Thread: Headstock to Tailstock alignment

Mobyturns has pretty much nailed my thoughts on it, except for one thing.

I like to experiment with forms, although admittedly the vast majority of 'em are best called firewood. Even so, where I really, really want the tailstock to be true is for those faceplate jobs which need to be reverse mounted. You'd think that there's nothing simpler or more accurate than mounting a secondary chuck to a MT and fitting it to the tailstock for the xfer, right?

Wrong. Not unless everything is perfectly aligned from the get-go.

Originally Posted by Skew ChiDAMN!!

Mobyturns has pretty much nailed my thoughts on it, except for one thing.

I like to experiment with forms, although admittedly the vast majority of 'em are best called firewood. Even so, where I really, really want the tailstock to be true is for those faceplate jobs which need to be reverse mounted. You'd think that there's nothing simpler or more accurate than mounting a secondary chuck to a MT and fitting it to the tailstock for the xfer, right?

Wrong. Not unless everything is perfectly aligned from the get-go.

Then there are the adventurous turners who are trying to turn using a chuck on both headstock and tailstock ends of a blank. Why, may one ask?

As Skew says you really want the lathe to be near perfect imo. Plenty of potential for some serious vibration.

Originally Posted by Mobyturns

Then there are the adventurous turners who are trying to turn using a chuck on both headstock and tailstock ends of a blank. Why, may one ask?

Some of the forms I've tried need to be reverse mounted very, very accurately. More accurately than I can easily achieve by simply dismounting from the headstock, flipping the piece over and then remounting. Especially when different sized jaws are involved.

It'd be absolutely luvverly if I could reliably bring up the chuck in the tailstock (with appropriate jaws), tighten it to the blank and then remove the chuck from the headstock end.

(FWIW, I'm not saying that I can't reverse chuck 'normally.' But it can take quite a bit of time to get things set up accurately and it's the turning I enjoy, not the fiddling. )

Originally Posted by Skew ChiDAMN!!

It'd be absolutely luvverly if I could reliably bring up the chuck in the tailstock (with appropriate jaws), tighten it to the blank and then remove the chuck from the headstock end.

You mean one of these:
NOVA CHUCK ACCESSORY TAILSTOCK ADAPTOR (SKU 5016 AND 71093) - NOVA, a Teknatool Brand

Other brands have the full length morse taper, which I prefer. That short one doesn’t hold well in my experience.

Originally Posted by Colin62

You mean one of these:
NOVA CHUCK ACCESSORY TAILSTOCK ADAPTOR (SKU 5016 AND 71093) - NOVA, a Teknatool Brand

Other brands have the full length morse taper, which I prefer. That short one doesn’t hold well in my experience.

To me that accessory falls into the great idea in theory category but falls short in the practical application department.

I agree with Colin, the MT2 arbor is too short for one, then the idea of having a chuck secured in the tailstock leaves me rather concerned.

The what IF's?
What if the turner wants to spin the piece to check the mount? One can't!
What if the turner turns on the lathe????

A far better, and safer, choice would be a Vermec Revolving Threaded Live Centres MT2 - Threaded Live Centres MT2 Revolving (vermec.com) well made gear!

It may be twice the price, but it has far more practical uses than the Nova accessory. Mine also serves as a lazy susan spindle shaft for my small spray turntable.

Originally Posted by Colin62

NOVA CHUCK ACCESSORY TAILSTOCK ADAPTOR (SKU 5016 AND 71093) - NOVA, a Teknatool Brand

Other brands have the full length morse taper, which I prefer. That short one doesn’t hold well in my experience.

Long or short, if they are not holding add a draw bar to them.

I posted here a little while ago on turning long thin spindles in which I ended up with chucks at both ends and a revolving centre in the tailstock to hold the chuck on that end. Here is the end result...

Long Thin Spindles - pulling not pushing

And here is where that experiment began with all the tedious detail along the way to getting that result...

Long Thin Spindles - pulling not pushing

The exercise wasn't about reverse chucking for precise crossgrain work, but the double chucking method could also be applied to that if the head and tailstock are in alignment.

I have used the technique successfully since on split spindle work where I didn't want the bother of gluing together then splitting and cleaning off the glue after that....

IMG_20210104_111011.jpg

Prototype 1 is finally done, had to wait for the laser diode from O/S but given it was $2 i am prepared to wait.

"Crude" is an understatement, but it just needs to work. However prototype 1 has issues:

1. The housing is too small, so I taped power leads to batteries and the connection is not solid. Button battery holder wont fit in this holder
2. Only way to access the switch or the adjuster is to pull it all out. Adjuster trimpot is less of an issue, but switch would be nice to reach easily. Otherwise I am going to break wires a lot pulling it in and out

So prototype 2 will need to have a wider housing, might need 60mm stock or so. I should then be able to sit the board flat in the base making the whole thing shorter. I can use proper button battery holders than will give me solid connection, which will be important as I start spinning it.

I am sure a whole host of other issues will come up when we get there, and I know I dont need this, but its just fun to try to make stuff work.

Hope to update on prototype 2 in a week or so.
20230326_225635.jpg

Originally Posted by NeilS

I posted here a little while ago on turning long thin spindles in which I ended up with chucks at both ends and a revolving centre in the tailstock to hold the chuck on that end. Here is the end result...

Long Thin Spindles - pulling not pushing

And here is where that experiment began with all the tedious detail along the way to getting that result...

Long Thin Spindles - pulling not pushing

The exercise wasn't about reverse chucking for precise crossgrain work, but the double chucking method could also be applied to that if the head and tailstock are in alignment.

I have used the technique successfully since on split spindle work where I didn't want the bother of gluing together then splitting and cleaning off the glue after that....

Neil, I like your solution for split turnings however as a solution it has limits or at least a limited application.

One thing woodturners must always be mindful of is the mass of the chuck or MT2 accessory live center used in the tailstock relative to the mass and cross section of the work piece. Similar to "unsprung weight" in motorcycles and vehicles it's best to keep the "driven mass" of any tailstock accessory to a practical minimum.

That is why turners such as Jean-Francois Escoulen when turning trembleurs only use string steadies. Andi Wolfe's Blog: Jean-François Escoulen class - Day 1

Initially, the blank mass etc vs tailstock accessory mass may be acceptable. The tailstock chuck or live center etc may be easily "driven" from startup as the turning torque is transferred through the blank to the tailstock accessories and accelerates the whole blank plus tailstock accessory to the desired turning speed. (Note - this is why it is recommended on VS lathes to slow the lathe before stopping, then to ramp up speed when restarting the lathe - it minimizes the risk of failures.)

A similar process occurs when the lathe is stopped - the work piece must have sufficient torsional strength to slow the rotational mass of the whole assembly to a standstill. However, that mass relationship rapidly changes as material is removed from the blank, and each start / stop cycle introduces another cycle of torsional / torque forces to the blank.

When initially started and whilst left running the cross-sectional strength of the piece may be of sufficient strength and may continue to appear to be strong enough. However, each cycle may be causing torsional fractures within the blank and those created flaws and a reducing cross-sectional area accelerate the damage with each start / stop cycle to the point of failure.

Given that spindle turning speeds are much higher than bowl / face grain turning lathe speeds this creates a potential hazard from any accessory secured with a MT 2 spindle in the tailstock. As the axial thrust is removed from the tailstock with a work piece failure, and as part of the blank may still be attached to the "tailstock chuck" there is a significant risk that the MT 2 spindle with chuck attached may wobble and eject itself from the tailstock.

Most turners will be familiar with a Jacobs chuck used in the tailstock for drilling and no doubt will have experienced how "exciting" it can become when extracting the bit from the wood, only to find the MT 2 ejecting from the tailstock instead.

Now a 1kg plus chuck can do quite some harm.

I would strongly advise any turner considering using this "solution" (chuck at tailstock end) to consider the above comments and to only use a MT 2 spindle with a draw bar - never without one.

Also look at the design of your live centers for thin spindle work. Some have only the cone point and inner race of the bearing being driven, others have all but the spindle center i.e. the point, body and bearing/s being driven. This makes a considerable difference!

Originally Posted by Mobyturns

...chuck at tailstock end... only use a MT 2 spindle with a draw bar

Ageed and is what I always do.

Originally Posted by NeilS

Ageed and is what I always do.

I had confidence that you would.

So many readers of these forums do not consider the "what if's" and could potentially come to grief.

Originally Posted by Mobyturns

I had confidence that you would.

The live centre M2 for taking my larger chucks that I got from Vermec came drilled and threaded ready to take a drawbar.

The one I got from McJing for the mini chuck I had to drill and tap myself...

Long Thin Spindles - pulling not pushing

M2 with drawbar.jpg