Ash bowl done wrong...

[stevebuk]

this was a bleeding nightmare from the word go, when i did the cherry bowl with doug we turned a spiggot on the bottom and mounted in the chuck, but no not me this time, i had seen penmans bowls with a hollow in the bottom and i liked the idea as i had trouble with a spiggot on my last Ash bowl disaster.
So i turns the bottom and sides

ok so far, mounted it in the chuck and it starts to wobble, so i thought i will true it up and all will be ok, so i proceeded to start taking the inside out, but the wobble came back, by this time i have removed quite a lot of stuff and couldn't remount it via the screw chuck in order to get the hollow bottom deeper.

anyway, i continued to see what i could do with it, the bowl was never at this stage ever going to be anything other than trial and error and as you can see from the photo's was not turning correctly at all, i had a catch with my chisel even though i was not using it at the time, i was looking at another part, and this led to me bringing the rim down to almost the beading.

The inside feared no better, with the oval turning it was nigh on impossible to get a decent cut, so i finished it up quickly and went and thatched the lawn, practise, practise, practise.

 

[CHJ]

Steve, was your socket a correct match size and angle wise to the chuck jaws, was the face of the socket a good fit up against the jaw face.

Sounds like something was not seating correctly.

 

[stevebuk]

hi chas
i believe now that the hollow was not correct, it seemed to fit against the chuck jaws ok, but i think the hollow was too shallow, and when i tightened the jaws it twisted the base.

 

[Paul.J]

Steve.
Did you cut the recess at an angle inwards,like a dovetail :?:

 

[CHJ]

Steve, as much as it is a temptation to give the chuck a bit of welly to get a better hold it is really a matter of experience to judge what is appropriate for any given wood/piece.
You need just enough to keep it on the jaws but not enough to deform the wood.

You will not be the first to have one come off, neither will you be the first to split the socket, in a few months time you will not think twice about what seems right for the piece.

 

[stevebuk]

Steve.
Did you cut the recess at an angle inwards,like a dovetail


errrrrrr..... No

 

[TEP]

Major problem with scroll chucks is the amount of pressure that can be generated against the wood. Basically what you are doing is reverse chucking, and if you tighten the chuck up too much you crush part of the recess and as wood is not always the same density all over the work can go off centre. Or lop sided.

Because of this I always prefer to mount on a spigot. The way to do it is hold on a screw chuck and turn the outside with spigot, but don't finish just get as good a finish as you can from the tools. Then reverse chuck and hold by the spigot, chances are it will move a little so move the tool rest around the back and go over the outside once more with a gentle sheer cut to remove any wobble. Now you can sand and finish the outside, move the tool rest back to the front and get on with the inside.

Also another reason I always use a spigot is that it is very easy to split a bowl under pressure from a chuck. Just turn it that little bit too thin and you can end up with two half's.

 

[wizer]

Steve don't worry mate. Take a look at this:

http://wizer.co.uk/archives/30

 

[stevebuk]

Steve don't worry mate. Take a look at this:

http://wizer.co.uk/archives/30

it dont look too bad Tom, i had the same problem with the cherry bowl, how is one supposed to get rid of the spigot without cole jaws.?? :?:

 

[stevebuk]

Because of this I always prefer to mount on a spigot. The way to do it is hold on a screw chuck and turn the outside with spigot, but don't finish just get as good a finish as you can from the tools. Then reverse chuck and hold by the spigot, chances are it will move a little so move the tool rest around the back and go over the outside once more with a gentle sheer cut to remove any wobble. Now you can sand and finish the outside, move the tool rest back to the front and get on with the inside.

thats a great piece of info Tam, never thought of that at all, i will have to write this down for future reference..

 

[wizer]

Steve don't worry mate. Take a look at this:

http://wizer.co.uk/archives/30

it dont look too bad Tom, i had the same problem with the cherry bowl, how is one supposed to get rid of the spigot without cole jaws.?? :?:

I probably would have knocked it off with a chisel and then sanded it. But you can make all sorts of reverse chucking gagets:

http://www.cumberlandwoodturners.com/ti ... 0Bowls.pdf

http://www.woodturningonline.com/assets ... tChuck.pdf

 

[Bodrighy]

how is one supposed to get rid of the spigot without cole jaws.?? :?:

Make yourself a flat round blank that can be mounted in your chuck, glue or cut a spigot to do this. Two methods then. Either cut a groove to correspond with your bowl rim or round it off to roughly match the inside of the bowl. Put the bowl onto this and bring up the tail against the tenon so that it is holding the bowl against the blank (make a dimple for this purpose when first cutting the tenon) I put some thick foam on the boartd when I do this as well. Now you can gently turn off the tenon until there is only a very small nipple left. This can be trimmed off with a sharp chisel. I always make the bottom slightly concave so that the bowl sits on a rim instead of trying to make the bottom flat.

Alternatively do as above but instead, make the end of the tenon nice and clean when first turning it and then use a small piece of wood on the end of the tailstock to hold the bowl onto the blank and shape the tenon to make an ornate foot. This is suitable for smaller bowls but is too unsteady fro most larger ones.

Hope this helps

Pete

 

[Paul.J]

Stevebuk wrote

how is one supposed to get rid of the spigot without cole jaws.??

Steve.
Richard Findley put a couple of piccys on not so long ago showing how he does it,but also take a look at Bobhams latest video.No11 shows you how,but the whole video is worth watching
Also Bob Chapman shows you on the fromt page in CHJs how to's.
I always use a parting tool to put the angle on the recess to match the jaws,than just take the rest out with a spindle gouge until you have a flat surface.But do not over tighten.
It is best to use a spuigot as Tam says

 

[Richard Findley]

Hi Steve,

It's all practice I'm affraid!!

I too use a spigot (rather than recess) when bowl turning as they are easier to remove and give a simpler and more effective grip (in many peoples opinion, not just mine!!)

My reversing technique is like this:

I think the picture is quite self explanatory but if you have any questions please ask!!

(This method does rely on you marking the centre with the point of a skew or similar BEFORE remounting on the spigot!!)

Hope this helps,

Richard

 

[Bodrighy]

OK Richard so you put it better than me :lol:
Pete

 

[Jenx]

Whats the best rubber for the disc ? Router Matting or something like that ?
:?:

 

[Richard Findley]

OK Richard so you put it better than me :lol:
Pete

A picture says a thousand words so they say :wink:

I use router mat. I always used the black as this is what I've got but I recently had it mark the rim of an Ash bowl, so I now have some white for pale wood bowls.

Richard

 

[Jenx]

Thanks Richard.
Must make one of those too ...

Steve, not to worry too much Pal, - it happened to me with a nice piece of Padauk the other night too .. expanding the chuckjaws into a dovetail as described, and was trying to be 'neater and finer' than my abilities really allow ! :lol: :lol: Little catch, and there was perhaps a tad too much pressure on too thin an area, and in a flash, bowl & chuck had a quickie divorce

All part of the 'education' !

 

[CHJ]

... bowl & chuck had a quickie divorce

If you are near completion and the wood is special and base has enough material to salvage, then try trueing it up mounted as per Richards pic, hot melt a scrap piece to it and turn a spigot for remounting.

Then when rounded up inside and out turn round again and remove scrap spigot and finish base.

 

[Jenx]

Thanks Chas ...
I have set it to one side, with a view to 're-hashing' it at some point in the next few days.

Keep meaning to make up the big MDF + Rubber disc - all the more reason to get round to it now ! 8) :lol: