10" 4 jaw chuck almost 4" center hole looks good to me

[lalatheman]

Just saw this chuck listed on ebay,

https://www.ebay.com/itm/1-pc-Lathe-Chuck-10-4-Jaw-Independent-Reversible-Jaw-K72-250-sct888/173108997903

The 4" hole is the selling point for me....when its needed , it would be priceless. Looks like the seller has sold a lot of these, does have 30 returns.

I have a nice older 10" 4 jaw that works fine,but this chuck could open doors ...any thoughts ?

Dave Lawrence

[danlb]

We don't know how big your lathe is, so it's not clear if the protruding jaws will be an issue in regards to hitting the ways.

The page that you reference on ebay does show interesting limits:
Internal Jaw: Clamping Range A-A1: 0.590"-5.118"

External Jaw: Clamping Range B-B1: 3.149"-9.842"

I suspect that the 2.5 inch wide ring of the chuck's body does not support the (approximate) 3 inch long jaws very well when the jaws are extended.

The good news? It will definitely clamp a 4 inch diameter piece inside the bore of the chuck without much of the jaws protruding.

Dan

[BCRider]

I'm not keen on the long unsupported length of the jaw extension for smaller items. But as a SECOND four jaw for where you want to take advantage of a 4" "pot" for the length of the chuck body I think it's a superb deal for the cost.

Of course if it arrives and the jaws wobble around a lot such that it can't hold the ends in any sort of parallelism then it won't be much more than a REALLY good paper weight. But if there's much of any quality at all then it's a helluva deal.

As I say I would not trash or trade your other four jaw. Or perhaps I would? Perhaps trade it for a 6" four jaw that can hold the smaller parts then bring out this one for the larger stuff.

Of course not many of us have a spindle that will take 4" stock. But I gather you'd be OK with the big hole only being the depth of the chuck body.

[Glug]

I have a nice older 10" 4 jaw that works fine,but this chuck could open doors ...any thoughts ?

"Could prop open doors"

Could be a fine deal. Others have already mentioned some points that come to mind. You didn't mention the lathe this is going on, and the spindle bore. Or maybe you aren't even going to put it on a lathe. Another thing I notice is the width of the jaws appears a bit narrow and light duty, especially for a large bore, with the unsupported jaw section. That makes the fit and area of the tongue-groove even more critical.

Curious what the weight is, especially with the fairly low shipping cost.

[OaklandGB]

I'm new to the forum and at 65, returning to amateur machining after decades, so may not be up to speed on newer imported equipment yet. However, I noticed in the OP's eBay link that the new Sanou chuck pictures showed quite a bit of staining for a new piece of machinery. I'd guess that they'd at least attempt a clean up for the photo shoot. I took delivery of a new lathe last week and the included...in a sealed box... Sanou 4 jaw chuck,...in it's zip lock bag..was significantly stained...new. My chuck is covered about 40% with this dark staining, but appears to be surface only and I assume will come off with some cleaning and Scotch brite, but makes me wonder.. is the Sanou factory roof is leaking. Or, are they packing these still wet with a water based cutting fluid?

[Mcgyver]

at around 10% of the cost of a Pratt, Rohm or Bison, I'm a doubting Thomas. otoh I keep hearing about people pleasantly surprised with new stuff out of China, so maybe worth a try?

as context, I'm of the view that the accuracy of a 4 jaw is quite important, more so than the 3 jaw. Newer guys thinks if you dial in work, what's it matter? (I once did) When you hold work with the 3 jaw, you're not expecting the surface held to be concentric to that turned. You use it when 1) tolerance allow or 2) when you can plan the workflow such it doesn't matter - i.e. all surfaces turned in one setting.

You use the four jaw mostly because you need the gripped surface concentric to the turned. If out much, it will make life miserable. Accuracy means does it clamp work parallel to the chucks/lathes axis? Dial in to .0002" at the chuck then move the indicator 3 or 4" inches out and check again - what do you get? A good one is it will be really close. A bad one might be 6 thou - what does that do to your careful efforts at accuracy and concentricity? There are ways around it, but its less than ideal and a time consuming pita imo verses dialing it in and having it pretty close.

[BCRider]

.......You use the four jaw mostly because you need the gripped surface concentric to the turned. If out much, it will make life miserable. Accuracy means does it clamp work parallel to the chucks/lathes axis? Dial in to .0002" at the chuck then move the indicator 3 or 4" inches out and check again - what do you get? A good one is it will be really close. A bad one might be 6 thou - what does that do to your careful efforts at accuracy and concentricity? There are ways around it, but its less than ideal and a time consuming pita imo verses dialing it in and having it pretty close.

This concern over maintaining parallelism of the longer internal jaw edges is what I was referring too above. And yeah, it would make or break the deal.

[Glug]

Dial in to .0002" at the chuck then move the indicator 3 or 4" inches out and check again - what do you get?

I call that skew. And if it is out you might even say it is Skewed Up :P

Of course an independent jaw chuck, or set-true, can correct offset but skew is more of a bugger, especially depending on the source. If they were two piece jaws you'd at least be able to shim that aspect. If they are a tooth-faced jaw than it is pretty clear the jaws were probably not ground in place (as a smooth face jaw can be).

I note the advert doesn't give any specs or tolerance. I suppose, before fitting a backing plate, you could lay the thing on a surface plate, chuck a TGP or similar rod, and then indicate along the vertical surface to check for skew.

[wierdscience]

at around 10% of the cost of a Pratt, Rohm or Bison, I'm a doubting Thomas. otoh I keep hearing about people pleasantly surprised with new stuff out of China, so maybe worth a try?

as context, I'm of the view that the accuracy of a 4 jaw is quite important, more so than the 3 jaw. Newer guys thinks if you dial in work, what's it matter? (I once did) When you hold work with the 3 jaw, you're not expecting the surface held to be concentric to that turned. You use it when 1) tolerance allow or 2) when you can plan the workflow such it doesn't matter - i.e. all surfaces turned in one setting.

You use the four jaw mostly because you need the gripped surface concentric to the turned. If out much, it will make life miserable. Accuracy means does it clamp work parallel to the chucks/lathes axis? Dial in to .0002" at the chuck then move the indicator 3 or 4" inches out and check again - what do you get? A good one is it will be really close. A bad one might be 6 thou - what does that do to your careful efforts at accuracy and concentricity? There are ways around it, but its less than ideal and a time consuming pita imo verses dialing it in and having it pretty close.

Note: Coversational tone of voice,not a rant

The same thing can be done with a 3-jaw and a set of soft jaws.Lash out the chuck,skim the jaws with a boring bar and presto,you are now working at the limits of the lathes spindle runout.Plus if you have 25 parts to do instead of the one,chucking times drop to 3 seconds each.

What pains me is the rise of the "4-jaws are wonderful and 3-jaws are junk" cult on the internet these days.Mostly led by people who don't understand how a 3 jaw works,don't know how to maintain one and who's only experience with one revolves around the 75 year old chuck that came on their clapped out (insert brand here) lathe.A quality 3-jaw chuck kept in good trim is capable of handling 95% of the work a given lathe will ever see IME.If the 3-jaw allows for running soft jaws,then that number climbs to 98% and infact allows work to be done that cannot be done in a 4-jaw (thin wall sleeve boring comes to mind).

And you are right,the quality and condition of a 4- jaw is important.Most of the ones I have worked with,in most shops I have worked in, were clapped out junk.Bellmouthing is a major issue either due to simple wear or people reefing on the chuck wrench with a cheater to get that last 5 thou pushed over

Most are cast iron bodies,not even semi-steel and certainly not forged steel which limits longevity and general stength.

I am not hating on 4-jaws,just defalting some of the bubble that's grown around them.They have their uses and it's a good idea to have one,especially the slotted type that can double as a faceplate.But the reality is even in the homeshop a 4-jaw will end up spending most of it's time gathering dust.

The chuck the OP posted will probably serve him as well as any other,assuming the jaws fit the slides tight and the machined surfaces of the slides are ground or atleast milled to a fine surface finish.Some China 4-jaws I have seen the slides looked like they where chewed in by a denture wearing Beaver.

Next year I may buy a new late for the shop.If I do I am seriously considering adding one of these to the arsenal-

https://www.ajaxtoolsupply.com/biscch8plmo4.html?cmp=googleproducts&kw=biscch8plmo4&gclid=EAIaIQobChMIxpzbwIez3AIVhYzICh3WQgGCEAQYBCABEgLylvD_BwE

I used one a couple years ago and they are nice,possibly the best of both worlds.

Rightnow I want one of these for my welding positioner-

https://www.ebay.com/p/1-PC-Lathe-Chuck-6-4-Jaw-Self-Centering-Reversible-Jaw-K12-160a-Sct888/6012078788?iid=173060102392&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D52475%26meid%3D9cf2621a80104e3c91938605570ffdba%26pid%3D100005%26rk%3D10%26rkt%3D12%26sd%3D173108997903%26itm%3D173060102392&_trksid=p2047675.c100005.m1851

[J Tiers]

Agree.

It IS true, though, that you probably want to finish all work in one chucking unless you do skim the jaws or use soft jaws. All 3 jaws have runout, and unless it is an adlust-tru, or bored soft jaw, there is not a lot you can do about it that works for repeat chucking reliably.

I keep one of the 3 jaw chucks on most of the time just for convenience. I have enough practice with the 4 jaw to get it set up fast, but no need to do it all the time. there are things only the 4 jaw will do, but they are not always required.

[smithdoor]

The one on ebay is a 4 Jaw Self Centering
They make 3, 4 and 6 Jaw Self Centering chucks

[wierdscience]

Agree.

It IS true, though, that you probably want to finish all work in one chucking unless you do skim the jaws or use soft jaws. All 3 jaws have runout, and unless it is an adlust-tru, or bored soft jaw, there is not a lot you can do about it that works for repeat chucking reliably.

I keep one of the 3 jaw chucks on most of the time just for convenience. I have enough practice with the 4 jaw to get it set up fast, but no need to do it all the time. there are things only the 4 jaw will do, but they are not always required.

Edit: Yes,of course you want to complete the part in one chucking whever possible,3/4/6 jaw or not,that's just common sense.

Repeatbility-Not necessiarily,on a quality 3-jaw the final step in manufacturing is to chuck a lash ring and then do the final grind on the jaw faces.When that is done,the pinion used to clamp the lash ring is marked.That pinion is known as the master pinion.It is the only one of the three that will produce repeatable runout because of the way a scroll chuck is designed.On a Bison 3-jaw the master pinion is marked usually with a -0- stamped in the chuck body right next to the master pinion.
On Bison chucks anyway,the jaws and slots are numbered 1-3 and so long as you always keep the jaws in their mating slots and use the master pinion the chuck will repeat.Some people insist on using all three pinions to tighten a chuck,that's fine,whatever storied talisman floats your boat,just so long as the last pinion tightened is the master.
This holds true throughout the whole use/truing of the jaw faces and or soft jaws.Always use the master pinion when taking out the lash before machining/grinding.

[wierdscience]

The one on ebay is a 4 Jaw Self Centering
They make 3, 4 and 6 Jaw Self Centering chucks

Read it again,the ebay listing says -Independent-

[Mcgyver]

What pains me is the rise of the "4-jaws are wonderful and 3-jaws are junk" cult on the internet these days.

gnostic athiest here, no cults for me . My post was really about how important 4 jaw accuracy is not about 3 jaws, which newer guys might not have thought of.

as far as three jaws are concerned, I accept the point about machinable jaws on a 3 jaws although I question their convenience on onesy twosies and if the accuracy is comparable to a properly set up 4 jaw. My comments come from my shop paradigm, where the jaws are solid.

[danlb]

I picked up a used 3 jaw scroll chuck this year. At 6 inches and only a 1.5 inch center bore, it's quite sturdy. It's a set true design, so I get the best of both worlds.

I've been leaving it mounted on my bigger lathe as the default. I can dial it in just like a 4 jaw, or I can just trust the scroll. It's currently dialed in for 3/4 inch and is within .001 TIR with 1/2 inch stock and 1.0 inch diameters too.

Now I need to make some soft top jaws for it. Does anyone know why they don't make master + top jaws for smaller scroll chucks like the ubiquitous 3 inch chuck that comes with the small lathes?

Dan