Turning off the end of the main lathe bed

[user 466]

I have been given some largish pieces of elm (still wet) and am not sure how I am going to hold these after the initial roughing out.

Usually, when I get some wet wood, I rough turn the bowl, leave it in shavings for several months and then put it back on the lathe, finish the inside and then remount it between a wooden friction chuck and the headstock in order to finish the outside and remove most of the tennon that I originally used to hold the piece when wet.

The problem is that the pieces of elm will not clear the lathe bed and I will have to turn them off the end of the main bed using a tool rest mounted on an extension lower bed (please see photo below). No problem so far but, after the initial turning and after allowing the wood to dry for a few months, how do I remount the bowl to finish the turning when I can't use the headstock (as it only fits on the main lathe bed - not the lower bed).

I hope that this makes sense and that someone with far more experience than I have can point me in the right direction.

 

[woodfarmer]

I have to say I am not really sure of your question.

when I work off the end I use a faceplate to hold the original rough blank and turn the bottom including making a foot for the chuck.
Then I turn the work around and rough cut the hollow centre.
pack in a big paper bag (chicken feed) with shavings and allow to dry.
When dry enough, re mount the blank on the chuck on the bottom spigot which was used before. Then finish turn the bowl which will re true it.

 

[Dalboy]

Why not make a large doughnut chuck for pieces like this which will mean that you can return the chucking point and a good way up the outside once that is done remount into you chuck and turn the remainder of the outside and inside. By using a doughnut chuck mean the piece is held in place and not fly off

 

[duncanh]

Mount on faceplate, turn the outside with a dovetail. Make it a bit bigger than normal to allow for a bit of warping.
Mount in the chuck and turn the inside, leaving to approx 10% of diameter.
Take of lathe and leave to dry
Mount in chuck. The dovetail will have warped but you should be able to get a secure enough hold with decent jaws (I use Nova Powergrip or something bigger for something like this)
Turn a dovetail socket on the inside and nothing else
Turn the bowl round and hold it on the dovetail socket to allow you to turn the outside of the bowl and form a good dovetail on the base
Turn the bowl round and turn as normal.

 

[SVB]

I think the concern is that the once round tenon may (depending on species and how wet), now be very oval.

My approach is to hold as well as possible (some light carving may be needed) on oval tenon, true flat surface on rim of bowl, reverse into homemade Cole jaws that I have slots to move the buttons to accommodate out of round, re-turn spigot and then go from there. Bit of a phaf and does need homemade Cole jaws as a 'jig' of sorts but quite quick for second and subsequent bowls.

S

 

[duncanh]

I think the concern is that the once round tenon may (depending on species and how wet), now be very oval.

My approach is to hold as well as possible (some light carving may be needed) on oval tenon, true flat surface on rim of bowl, reverse into homemade Cole jaws that I have slots to move the buttons to accommodate out of round, re-turn spigot and then go from there. Bit of a phaf and does need homemade Cole jaws as a 'jig' of sorts but quite quick for second and subsequent bowls.

S

If the tennon is good enough to turn the rim enough to fit onto cole jaws then it should be good enough to turn a dovetail recess in the centre, and that saves bothering with cole jaws. It can get a bit tricky with certain deep bowls which make it hard to operate the chuck key, but if the chuck takes a regular allan key then no problem

 

[SVB]

Good tip / suggestion Duncan, I'll give that a go next time.

Thanks,

Simon

 

[user 466]

Many thanks for the suggestions. The main question really is what is the best way to remount the piece in order to remove the tennon once the bowl has been completed - given that it is not possible to use the tailstock.

I guess using some form of donut chuck, as Dalboy suggested, or homemade large cole jaws suggested by SVB, is the only way if I do want to remove the tennon. I will have to look further into this to see what diameter they would have to be (!).

Thanks for the suggestion, Duncanh, which I don't think would work in my particular situation since the bowl would be too deep for me to use the chuck key, if I did turn a dovetail recess inside, unless I left a lot of wood thickness in the base when I rough turned it. I would still have the same problem removing the tennon. Although it would have been a way to change from a tennon to a mortice after the initial rough turning. This may well prove to be very useful for shallower bowls.

Alternatively, I could hold the bowl by expanding the chuck into a suitable dovetail socket whilst I rough turn the inside of it initially although I don't think that this is as solid a hold as when using a tennon. If I did use a socket, I guess that I would just have to accept that this would remain as part of the base of the bowl (or use doniut chuck or cole jaws as above).

Again, thank you for your suggestions.

 

[CHJ]

...Alternatively, I could hold the bowl by expanding the chuck into a suitable dovetail socket whilst I rough turn the inside of it initially although I don't think that this is as solid a hold as when using a tennon. ........

Regarding the above comment, on something like a Bowl or Platter with a reasonably wide base, a dovetail socket can be as robust as a spigot if not more so.

Most failures will be down to cross grain surface area and associated strength.

The surrounding surface area outside a socket can be much greater than a cross grain spigot which is prone to snapping off.

 

[paulm]

Many thanks for the suggestions. The main question really is what is the best way to remount the piece in order to remove the tennon once the bowl has been completed - given that it is not possible to use the tailstock.

I guess using some form of donut chuck, as Dalboy suggested, or homemade large cole jaws suggested by SVB, is the only way if I do want to remove the tennon. I will have to look further into this to see what diameter they would have to be (!).

Thanks for the suggestion, Duncanh, which I don't think would work in my particular situation since the bowl would be too deep for me to use the chuck key, if I did turn a dovetail recess inside, unless I left a lot of wood thickness in the base when I rough turned it. I would still have the same problem removing the tennon. Although it would have been a way to change from a tennon to a mortice after the initial rough turning. This may well prove to be very useful for shallower bowls.

Alternatively, I could hold the bowl by expanding the chuck into a suitable dovetail socket whilst I rough turn the inside of it initially although I don't think that this is as solid a hold as when using a tennon. If I did use a socket, I guess that I would just have to accept that this would remain as part of the base of the bowl (or use doniut chuck or cole jaws as above).

Again, thank you for your suggestions.

It's quite possible to remove a tenon from a large finished bowl and tidy it up off the lathe.

Cut most of the waste off with a handsaw and then pare away the remainder with chisel or gouge, then sand with your normal drill mounted pads and abrasive, creating a very shallow recess at the same time (1 or 2 mm) to allow the bowl to stand without rocking. The sanding can also be done by mounting the abrasive pads in the chuck and bringing the bowl to that. It's surprisingly quick to remove tenon stubs with something like 40, 60 or 80 grit to start with and you might even skip the chisel/gouge stage.

 

[selectortone]

Another way to remove a spigot from the base of a bowl is to use a large disc of plywood mounted on a faceplate. (I have one permanently mounted on an old faceplate so that it is properly centred). I use this method when the bowl is too big for my home-made cole jaws.

Mount the faceplate/disc on the headstock and centre the bowl rim on the disc (it helps to have some concentric circles marked on the disc). Bring the tailstock, fitted with a simple single-point live centre, up against the spigot to secure the bowl in position. It helps to mark the centre of the spigot when originally turning the bowl, but with a certain amount of trial and error it is usually possible to get the bowl running evenly even without a centre mark.

You can then - carefully and gently - turn off the bulk of the spigot (slowly... at the same sort of speed as if you were using cole jaws), leaving a small central stub which can be chiseled/sanded off. Using this method you can create any kind of foot you like.

Use a piece of old cloth between the ply disc and the bowl to protect the rim.

As the old saying goes... there's more than one way to skin a cat! (Hope mine isn't listening...)

 

[CHJ]

selectortone, the whole point of the thread is that Steve does not have a tailstock support option, he's turning off the end of the lathe bed.

 

[selectortone]

selectortone, the whole point of the thread is that Steve does not have a tailstock support option, he's turning off the end of the lathe bed.

Oops. In bed with a really heavy cold... my brain isn't working properly...

 

[Keithie]

I'm still plucking up the courage to try hot gluing a piece where the bottom spogit needs tidying to a sacrificial lump of wood ( placed in the jaws or outer faceplate in this case?) ...allowing for an easier parting. Others willknow how good an idea this is.. I've not tried it yet.

 

[CHJ]

I'm still plucking up the courage to try hot gluing a piece where the bottom spogit needs tidying to a sacrificial lump of wood ( placed in the jaws or outer faceplate in this case?) ...allowing for an easier parting. Others willknow how good an idea this is.. I've not tried it yet.

Hot melt gluing is very sound, I use it regularly, secret is to make sure the glue is well up to temperature (bubbling level) and that the Glue Gun is capable of supplying enough volume.
See the weight of the lump in this old thread.

 

[Phil Pascoe]

Our club pro uses three glue guns at the same time to ensure it's hot enough if the blank weighs more than about a hundredweight.

 

[Paul Hannaby]

if you can initially mount the bowl to be re-turned in the chuck you could turn the rim of the bowl so it was round and true again and then you could mount the rim in a jam chuck to allow you to turn the outside. Perhaps a combination of jam chuck and some hot melt glue would give some added security.

Another approach would be to mount the bowl in the chuck, turn inside and outside to the finish then off the lathe, plane or power carve the spigot off.