Morse taper stuck :(

[Simpo Two]

Myford ML8, 2-prong drive stuck in headstock. Normally I knock it out with a 1/4" steel rod and hammer from the outboard side, but this time despite even heavy clouts with a lump hammer, it's not budging and the rod is just bending. WD40 hasn't made any difference. Can't get too violent with it or the bearings will be damaged.

Hoping for some ideas please!

[Simpo Two]

Big Al. said:

Can you get a solid heavy rod up the headstock spout and knock it out?

You mean from the outboard side? (the driveshaft is hollow). That's what I'm doing. All I can find is the 1/4" rod which isn't man enough for the job. I'm worried that if I use too much force the bearings will be damaged.

[Simpo Two]

Thanks guys.

Mr Pointy said:

Would heating it up help? Maybe hot air gun rather than a blowtorch.

Thought of a blowtorch a la Edd China but it's too close the bearing which is full of grease

motco said:

This is the usual tool. Have you got/tried one?]

Too short and fat to fit down the driveshaft.

I tried a masonry drill in my hammer drill thinking the vibration might drive it out. Nope.

Various other candidates were either too short or too fat to fit, but eventually I found some studding. Clearly brute force was going to be needed, so to try to take the load off the bearings I found some tube that fitted over the prong drive and against the headstock, then a chunk of wood to brace it against the tailstock. Finally after a few wallops with a lump hammer it came out!

I think the problem may be that the shank of the prong drive has a fine ridging on it, as opposed to smooth. You can just feel it when you run your fingernail across it. Is there anything I could use to help it release next time? Talc perhaps?

[Simpo Two]

Thanks Motco, but there's no facility to use that on an ML8. Bashing it out from behind is the only way.

I've tried grinding out the ridges but no improvement. Can anyone recommend a good brand of prong drive?

[Simpo Two]

motco said:

Okay, Simpo Two. Sorry, it's not a conventional style with which I'm familiar.

No problem, I'm not sure that system existed in about 1955 when the lathe was designed!

[Simpo Two]

Maybe the difference is that the ML8 is a woodworking lathe... Does the ML7 have this slot?

[Simpo Two]

dickymint said:

Simpo Two - shouldn't the taper be held in place with the draw bar? In which case you unscrew it it a few threads and hid it?

Nope, the idea of a Morse taper is that it's a friction fit, just a tapering cone of metal. Push it in, tap it out. I suppose I could put the prong drive in a 3-jaw chuck next time... but it shouldn't need it.

[Simpo Two]

No thread at all. None of my Morse fittings have a thread, though some have a small flat section at the back for some reason..

[Simpo Two]

minivanman said:

The ML8 is a plain tube spindle with a thread at each end for inboard and outboard turning. There is (or should be) a plunger that stops rotation for changing faceplates. I wouldn't put the torque of stilsons through it though. No facility for a morse drift to remove it. I used to have a bit of 1/2" steel rod for knocking the drive out of mine. Then I got a supernova chuck and a chuck steb centre. Makes life so easy - the chuck never has to come off the lathe. I think I still have an ML8 inboard thread adapter on the shelf if you wanted it?

Thread adapter - 1" 12tpi to what? I have a Robert Sorby chuck (4 jaw) which seemed like a good idea but in practice its usefulness is limited. I was going to use a normal 3-jaw chuck as a workaround - it does reduce bed length of course.

[Simpo Two]

How do you find a stebcentre compares with a standard 2-prong drive?

I tried a Sorby 4-prong drive but once the chisel snagged and it bent three of them and snapped the fourth! Don't make 'em like they used to...

[Simpo Two]

minivanman said:

Steb drive is fantastic. If you get a catch the wood stops still and the drive keeps spinning. I have found in hard wood like yew it is best to get the piece centred on the spring point, then gently (and very carefully!) advance the tailstock while holding the workpiece still to create a bit of a groove for the teeth to run in. If you don't and have a catch it can skid off centre. I do have variable speed though so its quite easy for me to run at low speed to do this.

Hang on, if the teeth run in a groove how do they turn the wood round? The last thing you want is for the teeth to carve out a ring, no?

My current project (an enormous chunk of laminated plywood 13" long) proved just to big to turn inboard so I had to use the outboard side and faceplate - cue the whole lathe shaking back and forth until I got the worst off! It's now safely inboard (just) with tailstock so it's tamed now...