M14 Forum


Results of Bolt hardness test

This is a discussion on Results of Bolt hardness test within the The M14 forums, part of the M14 M1A Forum category; First let me say that I am not an expert material tester and have no certification in this field and am doing this strickly as ...


Go Back   M14 Forum > M14 M1A Forum > The M14

1Thanks
Reply
 
LinkBack Moderator Tools Display Modes

Old March 8th, 2011, 05:31 AM   #1
Lifer
 
MemphisMachinists's Avatar
 
Join Date: Dec 2009
Location: Memphis Tenn
Posts: 2,568
Results of Bolt hardness test

First let me say that I am not an expert material tester and have no certification in this field and am doing this strickly as a favor and for my own enlightnment as well as yours.
TRW back face 57.9 HRC
FA back face 40.5 HRC
TRW top near front 56.4 HRC
FA top near front 37.9 HRC

I have some others but I have decided that these are the most reliable. Most of the others of the FA bolt that seem fairly reliable are just under 40 HRC. My conclusion is that Thunders bolt is no where near as hard as a TRW. I am not sure what spec is for this if anyone knows for sure (no B.S., WAG-wild ass guess thank you very much) please lets us know.
Now I want to cut it up and make cross section specimens, but this will take time and is Thunders call not mine.
Oh, and yes I had to hold it steady for some of the test with my hand (probably not admissable in court) and that is not my hand in the pic but the hand of my furry co worker.

Edit: Anything below 40HRC is considered machinable with high speed cutters although it would be hard to do.
Attached Images
File Type: jpg Hardness test 2 001.jpg (42.2 KB, 63 views)
File Type: jpg Hardness test 2 002.jpg (45.5 KB, 61 views)
File Type: jpg Hardness test 2 003.jpg (43.0 KB, 61 views)
File Type: jpg Hardness test 2 004.jpg (47.8 KB, 65 views)


Last edited by MemphisMachinists; March 8th, 2011 at 05:43 AM. Reason: Thought of something else
MemphisMachinists is offline  
Remove Ads
Old March 8th, 2011, 06:04 AM   #2
Platoon Commander
 
Join Date: Jun 2005
Location: Everywhere
Posts: 548
Surprise,Surprise,Surprise......

Someone should test a Chinese M14 bolt, I bet that it would come out with somewhat higher hardness readings.

Fulton has some 'splaining to do........


Last edited by garandguy10; March 8th, 2011 at 07:10 AM.
garandguy10 is offline  
Old March 8th, 2011, 06:23 AM   #3
Scout Sniper
 
Join Date: Dec 2003
Location: NY
Posts: 824
Have not followed the site due to illness for the last few months; so I missed out on some things. Who makes the Thunder bolt?. I remeber Armscore use to make the Fulton Armory receiver to "Fultons" specs. Couldn't agree more about TRW bolts, a TRW bolt almost fit my Polytech with little modification.

bluedsteelnwood is offline  
Old March 8th, 2011, 06:29 AM   #4
Lifer
 
MemphisMachinists's Avatar
 
Join Date: Dec 2009
Location: Memphis Tenn
Posts: 2,568
It's not a thunder bolt it is Thunder's bolt. He is the one that bought it from Fulton.

Quote:
Originally Posted by bluedsteelnwood View Post
Have not followed the site due to illness for the last few months; so I missed out on some things. Who makes the Thunder bolt?. I remeber Armscore use to make the Fulton Armory receiver to "Fultons" specs. Couldn't agree more about TRW bolts, a TRW bolt almost fit my Polytech with little modification.

MemphisMachinists is offline  
Old March 8th, 2011, 06:36 AM   #5
Dodgin' The Reaper
 
Join Date: Nov 2003
Location: 91763
Posts: 5,255
Too bad you can't tell it's an FA bolt vs. TRW bolt, I would send those pics to FA.

NoExpert is offline  
Old March 8th, 2011, 06:38 AM   #6
Lifer
 
7.62bthp's Avatar
 
Join Date: Mar 2006
Location: Montgomery County TEXAS
Posts: 3,363
I'd get a refund from Fulton, publish the test results, and buy an LRB bolt, or a USGI. At this point the time and freight added to the FA bolt far exceeds the cost of a NIW USGI bolt.

7.62bthp is offline  
Old March 8th, 2011, 06:43 AM   #7
Squad Leader
 
Join Date: Nov 2003
Location: ELKIN N.C.
Posts: 265
I'm no expert but I think you have to use special means to check surface hardness of case hardened parts. The standard Rockwell test doesn't work.

SS100 is offline  
Old March 8th, 2011, 07:23 AM   #8
Scout Sniper
 
Vos Parate's Avatar
 
Join Date: Dec 2010
Location: Heartland, USA
Posts: 788
Doesn't Fulton supply M14 variants to the Army?

Vos Parate is online now  
Old March 8th, 2011, 07:23 AM   #9
Lifer
 
MemphisMachinists's Avatar
 
Join Date: Dec 2009
Location: Memphis Tenn
Posts: 2,568
I think you are correct. I spoke to someone I know with a lot of experience in this field and he said I need to build a special fixture to hold it and a "micro something" tester. We have a nano indenter, but I wouldn't use it for this. It is very expensive and complicated to use. Let me state again that I am not an expert in this field. If I slice it up and machine/polish the surfaces parrellel to one another then this type of test would be more conclusive. Even if I do all that it really won't matter because I am not certified to do it, but I have prepared plenty of samples for research work and the test results have been published.


Quote:
Originally Posted by SS100 View Post
I'm no expert but I think you have to use special means to check surface hardness of case hardened parts. The standard Rockwell test doesn't work.

MemphisMachinists is offline  
Old March 8th, 2011, 07:24 AM   #10
Professional Slacker
 
Join Date: Dec 2009
Location: Mississippi
Posts: 2,179
Surface Rockwell hardness D66-71, Core Rockwell hardness should be C33-C42.

ripsaw is offline  
Old March 8th, 2011, 09:09 AM   #11
Squad Leader
 
yellowthunder's Avatar
 
Join Date: Jul 2010
Location: Honolulu, HI
Posts: 294
Wow, the my Fulton bolt is over 35% softer than the TRW bolt. I think we have pretty solid evidence that the Fulton bolt is faulty. Even though Memphis didn't use a test fixture I think the test to the back of the bolt says it all due to the stability of the bolt against the test bed. Even if we don't have a "Micro" Do-hicky tester, I think the departure from TRW's spec is so far from each other that it's proof enough. I'm going to give Fulton a call about this.

Memphis, you sir and everyone here is awesome!
Maybe I should start my own company the produces quality M1A bolts and call it the "Thunder bolt" It has a really nice ring to it! I would definitely back my product up!

yellowthunder is offline  
Old March 8th, 2011, 11:23 AM   #12
Lifer
 
Ted Brown's Avatar
 
Join Date: May 2004
Location: Jacksonville, OR
Posts: 4,170

Awards Showcase

Wink Hardness Scales

M14 bolt drawings specify a case hardness of D66-71 as noted. This may be somewhat confusing to many since most hardness tests are done in Rockwell C measurements. I don't know what the conversion factor is, but the bolt for the M1 Garand rifle is listed as having a case hardness of C55-59. It's fairly safe to assume the M14 bolt should be the same as the M1. Therefor, the difference between the TRW and FA bolt are not quite as wide spred as thought here. Still, C40 is well below C55. The core hardness for M14 bolts is supposed to be C33-42. This makes me wonder where that leaves the FA bolt.

Ted Brown is online now  
Old March 8th, 2011, 11:57 AM   #13
Lifer
 
MemphisMachinists's Avatar
 
Join Date: Dec 2009
Location: Memphis Tenn
Posts: 2,568
http://www.carbidedepot.com/formulas-hardness.htm
This chart shows 56c = 67.7 40c=55.4d The TRW bolt fell right in the midrange not bad for a part that is likely 50 yrs old. It seems this test is not that far off. The tester is digital and you can select the scale electronically. I may look at it and see if I can do it in d, but I will have to figure out some other parameters as well.

Quote:
Originally Posted by Ted Brown View Post
M14 bolt drawings specify a case hardness of D66-71 as noted. This may be somewhat confusing to many since most hardness tests are done in Rockwell C measurements. I don't know what the conversion factor is, but the bolt for the M1 Garand rifle is listed as having a case hardness of C55-59. It's fairly safe to assume the M14 bolt should be the same as the M1. Therefor, the difference between the TRW and FA bolt are not quite as wide spred as thought here. Still, C40 is well below C55. The core hardness for M14 bolts is supposed to be C33-42. This makes me wonder where that leaves the FA bolt.

MemphisMachinists is offline  
Old March 8th, 2011, 12:00 PM   #14
Lifer
 
2336USMC's Avatar
 
Join Date: Feb 2007
Location: The Road
Posts: 2,987
Yes, I couldn't help but notice that the surface hardness numbers obtained, while maybe not perfect, fell in the accepted range for the CORE of the M14 bolt. In other words, if you pulled a bolt before it was case hardened at all and tested it you would get the same numbers MM got... Coincidence?

I for one would love to see this bolt sectioned thru the lugs as specified on the drawing, and the core compared to the case layer. I'll bet there's no case layer at all. (See the results with the file) In fact I'll put my money where my mouth is and bet $10.00 towards a new bolt, just to see this one sectioned.

2336USMC is online now  
Old March 8th, 2011, 01:02 PM   #15
Grunt
 
M14bear's Avatar
 
Join Date: Feb 2007
Location: Washington
Posts: 118
What is Fulton's responce? This looks damning to say the least.

M14bear is offline  
Reply

  M14 Forum > M14 M1A Forum > The M14



Search tags for this page

bolt hardness

,

hardness of a fastener is measured by what scale

,

hardness of a fastener is measured by what scale?

,
how to do a core hardness test on a bolt
,

howis the hardness of a bolt measured

,

lug bolt hardness

,

rifle bolt hardness

,
rockwell hardness c33 to c42
,

rockwell hardness for rifle bolt

,

rockwell hardness of m14 bolt

,

rockwell hardness of most gun bolts

,
t56 bolt batch failed hardness check
Click on a term to search for related topics.

Moderator Tools
Display Modes


Similar M14 Forum Discussions
Thread Thread Starter Forum Replies Last Post
Bolt Disassembly in the rifle, no bolt tool sailor45 Reference 28 April 19th, 2013 04:40 AM
Mounted my first Fulton Armory bolt in a Chinese M14 Gus Fisher Gus Fisher 15 August 18th, 2010 08:39 AM
"Best" bolt for Poly conversion ... Stoney The M14 11 November 1st, 2008 08:43 AM
USGI Bolt Hardness? ChevellRCR The M14 22 October 6th, 2007 01:19 PM
Field Test Bolt askimball Bill Ricca 5 June 15th, 2004 03:16 AM



Top Gun Sites Top Sites List