Can a steel flywheel be machined?

[AC sports]

I've got a rather expensive steel flywheel for a subaru turbo that I want to re use. it's got the usual concave wear pattern to it as well as heat spots. Is it possible to turn it flat in a lathe then use a rotating stone to finish? I dont have a dedicated flywheel grinder in my area. I'll obviously cut the step too.
Can the pressure plate be done also? Or is the worn plate usually replaced during rebuild? I'd like to try save that too if possible....its even more expensive.

[rebelrouser]

I live in the country and the nearest shop that will properly grind a flywheel is an hour away, so I understand your pain. But my experience is that when you try and turn them on a lathe the hard spots are harder than the lathe bit and or so hard the tool holder flexes and the bit rides over the hard spot, even though the surface looks good it still has high spots. Some brake drum lathes have a grinder attachment that with a little work you can get to work. Normally I just replace the pressure plate. I am lucky that we have a clutch rebuilding factory about two hours away, and they do customer work. I take all my high end clutch or obsolete stuff to them and have it rebuilt there. They can even custom set the plate pressures, and upgrade the lining materials.

[BCjohnny]

As long as the 'heat spots' don't run into cracks then yes

You don't need a 'dedicated flywheel grinder', any head re-surfacer and rotary table will get the job done, in the right hands ...... I'm not sure I'd 'rough' the face off first in a lathe, personally

Pressure plates are routinely resurfaced in 'reconditioned' clutches, but are disassembled at the strap rivets, the 'clamp' plate is then ground separately and the whole reassembled back into a complete unit ...... whatever is taken of the face is 'shimmed' back into the straps ...... just don't take too much off

Whether all this can be done economically, on a one off basis, is another matter ...... it's half a days work for a skilled machinist

[PackardV8]

As long as the 'heat spots' don't run into cracks then yes

You don't need a 'dedicated flywheel grinder', any head re-surfacer and rotary table will get the job done, in the right hands ...... I'm not sure I'd 'rough' the face off first in a lathe, personally

Pressure plates are routinely resurfaced in 'reconditioned' clutches, but are disassembled at the strap rivets, the 'clamp' plate is then ground separately and the whole reassembled back into a complete unit ...... whatever is taken of the face is 'shimmed' back into the straps ...... just don't take too much off

Whether all this can be done economically, on a one off basis, is another matter ...... it's half a days work for a skilled machinist

Not really; we'll have to agree to disagree on this one. Flywheel grinders exist for a reason.

I've seen attempts to use head surfacers, Blanchard grind, lathe cut, surface grind, but the result was never as good as a flywheel grinder.

[BCjohnny]

Not really; we'll have to agree to disagree on this one

Yes, I guess so ......

...... in the right hands ......

As someone who's 'corrected' several jobs done previously on a 'dedicated flywheel grinder', I'm happy with the advice

[AC sports]

So would it be better taking a skim cut with a carbide bit on a head resurfacing machine than on a lathe? The local guy has a new cnc rottler head skimmer. The step I can cut on the lathe. What about grain direction if done on a head skimmer though?

[PackardV8]

As someone who's 'corrected' several jobs done previously on a 'dedicated flywheel grinder', I'm happy with the advice

Just asking, because it has me wondering, how did they manage to screw it up? A flywheel grinder is probably the most simple-to-use, idiot-proof machine in the shop.

[modok]

Anything can be screwed up with enough foolishness.

A lightweight STEEL flywheel is not very rigid and prone to chatter especially if there are hard spots.
Probably need to mount it to a big faceplate and use a number of jack screws to support it around the perimeter. Check the runout on the engine, and make sure that it matches as setup on the lathe. If it has a lot of runout it will need to be rebalanced.
Most brake lathes and general purpose lathes can have grinding attachments.....you don't have that?

I don't like grinding on a regular lathe, makes a terrible mess, but of course you CAN.

You might be better off to send it flat if you have any large sanding machine of any kind. Big disk or belt sander?
Already has a bearing in the middle and is round, so it has the makings of a proper lapping arrangement, just need to make an overarm to hold it.

[BCjohnny]

Just asking, because it has me wondering, how did they manage to screw it up? A flywheel grinder is probably the most simple-to-use, idiot-proof machine in the shop

It's obviously a different discussion, but most of these 'single use' type machines are normally marketed along with 'no skilled labour needed' as a chief selling point

And, eventually, that's the biggest problem

[BCjohnny]

AC sports

Chances are if you try to skim it in a lathe you'll have every stray mutt within a mile or more radius scratching at the workshop door

With a large enough rotary table the machinist can at least selectively 'pack it out' with suitable material to help negate the likely banshee wail from employing the above .... it's not the milling but the set up that eats time

This whole discussion started because of lack of a 'dedicated machine' ..... which would be quicker and preferable ..... but in the real world it's not the only option

I only mentioned 'head re-surfacer' as it's the most likely machine most people would reference, but a good vertical mill would be equally usable, etc etc

And CBN would be better than Carbide, if you can't 'grind' it, but probably getting too picky now

[modok]

A flywheel grinder is just a SMALL rotary surface grinder.
often with grinders the bigger it is..... the better it works,
so, big ones are more common for general purpose use.
But you CAN use a flywheel grinder for a lot more than flywheels. Put a magnetic table on it and make shims and whatnot.

[BillK]

As someone who's 'corrected' several jobs done previously on a 'dedicated flywheel grinder', I'm happy with the advice

Just asking, because it has me wondering, how did they manage to screw it up? A flywheel grinder is probably the most simple-to-use, idiot-proof machine in the shop.

Just thinking the same thing.

[BCjohnny]

Well, you're basically going to get two kinds of prevailing opinion on this

Those that have invested financially in the convenience of a dedicated machine, need to ameliorate the investment, so will say it's the only way to do the job

And those that haven't, requiring more set up time spent on each job as presented ...... so the end cost will essentially be similar

At the end of the day the quality will mostly be down to the diligence of the 'machinist', on all but the very newest of equipment ...... but at least in the latter case you have a constant appraisal of tolerance occurring

[BillK]

AC,
I cant see what it would hurt to try. The bigger the lathe the better and you need to figure a way to really clamp the flywheel in good or it will want to "ring" and give a terrible finish. The heat spots are going to give you the most trouble. I tried doing one once a long time ago when my flywheel grinder was broken but I gave up and waited a day till I could fix the grinder.

If you can actually get it to cut nicely I don't know that you would absolutely need to do any more as far as finish. Virtually every new flywheel I have seen appears to have been done on a lathe of some type.

The only way I can see doing it on a "head resurfacing" machine is with a rotary table and a small grinding wheel. That way you can grind the step back also. Berco made an attachment like that for their grinders years ago.

As far as the pressure plate goes I cant imagine doing it without disassembling it first so all you have is the friction plate to mount in whatever machine you are going to use.

If you don't mind my asking, where are you located that there is no shop around that can grind it ? Is it worth paying UPS to get it to somebody to grind it ?

[SupStk]

I've been through all the drills cutting flywheels and pressure plates on lathes and head broaches. While it can be done with enough time and tooling its infinitely better and faster using a flywheel grinder.
A person can tell the machines that's been used for grinding, they are the ones with clapped out ways.