71 BB Half Shaft Finsih

[Sheldon S.]

I am just starting to restore my halfshafts and found much info in the archives. In there it says that the half shafts were shot peened including the cast ends but not the machined surfaces where the u joints go. What about the end piece that attaches to the u joint and the rear trailing arm. Was this just natural forged finish withoiut shot blasting as I assume it was not part of the shaft when it was shot blasted.
Thanks
Sheldon

[Chuck S.]

Re: 71 BB Half Shaft Finsih

I am just starting to restore my halfshafts and found much info in the archives. In there it says that the half shafts were shot peened including the cast ends but not the machined surfaces where the u joints go. What about the end piece that attaches to the u joint and the rear trailing arm. Was this just natural forged finish withoiut shot blasting as I assume it was not part of the shaft when it was shot blasted...

(Bump to the top)

My knowledge of big block cars is limited, but the assumption of the half shaft ends being masked during shot peening, and then half shafts assembled after cleaning would be a reasonable conclusion.

The yokes would be masked because the shot peening process would be destructive to precision machined fits in the yokes. (Edit: It's also possible the ends were not masked, but the process simply depended on trained operators that avoided direct impingement of the yoke ends.) The shafts would not be assembled because the shot peening process is also dirty, which could contaminate the needle bearings in the joints. It's quite likely only the tubing required shot peening anyway.

MHO...wait for big block expertise.

[Patrick B.]

Re: 71 BB Half Shaft Finsih

Even though I bought my 70 LT-1 when it had only 8000 miles on it, the half shafts were rustly already and the finish not discernable. Years later I bought a new set of the larger diameter half shafts from the parts department which were original in later cars. These half shafts had mirror bright extruded steel tubes with weld coloring near the flange welds. I don't know how you could restore old shafts to look like that without replacing the extruded tubes with new tubes.

[Terry M.]

Re: 71 BB Half Shaft Finsih

I am just starting to restore my halfshafts and found much info in the archives. In there it says that the half shafts were shot peened including the cast ends but not the machined surfaces where the u joints go. What about the end piece that attaches to the u joint and the rear trailing arm. Was this just natural forged finish withoiut shot blasting as I assume it was not part of the shaft when it was shot blasted.
Thanks
Sheldon

I may have some pictures at home. Hang in there.

[Chuck S.]

Re: 71 BB Half Shaft Finsih

Even though I bought my 70 LT-1 when it had only 8000 miles on it, the half shafts were rustly already and the finish not discernable. Years later I bought a new set of the larger diameter half shafts from the parts department which were original in later cars. These half shafts had mirror bright extruded steel tubes with weld coloring near the flange welds. I don't know how you could restore old shafts to look like that without replacing the extruded tubes with new tubes.

That is exactly what was original on small blocks, except I'm uncertain what half shafts were on LT1s.

If the shafts had been shot peened as (I'm told) original big blocks were, I expect the finish would have been dull and slightly roughened. Of course, we have to keep in mind that service parts constantly superceded original assembly parts...the specs for service parts could change if better, cheaper ways were found to make them without compromising the function.

If you have a small block, half shaft (and drive shaft) restoration is a challenge. Perfectionists have to consider how close they need to get, or simply get as close you can. I have seen some really nice shaft restorations regards tube finish and weld HAZ without resorting to tube replacement...I would be happy to get that close.

If perfection is your standard, then there are folks that will restore your shafts to new condition with new extruded tubing. Personally, JMHO, but I can't justify that. You're dealing with a perishable product that's going to look just like the old ones if you don't take extreme measures to keep them from rusting. The measures that aren't an never ending maintenance burden will lose you judging points. If I'm going to lose points, and/or eventually have to restore those shafts again anyway, I would rather just start by restoring my originals.

[John H.]

Re: 71 BB Half Shaft Finsih

The GM drawing of the half-shaft shows that the area to be shot-peened extends 3" from the centerline of the U-joint bore inboard, with the bores masked or shielded so they're not affected.

[Terry M.]

Re: 71 BB Half Shaft Finsih

The yokes would be masked because the shot peening process would be destructive to precision machined fits in the yokes. (Edit: It's also possible the ends were not masked, but the process simply depended on trained operators that avoided direct impingement of the yoke ends.) The shafts would not be assembled because the shot peening process is also dirty, which could contaminate the needle bearings in the joints. It's quite likely only the tubing required shot peening anyway.

MHO...wait for big block expertise.

Back in 1965 to 1968 the shoot peening processes I observed while employed in metallurgy research were automated. The product was prepared and placed on a conveyer and passed through a blast cabinet. The shot was dropped onto a rotating disk that flung the shot at the product.

I can't tell you all shot peening operaations were thus automated, but I would expect the production process for half shafts was.

[Chuck S.]

Re: 71 BB Half Shaft Finsih

Back in 1965 to 1968 the shoot peening processes I observed while employed in metallurgy research were automated. The product was prepared and placed on a conveyer and passed through a blast cabinet. The shot was dropped onto a rotating disk that flung the shot at the product.

I can't tell you all shot peening operaations were thus automated, but I would expect the production process for half shafts was.

Interesting. From your description of the shot peening process, Terry, it sounds like observation windows for manual operation would be impossible. Just as well...it eliminates the human element. Were the shot media particles actually spherical, and what approximate diameter would you estimate for the "shot"?

I had envisioned something like blasting the part with a coarse steel grit media. I have seen steel grit blasted surfaces (petroleum storage tank exteriors). Steel grit, with unlimited air volume and pressure, is extremely agressive.

[Dennis S.]

Re: 71 BB Half Shaft Finsih

Sheldon
What condition are your shafts in? Can you just clean them to preserve the original finish and then use a corrosion inhibitor? Here are pictures of the originals from my '69 BB, from an initial degreasing to moderate brass brushing and scrubbing with Scotch Brite pads. It took a lot of muscle to get them completely cleaned, because I wanted to avoid the glass media cabinet. The final picture shows them installed in the car after being sprayed with CRC SP-400. They've been in there one year, Florida humidity and all.

Not quite sure if you can see the shot peening. I suppose I should have had the welds re-hazed.

[Terry M.]

Re: 71 BB Half Shaft Finsih

Chuck,
I don't recall that I paid any attention to the configuration of the media. It is one of those "If I only knew then what I know now" sort of events. We were primarily doing metal forming lubrication research and shot blasting was only a diversion when we were visiting other processes more tuned to our work.

Someone previously posted in another thread the paragraph that gives the shot operation specifications for the big block half-shafts and I believe contained in that is a description for the media size and shape (perhaps in a brand name and or number) as well as the number of shot strikes per unit area. There is probably some kind of shot speed specified in that paragraph as well, or some means of identifying force involved.

[Paul O.]

Re: 71 BB Half Shaft Finsih

The photos that Dennis posted are exactly the same appearance that were on my 71 LT-1. A ruff finish almost like very fine pitting rust but not. The tube section and the welded areas were the only areas that had this appearance. The u-joint section did not have the same type of peened appearance or the coupling flange. They had a forged look to them.

Paul 18046

[Edward J.]

Re: 71 BB Half Shaft Finsih

Paul, Terry, I did a set of 70 big block shafts just recently for a ncrs member and recall the they were shot peened but the shafts looked nothing like Dennis shafts, The peening was more pronounced a easily visible. Being my judging is limited maybe you may have seen others.as I am not a seasoned vet.

[Paul O.]

Re: 71 BB Half Shaft Finsih

Ed I would think there would be varying degrees of finish from the peening process. Would be affected by the age of the shot or how long it was used for. Also it is my understanding that the shot was not a round steel ball but a course type of material jagged. Which wood explain the the course finish of the shaft.

Paul 18046

[Terry M.]

Re: 71 BB Half Shaft Finsih

I am just starting to restore my halfshafts and found much info in the archives. In there it says that the half shafts were shot peened including the cast ends but not the machined surfaces where the u joints go. What about the end piece that attaches to the u joint and the rear trailing arm. Was this just natural forged finish withoiut shot blasting as I assume it was not part of the shaft when it was shot blasted.
Thanks
Sheldon

Well, let's see how this works. A 1971 BB, I believe Manual trans 9K miles. No that is not rust -- see the yellow mark. You can rub your hand over it and nothing comes off on your hand. Sorry, this is as close as I got for this picture, maybe I can get closer next time.

[Terry M.]

Re: 71 BB Half Shaft Finsih

Let's try another one.
1972 BB with M40 -- 4 or so miles showing on the clock. Nice and close for you.

Damn V-Buletin will nto let me post the same picture again. See post #12 of this thread. I hope it was one of the ones you found in your search.

https://www.forums.ncrs.org/showthre...66806&uid=2320