Turning a wine "glass".....help!!!

[Davidf]

Hi,

As yoiu can see I ve got so far with it and I've juust turned it a round [to hollow it out], using my new chuck.

As carefully as I go though, the work jumps out of the chuck grip off centre and I have to re centre it.

I daren't put too much torque on the chuck or I know for a fact the wood will split.

Please advise, I certianly don't want to spoil it at this point.....



(sorry he pictures are blown but I think you get the idea. I'll do more and switch the flash off is needed))



TIA



David

 

[woodyturner]

Im sorry to have to say this but you should have done a spigot to grip in compression mode I really cant see a way out of this one unless you just take a chance and tighten the jaws up more also try drilling some of the middle out first

 

[tekno.mage]

Hi David,

Had I been making a goblet I would not have turned the outside shape before hollowing. Thinning down the stem as you have done is likely to cause more vibration when you hollow out and may cause your goblet jumps out the chuck. From your photos it looks like you are holding your goblet by expanding the chuck jaws into a recess in the base of the goblet - had you left a spigot on the base and held this in compression you would have been able to do up the chuck more firmly without the risk of the wood splitting which would also help.

Having said that, you are now where you are with this project and neither of my earlier suggestions are much immediate help!

What might help a little now would be to use a forstner bit held in the tailstock to drill out most of the core of the goblet bowl and to finish up by very gentle application of a scraper or hollowing tool - trying not to apply any kind of sideways load on the work. However, if the piece has already moved in the chuck too often, the recess you are holding it by may be too damaged for it to now properly hold or run true and you might do better to start again with this project.

 

[Davidf]

ok thanks

 

[CHJ]

I'm afraid as others have said, you have place yourself in a no win situation really on that one.

I know it's harsh but some times it's quicker and a lot more satisfying to start again having learnt a sound lesson.

Google "turning a Wine Goblet" should turn up a host of examples of how to tackle one.

As has been said,
Use a spigot not a socket when clamping in Spindle Mode unless the socket is way back in soundly supported (larger diameter) wood.
Sort out the internal cup first.
Slowly work back from the rim on the outer cup shape.
Do not reduce the stem in one go but in stages so that the maximum amount of wood is still providing chuck support.
If, when the stem is getting longer toward the base the cup is moving out of true or vibrating then support the cup with a rotating tail stock centre and a scrunched up tissue in the cup.

Whatever you do Do Not attempt to go back to the cup end with a turning tool once you start reducing the stem, nine times out of ten you will get a catch and wreck it due to flexing of the wood.

With the item you have, if you must finish it I would do as suggested and drill out the core and leave it at that.

Don't be put off with just making firewood on the lathe, I came away with two hours worth of it over last weekend having found hidden defects in partially turned pieces.
The satisfaction of having learnt when it's best to quit is just as satisfying in the long run.

 

[Tazmaniandevil]

I'd be tempted to put the tenon back in the chuck and use the wood to make an egg cup or a small box. (if using for a box, you could maybe salvage the foot for the lid?)

 

[Davidf]

I'd be tempted to put the tenon back in the chuck and use the wood to make an egg cup or a small box. (if using for a box, you could maybe salvage the foot for the lid?)

Good thinking...

 

[Paul Hannaby]

You might find this step by step guide on how to turn a goblet useful

 

[Davidf]

You might find this step by step guide on how to turn a goblet useful

Thanks.

Classic beginners mistake, huh?

New one started now.... compressions better, yes. Good idea.

 

[Paul Hannaby]

I ought to update that website - I don't use the beeswax to seal the wood any more. I switched to more modern finishes to achieve a waterproof surface.

 

[Davidf]

Im sorry to have to say this but you should have done a spigot to grip in compression mode I really cant see a way out of this one unless you just take a chance and tighten the jaws up more also try drilling some of the middle out first

Sorry for the stupid questions but i ve never quite got my head around this idea...... my chuck won't expand wide enough to make spigot of large enough diameter to use as goblet base. So, is the thing to do (or that is done?) to make an artificial one that is removed last thing (maybe sanded off?)?

I can certainly see that compression would be far better.

Thanks so far.

 

[Tazmaniandevil]

Turn the tenon to fit the chuck then turn the base in front of that. You will be able to reverse chuck the piece and taking very light cuts, take the tenon off.

 

[Davidf]

Turn the tenon to fit the chuck then turn the base in front of that. You will be able to reverse chuck the piece and taking very light cuts, take the tenon off.

Yes just looking at this again, I take it the first job really is to make the spigot (or tenon), then the job is revered in the chuck (as you say) and yoiu can start to holow out the inside.

The thought occured to me, whn you ve worked dwon to the base end, I suppose you have to be careful to allow sifficent base or foot (in the case of my goblet anyway) as some material will be lost when parting off?

Hmmmm, I think its coming clearer now.

I was just looking at the chuck; using different jaws it enables about 1.5 inch tenon but I suppose it doesn't matter as its going to be parted off anyway at then end.

 

[nev]

Turn the tenon to fit the chuck then turn the base in front of that. You will be able to reverse chuck the piece and taking very light cuts, take the tenon off.

Yes just looking at this again, I take it the first job really is to make the spigot (or tenon), then the job is revered in the chuck (as you say) and yoiu can start to holow out the inside.

The thought occured to me, whn you ve worked dwon to the base end, I suppose you have to be careful to allow sifficent base or foot (in the case of my goblet anyway) as some material will be lost when parting off?

Hmmmm, I think its coming clearer now.

I was just looking at the chuck; using different jaws it enables about 1.5 inch tenon but I suppose it doesn't matter as its going to be parted off anyway at then end.

Quite right
generally your piece of wood will need to be an inch or two longer than the finished article. This gives you plenty of meat to grab hold of.

Depending on which jaws you use the tenon/ spigot should be the optimum size for each set of jaws (see Chas's guide here) .
In short open your jaws till you have a true circle and measure the diameter. this will be the approximate size of the required tenon. you want as much of the jaw in contact with the wood as possible. If your tenon is too big you will be clamping with just the edges of each jaw which will not give you much support. Obviously this size tenon will be used whenever you use that particular set of jaws regardless of the finished product size.

So when doing a goblet...
spindle blank longer than needed.
mark centres.
place between centres (or grab across flats in jaws), rough to round and turn optimum tenon at tailstock end.
reverse wood and place tenon in jaws, bring up tailstock to centre the other end before tightening jaws.
you can now have a go at the cup end with either forstner drill bit or spindle gouge on its side and shape the inside.
turn outside of cup to rough size and remove some of the waste wood at the base of the cup (top of the stem) to allow you to shape the bottom of the cup. dont go too thin at this point.
I then shape, sand and finish the cup and bring up the tailstock and support (dont push!) the cup with a turned cone.
then work your way down the stem towards the base turning , sanding and finishing as you go. and NEVER be tempted to go back over the finished piece.
This way your work will always have the most support and and rigidity possible.

I hope that makes sense. It is not necessarily the correct way to do it but its the way i do it and it works

 

[CHJ]

Have a look at last two rows of images and notes HERE for method of finishing a base.

Not a goblet but the base treatment can be the same.

 

[gregmcateer]

Turn the tenon to fit the chuck then turn the base in front of that. You will be able to reverse chuck the piece and taking very light cuts, take the tenon off.

So when doing a goblet...
spindle blank longer than needed.
mark centres.
place between centres (or grab across flats in jaws), rough to round and turn optimum tenon at tailstock end.
reverse wood and place tenon in jaws, bring up tailstock to centre the other end before tightening jaws.
you can now have a go at the cup end with either forstner drill bit or spindle gouge on its side and shape the inside.
turn outside of cup to rough size and remove some of the waste wood at the base of the cup (top of the stem) to allow you to shape the bottom of the cup. dont go too thin at this point.
I then shape, sand and finish the cup and bring up the tailstock and support (dont push!) the cup with a turned cone.
then work your way down the stem towards the base turning , sanding and finishing as you go. and NEVER be tempted to go back over the finished piece.
This way your work will always have the most support and and rigidity possible.

I hope that makes sense. It is not necessarily the correct way to do it but its the way i do it and it works

Nev,
That's really helpful - thanks for posting it. Re the bit in red - Do you have to do it at tailstock end - ie is there a reason not to turn the tenon at the headstock end?
Thanks in advance
Greg

 

[nev]

Nev,
That's really helpful - thanks for posting it. Re the bit in red - Do you have to do it at tailstock end - ie is there a reason not to turn the tenon at the headstock end?
Thanks in advance
Greg

yes you could do it either end, the only reason i do it at the tailstock end is that the point of contact is smaller, i.e its a point! and so i dont have to worry about catching the prong drive if its a small tenon I'm going for. (or indeed if using a chuck at this stage the chuck will be in the way).

 

[Davidf]

Many thanks guys.

Back on shift today :-I so it'll be a bit quiet my end for a bit.

Thanks again.

 

[Tazmaniandevil]

Do you have a revolving centre for your tailstock? (live centre I think some call it?)
This video by Bob Hamilton shows how to easily turn a wooden cone for it. I use one with a bit of non-slip mat to supporthollow objects. The benefit is you can make one for every size of hollow.

 

[Davidf]

Do you have a revolving centre for your tailstock? (live centre I think some call it?)
This video by Bob Hamilton shows how to easily turn a wooden cone for it. I use one with a bit of non-slip mat to supporthollow objects. The benefit is you can make one for every size of hollow.

Looking at it earlier, its a pointed metal cone set into a bearing, which is in turn mounted onto the tail stock structure.

So, looking at it the other way, theres the 3/4 inch horizontal tailstock, on the end of which is mounted (some how) this metal cone, which spins freely.

Does that make sense.....if not I'll post a picture when I'm next free.

It doesn't look very flexible for mounting other stuff on it.....the cone is fixed.


Is it possible to obtain a tail stock to take a mandril... Or is that going to be dear?