Crankshaft Journals

[GG Gregory]

I’ve been dismantling the March 1927 spare engine I got recently. Everything looks pretty good except one co-rod bearing, it has a few missing pieces of Babbitt. My question is what is the limit undersize the journal can be without having to have the whole crankshaft turned? I hope I explained it correctly.

[Jerry VanOoteghem]

A journal being undersize does not necessarily mean that it needs to be turned, (re-ground). Journals may be undersize due to past re-grinds. What does matter, is that the journals are not out-of-round, tapered, pitted, or scored. I've heard of cranks ground as much as .060" undersize, but I would never go that far. My guess is that .030" under would be about the limit.

[GG Gregory]

Jerry, for instance the journal is standard 1.248, how many thousands out of round can a journal be and still be within specs without having the entire crankshaft ground ? I’ve not had the journals checked with a mic yet. I’m kinda new at this, thanks for the help.

[BRENT in 10-uh-C]

Jerry, for instance the journal is standard 1.248, how many thousands out of round can a journal be and still be within specs without having the entire crankshaft ground ? I’ve not had the journals checked with a mic yet. I’m kinda new at this, thanks for the help.

You are there already. I grind crankshafts to no more than about five-hundred thousandths out of round (0.00005") since I must plunge grind and finish with a cork belt.. You are basically 0.002" out now. Even if you were to accept 0.0005" runout, you are still 4X the maximum amount.

[Dan Hatch]

I never go under 20. T cranks are too small to start with.
If you have it ground, be sure to use someone that knows about T cranks.
Check the rear main first to see how small it is. They wear first.

[speedytinc]

Jerry, for instance the journal is standard 1.248, how many thousands out of round can a journal be and still be within specs without having the entire crankshaft ground ? I’ve not had the journals checked with a mic yet. I’m kinda new at this, thanks for the help.

You are there already. I grind crankshafts to no more than about five-hundred thousandths out of round (0.00005") since I must plunge grind and finish with a cork belt.. You are basically 0.002" out now. Even if you were to accept 0.0005" runout, you are still 4X the maximum amount.

?????????? Standard is 1.248.
There is no reported wear. Do your measuring & get back. A worn journal can be made round again if not out too far.

[Norman Kling]

You need to be very careful who you get to grind the crank. I took one in to be checked. You need to check with magnetometer to be sure there are no cracks and also check whether the crank is straight or crooked as well as whether the journals need to be ground. I took one in and they found no cracks and journals were OK. It was crooked. I asked whether he had equipment to straighten it and he said yes. So I let him do it. when I got it back it was 60 thousandths undersize. Apparently he just ground them until they were all in alignment. That was when I decided to buy a SKAT crankshaft. I took the reground one to an auction with the club and it had a tag noting the size of the grind. To my surprise, Tony Bowker bought it. I don't know whether he ever installed into a car?
Norm

[GG Gregory]

Jerry, for instance the journal is standard 1.248, how many thousands out of round can a journal be and still be within specs without having the entire crankshaft ground ? I’ve not had the journals checked with a mic yet. I’m kinda new at this, thanks for the help.

You are there already. I grind crankshafts to no more than about five-hundred thousandths out of round (0.00005") since I must plunge grind and finish with a cork belt.. You are basically 0.002" out now. Even if you were to accept 0.0005" runout, you are still 4X the maximum amount.

?????????? Standard is 1.248.
There is no reported wear. Do your measuring & get back. A worn journal can be made round again if not out too far.

Speedy, that was a for instance measurement, I haven’t checked yet. I don’t think I’m explaining correctly or know one is understanding. I have one bad rod that needs replaced. If for instance ALL rods are standard, good babbitt except one which is cracked. How much wear on the journal of the bad rod is allowable to put a standard rod back in its place?

[speedytinc]

0 is great, obviously. & is the goal.
.0005 is ok.
.001 or more wear, I would be using some fine emery cloth to get the journal to .0005 or better.
Use a long emery cloth strip to take the high/less worn areas down.
It's a tedious & time consuming process, especially working under the motor, but very doable.

[BRENT in 10-uh-C]

?????????? Standard is 1.248.
There is no reported wear. Do your measuring & get back. A worn journal can be made round again if not out too far.

John I probably didn't say that correctly as I was trying to put it in layman's terms. If hypothetically you are at 1.248", how are you measuring it? Are we using a set of calipers, a mic, or an Arnold Gage?? My point was Mr. Gregory is already at the maximum OoR tolerance. I do not have a print of a T crankshaft but I do have prints on A crankshafts which allows for no more than 0.0005 total axial (-0.00025 per side) runout. I guarantee he is at that now. Dan says he will go no more than 0.020 undersize. The issue is Ford used a cyanide heat treating that spec-ed a Brinell 402-444, but the penetration was only about 0.010" - 0.015" deep. That is about mid 40s Rockwell. Get thru that and there is not much left to make a hard surface for the bearing to ride on.

Yes, all crankshafts should (-i.e.:need) to be wet-magged prior to grinding. To go along with Norman's point, all someone needs to be able to straighten a crankshaft is a set of Vee Blocks, a test indicator, a blunt chisel and a large hammer. I don't use a mechanical or hydraulic crankshaft straightener as it will move as soon as I install it in the grinder. Most crankshafts will bend during the grinding process, but we just restraighten after the grinding process.

[Kerry]

Doesn't seem that you got an answer to your question, Ford specs allow up to .002" out of round bigends before replacing, up to 1925 the cranks were made from Type A Vanadium steel, I'm not aware of Ford ever doing any extra case hardening on them and can be ground without any issues. The formula and shape changed some for the 1925 AA and 26/27 EE cranks and I still have no evidence in Fords specs that they had any journal case hardening. The T is a low revving engine, built for a price not a million miles or to last more than several years in the day.

[GG Gregory]

Kerry, you win the cigar for actually reading and understanding my post and giving me the answer I needed ! Thanks!

[Kerry]

Back in the T days, Ford offered a changeover service for rods, listed are an oversize for a worn shaft.

[Jerry VanOoteghem]

My point was Mr. Gregory is already at the maximum OoR tolerance.

Brent,

How are you coming to that conclusion? He has not mentioned any measured out of round as far as we know. Are you basing that on the size being 1.248? That is the correct, standard size of a T crank journal and does not reflect any wear.

[Allan]

Perhaps this is more complicated than it needs to be. When i ran number 1 rod bearing on Henrietta, we took the damaged rod out through the inspection plate on the bottom. I then scraped/lapped a serviceable used spare rod and lapped it in with yellow timesaver. That was a couple of years ago now. i was expecting to have to make adjustments as the new rod got to know the crank, but even that has not been necessary. If this is a used engine, a used part may well be appropriate. Once you start grinding the crankshaft, things get expensive quickly.
Allan from down under.

[BRENT in 10-uh-C]

My point was Mr. Gregory is already at the maximum OoR tolerance.

Brent,

How are you coming to that conclusion? He has not mentioned any measured out of round as far as we know. Are you basing that on the size being 1.248? That is the correct, standard size of a T crank journal and does not reflect any wear.

Jerry, my conclusion is basically based on experience as a crankshaft grinder. Not being cocky or condescending but how many others in this conversation even own a crankshaft grinder, -or own the metrology to correctly measure a pin? If there are any, let them offer their experiences as I will gladly listen. I will however, bet a sizeable amount that this used crankshaft is out of specs. Again, if it has any wear at all it is out of specification, and Mr. Gregory has stated he has a bad rod.

Also, bringing this back to the beginning, take a moment to reread what Mr. Gregory initially asked, ..."how many thousands out of round can a journal be and still be within specs...". As I and John stated above, 0.0005" is about the max. Maybe I misunderstood but I didn't understand Mr. Gregory to ask 'how many thousandths can the journal pin be out of round and still be used'. Therefore I answered based on Ford engineer's prints and personal experiences. If someone else has different specs printed by Ford's engineers, I am truly interested so I can be the wiser on the next one.

[BRENT in 10-uh-C]

My point was Mr. Gregory is already at the maximum OoR tolerance.

Brent,

How are you coming to that conclusion? He has not mentioned any measured out of round as far as we know. Are you basing that on the size being 1.248? That is the correct, standard size of a T crank journal and does not reflect any wear.

Jerry, quite honestly, my conclusion is only basically based on experiences as a crankshaft grinder. Not being cocky or condescending but how many others in this conversation even own a crankshaft grinder, -or own the metrology to correctly measure a pin? If there are any, let them offer their experiences as I will gladly listen. I will however, bet a sizeable amount that this used crankshaft is out of specs. Again, if it has any wear at all it is out of specification, and Mr. Gregory has stated he has a bad rod.

Also, bringing this back to the beginning, take a moment to reread what Mr. Gregory initially asked, ..."how many thousands out of round can a journal be and still be within specs...". As I and John stated above, 0.0005" is about the max. Maybe I misunderstood but I didn't understand Mr. Gregory to ask 'how many thousandths can the journal pin be out of round and still be used'. Therefore I answered based on Ford engineer's prints and personal experiences. If someone else has different specs printed by Ford's engineers, I am truly interested so I can be the wiser on the next one.

[BRENT in 10-uh-C]

Brent,

How are you coming to that conclusion? He has not mentioned any measured out of round as far as we know. Are you basing that on the size being 1.248? That is the correct, standard size of a T crank journal and does not reflect any wear.

Jerry, quite honestly, my conclusion is only basically based on experiences as a crankshaft grinder. Not being cocky or condescending but how many others in this conversation even own a crankshaft grinder, -or own the metrology to correctly measure a pin? If there are any, let them offer their experiences as I will gladly listen. I will however, bet a sizeable amount that this used crankshaft is out of specs. Again, if it has any wear at all it is out of specification, and Mr. Gregory has stated he has a bad rod.

Also, bringing this back to the beginning, take a moment to reread what Mr. Gregory initially asked, ..."how many thousands out of round can a journal be and still be within specs...". As I and John stated above, 0.0005" is about the max. Maybe I misunderstood but I didn't understand Mr. Gregory to ask 'how many thousandths can the journal pin be out of round and still be used'. Therefore I answered based on Ford engineer's prints and personal experiences. If someone else has different specs printed by Ford's engineers, I am truly interested so I can be the wiser on the next one.

[Kerry]

Brent, Ford Model T service book, printed by Ford Motor Company, page 65 par 242, .002" 'out of round, the shaft should be changed.

[BRENT in 10-uh-C]

Geez, I guess I need more Caffine this morning!!

Mr. Gregory, I did NOT mean to insinuate that YOU had a bad rod, ...but merely the engine you were working on had a damaged connecting rod.

-also, I guess I need to go back to 2nd grade and learn how to correctly put together a sentence. What does "...my conclusion is only basically based on " actually mean?? [insert hillbilly jargon here]

[BRENT in 10-uh-C]

Brent, Ford Model T service book, printed by Ford Motor Company, page 65 par 242, .002" 'out of round, the shaft should be changed.

Thanks Kerry! I will definitely look at that.

[Jerry VanOoteghem]

Brent,

How are you coming to that conclusion? He has not mentioned any measured out of round as far as we know. Are you basing that on the size being 1.248? That is the correct, standard size of a T crank journal and does not reflect any wear.

Jerry, quite honestly, my conclusion is only basically based on experiences as a crankshaft grinder. Not being cocky or condescending but how many others in this conversation even own a crankshaft grinder, -or own the metrology to correctly measure a pin? If there are any, let them offer their experiences as I will gladly listen. I will however, bet a sizeable amount that this used crankshaft is out of specs. Again, if it has any wear at all it is out of specification, and Mr. Gregory has stated he has a bad rod.

Also, bringing this back to the beginning, take a moment to reread what Mr. Gregory initially asked, ..."how many thousands out of round can a journal be and still be within specs...". As I and John stated above, 0.0005" is about the max. Maybe I misunderstood but I didn't understand Mr. Gregory to ask 'how many thousandths can the journal pin be out of round and still be used'. Therefore I answered based on Ford engineer's prints and personal experiences. If someone else has different specs printed by Ford's engineers, I am truly interested so I can be the wiser on the next one.

Thanks Brent. Just to be clear, I was not challenging your experience & expertise in crankshaft grinding or metrology, but only wanting to know your thought process.

[TXGOAT2]

The crankshaft needs to be straight, and the crankpins need to be round. Being out, or "flat" by .002 isn't much, even on a skinny T crank, but it IS too much. Rod bearings will not hold an adjustment on a flat crankpin. Shafts that have been run a lot, or run with loose rods, will most likely have flat crankpins.

[Craig Leach]

Hi Gregory,
It's not uncommon to find missing Babbitt. Does not mean the crank is bad. If all the journals look good & measure round with little or no taper
no grooves & you know what size it is ( under already ? ) Buy a rebabbitted rod if the crank is a little under size that's what shims & timesaver
are for. I know the book states 0.002 for out of round, my experience is anything over 0.001 will require you to take shims out on a regular
basis every 500-700 miles. It is a Model T try not to over think it
Craig.