Crankshaft grinding

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rgould1910
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Crankshaft grinding

Post by rgould1910 » Mon Mar 25, 2019 3:53 pm

I need someone who can grind a Model T crankshaft in N. California. The guy who did my last one over 10 years ago is no longer in business. I hope to find someone who indexes off the flange, not the third main. If none are N. California, I suppose I can send it to someone within the USA who grinds a T crank correctly.
Most I've used do not index of the flange and the cranks come back with the outer edge of the flange not concentric with the center line of the mains.


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Re: Crankshaft grinding

Post by Dan McEachern » Mon Mar 25, 2019 4:02 pm

Richard- I sent you an e-mail. Dan


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Re: Crankshaft grinding

Post by hah » Tue Mar 26, 2019 11:38 am

Is indexing off the flange typicle to a model t, if so why?

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Matt in California
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Re: Crankshaft grinding

Post by Matt in California » Tue Mar 26, 2019 11:44 am

Richard,
Have you checked with Erik Barrett?

Here is his profile: https://www.modeltfordclubofamerica.co ... file&u=497

Matt


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Re: Crankshaft grinding

Post by Trentb » Tue Mar 26, 2019 1:52 pm

Yes, it is very important that Model T crankshafts be indexed off the crankshaft flange when regrinding!

Actually, a Model T crankshafts were originally ground between centers. This made the three main bearings on the crankshaft perfectly aligned.

But after 90+ years, the rear main bearings have been worn, reground, or both. If indexed off the third main bearing, the flange maynot run perfectly true and in alignment with the bearings. This will cause the flywheel to oscillate as it turns, which creates all kinds of nasty stresses, resulting in excessive main bearing wearing, and in extreme cases, it can cause crankshaft breakage.

You must find a crankshaft grinder who will grind your crank on the centers indexing off the flange (which rarely shows any wear whatsoever).

Respectfully submitted,

Trent Boggess


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Re: Crankshaft grinding

Post by Dave1 » Tue Mar 26, 2019 2:16 pm

Wondering why you would use the flange to index off rather than the lathe centers in the crankshaft ends?

Dave

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Re: Crankshaft grinding

Post by RustyFords » Tue Mar 26, 2019 3:10 pm

I'm only partially joking when I say that Ed Iskenderian is still alive and kicking (and keeping his shop open). He's probably turned a few T cams in his day. ;)

Of course, he's in So-Cal.
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Re: Crankshaft grinding

Post by rgould1910 » Tue Mar 26, 2019 8:38 pm

Dave I think the centers would be fine if they are in good shape. I read an article where a guy began by recutting the centers to clean them up and then index off them to grind. I guess you'd use a steady rest to hold the end you're recutting.

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Re: Crankshaft grinding

Post by BRENT in 10-uh-C » Wed Mar 27, 2019 9:14 am

Would it be a fair question to ask just how many here actually own a crankshaft grinder and are experienced in the proper use of it?

Why I ask is some things mentioned above may be giving some false concerns to others. I would be happy to mount up a T crank in my grinder and take some pictures to post here showing the basic process, but in a nutshell, the crankshaft IS mounted between centers on most crank machines. Some units have a 3 jaw chuck to help expedite the set-up, but the basic set-up is the same between both machines.

To begin with, ...generally speaking if someone has machined on the face of the flywheel, the crankshaft is not worth repairing. I'm not saying it can't be done but generally speaking the time necessary to correct it becomes too valuable to do the job. So the key thing in this is that most hobbyists or engine builders will not take the time to do a proper check of the crank. The crank is mounted between centers on the grinder and the surface under the timing gear is used to indicate one end, and the outer surface of the flange of the other end. This verifies the crank is on centerline with the machine only. Next I use an indicator to measure the runout of the center main. From there, the crank is moved into a straightening press and the crankshaft is straightened and peened to normalize it so the bend will set. When the necessary time has been taken doing this step to be within a tenth, then the rear flange will run true. This step often takes as much time as the grinding process does, and many grinders who are on time constraints (i.e: budget constraints) will either shortcut or omit this step. Once the crankshaft is straight again, only then should it be ground. I charge $300 to grind a crankshaft. There are others that will do it for less, and generally speaking the way they can offer it cheaper is to omit a step or two in the process to lessen the overall time it takes to do the job.


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Re: Crankshaft grinding

Post by Adam » Wed Mar 27, 2019 10:04 am

People don’t understand that the “centers” in most T parts aren’t necessarily the center of the part!

The centers in the part were for work-holding and quick setup, loading, and unloading of the parts. The centers of the machine doing the work may or may not have been properly at their center. If you then set the part up between proper centers, the center holes are not on the actual center and there is runout on the part surfaces.

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Re: Crankshaft grinding

Post by BRENT in 10-uh-C » Wed Mar 27, 2019 10:46 am

[quote=Adam post_id=19382 time=1553695455 user_id=138]
People don’t understand that the “centers” in most T parts aren’t necessarily the center of the part!

The centers in the part were for work-holding and quick setup, loading, and unloading of the parts. The centers of the machine doing the work may or may not have been properly at their center. If you then set the part up between proper centers, the center holes are not on the actual center and there is runout on the part surfaces.
[/quote]

Adam, this may be your point but just so we are clear, on a crankshaft grinder this does not matter as the heads on each end are adjusted to bring the journal runout into 0.000'. We are using the OD of the flange to determine this on the rear end the crankshaft, and we are using the surface under the crank ear to determine the centerline of the front.


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Re: Crankshaft grinding

Post by Adam » Wed Mar 27, 2019 11:03 am

Brent, You are absolutely correct and I understand that.

I think someone had made an observation about setting up based on the existing center and I was making an observation on that idea.


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Re: Crankshaft grinding

Post by Dave1 » Wed Mar 27, 2019 11:38 am

Thanks for the Technical expertise, you are correct in that most of us do not have access to a crankshaft grinder or the ability to operate one.
But it is helpful to know how a T crankshaft "should" be ground, If nothing else.

Dave


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Re: Crankshaft grinding

Post by Dave1 » Wed Mar 27, 2019 11:42 am

Brent,

I would for one like to see how you set up a crank for grinding and which surfaces you use as a reference.

Dave

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Re: Crankshaft grinding

Post by Fordfarm » Wed Mar 27, 2019 11:51 am

Crankgrinder2.jpg
Crankgrinder2.jpg (18.37 KiB) Viewed 3047 times
OK. I seldom involve myself in these sorts of discussions as every individual I have ever talked to who has done this sort of work has his own methods. I will, however, toss in a couple of pennies this time.

" When the necessary time has been taken doing this step to be within a tenth....."

Please explain how you do this when the center main is either badly worn or wiped out.

My machine is a Storm Vulcan No. 15. I absolutely agree that straightening the crank is a vital step before grinding, but I am not so sure that working to "tenths" during the straightening process isn't overkill. After all, these engines are not going to run 8,000 to 10,000 rpms at Daytona.

As Richard stated above, establishing an accurate center at the rear flange may be accomplished by steady resting the flange in a lathe and then recutting the 60 degree included angle with a single point tool. Dial-in the gear shoulder on the snout with a 4-jaw chuck. BTDT. This does not happen very often but it does crop up occasionally. These Model T parts have been in use for many years and some have been badly mishandled by would-be mechanics (the bigger hammer crowd) in the past.

Grinding a Model T crank is unlike any other in my experience other than a one cylinder stinkpot engine or two. Most other cranks are somewhat rigid. The T has a degree of flexibility you don't encounter with Model A or Model B cranks and certainly not with modern heavy crankshafts. Don't take my word for it; do the experiment yourself. Set up the crankshaft between centers and dial-in the center main with the indicator set at "0". Now give it a push with your thumb and tell me how much you deflected it.

Depending on your make of machine, some inward pressure, end-to-end, is exerted in the setup, not to mention the pressure exerted by the steady rest. It's not much, but remember we are doing a very delicate operation on a flexible workpiece in a very heavy machine. Imagine what that does to the crankshaft when it is in position. I was a bit skeptical about this phenomenon when an old timer (who had ground many T crankshafts on this machine) told me about it. Well, he was dead-nuts on about that! Your machine probably has a taper adjustment capability on the front table. You will probably find it necessary to use it while grinding a Model T crankshaft.

Further crankshaft grinding discussion might also include use of proper coolant, proper dressing of the grinding wheel (paying particular attention to the radius on each side of the wheel) etc. etc. This is enough for now. The instruction manuals accompanying the machines cover these subjects very well.

For those who want to discuss alignment of the transmission shaft vis. the crank flange, we can do that later. Wes Clover and I spent a considerable amount of time back in the '80's fooling with this and we found that an often-overlooked, seemingly-benign part (or two) would throw things out even when crank flange and transmission shaft were as true as we could achieve. It was a fascinating couple of days......and somewhat frustrating at the same time.

JMHO

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Re: Crankshaft grinding

Post by Mark Gregush » Wed Mar 27, 2019 8:07 pm

A lot of us don't have access to someone that KNOWS T cranks, so yes it important that we can communicate with our shop HOW a T crank needs to be set up.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Crankshaft grinding

Post by Scott_Conger » Wed Mar 27, 2019 10:07 pm

Phil

I am not a crank grinder, nor am I speaking for Brent, but so long as the crank is bowed, the flange (flywheel/output shaft face) will most certainly wobble. If the crank is straightened to dead-nuts, the flange (should) present a face that is either perfect or require only the most minimal "kiss" to true it up to perpendicular to the axis of the crank. If some bow is left, then the center main will require excessive grinding (or at least more than would otherwise be necessary) and the flange face will most certainly require refacing, with some loss of material. Similar run-out at the timing gear would I think, be immaterial.

I believe I understand exactly what Brent was saying, and if so, it does make sense to me to make the effort.

Am I completely mistaken? I appreciate your wading into this and am always looking to learn something new.
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Re: Crankshaft grinding

Post by Fordfarm » Wed Mar 27, 2019 11:06 pm

Scott -

That is correct. The point is that the crank does bow a little in the setup, at least with this machine which has a spring loaded tailstock spindle, a feature of the machine to control this "squeeze" on the shaft before locking it down. The crankshaft straightens out again when removed from the machine. And yes, if the flange is "out" any appreciable amount it will not revolve in the same plane as the rest of the shaft. But "a tenth"....? That is really splitting hairs and I applaud anyone who can perform this straightening work to such limits.

My question was aimed at what to do when there is no good indicating surface left due to extreme wear or a wipeout of the center journal.

The steady rest remains on the center main (which is ground first) throughout the rest of the grinding of the main journals. A second steady rest is used on the front or rear whichever is being ground at the time. The idea here is to make the shaft as rigid as can be when it is being ground to eliminate the potential chatter problem which can (and will) occur if the setup is loose. This "bow" is what causes the rear main (and to a lesser extent the front main) to achieve a bit of a taper as it is ground. That's where the taper adjustment feature comes into play.

Taking a "kiss" on the rear of the flange usually trues it up if it is found to be out. This is done between centers on a lathe after the grinding has been accomplished, and it is necessary if one expects to achieve a fair degree of accuracy in aligning the transmission shaft. If it requires more than that, the shaft has been forcibly bent and Brent is right in that it is not worth the time to correct it.

The T crank presents problems not usually encountered in grinding modern (or larger, stiffer) crankshafts. If one has not encountered one of these things before, the first grinding episode can be a real eye opener. I think it is a good idea to realize, as well, that we are dealing with job-shop type equipment which must be somewhat versatile simply due to the nature of the various jobs it will be called on to do. This is not the same as a production machine which does the same job over and over and over and over, ad infinitum.


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Re: Crankshaft grinding

Post by Joss » Wed Mar 27, 2019 11:39 pm

Will ask a silly question about crank grinding. Since all Model T cranks area likely to be 90+ years old all thus have all manner of metal fatigue why would one pay a couple hundred dollars to machine a crank and pay a few thousand for the rest of the rebuild to risk the crank will not break? Seems pay me now makes more sense and to use a new T crank.
Just my thoughts.

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Re: Crankshaft grinding

Post by Mark Gregush » Thu Mar 28, 2019 2:44 am

Simple; A decent rebuild is not going to cost the big bucks suggested on the other thread and frankly not everyone has that kind of money sitting around for a new crank. Also, not everyone needs to or wants to, spend that money to go to ice cream, maybe a few short tours or putting around town under 35 is the extent of their driving. I ran mine for years and lots of miles with original babbitt in block and rebabbitted caps till I lost the center main, had to get crank checked, ground and new babbitt. Yes I know someone that broke a crank. We found another one, got it ground to match the broke one and re-fitted it. Luckily the babbitt survived.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Crankshaft grinding

Post by BRENT in 10-uh-C » Wed Apr 03, 2019 11:30 am

Fordfarm wrote:
Wed Mar 27, 2019 11:06 pm
Scott -

That is correct. The point is that the crank does bow a little in the setup, at least with this machine which has a spring loaded tailstock spindle, a feature of the machine to control this "squeeze" on the shaft before locking it down. The crankshaft straightens out again when removed from the machine. And yes, if the flange is "out" any appreciable amount it will not revolve in the same plane as the rest of the shaft. But "a tenth"....? That is really splitting hairs and I applaud anyone who can perform this straightening work to such limits.

My question was aimed at what to do when there is no good indicating surface left due to extreme wear or a wipeout of the center journal.

The steady rest remains on the center main (which is ground first) throughout the rest of the grinding of the main journals. A second steady rest is used on the front or rear whichever is being ground at the time. The idea here is to make the shaft as rigid as can be when it is being ground to eliminate the potential chatter problem which can (and will) occur if the setup is loose. This "bow" is what causes the rear main (and to a lesser extent the front main) to achieve a bit of a taper as it is ground. That's where the taper adjustment feature comes into play.

Taking a "kiss" on the rear of the flange usually trues it up if it is found to be out. This is done between centers on a lathe after the grinding has been accomplished, and it is necessary if one expects to achieve a fair degree of accuracy in aligning the transmission shaft. If it requires more than that, the shaft has been forcibly bent and Brent is right in that it is not worth the time to correct it.

The T crank presents problems not usually encountered in grinding modern (or larger, stiffer) crankshafts. If one has not encountered one of these things before, the first grinding episode can be a real eye opener. I think it is a good idea to realize, as well, that we are dealing with job-shop type equipment which must be somewhat versatile simply due to the nature of the various jobs it will be called on to do. This is not the same as a production machine which does the same job over and over and over and over, ad infinitum.

Hey Phil, great to see your name again and to read your writings. I trust you are still pickin' that 5 string with your family!!

I too have a SV15 that I completely restored about 5 years ago. It has served me well as all I am doing is pre-war engines. While I am in agreeance that 0.0001" is probably 'overkill', it is my/our target. I also agree there is likely some deflection just by the weight of the crank sagging on the Vee-blocks however that deflection will be accounted for with the steady-rest during grinding. Also, we use a Last Word indicator on the face of the flange to verify/detect deflection either with the steady rest or the wheel. When your target is to grind to that tolerance, any minor deflection is generally corrected by a properly poured center main.



Mark, your comment about a decent rebuild is not going to cost big bucks as suggested is an interesting comment. If it was the thread I'm thinking about, the O/P started the thread by asking the cost on a First Class rebuild, --not a decent rebuild. I believe your comment is correct that not everyone needs a First Class rebuild. I'm sure you would agree that not everyone NEEDS a new diesel pick-up to pull their trailer, --and not every Model-T owner needs an enclosed trailer to haul their Model-T on to a tour, --and not every Model-T owner must spend $1,000.00+ attending a Model-T tour just to enjoy their Model-T …...however when I typically attend a T tour such as the recent Winter Tour in Florida, there sure were a lot of really fancy diesel pick-up trucks pulling some really nice enclosed trailers sitting in the resort hotel parking lot. Again, I must agree 110% with you that a first-class engine is not necessary however statistics show there is a whole lot of hobbyists who want a first class engine. Their motives may be different than your desires, -and that should be ok with the rest of us since afterall, it is their money paying for their wishes and not ours.


Joss, your concerns are valid asking about a 90+ year old crankshaft. Some of us have a magnetic crack checking machine that allows us to test for hidden flaws or cracks which is accurate to a high degree however it does not give certainty there will not be a future failure. Calculating the Risk taking vs. Budget spending generally dictates which is the proper direction for a customer to choose. Only you can know what is the correct decision for you. As I share with my customers in all facets of the restoration process, -'It is NOT my job to make the decision for them. It IS my job to thoroughly explain all the options available to them so they can choose the decision that most prudently applies to them!'.

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Re: Crankshaft grinding

Post by ewdysar » Wed Apr 03, 2019 2:56 pm

Hi Brent and Joss,

Two years ago, when my original 1914 engine was torn down (apparently for the first time ever) for a rebuild, we found that the original crank had a lengthwise crack that went through 2 neighboring journals. Who knows how long that crack had been there. I had the crank replaced, of course. The crank never broke, and the engine ran pretty well, with fairly worn rings and valves that were doing their job. The transmission had reasonable wear in most of the bushings and was noisier and less smooth in operation than my other T engines. I believe that one off the drums was replaced due to a crack there as well. The rebuild ended up being fairly expensive, but I consider it to be First-Class rebuild rather than merely a decent one. Considering that it was the engine's first rebuild in more than 100 years, I was willing to pay the premium. All my choice. And a "tip of the hat" to Larry at the Tin Shed for managing this project for me and giving me enough information to choose the appropriate path for my needs.

At the other end of the spectrum, when I was resurrecting my father's T after 30+ years of storage, Larry ground the valves, replaced the rings and the #1 rod and installed wood bands. That engine runs strong with iron pistons and an original Ford crank and is running so well that other than regular maintenance on the shims and bands, I would rather not take anything else apart to upset the magic in this 50+ year old rebuild.

Keep crankin'
Eric


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Re: Crankshaft grinding

Post by Adam » Wed Apr 03, 2019 4:40 pm

Shims should not be regular maintenance.

Under ordinary circumstances; If the crank is in first class condition, if the babbitt job is good, if the entire engine and trans was properly cleaned, if you drive 30-35, and regularly change your oil, you shouldn’t expect to remove a shim for tens of thousands of miles.


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Re: Crankshaft grinding

Post by delfi87 » Wed Apr 10, 2019 9:35 am

I will repair my crankshaft DIY. Now I find the methods that how to do detection crankshaft at home. I found something here http://www.newkidscar.com/vehicle-const ... %EF%BB%BF/.
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