade 8 bolts, there is also a Grade 9 (Mcmaster Carr sells them) and then there Bowmalloy, probable one of the best bolts out there......high tensile strength and high ductility.
A bit about Bowmalloy hardware:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjAAegQIBBAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Ffiles%2FSEPTEMBER%25202013%2FK-1756%2520Bowmalloy.pdf&usg=AOvVaw32J6Y0P8Z0gY5ncIcVdQzR
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjABegQIDhAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Fpdf%2Feng%2Fbrochures%2FK-25%2520Bowmalloy%2520Brochure.pdf&usg=AOvVaw3LzdU3i-1IpVE4jmZVZbQC
Stainless bolts aren't always the end-all greatest bolt out there. Besides Grade 8 bolts, there is also a Grade 9 (Mcmaster Carr sells them) and then there Bowmalloy, probable one of the best bolts out there......high tensile strength and high ductility.
A bit about Bowmalloy hardware:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjAAegQIBBAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Ffiles%2FSEPTEMBER%25202013%2FK-1756%2520Bowmalloy.pdf&usg=AOvVaw32J6Y0P8Z0gY5ncIcVdQzR
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjABegQIDhAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Fpdf%2Feng%2Fbrochures%2FK-25%2520Bowmalloy%2520Brochure.pdf&usg=AOvVaw3LzdU3i-1IpVE4jmZVZbQC
bob15
Well-known member
What is the application?
I have seen SS hardware fail in places and then struggled to remove the remnants of them after they have broken due to fatigue and being SS (much harder to drill out and remove due to galling). Is this grade 1 bolt going to be installed where if it fails, it will need to be drilled and a EZ-out used? If so, choose wisely......and never-seize if SS hardware is used.
You have stainless, galvanized and yellow-chromate which all have some form of corrosion resistance.
I have seen SS hardware fail in places and then struggled to remove the remnants of them after they have broken due to fatigue and being SS (much harder to drill out and remove due to galling). Is this grade 1 bolt going to be installed where if it fails, it will need to be drilled and a EZ-out used? If so, choose wisely......and never-seize if SS hardware is used.
You have stainless, galvanized and yellow-chromate which all have some form of corrosion resistance.
Ok, so 4.8 is strength not corrosion.
I just need corrosion, not strength.
So, I just need to look for 4.8 and also stainless?
4.8 and stainless does not exist. Metric grades (4.8, 8.8, 10.9, etc) are ratings for alloy carbon steel hardware.
If you need stainless, buy stainless. Stainless bolts and screws are available in various levels of strength, but aren't rated the same way because stainless hardware is not normally used for critical strength- it's used where corrosion resistance is the primary concern.
metlmunchr
Well-known member
- Joined
- Sep 10, 2011
- Messages
- 1,281
Most standard strength metric SS bolts are designated as A-2 for the equivalent of 18-8 SS, or as A-4 for the equivalent of 316 SS which has greater corrosion resistance in certain aggressive exposures like elevated temperatures, acids, etc.
For something that won't corrode in normal outdoor exposure, the A-2 material will work fine. As mentioned above, anti-sieze is a good idea.
For something that won't corrode in normal outdoor exposure, the A-2 material will work fine. As mentioned above, anti-sieze is a good idea.
nadogail
Well-known member
It's for an exhaust hanger bolt.
IMHO, Almost anything should be adequately strong enough to hang an exhaust pipe.
timgunn1962
Well-known member
The metric grading system for bolts uses two numbers. The first is the ultimate tensile strength. The second is the yield point as an approximate proportion of the UTS.
An 8.8 metric bolt has an UTS of 800 Newtons per square millimetre and a yield strength of 0.8 times the UTS: 640 N/mm2. This is the everyday grade of metric HT bolt: broadly equivalent to SAE grade 5.
Stainless bolts are usually either A2 (304 stainless) or A4 (316 stainless) and are not necessarily rated for strength. However, A2-70 is a fairly common grade and denotes an A2 bolt with a UTS of 700 N/mm2. That seems like a good bet for the application.
An 8.8 metric bolt has an UTS of 800 Newtons per square millimetre and a yield strength of 0.8 times the UTS: 640 N/mm2. This is the everyday grade of metric HT bolt: broadly equivalent to SAE grade 5.
Stainless bolts are usually either A2 (304 stainless) or A4 (316 stainless) and are not necessarily rated for strength. However, A2-70 is a fairly common grade and denotes an A2 bolt with a UTS of 700 N/mm2. That seems like a good bet for the application.
What is the application?
Stainless bolts aren't always the end-all greatest bolt out there. Besides Grade 8 bolts, there is also a Grade 9 (Mcmaster Carr sells them) and then there Bowmalloy, probable one of the best bolts out there......high tensile strength and high ductility.
A bit about Bowmalloy hardware:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjAAegQIBBAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Ffiles%2FSEPTEMBER%25202013%2FK-1756%2520Bowmalloy.pdf&usg=AOvVaw32J6Y0P8Z0gY5ncIcVdQzR
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjO1dyMjL7sAhWunOAKHa6ADRMQFjABegQIDhAC&url=https%3A%2F%2Fclassc.mscdirect.com%2FMedia%2FDefault%2Fpdf%2Feng%2Fbrochures%2FK-25%2520Bowmalloy%2520Brochure.pdf&usg=AOvVaw3LzdU3i-1IpVE4jmZVZbQC
Funny you should mention, my friend who in the process of making an impact wrench torque test bench that spits out ft-lbs numbers did so after picking up a box of 1" bowmalloy bolts for pennies on the dollar and thinking what he could make with them.
https://www.instagram.com/torquetestchannel/
To OP, like most people have to be reminded: stainless doesn't = better. People think since something costs more its stronger - it just means corrosion resistance. SS is not going to be better than a grade 5 bolt.
But for the application you mention, who cares really. Just use a bolt you can find that works.