Ordering a 6-jaw Chinese Chuck-

[ErichKeane]

So I currently have 2 3 jaw chucks, a 12" that requires an engine hoist to install, and a 8 inch that has a couple of broken teeth in the tightening mechanism. I typically use the smaller one, but it has quite a bit of runout as well. I also find myself switching between the 4 jaw, collet chuck, and smaller 3 jaw pretty often. I see that Abom79 has a 6 jaw that he says is better concentricity wise than a 3 jaw, so I figured I'd give it a shot!

I found a cheap backplate for my lathe that has been left unused for a while (L1 backplates are worth their weight in gold it seems!), and bought this: https://www.ebay.com/itm/6-jaw-chuc...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

My 4 jaw is the same brand and seems reasonably good, and I plan on surface grinding the face if it seems too far out. Despite being the cheapest one on ebay, the seller seems to have shipped via UPS quite quickly (despite a month long expected delivery date, I should be getting it in roughly a week overall, this Thursday). I'm cautiously optimistic that this 6 jaw will be good enough to just use on the lathe!

 

[aliva]

I'd be curious of the repeatability and concentricity. Hopefully it's within an acceptable range.
please keep us posted.

 

[ErichKeane]

I'd be curious of the repeatability and concentricity. Hopefully it's within an acceptable range.
please keep us posted.

Will do! I'm curious as well, I haven't decided whether I'll do a teardown before trying it out yet, but I likely will. I figure as long as it is close-ish it can take the place of my 3 jaws.

 

[mikey]

Abom's 6 jaw chuck is an adjust-tru type chuck. The one you ordered is not; it is just a 6 jaw scroll chuck so it will run out about as much as any scroll chuck does, about 0.002-0.003" or so.

 

[ErichKeane]

Ah, that makes more sense an adjust tru is just an undersized recess plus some set screws in the chuck to recenter it, right? If I feel motivated that seems easy enough to change on this one.

 

[mikey]

An adjust-tru has a set of 3 or 4 hardened dog nose set screws in the rear body plate of the chuck. Those screws bear on the nose of snout formed on the back plate to allow you to shift the chuck around. Your chuck does not have that provision. It is just a scroll chuck that happens to have 6 jaws instead of 3.

You can turn the register/nose/snout of your back plate a tad undersized and this will allow you to knock it into alignment. However, it will be aligned only for the diameter you used to adjust it. If you work with thin walled or plastic a lot then a 6 jaw makes sense. If you do production work with the same nominal diameter stock then you can adjust the chuck on the back plate to minimize run out and it will be pretty good for that diameter stock. If you change diameters then the setting will need to change if you must run tight tolerances. If you're just doing first operations work then none of this really matters; just use it.

 

[ErichKeane]

How does the adjust tru work for multiple diameters? Or does it have the same "single diameter" issue?

 

[mikey]

Okay, folks have the idea that an adjust-tru can be adjusted once and it will be as accurate as a 4 jaw independent and will work for any diameter you put in the chuck. This is not true, simply because it is a scroll chuck. The nature of a scroll chuck is that run out changes depending on where on the scroll you happen to be locking down on. If you are turning multiples of the same diameter then you can adjust the chuck to run that diameter accurately because you're locking down on the same spot of the scroll. However, if you change to another diameter then you have to reset the chuck.

Thing is, if you use a 3 or 6 jaw scroll chuck for first operations work - that means the first time you turn something - then that chuck will be accurate, even if it isn't an adjust-tru chuck. It is when you do second operations work on a piece that has already been turned or is accurately ground that you must have the adjustability of an adjust-tru or 4 jaw independent chuck in order to control run out.

Bottom line is that you ordered a scroll chuck and if you use it like any 3 jaw scroll chuck it will be fine. If you need the ability to adjust run out for second operations work and you need the speed of a scroll chuck then you need an adjust-tru chuck. Return the chuck you ordered and buy what you need.

There is one other option. You can buy a Bison combination chuck, which is a standard scroll chuck but each jaw is independently adjustable. Big bucks but it is a cool configuration.

 

[middle.road]

Not a Set-Tru? Check out this video from Joe Pie.

 

[darkzero]

6 jaw that he says is better concentricity wise than a 3 jaw

More jaws doesn't really make a difference for concentricity or accuracy. Really it's the quality of the chuck. As Mike said, it's just a plain back chuck, runout will be no better than a 3-jaw chuck. Even most quality name brands only guarantee .002" TIR for plain back chucks.

Will do! I'm curious as well, I haven't decided whether I'll do a teardown before trying it out yet, but I likely will. I figure as long as it is close-ish it can take the place of my 3 jaws.

IMO, every China chuck should be disassembled & gone through. In my experience Gator chucks are better but I still did. They get carried away with the amount of grease they put in them.

Unfortunately a 6-jaw chuck is not a replacement for a 3-jaw chuck IMO. More jaws doesn't mean more holding power on a scroll chuck. You mentioned that you have 12" chucks so you must have a decent size lathe. If you do heavy turning you may find that a 6-jaw will not hold as well as a 3-jaw & the work piece will slip, usually getting pushed back into the chuck. I don't have a big lathe & there's times where I had my 6-jaw slip. Because the scroll has to transmit force through 6 jaws instead of 3 you'd have to tighten the pinion(s) more than you would on a 3-jaw to get a really good hold of the work piece. A 6-jaw usually won't dig into a part like a 3-jaw or 4-jaw independent can, not necessarily a good or bad thing depending on your needs. Sure you can crank down on the pinion harder but if you do this repeatedly on short parts you risk bell mouthing the jaws over time.

6-jaw chucks are considered 2nd op chucks. They're more like a collet in a sense. Their main advantage is for holding thin wall parts, less chance of deformation. They don't hold parts well that aren't perfectly round. I use cold roll stock which is usually ok but if the stock is not very round a 6-jaw will have a hard time holding it. I find a 6-jaw chuck has less chance of leaving jaw marks on a machined part. So in that sense, they will hold a machined part better than a 3-jaw with less chance of damage to the part from the jaws. There's more but that's the basics.

I may make 6-jaw chucks sound like there are more disadvantages than advantages. That may be true to most. Unless you need the advantages of a 6-jaw chuck, IMO it's better to go with a good quality 3-jaw for a primary use chuck. With that said I still primarily use a 6-jaw chuck although I may not need it as much these days. They sure are sexy though. I love using my 6-jaw but I still use a 3-jaw too.

Ah, that makes more sense an adjust tru is just an undersized recess plus some set screws in the chuck to recenter it, right? If I feel motivated that seems easy enough to change on this one.

I'd be curious to see your method if you plan on doing this. Please share if you do. Most plain back chucks don't have room on the body for set screws to convert it into an adjust-tru. You can make it a tap-tru but without set screws to lock the chuck into place, under heavy turing they can possibly get knocked out of alignment.