Bolt question

Marian

Marian

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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
 
[h=1]ASTM A320[/h]
Quick Links​


[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][TABLE="class: unformat"]
[TR]
[TH="bgcolor: #DDDDDD"]L7 Alloy steel[/TH]
[TD="align: left"]AISI 4140/4142 Quenched and tempered[/TD]
[/TR]
[TR]
[TH="bgcolor: #DDDDDD"]L43 Alloy steel[/TH]
[TD="align: left"]AISI 4340 Quenched and tempered[/TD]
[/TR]
[TR]
[TH="bgcolor: #DDDDDD"]B8 Class 1 Stainless steel[/TH]
[TD="align: left"]AISI 304, carbide solution treated[/TD]
[/TR]
[TR]
[TH="bgcolor: #DDDDDD"]B8M Class 1 Stainless steel[/TH]
[TD="align: left"]AISI 316, carbide solution treated[/TD]
[/TR]
[TR]
[TH="bgcolor: #DDDDDD"]B8 Class 2 Stainless steel[/TH]
[TD="align: left"]AISI 304, carbide solution treated, strain hardened[/TD]
[/TR]
[TR]
[TH="bgcolor: #DDDDDD"]B8M Class 2 Stainless steel[/TH]
[TD="align: left"]AISI 316, carbide solution treated, strain hardened[/TD]
[/TR]
[/TABLE]


[h=2]Mechanical Properties[/h]
L7Up to 2[SUP]1[/SUP]/[SUB]2[/SUB]125105-150° F1650
L43Up to 4125105-150° F1650
B8
Class 1		All7530N/A3050
B8M
Class 1		All7530N/A3050
B8
Class 2		Up to [SUP]3[/SUP]/[SUB]4[/SUB]125100N/A1235
[SUP]7[/SUP]/[SUB]8[/SUB] - 111580N/A1535
1[SUP]1[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]4[/SUB]10565N/A2035
1[SUP]3[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]2[/SUB]10050N/A2845
B8M
Class 2		Up to [SUP]3[/SUP]/[SUB]4[/SUB]11095N/A1545
[SUP]7[/SUP]/[SUB]8[/SUB] - 110080N/A2045
1[SUP]1[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]4[/SUB]9565N/A2545
1[SUP]3[/SUP]/[SUB]8[/SUB] - 1[SUP]1[/SUP]/[SUB]2[/SUB]9050N/A3045

[TH="bgcolor: #DDDDDD"]Grade[/TH]
[TH="bgcolor: #DDDDDD"]Size[/TH]
[TH="bgcolor: #DDDDDD"]Tensile,
ksi, min[/TH]
[TH="bgcolor: #DDDDDD"]Yield,
ksi, min[/TH]
[TH="bgcolor: #DDDDDD"]Charpy Impact
20-ft-lbf
@ temp[/TH]
[TH="bgcolor: #DDDDDD"]Elong,
%, min[/TH]
[TH="bgcolor: #DDDDDD"]RA, %, min[/TH]


[h=2]Chemical Properties[/h]


[h=1]Bolt Grade Markings and Strength Chart[/h][TABLE="class: infotable, align: center"]
[TR="class: toprow"]
[TH="bgcolor: #EEE8C6, align: center"]Head Marking[/TH]
[TH="bgcolor: #EEE8C6, align: center"]Grade and
Material[/TH]
[TH="bgcolor: #EEE8C6, align: center"]Nominal Size Range
(inches)[/TH]
[TH="bgcolor: #EEE8C6, colspan: 3, align: center"]Mechanical Properties[/TH]
[/TR]
[TR]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Proof Load
(psi)[/TH]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Min. Yield Strength
(psi)[/TH]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Min. Tensile Strength
(psi)[/TH]
[/TR]
[TR="class: sectionheading, bgcolor: #F0F0F0"]
[TD="colspan: 6, align: center"][h=2]US Bolts[/h][/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-grade2.gif

No Markings[/TD]
[TD="align: center"][h=3]Grade 2[/h]Low or medium carbon steel
[/TD]
[TD="align: center"]1/4 thru 3/4[/TD]
[TD="align: center"]55,000[/TD]
[TD="align: center"]57,000[/TD]
[TD="align: center"]74,000[/TD]
[/TR]
[TR]
[TD="align: center"]Over 3/4 thru 1-1/2[/TD]
[TD="align: center"]33,000[/TD]
[TD="align: center"]36,000[/TD]
[TD="align: center"]60,000[/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-grade5.gif

3 Radial Lines[/TD]
[TD="align: center"][h=3]Grade 5[/h]Medium Carbon Steel, Quenched and Tempered
[/TD]
[TD="align: center"]1/4 thru 1[/TD]
[TD="align: center"]85,000[/TD]
[TD="align: center"]92,000[/TD]
[TD="align: center"]120,000[/TD]
[/TR]
[TR]
[TD="align: center"]Over 1 thru 1-1/2[/TD]
[TD="align: center"]74,000[/TD]
[TD="align: center"]81,000[/TD]
[TD="align: center"]105,000[/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-grade8.gif

6 Radial Lines[/TD]
[TD="align: center"][h=3]Grade 8[/h]Medium Carbon Alloy Steel, Quenched and Tempered
[/TD]
[TD="align: center"]1/4 thru 1-1/2[/TD]
[TD="align: center"]120,000[/TD]
[TD="align: center"]130,000[/TD]
[TD="align: center"]150,000[/TD]
[/TR]
[TR]
[TD="align: center"]Stainless markings vary. Most stainless is non-magnetic[/TD]
[TD="align: center"][h=3]18-8 Stainless[/h]Steel alloy with 17-19% Chromium and 8-13% Nickel
[/TD]
[TD="align: center"]1/4 thru 5/8[/TD]
[TD="align: center"] [/TD]
[TD="align: center"]40,000 Min. 80,000 – 90,000 Typical[/TD]
[TD="align: center"]100,000 – 125,000 Typical[/TD]
[/TR]
[TR]
[TD="align: center"]3/4 thru 1[/TD]
[TD="align: center"] [/TD]
[TD="align: center"]40,000 Min. 45,000 – 70,000 Typical[/TD]
[TD="align: center"]100,000 Typical[/TD]
[/TR]
[TR]
[TD="align: center"]Above 1[/TD]
[TD="align: center"] [/TD]
[TD="align: center"]80,000 – 90,000 Typical[/TD]
[/TR]
[TR="class: toprow"]
[TH="bgcolor: #EEE8C6, align: center"]Head Marking[/TH]
[TH="bgcolor: #EEE8C6, align: center"]Class and
Material[/TH]
[TH="bgcolor: #EEE8C6, align: center"]Nominal Size Range
(mm)[/TH]
[TH="bgcolor: #EEE8C6, colspan: 3, align: center"]Mechanical Properties[/TH]
[/TR]
[TR]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Proof Load
(MPa)[/TH]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Min. Yield Strength
(MPa)[/TH]
[TH="class: subheading, bgcolor: #EEE8C6, align: center"]Min. Tensile Strength
(MPa)[/TH]
[/TR]
[TR="class: sectionheading, bgcolor: #F0F0F0"]
[TD="colspan: 6, align: center"][h=2]Metric bolts[/h][/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-class8-8.gif

8.8[/TD]
[TD="align: center"][h=3]Class 8.8[/h]Medium Carbon Steel, Quenched and Tempered
[/TD]
[TD="align: center"]All Sizes below 16mm[/TD]
[TD="align: center"]580[/TD]
[TD="align: center"]640
[/TD]
[TD="align: center"]800
[/TD]
[/TR]
[TR]
[TD="align: center"]16mm - 72mm[/TD]
[TD="align: center"]600[/TD]
[TD="align: center"]660[/TD]
[TD="align: center"]830[/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-class10-9.gif

10.9[/TD]
[TD="align: center"][h=3]Class 10.9[/h]Alloy Steel, Quenched and Tempered
[/TD]
[TD="align: center"]5mm - 100mm[/TD]
[TD="align: center"]830[/TD]
[TD="align: center"]940
[/TD]
[TD="align: center"]1040
[/TD]
[/TR]
[TR]
[TD="align: center"]
hex-head-marking-class12-9.gif

12.9[/TD]
[TD="align: center"][h=3]Class 12.9[/h]Alloy Steel, Quenched and Tempered
[/TD]
[TD="align: center"]1.6mm - 100mm[/TD]
[TD="align: center"]970[/TD]
[TD="align: center"]1100
[/TD]
[TD="align: center"]1220
[/TD]
[/TR]
[TR]
[TD="align: center"]Stainless markings vary. Most stainless is non-magnetic.
Usually stamped A-2
[/TD]
[TD="align: center"][h=3]A-2 Stainless[/h]Steel alloy with 17- 19% Chromium and 8-13% Nickel
[/TD]
[TD="align: center"]All Sizes thru 20mm[/TD]
[TD="align: center"] [/TD]
[TD="align: center"]210 Min.
450 Typical
[/TD]
[TD="align: center"]500 Min.
700 Typical
[/TD]
[/TR]
[TR]
[TD="class: explanationrow, colspan: 6"]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]
[/TD]
[/TR]
[/TABLE]
 
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.
 
cm23uoc said:
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.
Click to expand...

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.
 
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