Today's Sherline Lathe Challenges

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06-21-2009, 01:16 PM
roland88

Today's Sherline Lathe Challenges

Sherline Lathe:

Chucked up an 1-1/2" x 5" alu round in a 3 jaw chuck. Need to part off 1/2", live centre in previously drilled centre hole - because I know it's going to need some tail support.

Parting off is a horrible job and yes it jammed 3 times locking up the motor and pulling my stock half out of the chuck. It's OK until you get about 1/2" into the stock.

My guess is that the cut off tool must be flexing as it gets further into the stock. I get good chips until it binds. I have low speed and cutting fluid.

Not sure what I am doing wrong, maybe the Sherline is not built for this size stock.

Got the 1/2" disc off in the end.

Rechuck the smaller disc put a centre drill in the large chuck on the tail stock. The centre drill wobbles as it comes into contact with the end of the stock - is this normal? Should I be knocking the taper harder into the tail stock before I start drilling?

After the centre hole I chuck up a 5mm drill bit in the chuck on the tail stock and succesfully drill a hole through my 1/2" disc. Now because I want a larger hole I go up to an 8mm drill bit, well this is a drama, the bit keeps jamming and ends up spinning the chuck in the tail stock. 4 or 5 attempts at get past the smaller taper made by the smaller drill until I am drilling again. Up to a 12mm drill, and yes the same problem.

Are the flutes on my drills too sharp? I have noticed that in a hand drill in thin metal stock the drill just wants to turn into a screw and near pulls the drill out of my hand.

The 3 jaw chuck certainly mars up the surface of the stock - is this normal for aluminium? I tend to tighten the chuck enough to make it difficult to unchuck, bring in a fear of skinned knuckles when using the tommy bars to release the stock.

If I don't tighten the stock up so tight it just moves on me.

I find that getting a clean finish is difficult since the handwheels don't seem to be so freely moving, they seem to bind ever so slightly part way through a full rotation - both cross slide and feed seem to be not so smooth.

Anyway, after reading this maybe you guys have some comments. Feel free to point out my short comings :)
06-23-2009, 06:12 AM
MechanoMan

The Sherline can handle this.
It is not right for the center drill to wobble. Are you sure you started it at the basic center of rotation?

I have had trouble where the tailstock isn't pointing dead center into the axis of rotation. You can kinda adjust the brass shim on the tailstock-to-rail mount.

Quote:

Chucked up an 1-1/2" x 5" alu round in a 3 jaw chuck. Need to part off 1/2", live centre in previously drilled centre hole - because I know it's going to need some tail support.

You cannot use the tailstock with the parting tool, at least you're not *supposed* to be able to do so by the book. Because the compression causes it to collapse onto the parting tool when the last bit of material gives way. If you keep tailstock pressure minimal this may not be a problem, but the disc needs to be able to fall away.

A SteadyRest will stabilize the 5" stock for end cutting.

Quote:

the bit keeps jamming and ends up spinning the chuck in the tail stock.

Make sure the tailstock is not fully retracted to the ejection position, pull back the jaws of the 3-jaw chuck so they fall below the surface, LOOSEN THE TAILSTOCK OFF THE RAIL, hold the tailstock wheel in your right hand for linear resistance and turning resistance, and *gently* tap the chuck with a hammer. It will stay.

Quote:

The centre drill wobbles as it comes into contact with the end of the stock - is this normal? Should I be knocking the taper harder into the tail stock before I start drilling?

It's not normal. Either the center drill hole was not completely on center (may have moved accidentally), or your tailstock chuck is not pointing towards center. Or your center drill sucks.

Quote:

Are the flutes on my drills too sharp? I have noticed that in a hand drill in thin metal stock the drill just wants to turn into a screw and near pulls the drill out of my hand.

No such thing as too sharp.
The coiling "swarf" is desirable. If you are getting chips, you may be turning too fast on the motor or not feeding it fast enough to keep the coil continuous. If it's not coil-swarfing, vibration may occur.

I'm not sure why you're enlarging a previous hole by choice. The bit is more stable on one big drilling operation.
06-23-2009, 06:30 AM
ZipSnipe

Quote:

Originally Posted by MechanoMan

The Sherline can handle this.
It is not right for the center drill to wobble. Are you sure you started it at the basic center of rotation?

I have had trouble where the tailstock isn't pointing dead center into the axis of rotation. You can kinda adjust the brass shim on the tailstock-to-rail mount.

You cannot use the tailstock with the parting tool, at least you're not *supposed* to be able to do so by the book. Because the compression causes it to collapse onto the parting tool when the last bit of material gives way. If you keep tailstock pressure minimal this may not be a problem, but the disc needs to be able to fall away.

A SteadyRest will stabilize the 5" stock for end cutting.

Make sure the tailstock is not fully retracted to the ejection position, pull back the jaws of the 3-jaw chuck so they fall below the surface, LOOSEN THE TAILSTOCK OFF THE RAIL, hold the tailstock wheel in your right hand for linear resistance and turning resistance, and *gently* tap the chuck with a hammer. It will stay.

It's not normal. Either the center drill hole was not completely on center (may have moved accidentally), or your tailstock chuck is not pointing towards center. Or your center drill sucks.

No such thing as too sharp.
The coiling "swarf" is desirable. If you are getting chips, you may be turning too fast on the motor or not feeding it fast enough to keep the coil continuous. If it's not coil-swarfing, vibration may occur.

I'm not sure why you're enlarging a previous hole by choice. The bit is more stable on one big drilling operation.

Exactly what I was going to say, you should have band sawed that piece first then face it off on the lathe, then centered drilled!!!!
06-23-2009, 10:04 AM
roland88

Quote:

Originally Posted by MechanoMan

The Sherline can handle this.
It is not right for the center drill to wobble. Are you sure you started it at the basic center of rotation?

I have had trouble where the tailstock isn't pointing dead center into the axis of rotation. You can kinda adjust the brass shim on the tailstock-to-rail mount.

You cannot use the tailstock with the parting tool, at least you're not *supposed* to be able to do so by the book. Because the compression causes it to collapse onto the parting tool when the last bit of material gives way. If you keep tailstock pressure minimal this may not be a problem, but the disc needs to be able to fall away.

A SteadyRest will stabilize the 5" stock for end cutting.

Make sure the tailstock is not fully retracted to the ejection position, pull back the jaws of the 3-jaw chuck so they fall below the surface, LOOSEN THE TAILSTOCK OFF THE RAIL, hold the tailstock wheel in your right hand for linear resistance and turning resistance, and *gently* tap the chuck with a hammer. It will stay.

It's not normal. Either the center drill hole was not completely on center (may have moved accidentally), or your tailstock chuck is not pointing towards center. Or your center drill sucks.

No such thing as too sharp.
The coiling "swarf" is desirable. If you are getting chips, you may be turning too fast on the motor or not feeding it fast enough to keep the coil continuous. If it's not coil-swarfing, vibration may occur.

I'm not sure why you're enlarging a previous hole by choice. The bit is more stable on one big drilling operation.

Thanks for the reply...

I have never checked the tailstock to headstock centre, the Sherline is still quite new and I would have assumed it to be correct. Will check by chucking up a dead centre and have the live centre in the tail stock.

Yes, use the Steady Rest - that makes more sense than using a live centre on the tail stock. I do understand that it's not safe to run the parting tool too far when using a tail centre.

"Center drill sucks" - shouldn't be, the chuck and center drill are both from Sherline. I assume that the center drill is OK to mount into the Jacobs chuck ??

Re: drilling a large hole. You mention to just use the final drill size rather than starting with a smaller drill. mmmm, OK - so need to ramp up the sizes.

Sorry to say that I don't have a bandsaw, so I am using the lathe to dimension stock.