3 jaw vs 4 jaw scrolling chucks

[Aaron_W]

I understand the use of a 4 jaw independent chuck for odd shaped or off center parts, but wondering why I would want a 4 jaw scrolling chuck? I guess it would hold square stock better, but are there other reasons?

 

[Ray C]

I understand the use of a 4 jaw independent chuck for odd shaped or off center parts, but wondering why I would want a 4 jaw scrolling chuck? I guess it would hold square stock better, but are there other reasons?

The more jaws you have, less pressure-per-jaw is needed to hold a part. In other words, with more jaws doing the holding, each one does not need to grab as tight. And for this reason, people often get 6 jaw chucks. They are much less likely to distort a part from applying too much pressure in localized areas.

Ray C.

 

[mikey]

I have a 4 jaw scroll chuck for my Sherline. I bought it to hold square stock and collet blocks. You can use a 4 jaw independent to hold square stuff but then you have to center it and that can take some time. A scroll chuck makes it fast and easy. Given the low cost of the chuck, I thought it was a good idea and I've used it numerous times. It will also hold round stock quite well, including pipe, so it isn't just for square stock.

 

[Ray C]

Another good reason for more jaws... If our are ever doing side-pressure knurling or parting, the workpiece is much less likely to get pushed sideways out of the jaws. Let's say you have a piece that happens to be the same diameter as the space between two jaws as they meet against the part. With high pressure against the side and low RPM, the part can get forced in the space between the two jaws.

Ask me how I know this.

Ray C.

 

[Aaron_W]

Ok, so it does have more use than just square vs round. I had seen the comments about 6 jaws causing less pressure so makes sense 4 jaw would do the same, as well as just in general holding the part a bit more securely. I wasn't sure how much of a specialty item it was.

3 and 4 jaw chucks are the special this month at Sherline, so my wallet was hoping you guys would say they were just dust collectors. If I can behave myself for two more weeks, being off sale will help the willpower.

 

[mikey]

I have two 3JC, two 4 jaw independent chucks, a 4 jaw scroll chuck and an ER32 chuck for my Sherline lathe. There are times when all are useful but the 4 jaw scroll is used least of them all. I vote for not buying it unless you work with a lot of square stock.

 

[mksj]

A couple of things to consider, a 4J independent is often used because you can dial out any runout if you need to be spot on with regard to TIR The downside of many 4J chucks is the jaws tips are often wide and rough, i.e. made to hold bigger stock. Both a 4J and 6J scroll hold a piece by opposing jaws, if the sock is not perfectly round and symmetrical it may no be firmly held. Probably less of an issue with thin wall tubing because it will deflect. Truth be told similar to Ray C, I have had smaller round stock squeeze through/twist from the jaws on my 3J scroll. One reason why I prefer a collet chuck for smaller round stock, but with one caveat. A couple of us use a combination 4J chuck, which has a scroll section with independent jaws that ride on the scroll plates. The jaw tips are 0.2", so you can hold quite small stock securely and you can adjust the pressure of each jaw independently and get the TIR way down. The scroll will repeat to better than 0.002", this is dependent on the pressure of each jaw. I use my 5C most of the time, followed by the 4J combo, much less frequently a 3J scroll Set-True if I have to do a lot of repeat in/out of the jaws, and a 4J independent rarely only for bigger heavier stock that I need to hold securely.

A 4J scroll would be low on my list (i.e. bottom), I would go with a collet system first, a 4J independent is more versatile while a combo offer the best of both. Of course all this is dependent on the type materials and size you are most frequently turning, along with the lathe size.

 

[Aaron_W]

Ok, back burner then, I'll put it on my watch for a great deal list unless I specifically find a need for it. My wallet thanks you.

 

[Suzuki4evr]

I understand the use of a 4 jaw independent chuck for odd shaped or off center parts, but wondering why I would want a 4 jaw scrolling chuck? I guess it would hold square stock better, but are there other reasons?

I just bought myself a 4jaw scroll bison chuck and I am very happy I did,because clamping is much better than the 3jaw. Although I still use the 3jaw,I prefer the 4jaw. My 2cents on the subject

 

[Aaron_W]

Out of curiosity does diameter play a part? I imagine the closer to maximum capacity with the jaws at their most distant, clamping force is at its weakest.

Just looking at the the typical 1/4-1/2" stock I work with and in my 3.1" 3 jaw chuck there isn't much room between the jaws for the work to slip out of. If I was turning a 2 or 3" piece on the other hand.