Carriage Top Pivot pins =1915 Buick

[Weldingrod1]

If it's a part subject to fatigue, strong steel is your friend.

You really can't say the brass and Aluminum are categorically weaker than steel... There's a wide range on all three. Nickel Aluminum Bronze and 7075 are both much stronger than many steels, but weaker than -some- steels.

Steel is kind of special in having an endurance limit. Below that stress limit, it doesn't fail in fatigue.

File:S-N curves.PNG - Wikipedia

en.m.wikipedia.org

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[Janderso]

Matching the thread did’t go so good.
I visually matched it with the mag glasses but I was a few thousands off.
Besides, I had the thread register in the middle of the threads.
No big deal, I’ll make another.

 

[Janderso]

Not too bad.
I did learn quite a bit, that’s what it’s all about.
I’m not sure what’s going on with the ragged root.
Probably too slow for a carbide insert.
I’ll use my Aloris “85” threading tool for the next one. I know Sharp HSS works well at slower threading speeds.

 

[Jimsehr]

Nitpicking here but if you are going to make another . I would also make a radius at the junction where tapered cut meets the radius. Sharp intersections are where breaks and cracks can happen.
Jimsehr

 

[Janderso]

Nitpicking here but if you are going to make another . I would also make a radius at the junction where tapered cut meets the radius. Sharp intersections are where breaks and cracks can happen.
Jimsehr

Jim,
I was planning on Adding a radius but didn’t have the means to make one.
What’s a good way to make a radius tool?
I have some O1 flat bar but couldn’t think of a way to copy the small radius. End mill at 7 degrees might work.
I can still doctor in a radius if I can figure out a way to do it.
Someone mentioned a router bit. My local Ace wanted $32. That’s not happening

 

[Jimsehr]

Jeff
Easy way is to grind it on your turning tool . I’ll go out to the lathe this morning and make a cut on a piece of stock and send you a pic. Are you using hss or carbide to turn with? How did you form the big radius on your part?
Jimsehr

Jeff send me an email Jimatcf@hotmail.com

 

[AmericanMachinist]

The only difference between my and @MrWhoopee suggestion is that I would do the big end first.

Wouldn't that mean the collet was holding the threads (only), no portion of un-threaded shaft? Is that generally considered acceptable give the dispersed and even pressure of a collet? (I don't have a collet chuck and am still ignorant).

 

[Jimsehr]

Wouldn't that mean the collet was holding the threads (only), no portion of un-threaded shaft? Is that generally considered acceptable give the dispersed and even pressure of a collet? (I don't have a collet chuck and am still ignorant).

You could finish all the turning on the part before you thread it. Or you could hold on the threads with a collet.

 

[Weldingrod1]

Right! The collet gives pretty uniform pressure over all the thread crests.

It's also possible to make a threaded split collet or a lantern chuck to do this kind of work.

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[Janderso]

Nitpicking here but if you are going to make another . I would also make a radius at the junction where tapered cut meets the radius. Sharp intersections are where breaks and cracks can happen.
Jimsehr

Ok, here we go.
I feel good about this part.
The owner said as long as the new ones match, they don’t have to be exact the same as the originals.
I used a piece of O1 flat bar stock, ground the form I thought would work. Hardened, honed etc. (I turned it upside down and ran in reverse.)