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4 jaw Self centering chuck

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dixie14/08/2010 18:57:34
31 forum posts
Hello. Are 4jaw s/c chucks any better with normal circular material than three jaw s/c chucks. I can see the advantage for turning a round on something perfectly square or drilling through the centre of a square, but are there enough advantages to justify the cost. I ask this question because someone said get your self a four jaw s/c, but could not say why when pressed. 
Bogstandard14/08/2010 19:39:00
263 forum posts
I use my 4 jaw self centring most of the time, except when using hex bar.
 
I have found over the years, all my 4 jaw sc chucks have slightly less runout than my standard 3 jaws. usually less than 0.002".
 
I find them just a little more versatile for my personal needs as I tend to use round and square stock more than round and hex.
 
For a first chuck, I would definitely go for a three jaw, then a four jaw a very close second.
 
Just as a point of interest, no matter which chuck you buy, get a set of soft jaws to fit at the same time. I won't buy a chuck unless soft jaws are available for it, and if used correctly, soft jaws can make precision machining a piece of cake.
 
Bogs
 
 
NJH14/08/2010 20:13:42
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2314 forum posts
139 photos
I guess that a 4-jaw s/c will hold round stock a bit more firmly than a 3- jaw and it's very useful for holding square stock. It won't however hold hexagon stock which is, perhaps, a more common requirement ( well for me anyway). I managed with a 3-jaw s/c and a 4-jaw independant for many years but recently treated myself to the 4-jaw s/c. Nice but if I could only have one I would go for the 3-jaw.
 
Norman
Stub Mandrel14/08/2010 20:46:01
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4318 forum posts
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In theory a three-jaw chuck will hold stock firmly with all three jaws, but unless it (and the material) is perfect a four-jaw chuck will only give full contact on three of the four jaws. Just as a three-legged stool will stand without wobbling on a flagstone floor, but you can spend hours ages making a four-legged table wobble free on a flat floor!
 
In practice I'd guess there is enough give in any decent chuck to mean this isn't an issue (i.e. you can always nip the jaws up a bit after they make contact). I reckon a badly worn 3-jaw will still grip the work (though it may run out badly) but a badly worn 4-jaw will probably allow the work to wobble.
 
Neil
 
 
dixie17/08/2010 20:00:53
31 forum posts
Hi Many thanks to all those who gave an opinion to my query, I dont think I need to get one just yet.. Thanks Again Brian.

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