Bolt question

[Marian]

I've been doing some research about bolts. I noticed that alot of the hex bolts have a L and then an 8 stamped on them. There are 6 lines on the bolt as well. From what I learned this is a grade 8 bolt but what is the "L"? Is this the foundry? If so what foundry and where? Inquiring minds want to know. Or at least this mind, while having nothing else better to do until the games start.
Marian

 

[Big_John]

"L" is the vendor mark.

 

[1978 NYB]

[h=1]ASTM A320[/h]

Quick Links​

• Heavy Hex Bolts
• ASTM A193
• Strength by Grade

[h=2]Scope[/h]Originally approved in 1948, the ASTM A320 specification covers alloy steel and stainless steel bolting materials for low temperature service. This standard covers rolled, forged, or strain hardened bars, bolts, screws, studs, and stud bolts used for pressure vessels, valves, flanges, and fittings. Like the ASTM A193 specification, unless otherwise specified, the 8UN thread series is specified on fastener larger than 1” in diameter.
Below is a basic summary of a few of the common grades within the ASTM A320 specification. A number of other less common grades of ASTM A320 exist, but not covered in the description below.
[h=2]Grades[/h]

L7 Alloy steel	AISI 4140/4142 Quenched and tempered
L43 Alloy steel	AISI 4340 Quenched and tempered
B8 Class 1 Stainless steel	AISI 304, carbide solution treated
B8M Class 1 Stainless steel	AISI 316, carbide solution treated
B8 Class 2 Stainless steel	AISI 304, carbide solution treated, strain hardened
B8M Class 2 Stainless steel	AISI 316, carbide solution treated, strain hardened

[h=2]Mechanical Properties[/h]

Grade	Size	Tensile, ksi, min	Yield, ksi, min	Charpy Impact 20-ft-lbf @ temp	Elong, %, min	RA, %, min
L7	Up to 2[SUP]1[/SUP]/[SUB]2[/SUB]	125	105	-150° F	16	50
L43	Up to 4	125	105	-150° F	16	50
B8 Class 1	All	75	30	N/A	30	50
B8M Class 1	All	75	30	N/A	30	50
B8 Class 2	Up to [SUP]3[/SUP]/[SUB]4[/SUB]	125	100	N/A	12	35
[SUP]7[/SUP]/[SUB]8[/SUB] - 1	115	80	N/A	15	35
1[SUP]1[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]4[/SUB]	105	65	N/A	20	35
1[SUP]3[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]2[/SUB]	100	50	N/A	28	45
B8M Class 2	Up to [SUP]3[/SUP]/[SUB]4[/SUB]	110	95	N/A	15	45
[SUP]7[/SUP]/[SUB]8[/SUB] - 1	100	80	N/A	20	45
1[SUP]1[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]4[/SUB]	95	65	N/A	25	45
1[SUP]3[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]2[/SUB]	90	50	N/A	30	45

[h=2]Chemical Properties[/h]


[h=1]Bolt Grade Markings and Strength Chart[/h]

Head Marking	Grade and Material	Nominal Size Range (inches)	Mechanical Properties
Proof Load (psi)	Min. Yield Strength (psi)	Min. Tensile Strength (psi)
[h=2]US Bolts[/h]
No Markings	[h=3]Grade 2[/h]Low or medium carbon steel	1/4 thru 3/4	55,000	57,000	74,000
Over 3/4 thru 1-1/2	33,000	36,000	60,000
3 Radial Lines	[h=3]Grade 5[/h]Medium Carbon Steel, Quenched and Tempered	1/4 thru 1	85,000	92,000	120,000
Over 1 thru 1-1/2	74,000	81,000	105,000
6 Radial Lines	[h=3]Grade 8[/h]Medium Carbon Alloy Steel, Quenched and Tempered	1/4 thru 1-1/2	120,000	130,000	150,000
Stainless markings vary. Most stainless is non-magnetic	[h=3]18-8 Stainless[/h]Steel alloy with 17-19% Chromium and 8-13% Nickel	1/4 thru 5/8		40,000 Min. 80,000 – 90,000 Typical	100,000 – 125,000 Typical
3/4 thru 1		40,000 Min. 45,000 – 70,000 Typical	100,000 Typical
Above 1		80,000 – 90,000 Typical
Head Marking	Class and Material	Nominal Size Range (mm)	Mechanical Properties
Proof Load (MPa)	Min. Yield Strength (MPa)	Min. Tensile Strength (MPa)
[h=2]Metric bolts[/h]
8.8	[h=3]Class 8.8[/h]Medium Carbon Steel, Quenched and Tempered	All Sizes below 16mm	580	640	800
16mm - 72mm	600	660	830
10.9	[h=3]Class 10.9[/h]Alloy Steel, Quenched and Tempered	5mm - 100mm	830	940	1040
12.9	[h=3]Class 12.9[/h]Alloy Steel, Quenched and Tempered	1.6mm - 100mm	970	1100	1220
Stainless markings vary. Most stainless is non-magnetic. Usually stamped A-2	[h=3]A-2 Stainless[/h]Steel alloy with 17- 19% Chromium and 8-13% Nickel	All Sizes thru 20mm		210 Min. 450 Typical	500 Min. 700 Typical
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing. Yield Strength: The load at which a material exhibits a specific permanent deformation. Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set. 1MPa = 1N/mm[SUP]2[/SUP] = 145 pounds/inch[SUP]2[/SUP]

 

[Marian]

Thanks. But, who is the vendor?

 

[Big_John]

Thanks. But, who is the vendor?

Here's about 120 pages of bolt markings and logos.

http://www.uspto.gov/web/offices/tac/fqa/active.pdf

 

[commando1]

So you're saying... Good Luck.

 

[Big_John]

So you're saying... Good Luck.

Kinda.... If I had to guess, I'd say the company name began with an "L".

 

[cm23uoc]

No idea why I have to look in such a list.
If you search with capital L you get 30 listings, but L 8 does not exist. It seems if a company was closed and by that did not renew their sign they're not included in there.

 

[Big_John]

No idea why I have to look in such a list.
If you search with capital L you get 30 listings, but L 8 does not exist. It seems if a company was closed and by that did not renew their sign they're not included in there.

I'm sure that list does not include all the bolt manufacturers. Looks to me it's a list of marking from approved vendors for the government. The L 8 may be there.... It may not.

It may not exist anymore either. A lot of manufacturers have been bought or closed over the past few years... or they changed their logo if they started manufacturing overseas. Anything is possible.

IMHO, the thing is to buy the bolts from a good source. In other words, go to a good bolt store rather than Home Depot or Lowes.

 

[1978 NYB]

Stan is the hardware expert......

Hey Stan...

 

[commando1]

Stan is the hardware expert......

Hey Stan...

You and Big John already said it all...

 

[commando1]

Except for this...........

And this........