Needed - 1" shaft

SteveB fired this volley in news:lro8t8$d08$1 @speranza.aioe.org:

Whatever alloy, they are usually case-hardened. Otherwise, they'll wear out at the pivot points very rapidly.

Almost every pin used on a tractor or loader is case-hardened, if it's original.

LLoyd

If the other parts have hardened bushings then cold rolled would be OK. If not then 4140.

I used unhardened O-1 drill rod for the pivots of the loader I built, running in brass water pipe bushings which withstand more compression pressure than Oilite, since my worst-case calculations ran over 5000 PSI over the projected area when the back wheels lift from a ground-level bucket impact. The working load was much less. When I took it apart about 5 years later one pin was slightly bent from crashing its side of the bucket into a rock but wear was barely detectable.

The loader moved mostly snow and I greased the pins often enough to keep occasional dirt out. The outer ends of the pins on mine are stationary relative to the frame and don't wear much anyway. Where I couldn't locate an accessible grease fitting on the frame I drilled the center of the pivot pin for a grease passage to the center of the bushing and turned a shallow groove at the crosswise hole to distribute the grease all around.

-jsw

My local source for polished, case-hardened steel rod is the scrap bin of the hydraulic cylinder repair shop. The case is less than half a mm thick and beneath it the steel turns nicely to a good finish.

-jsw

I have a couple pieces of 1" linear rail takeoffs. Probably cold rolled and case hardened. Some surface rust.

I need a piece of round shaft about 18" long. It is for the bucket on a loader, being the pin it swivels on. The ends are held in by mechanical stops, no welding or fancy stuff. Looking at Metal Depot and the like, and there are lots of different steels. Which steel should I use? I want one hard enough to resist repeated abrasion. It will be lubricated by common grease gun. Suggestions for number of steel type? I have found these for $25 or less. Final length to be determined by measurement. Anyone got a piece laying around? One inch diameter. Cold rolled would probably do the trick, but while I have it apart, I thought I'd put something in there that will last a long time.

Steve

=======================================================

You have recommendations here to case-harden. I'm not going to try to judge this, because I don't have experience with the application.

But, if you decide to go that route, here are two thoughts: The ideal steels for carburize-case-hardening are 1020, 8620, and 4620. You want to start with a low-carbon steel. And a job like this is not something to do with a torch at home. The best is to find a heat-treater who will throw your piece in with his next batch and do it cheap.

If he's running carbo-nitriding, that's good: harder than carburizing, softer than nitriding, the case thickness falls in between and should be adequate for your job.

I'm not recommending this, just pointing out the best way to go about making a case-hardened pin.

Another source is auto repair shops. Probably too small for this application but shock absorbers and mcpherson struts are a source of polished rods.

Dan

I've always saved them, never actually found a use for them. Every shaft, axle or pivot pin I've made has required some sort of machining such as threads, splines or holes.

The pivot pins for my loader had to be restrained from rotating in the frame because the total contact surface area was inadequate for a moving bearing if divided between the inner and outer elements. The allowable pressure is much higher if the parts don't move against each other.

I made the inner brass bushing as long as possible and the frame on either side 1/4" thick, and welded plates to the ends of the pivot pins that bolt to the frame. When some of the welds failed I cross-drilled the pivot pin for a 3/16" rod with a looped end to attach to the same restraining bolt. Even then the bearing pressure bordered on excessive, though they held up OK.

-jsw.

"Jim Wilkins" fired this volley in news:lrovin$9cu$1 @dont-email.me:

How is a bucket pivot or cylinder clevis pin going to work if _something_ doesn't rotated against another part? Nothing on a loader works in perfectly straight lines.

Lloyd

"Lloyd E. Sponenburgh" fired this volley in news:XnsA37FB7F9B440Alloydspmindspringcom@216.168.3.70:

Duh... if something doesn't _rotate_...

Lloyd

Was my description unclear? I write this stuff for practice.

The pivot pin is secured to the thinner outer plates of the joint. Only the wider inner element rotates on the pin, which both maximizes the length of the bearing to reduce contact pressure and helps keep dirt out since grease flows into and blocks the outer non-moving pin clearance.

-jsw

"Jim Wilkins" fired this volley in news:lrp1tf$o0v$1 @dont-email.me:

That makes more sense, but something MUST move, or you could just weld it together!

Lloyd

A much simpler way to get a case hardened pin is to buy a piece of linear bearing shaft, aka Thomson shaft. The base material varies depending on the manufacturer, but is most often 1060 or 1566. The case is around Rc60 and probably .060-.090 deep on a 1" shaft.

A 1" dia x 18" length is $21.60 from McMaster. And it's ground and polished to boot.

Ned Simmons fired this volley in news: snipped-for-privacy@4ax.com:

Heck yes! Who the hell recommended doing the case-hardening himself? Case-hardened cutoffs and short stock pieces are available all over. Why the heck would one make a case-hardened _standard_ part? Just buy or find a chunk. If it's over-length, cut it off with an abrasive saw.

Before designing the loader attachment I studied, measured and reverse-engineered construction equipment, reconstructing the joint forces from the dimensions, load ratings and hydraulic pressure, then comparing them to the information in the mechanical engineering textbooks I bought second-hand to struggle through. Once I had the stress values it was much easier to see why they design them as they do, and make sense of details like the pivot pins.

I still don't know how to design a four-bar linkage that articulates the bucket by other than trial and error or copying existing link length ratios.

-jsw

Have you ever encountered a similar-looking rod that's hardest in the center? There's no marking beyond a hand-written part number on the box. My guess is that it was rejected for insufficient annealing.

-jsw

"Jim Wilkins" fired this volley in news:lrp50n$9q5 $ snipped-for-privacy@dont-email.me:

I built a custom Scott Russell straight-line mechanism for a finished- parts picker in one my customer machines.

It's all in the trig and circle diagrams. It's not hard, but takes a bit of 'thinin' to get it all figured out. Once you have a drawing with all the circles and trig annotated, DON'T throw it out!

Lloyd

Have you ever encountered a similar-looking rod that's hardest in the center? There's no marking beyond a hand-written part number on the box. My guess is that it was rejected for insufficient annealing.

-jsw

========================================================

A heat-treated part that wasn't sufficiently protected against decarburization will have that exact characteristic. Take a piece of high-carbon steel, heat it in an oven without a muffle, or a carbon boat, or a high-carbon atmosphere, and that's what you get.

It's like a roast of beef that's well-done on the inside and raw on the outside. d8-)

What, your loader _doesn't_ use superconducting magnetic bearings, Lloyd?