"Adjust Tru" Chucks

That's up to each to decide for himself.

I have a Buck Adjust-Tru that I got used 20 years ago. The D1-4 backplate I had to buy cost more than the chuck. That investment has definitely been a good one for me since that chuck is what's on my lathe 95% of the time. I'm a hobby machinist, production is not an issue but convenience is at times.

Work can be centered accurately in a 4-jaw but it takes a couple of minutes of screwing around.

The adjust-tru isn't accurate for all diameters unless adjusted, but it's more accurate than my other 3-jaws and it's well under a thou for

1" dia stock -- or such other dia as I may find it worth the bother to tweak. That's close enough for my needs most days. For closer, 4-jaw is actually more convenient.

One problem is that they are longer and thus further out from the headstock. Thus there is a progressive loss of precision and rigidity which trades off against the added precision of centering. The smaller the lathe the worse this trade-off becomes.

If your lathe is big enough for even a small Adjust Tru...and you need a

3 or 6 jaw chuck that is dead nuts..yes..they are indeed very handy to have. Ive got {2} 6" ones and a couple 8" ones...and one 10" one..and they have saved my bacon on more than one occasion .

But most people, for rough turning, really dont need one. They are very handy for returning Stuff that has been turned before.

Gunner

"First Law of Leftist Debate The more you present a leftist with factual evidence that is counter to his preconceived world view and the more difficult it becomes for him to refute it without losing face the chance of him calling you a racist, bigot, homophobe approaches infinity.

This is despite the thread you are in having not mentioned race or sexual preference in any way that is relevant to the subject." Grey Ghost

...

Like Don and Gunner, I too have an adjust true three jaw. I set mine up once years ago and don't touch it. Really close for most work. It should be noted, I could have done nearly as well by boring my hard jaws. Scott Logan of Logan lathes has a great write up on his web site for this task.

But, when I need dead nuts...

Soft jaws are the way to go.

Soft jaw in a lathe is something you have to do a few times. Once you're past the learning curve, you can quickly bore a shave off your softjaw and then insert your work and its absolutely dead nuts on. When you need to turn a part from both ends and have the same diameter meet in the middle, this is the best way to go.

Karl

Depends on what you need, they aren't really essential. I didn't have a three-jaw so the extra cost wasn't so bad. In practice the more accurate centering has only been useful for parts that don't fit 5C collets and need to be removed to test a fit, then replaced and trimmed slightly. Most of the time a small light-weight chuck on a 5C mount (i.e. easily removed and replaced) would work as well for that. The Sherlines are nice, for me the stronger 3" Enco is about the weight limit for checking the feel of a light press fit.

Of course if I need to test the fit with a hammer I have to remove the part from the chuck. In that case the Set-Tru is less trouble to recenter than a 4-jaw, the machined surface may be difficult to indicate if it's scuffed or threaded.

jsw

That is not universally true. My Kalamazoo Chuck's Zero-Set mounting adapter threads right up to the boss on the spindle. Once the proper thread form was achieved, it spun on like a bank vault closing.

I've really not felt the need. I don't do long production runs of the same stuff, after a bit of practice, centering up in a 4-jaw doesn't take that much time and you'd have to go through the same gyrations to set the adjustments on the fancy 3-jaw, since they aren't going to be the same for every spot on the jaws' scroll. You've still got to check run-out with an indicator. I've got a 3-jaw, but it's seldom on the lathe. I find a 6-jaw to be more useful.

Stan

My Buck Adjust-tru chuck is no longer than a similar-size Rohm. If anything it's a bit thinner.

Which chuck -- a standard 3-jaw chuck, or a collet chuck?

For the former -- it will only be true at the one size which you adjusted it for -- and only as long as you use the same key hole (ideally the one marked '0' or something similar) for tightening it.

The adjust-tru can tune out errors in the chuck, but the scroll plate can have a sensitivity to where it is in its cycle. So tune it for true in one position, and it will be fine there, but have varying degrees of error at other workpiece diameters. (It will be right on for sizes larger and smaller than where you tuned it which are precisely an integer number of jaw teeth larger or smaller -- because the scroll plate will have turned precisely an integer number of turns and it will be back where it was.

With a good *new* chuck, there should be little error. If it is used, the scroll plate will have varying amounts of wear in different rotational positions.

If you are doing a lot of work with the same size stock, and if your finish diameter is barely smaller than the raw stock, then this could save you time.

But -- you could also get the chuck with two-piece jaws, and get some soft jaws which you can bore to a precise fit for that stock diameter. That will probably cost you less than the adjust-tru feature.

And if you will always be making parts from stock with is not just barely larger than the desired finish diameter (of the largest part), you can just chuck up the stock, turn to the desired diameter, and finish all the other work before you release it from the chuck. Don't expect to turn the workpiece around in the chuck and finish the other end to precisely the same surface unless you take the time to use the adjust-tru to truly center the workpiece on an exposed area which has already been turned. It is easier to turn workpieces around if you are turning between centers instead of held in a chuck.

If, instead, you have a collet chuck (which Bison also makes) you can use the adjust-tru to get the collet running truly on center and will be able to exchange collets with very little error -- given good collets.

Good Luck, DoN.

I replaced an old worn out 3 jaw on my Atlas 10 inch lathe with an "adjust tru" 6 inch chuck. I love it, but then I am not making diesel injector parts on a regular basis. One additional note to add: If you have a piece of stock that is exactly the finished size, you can use the "adjust tru" feature to zero it up once it is mounted in the chuck.

Pete Stanaitis

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D> >

--I've got a 5" Buck 6-jaw on my Myford Super 7. Had to make a backplate as none were available but worth every bit of heartache to get it done. If Buck makes a chuck small enough to fit your lathe go for it. Nice thing about the 6-jaw: you can leave one jaw out, if necessary, to accomodate lumpy castings, etc but the full 6 gives you the ability to grip relatively small stuff: 3-jaw chucks tend to have fairly blunt gripping ends but the 6-jaw variety are much pointier, so to speak.

Also -- another significant advantage to a 6-jaw is that when clamping thin-walled tubing the 6-jaw introduces less deflection than the 3-jaw does.

However -- a benefit for the 3-jaw. With an irregular surface on the workpiece, a 3-jaw *always* gets full contact with each jaw. (3-points are self centering). With 6-jaw, it is likely that one or more of the jaws will not be making proper contact, reducing it in effect to a 3-jaw with skinnier points.

And for either 3 or 6 jaw -- if the chuck has a separate backplate, it is possible to make a spacer with some other features to turn it into an Adjust-Tru (or any of a number of other trademarked names, depending on the maker of the chuck. :-)

First -- you turn a recess in the center of the mounting plate, and mount a round piece of steel in that, with several countersunk bolts. Best if it is a good tight fit in the recess so it can't shift in there.

Then -- turn up a spacer ring to go between the chuck body and the backplate. Drill and countersink it for bolts to attach it to the chuck body which go into the threaded holes which the backplate normally bolts to.

Drill and tap four radial holes at 90 degree intervals around the ring for setscrews to press on the original round piece of steel.

Then drill and tap holes in the ring to match the holes in the backplate, enlarge the backplate holes (and countersinks if present) a bit to allow motion, and attach the ring to the backplate with these.

In use -- loosen the backplate bolts to finger tight, and use the radial setscrews to shift the chuck to true (relative to the backplate) for the workpiece size in use at the moment, and snug the backplate bolts and re-check the centering. If it is still on center, snug them down firmly and triple check the centering. You are now ready to turn.

Enjoy, DoN.

I guess both. But I don't know if either is even worth it for a mini lathe projects, unless I'm doing production stuff.

I need to turn a variety diameters. But may also be getting into a project involving "piston and bore" accuracy.

BTW. I wondering if one of these eBay chucks can be adapted to my lathe: A) 320527041801 B) 350349970482

564

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Could you bother saying what the size of the lathe is? "Mini-Lathe" does not devine it for me.

Anyway -- the first one is 4" diameter, and a 3-jaw chuck normally should not be much larger than 1/2 the swing of the lathe. At a guess, your "mini-lathe" could be one of the 7x10" lathes, which would put a maximum 3-jaw chuck size of 3-1/2". (4-jaw chucks can be, and often are, larger.) This chuck is for at least an 8" swing lathe.

Anyway -- as supplied, with a #10 B&S taper, it is not likely to fit anything which qualifies as a "mini" lathe, though replacing the taper with a different chuck backplate could cure this.

Both auctions are closed, so it does not matter anyway.

I think that this is intended to be held in a larger chuck (or a in a *very* large collet) to do a makeshift adaptation to 5C collets. I can't see clearly whether the black end has a proper taper for closing a

5C collet or not. The other end certainly does not.

If the black end has the taper for a 5C collet, you thread the collet into the separate ring (which I presume has threads on the ID to match a 5C collet) chuck the silver part in the chuck or very large collet, and use the tommy bar to rotate the black part to close the collet.

It is sort of like the square and hex collet blocks for use with a milling machine. To see examples of these, see eBay auction:

400116973584

Anyway -- I don't see what you have illustrated as being any use in a lathe which qualifies as "mini". :-)

Good luck, DoN.

Sorry. I have a red 7" x 14" Microlux. The newer one is exactly the same, but gray. (That's "grey" in the U.K.). :-)

The seller may put them back up, but obviously money is better spent on something more useful for my machine. Thanks.

I added three clearer pics of it taken apart:

I can see some sort of taper inside the opening at the non-threaded end of the black part that starts at about 1-7/16" in diameter. It tapers down for about a 1/2" before the I.D. straightens out the rest of the way at about 1-1/4" diameter).

Also,a s you can see there are eight threaded holes that are about

7/16" deep, on the outside circumference of the black part.

The I.D. of the small ring is threaded. (The two bars don't seem to serve a purpose).

Yes, I have both. The square and hex.

I also have a full set of 5C collets at every 1/32nd for when I was thinking of milling larger diameter stock than 3C would allow. But since I now have a mini mill/drill project that I plan to fix I probably won't need all the MT3 stuff. (Like the endmill holders). Now I'll need R8 tooling.

564

Sorry. I have a red 7" x 14" Microlux. The newer one is exactly the same, but gray. (That's "grey" in the U.K.). :-)

The seller may put them back up, but obviously money is better spent on something more useful for my machine. Thanks.

I added three clearer pics of it taken apart:

I can see some sort of taper inside the opening at the non-threaded end of the black part that starts at about 1-7/16" in diameter. It tapers down for about a 1/2" before the I.D. straightens out the rest of the way at about 1-1/4" diameter).

Also,a s you can see there are eight threaded holes that are about

7/16" deep, on the outside circumference of the black part.

The I.D. of the small ring is threaded. (The two bars don't seem to serve a purpose).

Yes, I have both. The square and hex.

I also have a full set of 5C collets at every 1/32nd for when I was thinking of milling larger diameter stock than 3C would allow. But since I now have a mini mill/drill project that I plan to fix I probably won't need all the MT3 stuff. (Like the endmill holders). Now I'll need R8 tooling.

Thanks again.

Darren Harris Staten Island, New York.

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Better. You probably *could* make alternate backplates for those chucks, but you would have to be *very* careful never to back the jaws out enough so they could hit the bed under power. Better to have the 3-1/2" chucks and be *sure* that they will be clear.

O.K. So it works the way I expected.

For threading a bar into to closing the collet by unscrewing the black part a bit.

The pin in the bore of the silver part is to engage the key in the collet to prevent it from rotating as you attempt to close or open the collet with the black ring.

The small ring should thread onto the back of a collet. You say that you have a set, so try it.

The larger bar probably threads into the black part to apply force to it to close or open the collet while it is gripped in the chuck of a larger lathe.

The smaller bar I suspect is for turning the small threaded ring to capture or release the collet when you need to change collets.

Pick up the parts, and an example collet and play with them to see how they go together. This particular design is probably not as precise in centering (even if tuned on center with a 4-jaw chuck), but has the advantage that it closes the collet without drawing it back so the workpiece position does not shaft towards the headstock as it is closed.

So you know how they work.

But the collet blocks and the collets can be used with the mill and a vise to cut square or hex ends on workpieces.

You will need a set of R8 collets, or some R8 shanked end mill holders however. *Don't* try to hold an end mill in the drill chuck. It is poorly designed for that task.

Enjoy, DoN.

I assume that I'd have to be just as mindful as when and if I get a regular 5" chuck for this lathe.

Ok. So the larger bar in the pic is what I'm supposed to thread in order to use it.

Ok, I'll have to dig those out of storage.

You lost me there. There is nothing apparent about how the small bar might work with the other parts.

I'll keep it for light duty stuff, since the work would be pretty far away from the spindle.

That's the plan. I just have to figure out what to do with tolls like the MT3 endmill holders.

Yes. that JT33 drill chuck came with the mill/drill.(So now I have two).

564

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Yes. What size chuck comes with the lathe? I would not expect much larger than 3-1/2". On my 12" swing Clausing, I use a 6-1/4" Bison

3-jaw chuck, but a 10" Burnard Pratt 4-jaw one. (Or sometimes, such as tonight, a Sherline 3-1/2" or so 4-jaw on a 5C collet spindle. When I don't need the size, it is a lot lighter to install. [ ... ]

Yes.

Look at the small ring. It threads onto the back of the collet to hold it in the body. There needs to be some way to turn the ring when threading it onto the back of the collet. Often, the ring will either have a split screwdriver slot (continues on either side of the large hole in the center), or a hole or two for a pin spanner wrench. In this case, my *guess* (since you gave no photos close enough to the ring and the bars to give any details) is that there is a hole in the face of the ring.

To assemble the collet, you first screw the black piece fully into the the white one, slide the collet in through the black, aligning the key with the pin in the white part. then turn it over and drop the small ring into the recess on the back, stick the small bar into one hole to turn the ring around the end of the collet to screw it on and retain the collet in the chuck. To close or open the collet, you turn the black part with the bar, and then *carefully* remember to unscrew the bar before you turn on the spindle motor. :-)

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I really think that it would not work well in a lathe as small as yours. Keep it for when you get a larger lathe, or find someone to sell it to.

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Why do you have them, if they do not fit your mill?

:-)

Good Luck, DoN.