[TR] Threads and Bolts

Bud R levilevi at comcast.net
Thu Nov 24 09:04:38 MST 2016


I’m working on the Spitfire’s traverse leaf swing spring rear suspension and can’t find locally the 7/16”  fine thread (20 tpi) by 3 1/2” bolts that were holding the vertical link and to the trunnions and to the swing spring bushings.

I can find the right sizes in a coarse thread (12 tpi) grade 8 bolt and thats my plan. The old ones are grade 5 or in one case a bolt with no slash marks on top. I don’t know what it is.
Do these bolts need to be fine thread for any particular reason, e.g. for safety, torque specs, etc.? Is a grade 8 bolt a good idea where it will be stressed with all the up and down motion with the vertical link? Too brittle? Usually I go for grade 8 whenever possible but I’ve heard there are instances where it might not be the best solution.

An aside for Thanksgiving: 
My son and his wife teaching in Shanghai said the Chinese love to celebrate American holidays (they know them from American TV and movies) but their take on Thanksgiving is that you thank people who do nice things for you. So they got cards from their students thanking them for teaching. Kind of a different twist but a good one I thought.

Happy Thanksgiving to all.

Bud Rolofson

Extreme Parts Racing (more than just a haircut)

71TR6 CC57365 (Good 6)
71 Spitfire MK IV Race Car #3
69 Spitfire MK 3 (back up FE engine/dinghy car)
93 Minnie Winnie Race Support Vehicle 
77 Z-50A Hardly Davidson Honda Mini-Trail Bike (Triumph Pit Bike)

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