How many times can a flywheel be re surfaced?

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my68barracuda

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the OE flywheel was previously resurfaced approx 10 years ago after 100K daily drive use when the 83 D150 was taken down to the frame for restoration.
Fast forward to today, 50,000 miles later, I am changing the clutch out, the pressure plate failed, got into hard shifting found over .260 difference from high to low on the clutch plate fingers.
I don't see any scoring on the flywheel but there is wear that I can feel at the outer edge where the clutch disk runs.
This is a slant six vehicle so replacement flywheels are not readily available.
I measured the thickness of the flywheel and it is .858 thick and uniform in the three places that I measured.
Can it be cut again?
 
the OE flywheel was previously resurfaced approx 10 years ago after 100K daily drive use when the 83 D150 was taken down to the frame for restoration.
Fast forward to today, 50,000 miles later, I am changing the clutch out, the pressure plate failed, got into hard shifting found over .260 difference from high to low on the clutch plate fingers.
I don't see any scoring on the flywheel but there is wear that I can feel at the outer edge where the clutch disk runs.
This is a slant six vehicle so replacement flywheels are not readily available.
I measured the thickness of the flywheel and it is .858 thick and uniform in the three places that I measured.
Can it be cut again?

I have a large register flywheel I believe is still original. Would you like me to measure it for comparison?
 
I have a large register flywheel I believe is still original. Would you like me to measure it for comparison?
FSM should tell. May be not. The machine shop doing the grinding may/should know. May Be not.
 
I wouldnt resurface that flywheel any more than three or four more times.
That would be my guess. "Hard spots." You have to take a fair amount sometimes, to get "down" around the hard spots. I'm thinkin 2-3 times with hard use
 
Since the pressure plate bolts are have a larger shank diameter than thread diameter to locate the pressure plate, it would be possible to bottom out the shank before the pressure plate bolt is tight against the pressure plate if the flywheel was cut too much. This could be corrected by putting a flat washer under the lock washer or drilling the shank part of the flywheel pressure plate hole deeper but if you run into this problem then you probably cut the flywheel one too many times.
 
Since the pressure plate bolts are have a larger shank diameter than thread diameter to locate the pressure plate, it would be possible to bottom out the shank before the pressure plate bolt is tight against the pressure plate if the flywheel was cut too much. This could be corrected by putting a flat washer under the lock washer or drilling the shank part of the flywheel pressure plate hole deeper but if you run into this problem then you probably cut the flywheel one too many times.


I use locktite and never a lock washer on a pressure plate or flywheel bolt. They can and will fail. When they do the end result is catastrophic. If you are using a washer it needs to be a hardened, parallel ground flat washer.

On certain pressure plates (the McLeod Borg&Beck/Long covers) you don’t use any washer. Ever. If you do, the cover will fail. BTDT.
 
I use locktite and never a lock washer on a pressure plate or flywheel bolt. They can and will fail. When they do the end result is catastrophic. If you are using a washer it needs to be a hardened, parallel ground flat washer.

On certain pressure plates (the McLeod Borg&Beck/Long covers) you don’t use any washer. Ever. If you do, the cover will fail. BTDT.
Yes, this is a B&B pressure plate, so cutting the mounting surface simply moves the pressure plate fingers x thousands of inches away from the TOB, which can be taken up with normal adjustments. The mounting bolt holes in the flywheel are through holes, so no issue with those bottoming out.
My concern was more about the strength of the spinning mass.
 
I just did a cursory internet search and one thing I hadn't thought of was that with enough resurfacing eventually the disc springs are going to hit the crank bolt heads.
 
I just did a cursory internet search and one thing I hadn't thought of was that with enough resurfacing eventually the disc springs are going to hit the crank bolt heads.


I’m ashamed to say it but.....BTDT.

I tore up a clutch disc my senior year in high school. It mangled the brand new Hayes FW I had. My HS metal shop had a lathe big enough to swing a FW so I stuck it in there, indicated it in and started taking cuts.

That clutch always had a bad shake to it. I found it it wasn’t machined parallel to the crank so I trimmed it off until it cleaned that up.

And the springs on the disc hit the crank bolts. I was pretty pissed I didn’t catch that before I started machining on it, and my shop teacher gigged me pretty hard for that one.
 
I don't have an extra /6 FW laying around to check but on a typical 10.5 V8 factory FW there is a step where the working surface meets the body of the casting. As a FW is used and reused, that distinct ridge disappears with resurfacing. I take that to be like wear indicators on tires. (Bars or holes) I have heard that is a good way to judge if a FW is serviceable or not.

Always better to surface grind FWs, not lathe turning.
 
I don't have an extra /6 FW laying around to check but on a typical 10.5 V8 factory FW there is a step where the working surface meets the body of the casting. As a FW is used and reused, that distinct ridge disappears with resurfacing. I take that to be like wear indicators on tires. (Bars or holes) I have heard that is a good way to judge if a FW is serviceable or not.

Always better to surface grind FWs, not lathe turning.


I agree about grinding. But sometimes you gotta get it done and grinding on the FW that I hurt would have been a nightmare.

In reality, I probably should have put it in the grinder and taken a finish cut on it, but it had a pretty nice finish and I ran an indicator all over it and it was pretty flat.
 
I don't have an extra /6 FW laying around to check but on a typical 10.5 V8 factory FW there is a step where the working surface meets the body of the casting. As a FW is used and reused, that distinct ridge disappears with resurfacing. I take that to be like wear indicators on tires. (Bars or holes) I have heard that is a good way to judge if a FW is serviceable or not.

Always better to surface grind FWs, not lathe turning.
Interesting comment on grinding vs turning a flywheel.
I have always heard that a renewed flywheel is ‘turned’. When I think of grinding I think of finishing crankshaft mains and pins.
So why would grinding a flywheel be preferred?
 
Interesting comment on grinding vs turning a flywheel.
I have always heard that a renewed flywheel is ‘turned’. When I think of grinding I think of finishing crankshaft mains and pins.
So why would grinding a flywheel be preferred?

Grinding is what's actually done. Most everybody refers to it as turning, but it's not the same as turning a rotor on a brake lathe, for example. A flywheel is properly resurfaced on a machine that has a large grinding stone that spins while the flywheel also spins, but off center of the stone, to achieve a non directional or "swirl" type finish. I've seen people chuck them up on a brake lathe before and do a real purdy job, but it's incorrect and will lead to clutch chatter and wear the clutch disc prematurely. But yes, technically flywheels are indeed ground. I've never said "I've gotta get my crankshaft ground", either, I've always called it "turned" but they are also ground of course.
 
Grinding is what's actually done. Most everybody refers to it as turning, but it's not the same as turning a rotor on a brake lathe, for example. A flywheel is properly resurfaced on a machine that has a large grinding stone that spins while the flywheel also spins, but off center of the stone, to achieve a non directional or "swirl" type finish. I've seen people chuck them up on a brake lathe before and do a real purdy job, but it's incorrect and will lead to clutch chatter and wear the clutch disc prematurely. But yes, technically flywheels are indeed ground. I've never said "I've gotta get my crankshaft ground", either, I've always called it "turned" but they are also ground of course.
Thanks, I did not know that. I honestly thought flywheels were turned on a lathe. I am working with a competent machine shop on getting that flywheel renewed, but I did not think to ask what process they use on flywheels. I will give them a call tomorrow.
 
Thanks, I did not know that. I honestly thought flywheels were turned on a lathe. I am working with a competent machine shop on getting that flywheel renewed, but I did not think to ask what process they use on flywheels. I will give them a call tomorrow.
I called the shop, they said my flywheel will be ready for pickup today after 2:00 pm and that they use a grinding process.
 
I called the shop, they said my flywheel will be ready for pickup today after 2:00 pm and that they use a grinding process.


You’d be surprised by how many shops don’t have a lathe with enough swing to face a flywheel. And yes, they should be ground. And they are ground with the crank flange sitting on a parallel ground spacer or something so the face is parallel to the crank flange.

I suppose you could make a fixture to bolt to the FW so you can Chuck it in a lathe and face it, but that’s way more work than it’s worth. FW grinding is relatively inexpensive.
 
That would be my guess. "Hard spots." You have to take a fair amount sometimes, to get "down" around the hard spots. I'm thinkin 2-3 times with hard use
You can't totally remove the hard spots they will come right back.
 
When I was young and stupid, we had a disk lathe and somewhere I'd read (the destructions) about turning a flywheel. What a disaster. HARD SPOTS. Pretty soon the thing looked like a stone/ concrete sidewalk. Big "welts" sticking up were the hard spots, with low spots where the tool and "sprung" down and cut deeper. had to find someone with a surface grinder That was around 1975, I don't remember the details
 
Thee actually IS a flywheel facing attachment made by Ammco for their older like 4000 series brake lathes.....and it does work and does it correctly. It looks like this.....

FLYWHEEL GRINDER.jpg
 
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