Piece spinning while roughing

[Dino]

The drive centre is in pretty poor condition I think, I hadn't noticed until the piece started spinning.

I'll sharpen it up and make sure my tools are sharp before I go for the next attempt.

The octagon idea is a good one, as are the drilling holes / cutting slots for the centre to properly slot in. I'll try them all.

Thanks for the input, much appreciated.

 

[procell]

Something else to try is to add a little more pressure from the tail stock end to keep the drive centre seated into the wood

 

[Grahamshed]

Something else to try is to add a little more pressure from the tail stock end to keep the drive centre seated into the wood

That is just what I was going to say
Normally there would be no room for the piece to come forward off the prongs.

 

[Tazmaniandevil]

Ah, but, the issue is not the piece coming off'f the prongs. It's the prongs working like a flat bit and cutting into the timber. Increasing the pressure will cut a bigger hole.

 

[Random Orbital Bob]

correct. The head stock drive centre just spins in the wood, leaving a central hole where the nose cone is and a circle outside that where the prongs are slipping and "drilling" a groove.

 

[Grahamshed]

Really ?
I assumed the central spike was marginally longer than the prongs, a bit like a brad point drill bit, and it was spinning on the spike. The prongs of my four prong drives don't seem sharp enough to cut a hole.
If that really is what is happening then a lighter touch does seem to be the answer.

 

[Random Orbital Bob]

Trust me, that's what is happening The secret is definitely a combination of all that's already been said ie very secure drive centre to start with coupled with sharp tools and light pressure.

 

[Grahamshed]

Right you are Bob. Consider yourself duly trusted

 

[Random Orbital Bob]

I've stood there watching it with my own eyes when its happened to me.

More so with the chuck centre than the morse taper one because the chuck centre has smaller spurs that don't grab as well. Best "drill" I've got

 

[CHJ]

If you have a particularly awkward piece, short/not enough waste for good centre grip or whatever try applying Hot Melt Glue to Centre/Piece interface, usually provides adequate drive for use with care.

 

[duncanh]

If all else fails just try to turn down one end enough so that you can hold it in the chuck.
Then go out and get yourself a better drive centre!

 

[Robbo3]

Using a two prong centre rather than squaring your blanks is poor practice in my opinion.
Regards Mick

That's not fair Mick. You are presuming that what happens in your workshop is the same for everyone.

Now that I've gained a reputation for being a bit of a wood hoarder, I mean turner, I get given bits of branch wood of all shapes & sizes with few bits being cut square. Hand sawing them is often more than I can manage but I can mount them on the lathe with a two prong centre & true them up with little effort on my part.

 

[Spindle]

That's not fair Mick. You are presuming that what happens in your workshop is the same for everyone.

Hi

Sorry if my explanation was less than clear.

I'm not suggesting that all blanks are reduced to square section, just that the ends are made square to their axis. This ensures that the drive centre will be optimally engaged with the work.

Anyone with a lathe can do this by mounting the work between centres as best possible, (cutting the ends square by eye will be sufficient), then using a parting tool square off the tailstock end. Remove the pip in the centre if needs and remount the work reversed. The interface between the drive centre and work will now be at it's best.

Regards Mick

 

[dickm]

Noone seems to have suggested what is a very simple solution, even for a tatty drive centre. Drill small recess where the point of the centre is to go, then with a WOODEN MALLET, tap the centre into the end of the blank, using the hole as a guide. This will leave two (or four) marks where the wings of the drive centre go. With the blank held in a vice, chip out slightly deeper recesses on the marks with an appropriately sized chisel, and you've got a firm seating for the drive centre. Obviously, it can still spin and become a Forstner bit if you are too heavy handed, but for most turning, it works well.

 

[Dino]

I think it was suggested, as I already did that and it worked pretty well.

I only need it to work well enough for me to be able to put it in the chuck anyway, which for now seems to be easy enough.

 

[Spindle]

Hi

Rather than drill holes to locate centres or beat them into place , I use one of these automatic centre punches.

Tailstock pressure on a Stebcentre is enough to then secure the drive - a four prong centre is located either by a couple of saw cuts or a tap with a nylon faced mallet.

Regards Mick

 

[Grahamshed]

+1
I may not know much but I do know the stab centres are easy to use and very efficient.

 

[chipmunk]

Steb centres can still slip though - and when they do they saw a very efficient round slot if you're not careful. Also bear in mind that too much tailstock pressure is neither good for tailstock ram or spindle bearings.

Simon Hope had a good tip and that's when seating the Steb on a large workpiece to apply a bit of tailstock pressure and then work the piece forwards and backwards on the points of the steb before winding in a little more tailstock pressure. If you do this a few times the teeth of the Steb have a better seating and it can save slippage.

HTH
Jon

 

[Robbo3]

Mick - yes I meant squaring the ends of the log.

I think that the point that is being missed here is that the lathe needs to be stopped for the drive to be re-established otherwise it just continues to bore a hole.