[manchildau65]

Alright so as the title says, I need to clean up the face of my manual flywheel (years of sitting) and wasn't sure of the surface finish I needed. I mean, I work in a machine shop and can go as minimal as a turn finish or as fine as a mirror finish... Help me out, I'm not sure what type of finish I should be gearing towards!

 

[BogiesAnnex1]

Alright so as the title says, I need to clean up the face of my manual flywheel (years of sitting) and wasn't sure of the surface finish I needed. I mean, I work in a machine shop and can go as minimal as a turn finish or as fine as a mirror finish... Help me out, I'm not sure what type of finish I should be gearing towards!

A turn finish is just right, some tooth is needed for the friction plate to bite, a mirror finish is too slick. A Blanchard grinder turned finish is better as the roughness doesn't follow the roation.



Bogie

 

[FmrStrtracer]

Check with the clutch manufacturer, different clutch materials like different finishes.

 

[manchildau65]

So I'm going to blast it first to see how well it cleans up (Wheelobrator)... but I'm guessing I'll have to take a quick skim off with one of the lathes.

 

[ericnova72]

Centerforce reccommended that we sand blast or bead blast the surface after turning it to take some of the harshness away from what the lathe leaves. Said the clutch would break-in quicker and more evenly. Sounded like much the same as honing after boring a block.

 

[manchildau65]

Interesting but it makes sense, the wheelabrator media is more of a cleaning media but will effect the surface finish slightly... I think I'm going to check the metallurgy of the flywheel as well, you think the flywheel is low... high carbon steel? what kind of hardness you guessing? I'm thinking it will be moderate to high carbon with a surface hardness RC of around 30.

I'll take some more readings tomorrow

 

[PatM]

I recommend you take the readings on the backside (crankshaft facing side) so that the heat effects of many years don't influence the readings.

 

[ericnova72]

If it is a factory flywheel, it's just gonna be plain old iron or nodular iron.

 

[manchildau65]

Good feedback, I was planning on taking a reading on both the welded gear set as well as the flywheel... might take a 'nupe' reading to see if there was a designed case depth. I'm afraid if I skim the face, I'll cut the case depth too far.

 

[cboy]

Interesting discussion. What would be the pros and cons of a DIYer touching up the surface with just a longboard and some 1000 or 2000 grit paper OR running the plate through the blasting cabinet without first turning it on a lathe? The surface looks pretty good to the naked eye but I thought since I have everything torn apart at the moment that I might freshen things up if possible...but not go to the expense of totally resurfacing.

 

[manchildau65]

Honestly, the best method would probably be to contact the clutch manufacturer (as stated above) to find out what the optimal surface finish would be for break-in purposes. If the flywheel is as soft as I think it is, then the initial surface finish will only be effective for break-in. So the larger benefit will probably be for clutch break-in/longevity.

 

[sbchevfreak]

I personally don't reccommend a lathe cut, as in my experiance it will not cut dowm the high, hard spots created by over heat. I have had many back from the machine shop that looked ok, but when you ran your hand over them you could feel where every hot spot was. A dedicated flywheel grinding machine is the best, IMHO.

 

[Frisco]

A Blanchard grinder turned finish is better as the roughness doesn't follow the rotation.

Bogie

I agree 100%. It has been my experience that this will yield the best results and would be my first choice.

 

[4 Jaw Chuck]

Grinding works best since this machining method is relatively unaffected by hardness of the material. You can turn on a lathe if you get under the hard spots, they should be removed anyway as they lead to cracks.

Finish is relatively unimportant as it will soon be polished smooth by the clutch plate once it is broken in.

Everything else is cosmetic and not worth the money people pay extra for.

 

[manchildau65]

So a couple things, first off the material (like someone stated above) is simply grey iron. So when I was talking about heat treatments, case depth, etc. there really is nothing factory to speak of. I simply mounted the flywheel to a lathe mounting plate and turned ~.010" off of it. This flywheel had never really been run (broke the SM465 main shaft within 4 hours of last engine rebuild) so I wasn't worried about 'hot spots'. I'm not 100% sure what the surface finish ended up at, but I'm guessing it to be around RA 32-40 which should give a good break in for the new clutch (appears similar to the pressure plate).

Thanks again for everyone's input! :welcome: