Misplaced jaws ... dangerous ?

[KBs PensNmore]

That's the trouble with a lot of places, the equipment is there, but members either don't know where it is kept or can't be bothered looking for it.
I help out at the local Day Centre in a shed that is there for the clients, some of the things I've seen make me shudder, using the bandsaw at its maximum height, because they can't see the line, a 4 prong drive centre mounted in the 4 jaw chuck gripped at its narrowest point. The main culprit was reprimanded several times over these, eventually he lost several fingers on one hand, fortunately/unfortunately he did this at home. Hopefully he has learnt his lesson. Sorry for being blunt about it, but sometimes that is the only way some people learn.
Kryn

[Colin62]

That can only occur from operating the chuck with the stop pin removed and / or the jaws over extended.

To be fair, the jaws aren't over extended in that picture, and the tension on the jaw inserts would be no more than that on a cole jaw with a similar clamping radius.

And having said that, no, just no!

[Mobyturns]

To be fair, the jaws aren't over extended in that picture, and the tension on the jaw inserts would be no more than that on a cole jaw with a similar clamping radius.

And having said that, no, just no!

I agree that the jaw slides are within the recommended ranges so potential damage to the scroll is not likely in this example, BUT if they are doing this it does not take much a stretch of the imagination & ingenuity to extend them a little further - just this once.

The hazard & risk associated with such practices is relative, so turners must assess the whole operation and likely events.

Whether the jaw placement on the slides is potentially unsafe depends entirely upon what work piece is being held, its size, mass, operating lathe speed, turning operation etc. It may be quite safe if this "work around" is for a thin disc & light cuts but it would be potentially quite hazardous and very high risk if it was for a large bowl with a turner known for aggressive cuts etc.

Definitely not a recommended work practice though.

[Sawdust Maker]

Ok, an exercise for everyone

take your chuck with your standard jaws
remove 1 (one) jaw
move it out one bolt hole
securely affix it to chuck

essentially you cannot because the 'ridge' (?) precludes proper seating except where it should be seated (hope this makes sense)

the whole exercise just hurts my sensibilities as the jaws and chuck were not designed to do this and ...

[Mobyturns]

Sadly we are seeing more of this sort of "ingenuity." I am wondering if the jaws are even for that model chuck? I guess they are???

Ok, an exercise for everyone

take your chuck with your standard jaws
remove 1 (one) jaw
move it out one bolt hole
securely affix it to chuck

essentially you cannot because the 'ridge' (?) precludes proper seating except where it should be seated (hope this makes sense)

the whole exercise just hurts my sensibilities as the jaws and chuck were not designed to do this and ...

That is why I made my original comment. I prefer QLD made Vicmarc chucks so not knowing or having first hand experience with some chucks on the market made me immediately question how this was achieved. Maybe their ingenuity extended to removing the locating ring from the rear of the jaws too???

[Sawdust Maker]

no locating ring still in there

I went to service the shed's chucks yesterday only to find that one of the supervisors did them on Tuesday (no doubt as a result of this)

oh and no one has said "I did that"

[Oldgreybeard]

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This thread encouraged me to check my chucks. Fortunately all screws were very tight - more good luck than good management because I am guilty of not checking them often enough.

But one chuck - an old Bonham (old and in need of some TLC) had fitted a set of jaws with only one screw in each jaw and obviously manufactured as such.

Curiosity got the better of me, so I got a Nova jaw and checked if it could be mounted to the Bonham Chuck: YES - it could be fitted with 1 or 2 screws (see image 1). Further the jaw sat flat on the slide - not tilted due to the ridge as Mobyturns experienced. (see image 2 top view and image 3 bottom view). The ridge was located neatly at the end of the slide - as if it was meant that it could be mounted in this fashion.

Apart from all of the risk factors mentioned in the above posts, if you look carefully at image 4 the ridge does not fit tightly against the end of the slide (indicated by arrow) and any attempt to "centre" the jaw immediately loosened the screw.

Any experienced operator, and I have been using metal and wood lathes for 30+ years, would not consider mounting jaws in this fashion, but I can understand an inexperienced turner doing so, particularly if it looks as though it was "intended" to be an alternative mounting option.

While it is easy for us to blame the operator, I feel that some blame must be attributed to the manufacturer. Top quality manufacturers ensure that the jaws can only be fitted in the correct manner or it is very obvious by not seating properly, for example, that this is not the correct way to fit the jaws. While operator error or lack of training is most often reposible for the use (or abuse) of the chuck in this manner, it is also a serious safety concern which needs to be addressed by some manufacturers.

Bob