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Aky321
09-26-2011, 06:34 PM
I am in the process of trying to lighten a flywheel but my HSS tool bits wont make a cut in it whatsoever. Would a carbide tool cut it? Open to suggestions! Thanks

Anvils
09-26-2011, 06:42 PM
Flywheels build up a surface like glass after some use and misuse. Back in my racing days ( a long time ago ) we never lathe turned a flywheel something about building stress risers in the lathe cuts. They were always ground.

Norm

loose nut
09-26-2011, 06:43 PM
possibly, probably actually but the finish might not be to good. what material is it IE: cast iron etc.

Bob Ford
09-26-2011, 06:56 PM
A 10 inch wheel turning at 30 RPMs gives you 78 fpm on the tool. This is high end for turning with HSS. Much higher RPM and all you do is burn the HSS bit.

Bob

KEJR
09-26-2011, 07:36 PM
I know when I tried cutting my 6" back plate it was eating up HSS bits at anything but the slowest speeds in back gear. I vented on here and got soem good ideas. It became clear that attention to the cutting speed was important. Cast Iron in general is pretty hard stuff, and carbide has a higher SFM speed, so carbide would be warranted if you have it. Thats what I ended up doing.

I'm not sure I would worry about stress risers if you can get a good finish. Some application of fine sandpaper and oil over a file would probably get rid of most of the tool marks to approximate grinding.

KEJR

PixMan
09-26-2011, 07:48 PM
Yup...gotta know what the material *and* the cutting speed is before a good diagnosis can be done.

Another thing that can help is if the OP and the first responder would please add a location to your profiles. Lord knows, you could be around the corner from me and I'd run over with tooling to solve the problem.

Aky321
09-27-2011, 06:15 AM
Thanks for the replies so far guys. I think the material is iron/steel, dont think it is cast though?

Yeah think ive been running too fast seem to be burning my HSS bits, dont want to knacker them!

Im in Scotland so dont think youll be around the corner ;)

willmac
09-27-2011, 07:00 AM
The problem is almost certainly too high a speed for the diameter of the work and your HSS tool. However, the cast iron or steel may also be very hard, so even if you used a slower speed you might still run into problems. Can you check whether a file will bite on the surface that you are trying to machine? Be careful not to mark any area that is important. If a good file just slides off the surface then you will struggle unless you get the correct grade of carbide and possibly even then. Just as Anvils describes - a hard glaze may be really difficult to turn.

jugs
09-27-2011, 07:49 AM
Thanks for the replies so far guys. I think the material is iron/steel, dont think it is cast though?

Yeah think ive been running too fast seem to be burning my HSS bits, dont want to knacker them!

Im in Scotland so dont think youll be around the corner ;)

I'm round the corner 'ish :D

Even with carbide @ 10" with a hard glaze rpm will be low 20s, & you'll need a heavy cut to get under the glaze -loads of power - will your machine be rigid enough????????

grinding may be your best way,....... if you've got a light machine - its the only way. You'll need a toolpost grinder, a good shop vac & cover EVERYTHING with oil soaked newspaper.

What lathe have you got ????

hemmjo
09-27-2011, 07:55 AM
The other guys have handled the machining questions. My concern is why do you want to lighten the flywheel?

Lots of times flywheels are lightened for racing purposes often with disastrous effects. I have seen an improperly reworked flywheel explode while in use. The result was devastating, almost cut the car in half with severe damage to the drivers legs. Be sure you have it mounted with no run out. It will most likely need to be rebalanced after cutting it, unless it is for a VERY low speed.

Please read this article;
http://www.pumaracing.co.uk/FLYWHEEL.htm

Pay special attention to the part about 1/2 way down that starts out "If you are going to get your standard cast iron road car flywheel lightened then be sure to take it to a proper vehicle engineer and not just your local machine shop."

I just could not let this go and risk someone being injured without sending a word of caution. The memory gives me shivers....

Be Safe,

John

Ian B
09-27-2011, 08:01 AM
Would this happen to be a flywheel off a vintage scooter?

Ian

Jaakko Fagerlund
09-27-2011, 11:14 AM
Even with carbide @ 10" with a hard glaze rpm will be low 20s, & you'll need a heavy cut to get under the glaze -loads of power - will your machine be rigid enough????????
Haven't yet seen a carbide that likes 20 m/min cutting speed (10" @ 20 RPM), I would more likely start from the 150 RPM and adjust as necessary.

If carbide won't bite good enough, there is always the option of grinding the surface as suggested or using a ceramic insert. They are very fragile though, can't take interrupted cuts quite much at all and they have to be used above certain surface speed or they'll shatter. And DOC would be like 0.15-0.3 mm with a small feed.

Aky321
09-27-2011, 11:55 AM
Hi guys,

in relation to the flywheel its off a vintage Lambretta, the original flywheels are too heavy at 2.6 kg for anything other than standard barrels, 2kg is the optimum weight. It is common place to have them lightened.

In relation to the turning, I gave it a try using the back gears to slow it down and my HSS tool were cutting it.... to begin with, now my wee lathe seems to want to slip the drive belt and stop the workpiece even with light pressure from the tool! The tool is sharp, speed is low and was cutting, now this bloody belt is slipping!!!! Help!!

Alistair Hosie
09-27-2011, 12:19 PM
I am in Scotland Dunoon and oil mac is not far from you either in Motherwell .try the file test always on metals if the file doesn't make a mark then your in trouble. Alistair

rmwise
09-27-2011, 12:57 PM
There are a number of issues to deal with when turning flywheels. If it's a used one there are likley to be hard spots. Blue/black marks on the friction surface means hard spots. At minimum you will need positive rake carbide. Some of my customers attempt to turn flywheels on brake lathes and almost always end up with a crappy finish (and they don't care :( ) or they send them out to be ground. Hard spots also means that you will need more than just a clean up cut, you have to get under the hard spots to get a good finish.

If it's a stepped flywheel then you have to accurately measure the depth of cut on the friction surface and remove the same amount from the step that the pressure plate mounts to or you lose clamping force.

You will likely chew up a set of inserts to do one unless you are really lucky.

Like others mentioned, setup with minimal axial runout is wanted, a little radial runout will not hurt it.

Good luck.

Aky321
09-27-2011, 06:04 PM
Its not that kinda flywheel, its from a 2 stroke, it has nothing bolted to it clutch wise, its purely an inertia wheel that bolts onto the end of the crank with magnets to generate electricity over its stator plate.

I will try the file test, i take it means holding a flat file against the surface to see if it grinds down any?

In relation to the belt, is there any way to stop it slipping when cutting? Im not even taking large cuts?

Toolguy
09-27-2011, 07:14 PM
How about belt dressing?

Black_Moons
09-27-2011, 07:18 PM
the belt may of loosened or motor shifted.. But more likey, your tool went dull and needs resharpening.

bobw53
09-27-2011, 08:04 PM
or using a ceramic insert. They are very fragile though, can't take interrupted cuts quite much at all and they have to be used above certain surface speed or they'll shatter. And DOC would be like 0.15-0.3 mm with a small feed.

Jaakko, ceramics can take an interrupted cut, they are just "different", actually they are pretty much the pure opposite of any cutting tool you've ever used.

You need to think about how they work, they essentially create a ton of heat, and plasticize the material and then wipe it away. Too fast, you get liquid metal and bad things happen, too slow, you get solid metal and bad things happen. Its a pretty crazy balancing act, especially when you are in cut for a long time.

On interrupted cuts, you aren't in the cut as much, so you aren't generating as much heat, you simply need to go faster in an interrupted cut. Total opposite of any other cutting tool on the face of the planet.

Here is a good article from back when MMS actually had good articles, helped me out a lot.

http://www.mmsonline.com/articles/successful-application-of-ceramic-inserts

Neat tools, its like strapping a lego into your cutter body. Except it works.

chipmaker4130
09-27-2011, 11:05 PM
I will try the file test, i take it means holding a flat file against the surface to see if it grinds down any?

The file test is a gentle stroke by hand across a representative surface. If you spin the part on the lathe and apply the file, you will trash the file if the part is hard.

willmac
09-28-2011, 05:40 AM
Aky -

No - don't do the file test with the flywheel spinning. As has been said already, you could ruin your file when all you need is to feel if the file will bite. It could also be dangerous, given what I think the flywheel may look like.

I'm trying to get a clearer picture in my mind of what you are trying to machine. I assume you mean the type of flywheel that has an integral fan on the outside face - perhaps aluminum, then a heavier steel center that fits on a taper to to the crankshaft and finally a ring of permanent magnets around the outside of the steel core that energise the generating coils that are fastened to the crankcase. Is this the right picture?

If so I'm not certain what part you are trying to machine. If you are trying to turn the magnet area then I think you are will have great difficulty regardless of feeds, speeds and tooling. These are likely to be really hard and brittle. Grinding would be the best or only way of attacking these and even then you would need to be very careful not to lose the magnetism. If you increase the gap to the coils then the charging efficiency will drop off fast.

Can you clarify and also describe the general setup you are using to hold the flywheel on your lathe?

jugs
09-28-2011, 06:15 AM
Aky -

No - don't do the file test with the flywheel spinning. As has been said already, you could ruin your file when all you need is to feel if the file will bite. It could also be dangerous, given what I think the flywheel may look like.

I'm trying to get a clearer picture in my mind of what you are trying to machine. I assume you mean the type of flywheel that has an integral fan on the outside face - perhaps aluminum, then a heavier steel center that fits on a taper to to the crankshaft and finally a ring of permanent magnets around the outside of the steel core that energise the generating coils that are fastened to the crankcase. Is this the right picture?

If so I'm not certain what part you are trying to machine. If you are trying to turn the magnet area then I think you are will have great difficulty regardless of feeds, speeds and tooling. These are likely to be really hard and brittle. Grinding would be the best or only way of attacking these and even then you would need to be very careful not to lose the magnetism. If you increase the gap to the coils then the charging efficiency will drop off fast.

Can you clarify and also describe the general setup you are using to hold the flywheel on your lathe?

& what lathe (make & size), + what size is flywheel :confused:
we need more info. :confused:

Ian B
09-28-2011, 07:29 AM
Is it something like this?

http://www.ebay.co.uk/itm/lambretta-sx200-flywheel-and-stator-/150667930396?pt=UK_Motorcycle_Parts&hash=item2314822b1c

If so, which area are you trying to machine?

Ian

willmac
09-28-2011, 08:37 AM
Ian -

Precisely my point and a good photo of what I think the OP is trying to machine.

noah katz
09-28-2011, 04:21 PM
Back in my racing days ( a long time ago ) we never lathe turned a flywheel something about building stress risers in the lathe cuts.

I don't see why stress risers matter, as I don't believe flywheels are subject to bending loads.

willmac
09-29-2011, 06:36 AM
I don't see why stress risers matter, as I don't believe flywheels are subject to bending loads.

I would agree that is true for a strictly cylindrical disk type flywheel, but the the flywheel under consideration is definitely not that. We need a response from the OP, but I would guess that a section through the flywheel would be roughly 'C' shaped with most of the mass near the periphery, so there certainly would be bending stresses. Whether these matter and whether he is machining in that area is not clear.

Aky321
10-04-2011, 06:40 PM
Sorry not been on for a few days, thanks for replies so far.

Yes the flywheel is as above, the part i am trying to machine, which has beend one before, is the backof where the magnet is. I will try and post a before and after pic of one done before.

If only i couldget the drive belt to stop slipping at low speeds id be there. It is an old lathe, cant remember the make of my head!

jugs
10-05-2011, 03:08 AM
cant remember the make of my head!

Worzel gummidge did a good range of heads, http://www.youtube.com/watch?v=eOTNAe3j7Bs&feature=related is it one of them :confused: :)

http://t1.gstatic.com/images?q=tbn:ANd9GcREtmIEXnkux9ctz6h0cQhIGdlo4WHY4 SdZcBFBV9rfHE7QClkY

http://t3.gstatic.com/images?q=tbn:ANd9GcRehiMV3YtoD3e6wNcGR0Q6WfybRe40I FVp1Mi_iUdOovlOJv4o


If only i couldget the drive belt to stop slipping at low speeds id be there. It is an old lathe,

post a pic of the lathe we might be able to see the problem