i need a 851d ford

itmeagain

Member
i am looking for pto shaft for my tractor 851d ford.. my is broke having problem find one that does fit.. last one i got was 1 inch and 1/2 to short..
 
Larry, I seemed to pick up somewhere that the hardened ones had an H stamped on the end, have you ever seen one like that?
 
I am not a metallurgist, but in my simple layman's brain, it is my understanding that hardening is achieved by heating to a certain point followed by controlled cooling, which makes the exterior shrink more than the interior, and so there is a "surface tension" on the exterior surface that is the "hardening". And anything that compromised that surface tension (like maybe stamping an H into the surface) would compromise the hardening. Maybe I'm wrong on that, it was just how I understood it when it was explained to me a long time ago.
 

How long is the old shaft?
All I'm finding for that model are 32 11/16" long, part # NCA710-38 on this site.
Shafts for 8N are 30 7/8" long
Shafts for newer 3 cylinder models are 29 1/2" long
 
Sean,
While working for The Timken Company in the late 70's- early 80's as a computer analyst,
I worked on several projects to assist the metallurgical Engineers / Heat treating Group.
I gained a fair understanding of what Timken did to "Harden" the bearings.
One of the biggest factors in the technique used to harden was the bearing size.
Also I should note that Timken did NOT want the bearing to be "THRU" hardened.(more later)

A small bearing, like a wheel bearing can be hardened by some pretty easy steps. First the Alloy of the steel was chosen.
We used some pretty exotic chemicals to produce the desired hardness while minimizing costs (One of the studies I did).
The bearing was cut from the raw steel tube, the tube being handled to make it as soft as possible.
Then the bearing was treated to add extra carbon to the outer layers of the bearing. A process known as "Case Carbonization".
Small bearing were heated in a large drum resembling a cement mixer that had a high carbon atmosphere.
The exact amount of Carbon, Heat and Time were tightly controlled to obtain a specific thickness of a high carbon layer on the surface of the bearing (another study I did).
After this process, the bearing was heated in a furnace to change the crystalline structure of the steel. Look up Austenite, Pearlite, Bainite and Martensite.
Again the precise temperature and time at temp were tightly controlled (More studies LOL!).
Even more critical was the cool down time as the crystalline structure would change if it was cooled too fast OR too slow.
Some steels required a fast cooling, within seconds of the heat being removed, the bearing had to be "OIL" quenched to quickly bring the temp down.
Other steels were water quenched, air quenched, or held at certain temps for certain periods.

After all this the bearing was ground to final size and shape.

At least for bearings, we did not want a "hard all the way thru" product. Hardness brings with it brittleness.
While we wanted a hard outer layer that wore well, we also needed a pliable center that would allow for impacts.
Just think of the wheel bearings on a jet at landing or even worse the space shuttle.
It would have been catastrophic if the large rib of the bearing cracked off and the wheel came off on touchdown.
We would also use special furnaces when melting the steel to eliminate gas bubbles (Vacuum Degas).
Probably more than you wanted to know.
Keith
 

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