6 jaw vs 4 jaw chuck

[3strucking]

I am wanting to purchase a better quality chuck to replace my current 8" 4 jaw. I will use it for anything over 1.375" as I have collets up to that. Would a 6 jaw gator be better than a 4 jaw? I will also need a DIN 55027 back plate. Any recommendations on brand? I would like to stay under $1k.

 

[FOMOGO]

A 6 jaw chucks major advantage is holding thin wall material to keep it from deforming. A 4 jaw chuck is used for holding odd shaped work pieces, and for achieving minimal runout as all 4 jaws can be adjusted indepently. With 3 and 6 jaw chucks all the jaws close simultaneously. Mike

 

[Silverbullet]

As the others may tell you. It's a good idea to have a four jaw independent chuck , it allows you to indicate the work piece to at least half thousandth concetricity. But the six jaw chuck will also give you two jaw , three jaw , and the six jaw all in one. Now let me add a joker to the deck. There are four jaw scroll chucks that work like a three jaw. Years ago they made the four jaw with both independent and scroll in one. They may still be around but I bet they are costly. Have I confused you I hope Not , but trying to help you understand about chucks.

 

[Doubleeboy]

in my experience 6 jaw does not have holding power of 4 jaw, nice for delicate thin wall parts though

 

[mksj]

A 6 jaw chuck can have more issues with swarf build up, but this is often an issue no matter what chuck you use. Standard 4J independent chucks often have fairly wide and coarse jaws, so you are limited to mostly larger stock and they take longer to setup (dial in the TIR) if an independent. The latter is time consuming if you do any repeat work. They do make both 4J and 6J in a scroll versions, at that price level I would strongly recommend going with a set-tru type of chuck. Bison does make a 4 jaw combination chuck which has both a scroll and independent jaws. A few of the forum members use this chuck, they work very nicely and their 8" chuck can hold small stock down to 0.200". The repeatability of the scroll is around 0.002", and with the tweaking of the independent jaws you can get the TIR down to nil and holds the work very securely. I do find that often stock may not be perfectly round or rough on the surface, so a standard scroll 4J or 6J may not apply symmetrical pressure on all the jaws. With a combination chuck, you can tweak each jaw which may be a benefit. I machined twin keys for my combo Bison, takes about 30 seconds to tweak the TIR, and love the scroll for getting parts in and out quickly.

If you look at the Bison chucks, the price for a Set-Tru 6J is less expensive than their 4J combination in a 8", the set-tru backing plate is more expensive so the total price is probably pretty close. They have gone up about 25% in cost since I purchased mine about 4 years ago. Since the combination chuck takes standard backing plates (you may need to tweak the register) it gives you more options. On my Bison 8" combination, I use a Gator backing plate, which was 1/2 the price of the Bision version. Quality Machine Tools sells Bision chucks, may be worth checking into, Grizzly also sells them and sometimes you can get a 5% discount when you sign up for their catalogue.

So other less expensive options, Gator is somewhat hit or miss these days, and the pricing is often about10-15% less than Bison so not worth the difference in my book. Shar's carries their version of a Zero-Set 6J scroll chuck that another forum member purchased and was pleased with it's performance, but I do not believe they make a corresponding DIN 55027 back plate. If you do not use the larger chuck frequently, then maybe consider a better quality 4J independent or a set-tru 3J scroll in an 8". Unless you do a lot of thin stock, then a 6J scroll does not add a lot.

 

[Wreck™Wreck]

A 6 jaw chucks major advantage is holding thin wall material to keep it from deforming. A 4 jaw chuck is used for holding odd shaped work pieces, and for achieving minimal runout as all 4 jaws can be adjusted indepently. With 3 and 6 jaw chucks all the jaws close simultaneously. Mike

Actually there are 4-Jaw scroll chucks available from Bison for instance, excellent for square work but good for rounds of course.

Last year I told my employer that I needed an independent 4-Jaw for a job, he ordered the wrong thing and a scroll chuck turned up the next week, it went right back naturally.

 

[bss1]

Mark

Do you find yourself using your Bison 4J combo or your P&B 3 jaw more? Or does the use depend more upon the job?

 

[mksj]

Do you find yourself using your Bison 4J combo or your P&B 3 jaw more? Or does the use depend more upon the job?

Well I use my 5C most of the time, usually for anything 1" and under, it is just easier and safer on the hands. But when I need to do very close tolerance work where I need a repeatably of better than 0.001" like where parts need to fit together very precisely I use the 4J combo because I can pretty much zero out the TIR and it holds the pieces very true in the axial dimension. Also the jaws and profile do not stand out as much as a conventional 4J, i.e. the piece/jaws hold the stock in the chuck where a standard 4J has taller/larger jaws from the body. The 4J combo also works very nicely for both large and small stock. It will hold small stock better than a 3J. The 6" PBA is a Set-tru Scroll chuck I use when I need to do a lot of repeat work, so if I need to make a lot of pieces from stock it is much quicker and for the most part it maintains a TIR of better than 0.0005". The PBA uses two piece jaws and I did have a recent issue when I reversed them to hold some large stock, and then flipped them back the other way I had some problems with having to reset the chuck alignment screws. The two piece jaws also needed to be lightly tensioned on some round stock in order to be aligned correctly when clamping them down. So now I always recheck the TIR whenever I flip the jaws and make sure they are properly seated.

So I use all three, ranking wise and think it depends a lot on what you work on. If you do a lot of barrel or long bar work and need to be on the money, then the 4J combo will hold the stock very securely and you are able to get it very true. If you are only occasionally are doing large stock, odd pieces than go with a standard 4J independent. Because I do a lot of dimensional work piece that are not turned and then cutoff, and I need to flip it back and forth in the chuck, a Set-Tru chuck dimensional stacking errors of repeatedly rechucking a piece would be expected to be less than a conventional scroll. I also sometimes mark the piece relative to a chuck jaw so it is always held in the same position. I have not had good success with holding small pieces in a 3J scroll, I find they often twist or get damaged.

If you need just 1 chuck, then my vote would probably be a 3J scroll set-tru, then some form of collet system for small stock (this could be also something that mounts in a larger chuck). I got the 8"Bison 4J combo at the time as my second chuck, I needed something to hold larger stock and the 4J independents was a real PTA to remove stock and then redial the chucks back in. I love using the 4J combo, and it is surprisingly smooth at speed (it is also heavy). I eventually went with a 5C collet system, accumulated collets over time. So I use all of them, they each have their strengths, if you can afford a 4J comb as a secondary chuck then I recommend it.

 

[Firestopper]

I second everything Mark has posted on the 4J combo chuck (Bison). Its a great improvement for 1" and larger work that requires reset-up. I seldom use my 3J scroll chuck these days. I also added a 5C collet system that was overdue, another great addition for 1" or less work as Mark also mentioned.

 

[Silverbullet]

If I had the need , now I know they still make the dual four jaw chuck it would be highly prized in my collection . I shall now attempt to try to make one mine . If you think about it three jaws if they had adjustments on there jaws would make them more dependable. I know adjust true chucks will for the set , I was just thinking of them independently. If you wanted to run a oblong or egg shape.