1970 spindle bolt hardness grade (1 Viewer)

[MartynFJ4071]

Found this thread after landing in the same boat. Any luck on a source for these bolts? I have one broken one and found they are NLA
Interested in what you ended up doing?

I’m in New Zealand so my search results may vary if in the US. I bought suitable 10.9 bolts from EBay from a US manufacturer, cut them to length, made a drilling jig and drilled them myself
They turned out good..

There are a couple of places that sell them pre drilled in the US. One place is called Drilled head bolts funnily enough. Otherwise is should be easy to source the Jis type bolt there. I struggled finding bolts in 30mm with the right amount of clear shank so had to go up to 35mm and cut them back.
I think you want that clean shank and length right at where the factory had it.

I’ll have a search tonight for the other suppliers I found if you’d like. Let me know.

 

[MartynFJ4071]

But if you can get 2nd hand ones will save all the drama.

 

[MartynFJ4071]

Because the bolts don't have any markings on the heads means they are probable grade 5.8 or below. Drilling hardened bolts would require using carbide drill bits instead of standard tool steel bits.

View attachment 2796605

They do an important job so the consensus at the time was to go 10.9 if replacing abs get an upgrade at the same time.
They were reasonably time consuming to drill out though. And difficult to extract all the broken drill bits out of the heads.

 

[B y r o n]

They do an important job so the consensus at the time was to go 10.9 if replacing abs get an upgrade at the same time.
They were reasonably time consuming to drill out though. And difficult to extract all the broken drill bits out of the heads.

Stronger/harder isn't always the best choice in every situation. Lower strength/softer bolts can absorb shock without breaking better than harder bolts. With the number of bolts there I doubt that 10.9 bolts were required to hold things together. Any time I see bolts that are safety wired my belief is that they are more worried about vibration backing them out instead of clamping force/strength needed to keep things together.

 

[MartynFJ4071]

I was just going off of advice given as I’m no expert.

 

[MartynFJ4071]

I have several hundred of these. Happy to donate a few to anyone placing an order with me.

I wish you’d said that earlier

 

[FJ62DadWagon]

But if you can get 2nd hand ones will save all the drama.

Appreciate the response. I’m going to checkout the Drilled Head Bolt company and see what they got. I like the idea of having a hardier bolt there.

It took a bit for me to accept keeping the drum brakes for now and then realizing how small these bolts are almost feels like a little too much.

 

[bikersmurf]

The originals weren’t very strong. I once had the bright idea to use them to bolt in my rear FF axles. They looked great… but didn’t last long. Less than a year later every one on the right axle sheared off, Back to studs, Nuts, and regular torque checks.