Mikel Levy
Aluminum
- Joined
- Oct 19, 2009
- Location
- Seattle
OK, so it will make an effective door stop also, but seriously, are there other work-holding functions it can provide that add to its repertoire?
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Is a scroll/self-centering 4-jaw chuck useful for more than holding square work?
- Thread starter Mikel Levy
- Start date
- Replies 17
- Views 3,784
dsergison
Diamond
- Joined
- Oct 23, 2003
- Location
- East Peoria, IL, USA
octagonal work! lol.
bored in place soft jaws.
bored in place soft jaws.
DJ2
Aluminum
- Joined
- Feb 12, 2007
- Location
- Ontario, Canada
Believe it or not, a scrolling four-jaw chuck securely holds a six-sided bar too, try it out.
And it still holds round bar, with the additional holding power of an extra jaw vs. a three-jaw chuck.
And it still holds round bar, with the additional holding power of an extra jaw vs. a three-jaw chuck.
awake
Titanium
- Joined
- Jan 24, 2006
- Location
- Angier, North Carolina
Also useful when you need to turn something off-center by a specific amount, e.g., for a cam mechanism.
greggv
Hot Rolled
- Joined
- Feb 15, 2006
- Location
- so cal, usa
And it's good for really dialing in round work!
Danny VanVoorn
Titanium
- Joined
- Nov 3, 2002
- Location
- St.Louis, Missouri, USA
Some may find them perfectly suited for their class of work and I say this with no mal-intent but I can't see it working well for anything including square stock unless the stock is perfectly proportioned to inaccuracies in the chuck. I guess for quick square stock it would center the work for a light face off and a center drill but it seems like one jaw will always have less contact than the others?
Dan
Dan
Mikel Levy
Aluminum
- Joined
- Oct 19, 2009
- Location
- Seattle
I would think that unless the geometry of both the chuck and the round part were perfect, the clamping force exerted by each jaw would be different from its neighbor; conceivably a badly made chuck could effectively be clamping on only two opposing jaws (this would be true for square stock as well}.
Mike
Mikel Levy
Aluminum
- Joined
- Oct 19, 2009
- Location
- Seattle
awake
Titanium
- Joined
- Jan 24, 2006
- Location
- Angier, North Carolina
Oops - strike my earlier comment. Like others, I automatically thought of an independent-jaw chuck. Apologies!
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Derek Smalls
Stainless
- Joined
- Jan 6, 2014
- Location
- Coventry RI
They are on all the chucks of this type I've seen. It would seem to me they would absolutely need to be, or at least one jaw would not be doing any real clamping, as others have noted.
The ones I've seen have a scroll which moves all the jaws at the same time, as well as an adjustment on each jaw, just like a regular four jaw has.
I actually have one of these chucks but it doesn't fit anything I own so I've never used it. It's about 16"-18" with a L 2???mount if anyone is interested in it I'll get more details.
HuFlungDung
Diamond
- Joined
- Jan 19, 2005
- Location
- Canada
I have a milling fixture I use that has quantity of four eight inch 4 jaw scroll chucks set on a subplate. These are cheap Shars chucks but surprisingly, they seem to do a good enough job of gripping. I use this to make one product from a 5" aluminum round about 2.25" high. I'm not concerned about the repeatability of their centering, because the part gets located elsewhere by a feature milled in the first side operations. Rather it was a matter of getting access for a long endmill to actually dip down through the bottom of the stock on opposing sides of the part, so a 3 jaw couldn't work.
I chuck these parts with their 'as extruded' OD (which is not very round) and face them and interpolate a good circle to grip on, then turn them over and chuck firmly on the accurate round. Either way, I've never had issue with the stock lifting or moving, so the chucks work well enough.
There are a lot more leverage forces going on when the work is revolving in a lathe. So without individual jaw adjustments, a 4 jaw scroll won't be useful for chucking solid bars, but may do a good enough job if thin wall pipe is being gripped.
I chuck these parts with their 'as extruded' OD (which is not very round) and face them and interpolate a good circle to grip on, then turn them over and chuck firmly on the accurate round. Either way, I've never had issue with the stock lifting or moving, so the chucks work well enough.
There are a lot more leverage forces going on when the work is revolving in a lathe. So without individual jaw adjustments, a 4 jaw scroll won't be useful for chucking solid bars, but may do a good enough job if thin wall pipe is being gripped.
Mikel Levy
Aluminum
- Joined
- Oct 19, 2009
- Location
- Seattle
Interesting. All the ones I've seen have the scroll but no other adjustment mechanism.
---Mike
Nope, they're just junk. I say that from personal experience. My first boss bought one, because at a glance it seems like a good idea, in practice they're crap. The problem has already been posted, the accuracy of the jaws opposite the other needs to be very tight, let alone what you are trying to hold.
R
R
L Vanice
Diamond
- Joined
- Feb 8, 2006
- Location
- Fort Wayne, IN
Post No. 1 asks about a 4-jaw scroll chuck, which has all the jaws operated only by a scroll. Some replies confuse it with a 4-jaw independent chuck, which has no scroll. Other replies confuse it with a combination chuck or "System Wescott" as the Germans call it, which has both a scroll and independent jaw adjustment.
I have a Swiss 165 mm 4-jaw combination chuck that is very useful indeed. It can be one's only chuck if one wishes, because it can hold about any shape with all the jaws gripping and it can be adjusted to perfectly center the work. See the first two pictures.
It is not my only chuck, so I tend to just use it for a job the 3-jaw and 6-jaw adjustable chucks do not do well. Which is turning batches of eccentric cams.
Some of the chuck companies also make combination chucks with 3 jaws. They can grip round and hex stock and can be adjusted to center as well as an adjustable chuck, but have more adjustment range, also good for turning eccentrics. See the last three pictures.
One disadvantage of combination chucks is the body is thicker and heavier than a plain scroll or independent chuck.
One excellent use for 4-jaw scroll chucks that has not been mentioned is for holding approximately square pieces of wood. The wood compresses so that all four jaws grip securely, even if the wood or the chuck are not perfectly accurate.
Larry
I have a Swiss 165 mm 4-jaw combination chuck that is very useful indeed. It can be one's only chuck if one wishes, because it can hold about any shape with all the jaws gripping and it can be adjusted to perfectly center the work. See the first two pictures.
It is not my only chuck, so I tend to just use it for a job the 3-jaw and 6-jaw adjustable chucks do not do well. Which is turning batches of eccentric cams.
Some of the chuck companies also make combination chucks with 3 jaws. They can grip round and hex stock and can be adjusted to center as well as an adjustable chuck, but have more adjustment range, also good for turning eccentrics. See the last three pictures.
One disadvantage of combination chucks is the body is thicker and heavier than a plain scroll or independent chuck.
One excellent use for 4-jaw scroll chucks that has not been mentioned is for holding approximately square pieces of wood. The wood compresses so that all four jaws grip securely, even if the wood or the chuck are not perfectly accurate.
Larry
Mikel Levy
Aluminum
- Joined
- Oct 19, 2009
- Location
- Seattle
Funny enough I ordered a 6" 4-jaw scroll chuck just a couple days ago, should be here tomorrow. In my case the idea was to have an extra support jaw as it'll be gripping close to its max capacity which leaves a lot of room between jaws in a 3 jaw, it'll live with bored to size soft jaws all the time which should help get a more even gripping force on all jaws I hope. Worse case its just another $1k spent on a toy I guess.
Well, it just arrived.
This is a Bison brand, so pretty good/tight and brand new.
As expected if you're chucking mostly rough round bar, you're better off with a 3-jaw to get contact on all 3, or an independent 4 jaw.
But if the work is round within a couple thousands it looks like it should hold ok, but over years of use/wear who knows. I guess I'll find out.
I can always use it as a 2 jaw chuck too if needed and it might have other uses on the mill.
Anyway, back to work...
This is a Bison brand, so pretty good/tight and brand new.
As expected if you're chucking mostly rough round bar, you're better off with a 3-jaw to get contact on all 3, or an independent 4 jaw.
But if the work is round within a couple thousands it looks like it should hold ok, but over years of use/wear who knows. I guess I'll find out.
I can always use it as a 2 jaw chuck too if needed and it might have other uses on the mill.
Anyway, back to work...
StinkyDan
Aluminum
- Joined
- Jun 6, 2016
- Location
- Outside chicago
Could be used for anything you could make jaws for really. Just like a 3 jaw but with 1 more jaw in it. Dont overthink it.
