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View Full Version : really, really basic technique???



rmatel
10-07-2003, 12:44 PM
Hi,
Being a newbie (2yrs) I need some "larnin' up" about facing(?) techniques. I am building an engine and am working on the flywheels-- from solid stock-- thining out what will be the spokes/webbing.
What are some techniques for cutting into the face and shouldering against the hub on one side and the ID of the rim on the other? It is so simple to do with "normal" turning but I'm having a heck of a time with this one.
Bob

Dr. Rob
10-07-2003, 01:02 PM
How much elbow room do you have in there? I mean, what are the approximate diameters involved? And how deep?

Cass
10-07-2003, 01:46 PM
I haven't tried making flywheels but I think I would want to mount the disk on the shaft it is going to run on and then put that in the lathe chuck so that the flywheel runs true to the shaft when you are done. If the shaft is large enough you can hold it between centers and cut out the material from each side without removing the assembly or you can flip it around and chuck the other end of the shaft.

darryl
10-07-2003, 07:23 PM
Bob, it seems to me that what you need is a left hand, and a right hand cutter, one for cutting towards the rim, the other for cutting towards the hub. When the setup is ready, clamp the carriage screw, and feed in with the compound, traverse the disc with the crosslide. You may have to change from cutter to cutter more than once, to be able to remove enough material to get the job done. However you mount the disc, for initial turning to diameter, leave that setup in place while you face and undercut one side, preferably machining the bore at this time, as well. Then make an arbor to fit the bore, and without removing that from the lathe, mount the disc to it, for facing and undercutting the opposite side. That way, you'll have a true running flywheel. If you have the bore done already, then make the arbor to fit the disc on, machine the diameter, face, and undercut, turn over and machine other side. Don't unclamp the arbor until all operations are done to the disc. You may have to tap and thread the arbor to give you a way to hold the disc onto it, without slipping. Or maybe a piece of threaded rod with a nut on it, to pass throgh the arbor for a holding method. Whatever you do, leave the final diameter of the arbor for the last machining operation on it, so it will be true when you use it. By the way, if you have any option to make a tapered spot for the flywheel to tighten up on, consider doing that, as it will give you a play-free fit for the flywheel. Makes machining both sides a little tougher, though it's just a matter of method.

rmatel
10-08-2003, 09:23 AM
The hub is 3/4" dia., the ID of the rim is 3 3/4" dia. The shaft is 3/8". I guessed at darryl's method of switching between left and right hand cutters but since that is such a PITA, I was looking for suggestions of a better system.
BTW, the plan suggests machining one side then use a four jaw in the ID of the rim to hold the piece for machining the other side and the axle hole.

Dr. Rob
10-08-2003, 09:50 AM
Well then, you have plenty of room to move around in.

Maybe a rhomboid IC tool, with a bit of a radius on the nose would help keep you from changing tools all the time. You just swing the toolpost around a little bit. You can even take deeper cuts so you get something done.

Evan
10-08-2003, 01:38 PM
I agree with the instruction to hold it with the four jaw. A 3/8 shaft isn't stiff enough to hold it for machining. I would do it in this order assuming your four jaw has insignificant runout on the jaw faces.

1: Invert 4 jaw jaws to hold work on the OD.

2: Put rough stock in 4 jaw, gripping on outside of work. Center the stock as best as the OD allows.

3: Use a tailstock bull nose center or a dead center against a block of wood to provide considerable pressure on the stock when tightening the jaws. Back off center.

4: Face off the work.

5: Reverse work

6: Use tailstock center to apply pressure again while centering approx, tighten jaws, back off center, face it off.

7: Using a small radius straight nose tool cut to the required web depth from rim to hub, leaving some extra material at the inside of the rim and the outside of the hub. You may want to change the angle of the tool at the rim and hub.

8: Switch to a small radius right hand tool cut the inside of the rim (tool point towards you) to dimension and to meet the web.

9: Switch to left hand tool and do the same for the hub.

10 I will assume that a good portion of the OD extends past the jaws. Take a cut on the OD to provide a surface that is concentric to the hub.

11: Invert the jaws and reverse the work, gripping it inside the rim. Indicate to the OD you machined, using pressure from the tailstock, tighten the jaws.

12 Center drill the bore and apply a live center from tailstock.

13: Machine the web, rim and hub as before.

14: Machine the OD.

15: If the work is securly held (this depends on the depth of the rim undercut) then remove center and bore the hub. Done.

16: If the depth of the undercut of the rim is not enough to hold it securely with no center for the boring operation then:

17 Remove work, invert jaws, replace work holding on OD and with pressure from tailstock, indicate to the OD or hub, bore the hub. Done.



[This message has been edited by Evan (edited 10-08-2003).]