[TR] Threads and Bolts
dave1massey at cs.com
Thu Nov 24 11:51:09 MST 2016
Bolts with no slashes are grade two. The grade of the bolt is indicated by the number of slashes plus two. I do not recommend grade two for suspension duty.
I've heard said that the trade-off with Grade 8 bolts is that they are stronger but more brittle. Since I am not a mechanical engineer I cannot make a recommendation on substituting a grade 8 for a grade 5 but I would be concerned that the increased brittle nature may be a detriment. Considering the seriousness of the consequences of a suspension failure I would think again about making substitutions. And just about anything you need is available next business day from McMaster Carr (and other sources, certainly). But you may have to buy more than you need and pay shipping.
I don't think fine thread vs coarse thread makes much difference.
Just my opinion.
From: Bud R <levilevi at comcast.net>
To: Triumph Mail List <triumphs at autox.team.net>
Sent: Thu, Nov 24, 2016 12:38 pm
Subject: [TR] Threads and Bolts
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.
Extreme Parts Racing (more than just a haircut)
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