I dismantled four 1931 type pinion assemblies yesterday hoping to find some good original components for a rear axle rebuild with a new CWP.

All of the distance spacers have suffered from fretting, the worst with 29 thou wear and the best with 6 thou. Measuring the unworn ridges shows them to be two lengths. Two were originally 0.63" and the other two were 0.628"

One pair of angular contact bearings are Skefco ALS8A

The other three pairs are all Ransome and Marles 3LJT1

New bearings that I ordered are RHP "LJT 1" GROUND" and were described as 8LJT1. The quality of the modifying is very poor.

What does the number prefix for the LJT's signify?

Henry,
LJT stands for light journal thrust.

Location: Deepest darkest Kent.

The number 8 signifies that the bearings have been ground for special application - in this instance reduced (possibly) by 1/32" on the outer rim each (from memory).

Why an 8? I don't know.

Not to worry R, I am sure Bob will be along in a moment with an interesting aside whilst we wait for the actual answer a bit later from Tony Press.

Location: Auckland NZ

The prefix on RHP bearings denotes a modification or special application. I believe there were 2 variations of the AC bearings fitted to pinions - 3/LJT1 and 8/LJT1, possibly a different pre-loading or width of the outer track.
Another common one is 2/MJT1-1/8 for the narrow front mains,and some original gearbox bearings have prefixes denoting position of circlip grooves, or special loose fit for alignment etc.

Henry,

"All of the distance spacers have suffered from fretting, the worst with 29 thou wear and the best with 6 thou. Measuring the unworn ridges shows them to be two lengths. Two were originally 0.63" and the other two were 0.628"

The spacer was originally nominal 5/8". Were the bearing seatings worn?

"One pair of angular contact bearings are Skefco ALS8A
The other three pairs are all Ransome and Marles 3LJT1
New bearings that I ordered are RHP "LJT 1" GROUND" and were described as 8LJT1. The quality of the modifying is very poor.
What does the number prefix for the LJT's signify?"

As mentioned above by the unfortunately named Hank Shaft - the Austin angular contact bearings had narrow outer rings - 1/32" less than the inner ring width- hence the prefixes and suffixes.
SKF used W 6898 for the special - but apparently Skefco used ALS8A.
The R&M 3LJT1 was the original special bearing - from memory Austins changed the bearing arrangement from 2 thou loose to 2 thou preload - I assume the 8 signified this.

It is possible to get narrow outer ring bearings produced but the preload would now be up to the assembler and difficult to arrange.

Quite a few diffs have been assembled with narrow outer ring standard bearings without too much noise so unless you want to be completely correct (remembering Austins originally used no preload) then I would use the bearings as supplied (although I would be concerned if as you note "The quality of the modifying is very poor" ).

Tony.

Location: Australia

hi henry, is this due to the modification being done without seperateing the inner and outer race.

or is it from the method used.

i would have thought bearings would need to be put on a surface grinder. the grinder would only take of 2 tenths of a thou at a time without over heating the metal. which means if you get 12 bearings on a magnetic chuck at a time. it takes a long time to grind 12 bearings.

also if they have been done on a magnetic chuck, have you checked to see if they have been demagnified properly.

tony

Location: huncote on the pig

We have them machined locally by an engineering firm using a ceramic cutting tool.

Disassembling runs the risk of damaging the balls and track.

All methods need careful cleaning and re-coating with rust preventive after, as well as Tony's suggestions.

Tony P.

Location: Australia

Sorry to disagree with some, but I think there is a danger of over-complicating this "problem". I have modified numerous standard bearings to get the required width of the outer race and have had no subsequence problems with the method used. This is to press the bearing apart and, as there are usually two bearings needing treating, make sure to note and keep the balls and inner race separate and identified with their outer race.
The two outer races and an old outer race are taken to a reputable machine shop. Here the three outer races are mounted on the surface grinder and metal is removed until a faint witness is left on the old outer. The bearings are then reassembled.
Ron Hayhurst

With this 'surface ground' method how do you machine the radius on the outer rim of the ground face?

Still not convinced that dismantling AC bearings by pressing apart is a good thing for balls and track.

Tony.

Location: Australia

I've decided to use un-modified LJT 1's.
The extra 0.060" will ensure that the threaded locking ring tightens up against the bearing outer races and not the pinion housing.
I'll also make a new 'inner distance piece' with a larger OD so it bears fully on the inner races.

It doesn't seem right to me to knock angular contact bearings apart.
I'm reminded of this quote from Forrest Addy on the Practical Machinist.com forum;

"Install these bearings by thermal expansion over a room temp shaft. Move quickly observing cleanliness and bearing face orientation.

Installing or attempting to remove an angular contact bearing by the outer race may pull it off the ball cage. The balls will fall out randomizing them. They are installed graded by diameter from small to large around the cage alternating from the first to the last. Installing the balls at random and reassembling the race will result in a greater preload than intended for the larger balls and reduced bearing life and capacity. A separated bearing will also be brinelled on the outer race. Regard a separated bearing as destroyed for precision use."

Henry,

If it is the early AC bearing differential, using standard bearings will move the pinion 1/32" (around 30 thou) into mesh with the pinion, the later two piece torque tube will do the reverse. I think the pinion shaft end adjustment won't fix these problems.

As I noted - if the spacer is worn then the bearings must be moving on the shaft when they should be a tight fit!
Altering the spacer wont help stop a loose bearing moving on the pinion shaft!

You quote-

"Installing or attempting to remove an angular contact bearing by the outer race may pull it off the ball cage. The balls will fall out randomizing them. They are installed graded by diameter from small to large around the cage alternating from the first to the last. Installing the balls at random and reassembling the race will result in a greater preload than intended for the larger balls and reduced bearing life and capacity. A separated bearing will also be brinelled on the outer race. Regard a separated bearing as destroyed for precision use."

The balls in each bearing are graded for size within tolerance of each other and related to the inner and outer ring sizes - not graded from large to small in any one bearing.

The comment about brinelling a bearing by forcing the rings apart is correct however.

Tony.

Location: Australia

Tony,
If the angular contact bearing is worn but not worn out (no visible damage to either inner or outer races or balls,)but the bearing is more easily disassembled than if it was brand new, would this cause spalling,seeing as you don't have to provide much force to take it apart? The A7 bearing's duties is not an application as accurate as say a machine tool spindle.
I'm asking because I don't like chucking things away if I can get more use out of them.
Dave.

Location: Sheffield

I dont know about current ones but I always found Seven a/c races came apart if just tapped with a wooden mallet, or dropped! (when the balls disappeared, hence the recent comments about mixing balls!)
The situation installed is different as rings then expanded/contracted. For those saving every penny a/c races can be easily examined for any hint of pitting. Any back to back clearance can be restored with a thin shim. If races reversed life further extended.

The RP era ball pinion race tends to be short lived and false economy to reuse.

Location: Auckland, NZ

Anyway, why take apart?

Location: Auckland, NZ

There is more hogwash written about bearings than almost anything else. However Forrest Addy is a man who's opinion I have valued over many years but I am perplexed about the " different sized balls in one race " comment. Do you have a link to the article Henry?

The fact to remember about bearing precision, whether it's ABEC 7 spec bearings in a Bridgeport spindle or the AC pairs in an Austin 7 axle is that is fades after the first use. Partly worn bearings are part of owning a second hand milling machine or a second hand car and having a feeling for what is acceptable is important. The two worst things for bearings are rust and brinnelling.

Charles

If the AC bearing is worn such that it will come apart easily then it won't be of much use in locating the pinion- with a CW&P set costing A$675 (UK£330) and the bearings at A$160 (UK£80) a machined pair, I think the cheaper option is put in new bearings.

The pinion will wind in and out of mesh if the thrust bearing is worn or not properly locating the pinion. There is a small allowance but why run the risk?

I know prices have risen but the Austin 7 is still quite a low cost vintage/post vintage car to maintain.

Tony.

Location: Australia

There is a fabulous piece by the sainted Jack French in the Special Builders Guide where he describes how to test bearings.
I seem to recall that one of the places that he identifies as intolerant of suspect bearings is the pinion.

"If races reversed life further extended"

Not an appropriate suggestion - especially not in the pinion Angular Contact bearings!

Tony.

Location: Australia

Good to hear that your practical experience, over numerous applications and miles, works Ron - thanks for taking the trouble to share.

Tony,
Thank you for the explanation.
Dave.

Location: Sheffield

Ron,

Still like to know-

With this 'surface ground' method how do you machine the radius on the outer rim of the ground face?

Still not convinced that dismantling AC bearings by pressing apart is a good thing for balls and track.

You might get away with pressing some bearings apart but the full ball set has to be forced past the outer ring lip, both with the same hardness (if I remember 60 Rockwell C). It is very easy to cause brinelling damage to a bearing with force.

Tony.

Location: Australia

My word, there's been quite a bit of chat since I last looked!
Tony makes a good point about the loss of radius. The good news is that there is a generous radius on the bearing and enough of it remains after machining for it to still fit in its housing. On the outboard face of the adjacent bearing there is not even a need for a radius.
As has been mentioned, they tap apart without too much effort, and I have it on good authority from a bearing supplier, that there is no danger of the surface being damaged if done in a sensible manner. Certainly, I have never had any evidence of brinelling and the bearings have since run for thousands of miles.
By the same token, if an angular contact bearing comes apart when removing a crankshaft, just make sure to collect all balls together so they can be associated with that bearing and, when all is apart, check the now fully exposed races and decide if they are fit for further service. Clean up, reassemble and make the usual checks in the vice (as described elsewhere) to see if they can be used again.
Let's face it new ones are now very expensive and old ones should not be tossed aside simply because they have come apart. If buying new, avoid Chinese ones.
Ron