Chuck jaws

[duncanh]

I've wondered about this whenever I read my chuck jaw instructions so thought I'd query it here...

the booklet which comes with every set of nova jaws gives dovetail, spigot, recess dimensions and maximum sizes for all jaws in the range.

There is also a table of maximum recommended speeds. The maximum for most jaws in expansion mode is 684rpm. The maximum in contracting mode ranges from 1440 for the smaller jaws to 400 for the larger ones.
The power grip jaws for example are limited to 684 in both modes. This seems pretty low for such large jaws capable of gripping over a large area.

My lathe is capable of over 3000rpm - am I expected to not go that high with my chuck? I often do, and regularly exceed the recommended speeds of all my jaws.

Surely the speed used should come down to personal judgment and experience. Do other makes of jaws/chucks have similar recommended speeds?

Duncan

 

[Bodrighy]

I suspect that this is just their way of covering their backs. If something happenned when you were turning a large bowl at a higher speed you couldn't blame them. I rarely use the slow speeds apart from initial turning and if it is off balance or particularly large and heavy, wet wood over about 6" dia for example. So far I have had no problems. I am sure that some more experienced turners will come on and either agree or disagree soon.

Pete

 

[Russell]

The general rule is the larger and heavier the piece the slower the speed. this also depends how the work is balanced and supported. I don't bother looking at the speed I just turn the speed up until I feel comfortable if there is a slight vibration I will speed up to pass it if it gets worse just back it down. What is important is that you start slow an speed up and not the other way round.

Remember is the peripheral speed that is important ie how much timber is passing the tip or your chisel so diameter is important.

 

[TEP]

As already mentioned it is probably because they are trying to cover their own backs.

With some of the larger jaw sizes (100 & 130mm) if you get a heavy dig-in it is possible to tear off the spigot if the grain is running across the bed. This being one of the reasons a lot of people use face plates for the bigger pieces.

BUT repeating what has already been said if you take care and use light cuts you can turn at whatever speed you are comfortable with on a spigot/recess. It all comes down to personal ability and experience.

 

[duncanh]

I thought it was probably down to them wanting to cover themselves in case of an accident.

I tend to use whatever speed feels right

 

[caretaker]

Just asking as we are talking about chucks, I was unscrewing my K10 chuck and one off the jaws fell out, so I popped it back but did not line up with the other 3, after a bit of jugerling I managed to line all 4 jaws up.
Did I do this correctly?

 

[TEP]

Hi Reg.

The teeth on the bottom of each jaw mesh with the scroll inside the chuck. Therefore the teeth on each jaw are a little offset so that when centered they all line up together.

Which means as you undo the chuck the jaws will come out one after another as the end of the scroll leaves the teeth. As such they must be replaced in the reverse order they came out in for them to line up in the centre once more.

Here endeth lesson 1. Don't undo a chuck too far. :lol:

 

[CHJ]

Just asking as we are talking about chucks, I was unscrewing my K10 chuck and one off the jaws fell out, so I popped it back but did not line up with the other 3, after a bit of jugerling I managed to line all 4 jaws up.
Did I do this correctly?

As long as they run true they must be correct.

The reason they did not line up the first time was because you did not start the jaw location on the scroll in the correct sequence, picking up the scroll a complete turn out.

If this happens in the future it may be easier to undo the chuck far enough to disengage all jaws then start engaging them in the scroll in sequence.
In most chucks this is in order of numbers, on chuck body and jaw, may be just dots and not numbers. 1-2-3-4 but there are some weird ones out there with odd sequencing.

One way to do it if you are still having trouble is to place all the jaws in their correct slots and put an elastic band round them to hold them in against the scroll.

Then unwind the chuck until you see the number one jaw lift and drop back on the scroll.

From this point tightening up the chuck should engage all the jaws in the correct sequence.

 

[caretaker]

Thanks for the help, I will not be opening the chuck in hast again.
They seem to be closing alright now.
Ever time I come on this forum I am very pleased with the excellent help I receive for all of you.