[Fot] Have you ever wondered?

[Bill Tobin]

Thanks. Great info.

Stay warm. I skied yesterday in Western NY: 3 degrees at 9AM. Warmed up 
to 12 by 1PM.

Cheers, Bill

On 1/11/2022 9:13 AM, Phil Gott via Fot wrote:
> FRIENDS:
> Have you ever wondered what those little letter marks mean on the 
> heads of bolts in our Triumphs (and other British cars)? You know, the 
> letters at the bottom, below the manufacturer's name (Rubbery Owen, 
> etc.).
> Well, I did as well when looking at the best way to secure the cam 
> sprocket to the camshaft.
> Those letters designate the minimum tensile strength of the material 
> in the bolt, just as the hash marks do on the heads of SAE bolt.  So I 
> put together the attached handy chart showing what the marks mean.  I 
> threw in some Metric as well, just for fun. When you go to the store 
> you can pick the proper (or stronger) grade of bolt to replace the 50+ 
> year old fasteners in your next project.  If reusing the original 
> fastens, which are perfectly fine for many applications, you will be 
> sure not to mix up the fasteners from one application to the next 
> (using a thermostat housing bolt on the cam drive could lead to 
> disaster....).
> Of course, when replacing bolts with new ones it is a REALLY GOOD idea 
> to make sure the threads are not put in shear by using a shouldered 
> bolt.  To do this for the cam drive I needed to go to ARP and special 
> order a 5/16-18 bolt with the proper grip length, and then shorten it 
> so it won't bottom on the threads.  ARP part number 3AG1.250-2S (about 
> $6 each direct from ARP)
> And yes, I've totally ignored the world of Whitworth.
> Enjoy.
>
> Phil Gott
>
> Bolt Grade 	Minimum Tensile Strength (000 psi)
> AN*** 	SAE* 	British** 	Metric* 	50 	60 	70 	80 	90 	100 	110 	120 
> 130 	140 	150 	160 	170 	180
> 	2 > 3/4" 				60 												
> 	2 to 3/4" 					74 											
> 		P 				70-90 									
> 		Q 					80-100 								
> 		R 						90-110 							
> 		S 							100-120 						
> 		T 								110-130 					
> 			8.8 to 16mm 							116 						
> 			8.8 > 16mm 								120 						
> 	5 										120 						
> All 											125 					
> 		U 									120-140 				
> 		V 										130-150 			
> 		W 											140-160 		
> 	8 													150 			
> 			10.9 											151 			
> 		X 												150-170 	
> 		Y 													160-180
> 			12.9 													177
> Sources:  *Bolt Depot Inc. and 
> **Trojansf.co.uk/technical/fastener-grades and ***Skyshop
>
>
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