Thread: Which Chuck

Doesn't all this become irrelevant when you place a bit of timber in the lathe and the jaws sink into the grain just a little more in the soft stuff maybe and less in a hard bit of grain? How do you control that.
I'm sure I've seen a pro somewhere tap the job gently into line before tightening, rechecking, repositioning, tapping retightening, when rechucking - all done by eye with reference to the tool rest 1mm from the edge of the job. This is what I do and I find sometimes you just can't get it spot on, but it ain't the chuck. I reckon its the grain variation of the timber.

Cheers,

FrankG

Originally Posted by efgee88

Doesn't all this become irrelevant when you place a bit of timber in the lathe and the jaws sink into the grain just a little more in the soft stuff maybe and less in a hard bit of grain? How do you control that.
I'm sure I've seen a pro somewhere tap the job gently into line before tightening, rechecking, repositioning, tapping retightening, when rechucking - all done by eye with reference to the tool rest 1mm from the edge of the job. This is what I do and I find sometimes you just can't get it spot on, but it ain't the chuck. I reckon its the grain variation of the timber.

Cheers,

FrankG

Yes.

Originally Posted by efgee88

Doesn't all this become irrelevant when you place a bit of timber in the lathe and the jaws sink into the grain just a little more in the soft stuff maybe and less in a hard bit of grain? How do you control that.
I'm sure I've seen a pro somewhere tap the job gently into line before tightening, rechecking, repositioning, tapping retightening, when rechucking - all done by eye with reference to the tool rest 1mm from the edge of the job. This is what I do and I find sometimes you just can't get it spot on, but it ain't the chuck. I reckon its the grain variation of the timber.

Cheers,

FrankG

This is true Frank but when the chuck wobbles to start with (bad machining) it makes the whole job harder.

What chance do you have of finishing a bowl nicely when the cole jaws, donut chuck, longworth chuck wobbles by about 1/4 inch before you mount the bowl.

cheers

Originally Posted by Calm

What chance do you have of finishing a bowl nicely when the cole jaws, donut chuck, longworth chuck wobbles by about 1/4 inch before you mount the bowl.

I have only started following this thread in the last day or so, thought for a minute it was in the wrong forum! With all those dial indicators I thought I was in the the metal working forum.

David, I would be worried too with a 1/4" wobble in any chuck, metal or wood, but I thought you guys were talking around the 5 thou mark? If it is 5 thou, that equates to 0.127mm in real measurements, I would have thought the wooden bowl would expand and contract by more that on any given day?

Having said all that, I have 3 Nova chucks, a Nova G3 and 2 Nova Compacs. They seem to be doing what they are supposed to be doing but I haven't put a dial indicator on it to look for TIR. I have however had QC problems with Nova Pin Jaws, made in China, a not uncommon occurrence unfortunately.

Originally Posted by rsser

Interesting Ed.

With the test on the face of the jaw slide how did you ensure the slides were seated?

not understanding the question, Ern. If you mean vertical play, there is none. If you mean horizontal play, yes there is.
Understand that I'm not an engineering type (I had to work for a living when I was younger), so when topic starts with words like co-axil, etc. I tend to glaze over

Calm, my point was about the difference between an off centre error that was coaxial (eg. run out same at bottom and top of chuck body measured parallel to the bed) and one that was not coaxial (chuck axis not parallel to the lathe bed). With my meagre imagination it seems that only that second would show a multiplier effect and that only the deeper the bowl.

Jeff, the big point of difference between Vicmarc and Nova chucks is that when you want to step up to a bigger chuck, with VM you have to buy all new jaws but with Nova you don't. That's why I have one VM and two Novas. (Over time however I don't like the way Nova jaw design has gone so the big difference doesn't count so much for me.)

Jim, your point is a good one and in practice the effects of run out may well be less than that of remounting or bowl warping. But GJ tells me it doesn't cost any more to machine accurately so why should buyers have to cope with that unnecessary variable?

Originally Posted by Calm

Ern i had never noticed coaxial runout (probably didnt look to be honest)

Ed this is where i noticed the problem and what i have done now is fit the insert then my mate placed the chuck in his metal lathe against the face you measured and "faced off" the insert so that it eliminated this runout when fitted to the wood lathe.

Problem is if only one jaw runs out this wont work. Edit: - looking at photos again it would be interesting to see if "facing" the insert would eliminate this runout, jaws 3 & 4 are both high so the chuck appears to be "tilted" on the spigot.

Edit: - Ed is it possible to remove the insert and fit only it to the lathe "backwards" and check the runout of the face/shoulder that locates againt the lather spindle. One would assume the face that locates inside the chuck would be machined of properly but the outer one may not be touched after manufacturing the thread etc.

Will try that one tomorrow

Might have to take Jims advice and just go out to the shed and turn. Still its annoying when you finish the outside of a bowl and chuck it to do the inside and it wobbles too much to be left. All that sanding gone to waste.

Cheers

.

I am also late in following this thread. In my opinion the best chucks are genuine Vicmark. Having said that, I never use a chuck to make a bowl, they are not accurate enough, limit your design choices and increase the time taken to make a bowl. I always use faceplates for making bowls and chucks for making boxes.
You can buy ten faceplates for the cost of one chuck.

Originally Posted by KenW

You can buy ten faceplates for the cost of one chuck.

Yes, if you've got a common spindle thread - I won't start on the Nova's 1 1/4 x 8

But generally with bowls and chucking I don't find much difficulty with changed axes or radiuses as most of the bowls I finish turn are dry and stable enough. Two lines can be blended at the sanding stage. If the rim thickness varies noticeably then it gets tossed.

Edit: - Ed is it possible to remove the insert and fit only it to the lathe "backwards" and check the runout of the face/shoulder that locates againt the lather spindle. One would assume the face that locates inside the chuck would be machined of properly but the outer one may not be touched after manufacturing the thread etc.

OK Dave...did that and there was a thou + and - as the spindle was revolved. Did the same procedure on the face of the spindle and it stayed dead on "0".

Ken W ...I tend to agree with you on the use of a chuck vs. faceplate (in view of what has transpired with the Super Nova)
For years faceplates were used for my bowls and never had a (significant) problem when reverse chucking to finish the bottom. My first dealings with a chuck were in 1996 or 07, when I bought the Nova (lever type) and did notice that when reverse chucking the bowl that it was running somewhat off-center, but still not enough to worry about. The situation with the Super Nova is that reverse chucked bowls are significantly off-center which is a real problem when you want to incorporate a few circles as part of the bottom's design.

Might just have to go back to using faceplates again for bowls.

Accuracy of a wood chuck does matter Ornamental Turning relies on it decorating surfaces even using a chatter tool would be noticable

One of our members does 15"bowls and clock faces which are then have routered edges if the runout was 1mm at centre it could be that one side of the platter has deep and the other shallow cuts.

hmmmmm....so what kind/brand chucks do the ornamental turners use, Whellin?

sounds like the insert needs trueing up . in metal work they use centre to centre work for lathe shaft to make the true ! but i think 6-8 thou would be really hard to see . perhaps you should look at a 4 jaw independant metal work chuck if you need real accuracy . would guess tekna tool made to a reasonable/ price cheers

Course we don't have comparative data here do we ... for older Nova chucks or Vicmarcs. Mebbe they're in the same ball park.

Might get out the dial gauge this arvo.

Originally Posted by Ed Reiss

hmmmmm....so what kind/brand chucks do the ornamental turners use, Whellin?

Supernova, early Nova's, G3 I have 2 of them but as I said ealier we have 2 members now have trouble, H&F scroll chucks which seems to be ideal and all run true.

Here are the variations on mine.

A = the face of the chuck at the perimeter, without jaws and skipping the slides (cos they have to have some movement)
B = the side of the chuck body next to the face
C = ditto at the headstock end

so where B and C are different there'll be some degree of wobble; and the run-out figures (variation from the axis) will be half the measurement as they're taken at the circumference.

The dial gauge used was a Mercer on a magnetic stand.

Both Teknatool chucks are NZ made with the SN2 having a recent factory replacement insert and the Titan has a Vermec insert.

Vicmarc 100: A = 1 thou; B = 0.5, C = 1
SN2: A = 1 thou, B = 1, C = 1
Titan: A = 3 thou, B = 3, C = 2

Hope this makes sense.

Nothing to lose sleep over.