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Peter-L
Peter-L
Schilde, Belgium
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DavidP Offline OP
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Not hash marks, as on most American bolts. The only similar markings I can find in a search are numbers on certain metric bolts. I really wonder who would've made a bolt with British threads and unified heads? The first time I removed the head I didn't think twice about it, everybody "knows" that they went unified in '69. laughing
I'm not doing anything until it gets to at least 40 degrees in my shop. It's in the teens now.


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71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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N
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The head bolts never went unified on the a65's.
Chances are someone has just run a die down a cut off 3/8 unified bolt.
Or put it in a lathe and threaded it BSF.
Triumphs did not change for a while as well, use up existing stocks etc.

The OEM bolts are grade 8 that would mean 6 lines on the head in later terms
3 lines = grade 5.

https://www.fastenerdata.co.uk/fastener-grades#ugrade

Last edited by NickL; 02/17/21 7:48 am.
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Nick L recons :

buy either grade 8 or allen bolts (grade 12 or 14) easily

grade 12 cap screws are excellent material .........very high tensile , but still machine able / tap able , (just) best to power tap the sods though , probably 4140 grade .....i often buy a few realy long cap screws with a short thread as they are a very cost effective way of getting just a few inches of good grade material without having to go to a steel merchant who will want to sell you a 3.6 meter bar minimum!

if you get them with a unf thread, or even metric fine series and tap them to what ever size you need you have made a top of the line thread insert , retap the offending hole using a 2nd cut or taper tap and wind then in as hard as you can the hack them off with a hacksaw , file them flush and you have a forever repair ! done that countless times

oh and by the way .......when tapping high tensiles always go .0,1-.0.2 mm above the drilling size (much more on large diameters ) , depending on pitch and diameter , 80% thread is plenty on that stuff and you wont get so many busted taps

Last edited by Ignoramus; 02/18/21 5:17 pm.

"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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DavidP Offline OP
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Recoil inserts are now installed with red Loctite to make sure they don't move.


Knowledge speaks. Wisdom listens.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
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Originally Posted by DavidP
Recoil inserts are now installed with red Loctite to make sure they don't move.

This is what I do. Just run a tap down them just to make sure none of the locktite has oozed through the wire and blocking the internally threaded area.


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68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
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Helicoil has been used in Aircraft engines for at least 70 years or so (aircraft is my trade, for 40 years) they are used in some new construction and are approved as a repair in most situations. I've never seen a properly install Helicoil fail. Recoil appears to be the same. BUT, as noted, the length of the coil can be critical. for instance, BMW oilheads (and some airheads) have very high head bolt torques that are right on the verge of pulling threads in the aluminum. it's a common repair on those bikes. but it only works with the long coils, the standard short coils tend to pull out

Last edited by Mitch; 02/19/21 8:30 am.
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I believe ARP makes a bolt kit for our engines. You have to go on their web sight to check it.

Yes helicoils. Use to machine electrical chassises for Raytheon. The main mounting holes where all helicoiled.

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