stuck drive centre

[Woodmonkey]

So after turning my Easter egg today I can't seem to get the drive centre out. Never had any problem on my old lathe, this is the first time I've used the drive centre on my new lathe (nova 1624) and it just won't budge. Been clouting the knock out bar with a hammer, I'm worried if I hit it too hard I will damage the bearings, am I missing something?

 

[Random Orbital Bob]

make absolutely certain the knockout bar isn't actually hitting a shoulder inside the spindle. There's one in the tailstock of my CL4 that you have to wiggle past before it contacts the back of any centre in the morse taper.

You could try a dash of penetrating oil overnight. Or if feasible, gently heating the casing around the taper. Worse case, wrap some thick cord around the back of the prongs so you can pull it out from the front. Tie the other end of the chord to a lever and use mechanical advantage to lever it out in a direct line from the front.

 

[woodfarmer]

If it was oily it may have formed an hydraulic lock on the taper. For this a bit of warmth or continuous pressure will probably work.

 

[Nick Arnull]

DO NOT USE HEAT, This will damage the bearings for sure
The only advice I can offer is to hit it with a bigger hammer make sure you are on the end of the taper and not inside it. Don't just taps it hit it with a sharp knock, this should do the trick.
Some drive centres are hollow but the bar should be large enough in diameter to do its job .
Nick Arnull. Professional Turner, Author Tutor.

 

[Woodmonkey]

Maybe the bar diameter is the problem- I'm using one from an old lathe with a smaller spindle diameter since I didn't get one with this lathe....

 

[Tazmaniandevil]

I had a drive centre stick once. I used a ball joint splitter which I managed to wiggle behind the centre and use as a lever to loosen it.

 

[NickWelford]

too late this time, but I always use a thread protector that I unscrew to remove the centre.

 

[Woodmonkey]

Aaah wondered what that bit was for! Got it out in the end using a Thicker piece of bar I found.

 

[chipmunk]

You could try putting the spindle lock on and using a pair of water-pump pliers round the front of the drive centre.
This often works for me when I can't find the knock-out bar.

HTH
Jon

 

[Woodmonkey]

Water pump pliers? That's a new one on me...

 

[chipmunk]

Sorry Woodmonkey. Do you mean you don't know what they are or that you've never tried them.

In case it's the former then this is what they look like...

You can get quite a lot of leverage on them if you have 9+" ones. It does tend to scuff-up the outside of the drive centre but it's a small price to pay IMHO - and you can always run a file over the outside afterwards with the lathe running if you're precious about it.

HTH
Jon

 

[Random Orbital Bob]

too late this time, but I always use a thread protector that I unscrew to remove the centre.

My CL4 has a thread protector too. I always use it and recommend you do the same. I will say that frequently the spur drive gets so tightly jammed that even the thread protector wont shift it just by hand, but they always have a grub screw type hole in the side (though bigger than for a grub screw) that allows you to put an appropriately sized metal bar in to give it the extra leverage necessary to pop through the stiffness of the spur drive.

 

[NickWelford]

my thread protector has flats on which you can apply a suitably sized spanner. Usually have to lock the spindle. I'm told I should have a leather washer on the thread before the protector to allow easier unthreading. Never did get round to it.

 

[Random Orbital Bob]

like that.....flats on the side, nice easy way to get fast leverage on it.

 

[Grahamshed]

Glad you've got it sorted Woodmonkey

 

[Woodmonkey]

Thanks everyone. Water pump pliers, I have some of those but I didn't know that's what they were called. I've just had a look and the thread protector's inside diameter is larger than the drive centre anyway so that wouldn't help unfortunately. The downside of having such a beefy spindle I guess (1-1/4").

 

[chipmunk]

This is just another thought and it's "locking the stable door" a bit like the other suggestions and that's to use a Morse taper carrier in your chuck.

That way you can always remove the drive on the adaptor. It then just requires a block of wood with a hole and a big mallet to free the drive from the carrier.

HTH
Jon

 

[Spindle]

I've just had a look and the thread protector's inside diameter is larger than the drive centre anyway so that wouldn't help unfortunately.

Hi

Find an appropriately sized washer and place it between the thread protector and the drive centre, or for a better solution bond the washer to the thread protector thus converting it into an ejector.

Regards Mick

 

[Spindle]

Hi

To everyone who identified with the issue of stuck centres - you are probably using too much force when you fit them. I only ever slide them in smoothly under hand pressure, the 'click' as the tapers match indicates it's sufficiently locked. Never had one slip yet and always come out using the ejector by hand, (no additional tommy bars or C spanners).

Regards Mick

 

[procell]

+1 for the thread protector. I forgot to put mine on once and spent a whole afternoon removing the drive spur. with the thread protector it always comes out easily with a tommy bar in the hole in the the thread protector. I do like the idea of flats on the protector as the hole is very shallow and does tend to get rounded edges over time.