Question about machining a chuck adapter for a Hendey 14x6 lathe

Warning: I'm long winded.

Hi everyone,

I have a fairly early Hendey 14x6 conehead lathe. If it makes any difference, the serial number is 5180. It's an earlier model than the tie bar model.

I haven't had good experiences taking work out of the chuck and putting it back in and getting any consistency. I should mention that I am really new to machining, and this probably does not help me at all.

When I bought the lathe, the gentleman who owned it told me that I really should replace the chuck, but he didn't go into any detail with me about why (and I didn't know enough to ask). Now that I am actually trying to make parts with the lathe, I see the current chuck as a liability when trying to make parts that require chuck removal and reinsertion. I have tried turing between centers, but I usually end up with chatter during the cut; I do not have a follow rest for the lathe yet perhaps that could help.

I purchased a Pratt Burnerd 8 inch 3 jaw chuck without any adapters, and I plan to make the adapter. This is really what I am worried about. No matter how accurate the chuck is, if I don't do a good job on the adapter, the new chuck will be $1200 bucks worth of paper weight.

I know that the spindle threads are 8tpi, but I am pretty naive about threading in general and I am a bit confused by all of the posts I read about threads. I know there is a lot of engineering behind how the different types of threads work, and I really don't know how to figure out what type of threads the Hendey spindle has. I can do trial and error, that's proabably about the only thing I have going for me, but that's not cheap considering the cost of the stock I'm going to need in order to make the adapter. I'm a bit ashamed to admit that right now it's not uncommon for me to make a part 3 times before I get it right, and that's with pretty simple stuff.

Is there any advice anyone can give me about cutting these threads? Is it important that the adapter always go onto the threads the exact same distance everytime I take the chuck off and put it back on the lathe spindle? Does the adapter need to stop precisely at the same spot in relation to the spindle threads? I planned to create the threads, spin the adapter onto the spindle, and then machine the face for the chuck.

Are there any tricks that can help me so that removing and reinstalling the chuck will allow it to run very close to true every time?

Thank you for your help,

Dan

You have to take your time and learn what is needed before you cut any iron

There is more to it than TPI. You need to document what you have now, and that will require whatever tools and whatever knowledge are needed to get that done

The very best approach once you have all the measurements is to make a duplicate of the spindle nose that can be used as a gauge when making the new back plate. It is important to grasp that you want Hendey's vesrion of what the spindle nose thread is, so we are not talking about a TAPPED hole, we are talking about single pointing an internal thread on the lathe.

Hendey added a feature to assist you with threading - and here is my old write up about that starting at Post #17 in this linked thread

http://www.practicalmachinist.com/v...-emergency-113621/?highlight=Hendey+Threading

And not to be discouraging, but the fact of the matter is that three jaw chucks are not perfect, and only get worse with the passing of time. You might want to read up on the subject of ADJUST TRUE chucks

As to how far the chuck screws on, invariably you screw it on until it stops against the shoulder Hendey provided

You might buy a face plate that fits your thread/lathe and the chuck..drill it for your chuck with .015 mounting bolt clearance for centering adjustment..yes true cut a skim cut when on register.

* Qt johnoder [As to how far the chuck screws on, invariably you screw it on until it stops against the shoulder Hendey provided]... yes consider and ask few question to be sure it might fit your lathe.

hendey lathe 518 spindle thread photo - Google Search

Ot: [Is there any advice anyone can give me about cutting these threads?]
Practice OD threads to have that down-pat easy as pie .. then think about ID threads.

Ot[that removing and reinstalling the chuck will allow it to run very close to true every time]..bolted to a true face plate and not removing it will make it run true..Most things intended to be removed should have a line -up mark so going back on the very same way and same bolt holes for each bolt..

Thank you for the advice. I will start looking deeper into threads. It's sort of an area where I've been a little too happy to remain oblivious to the actual details...but now is the time to really start to develop an understanding. I will also read your write up in post #17. I will look into the ADJUST TRUE chucks. I think the chuck I have ordered has something similar, but it is called SetRite.

I have the lathe gearbox apart to fix the 8tpi quick change gear, once that is complete I'll start work on duplicating the spindle threads.

There are a few posts about threading back plates for lathe spindles on this forum .
Here are a couple of links where the subject was discussed that may give you some ideas even if the links aren’t specifically for Hendey.
http://www.practicalmachinist.com/v...nother-thread-300730/?highlight=Dummy+Spindle

http://www.practicalmachinist.com/v...aking-threaded-lathe-chuck-backplates-254389/

Regards,
Jim

dmann said:

Thank you for the advice. I will start looking deeper into threads. It's sort of an area where I've been a little too happy to remain oblivious to the actual details...but now is the time to really start to develop an understanding. I will also read your write up in post #17. I will look into the ADJUST TRUE chucks. I think the chuck I have ordered has something similar, but it is called SetRite.

I have the lathe gearbox apart to fix the 8tpi quick change gear, once that is complete I'll start work on duplicating the spindle threads.

Click to expand...

Setrite is the Pratt Burnerd trade name for an adjustable chuck. Ajust-Tru is Buck's trade name and the other chuck makers also have their own trade names.

With regard to an adapter for a Setrite chuck, know that you must provide a thick boss on the front of the adapter that enters into the deep counterbore in the back of the chuck. The chuck has four set screws that bear against the side of the boss to dial the chuck into near-perfect alignment. So there has to be about .030" clearance between the boss and the chuck to allow for a little adjustment. If you have a thin plate on your new adapter, you can make a separate boss and attach it to the plate with two steel dowels and two screws.

It is almost imperative that you make an accurate replica of the threaded end of your lathe spindle. You do not want to remove your new adapter from your lathe while boring and threading it. You use your replica as a gage to determine when the threads are right. In turn, it helps to make the spindle replica if you have a well-fitting dog driver or faceplate to gage the threads of the replica as you make it. Otherwise, you need good measurements of the spindle thread with a micrometer and thread wires.

Larry

I'm surprised nobody has yet suggested the OP get a 4 jaw chuck and learn to use it. A lot of these concentricity issues go away. The backplate can be a lot sloppier fit as well, as long as it fits reasonably and doesn't move about under load.

Yeah you have to learn to use a dial indicator. Guess what? Each different diameter you machine in a set-true type chuck, odds on you're going to have to dial in the first piece with a dial indicator anyway.

Which is why I don't have one, and only ever use a 3-jaw when I don't really care about its runout or I'm going to machine the workpiece in its entirety in a single setup (and it won't fit in a collet).

PDW

Odd-man-out here. I'd suggest putting the 3-Jaw chuck aside for a while.

Figure you will be on your third backplate before you are up to making a really, good fit into the set-tru 3-Jaw's arse-end AND the Hendey threaded spindle.

Meanwhile, make your first backplate for a 4-Jaw instead. Most errors, you can correct with the chuck itself, so you get something "useful" Real Soon Now. You DO still have the worn-out 3-Jaw, after all.

Even a poor-condition used US-made 4-Jaw, or any new even-if-never-was-great Chinese-made 4-jaw is cheap - and inherently a more forgiving critter than a 3-Jaw scroll can be.

That because the degree of precision or repeatability is entirely in your own hands - each go - and wants more "patience" than cash.

Come back and do the 3-Jaw once more comfortable with all of it. Might be two weeks. Might be two months. Not likely to be two years.

The detour by way of 4-J land will be an educational and useful one, regardless.

Another thing that is handy on a machine that size is a small 4jaw chuck. I have a 6” that I fitted to my 13” SBL by boring out the 1 1/2 8 and making it 1 7/8 8 thread. I did it on the faceplate so I could use the spindle as a model. Later I made a model of the spindle for the next time,and for flea market shopping. I also have a full size 4jaw for that machine. My collets only go to 11/16.

my collection of stuff is getting quite extensive. Let me know what size it is when you figure it out. I thin i have an adapter for a 14" i own that will never get back together.
My opinion isitwill be hard to thread on a machine you already are having trouble with.The 4 jaw is the way to go.Istarted green coupleyears ago and it really made my parts better being able to dial it in again to zero to machine other end or taking out of chuck to check a fit.

If I were stuck with just one chuck for my lathe, it would be a 4 jaw chuck with individually adjustable jaws. You can chuck odd shaped jobs, turn eccentric work, and you can get a job to run dead true by adjusting the jaws.

In HS, a long time ago, in our junior year, our teachers told us we were no longer going to be using the three jaw chucks. We had to learn to set up our work in 4 jaws chucks and get it "bucked in" by eye to within about 0.005" runout. When we had the work running that true, using just the back of a tool holder as a fixed reference point, the teacher would let us use the dial indicators. A 4 jaw chuck holds a lot better than a three jaw "scroll chuck", aside from all its other virtues.

A "Set Tru" or similar adjustable 3 jaw chuck is essentially doing what a 4 jaw chuck does by way of jacking screws in the mounting plate. A "Set Tru" or similar design chuck will typically run true only for the diameter of work for which the adjustments were made on the mounting plate. Move to some other diameter and you are working off another part of the scroll and other parts of the jaws, so things may not run so true. No three jaw chuck can ever be expected to run absolutely true, even when new. As the scroll and jaws wear, the chuck will start holding work with increasing amounts of runout. Sometimes, by rotating a job in the jaws and trying it for runout, a person can find the sweet spot and minimize runout. Another trick when a 3 jaw chick has really bad runout is to put a piece of shim stock of the appropriate size on the jaw where the "low spot" happens to be on the work.

Machine shop work takes care and patience. I like to say that the bulk of machine shop work is "head work"- figuring the job, which means doing the "shop math" for things like thread depth, diameter to bore to for an internal thread, size of the flat and helix angle on your threading tool bit, and then the setup you will use to hold the job and sequence of cuts, tools needed, etc. Start by mastering turning stock to exact outer diameters, then progress to grinding threading tool bits and cutting external threads. Cut some common threads like 1/2"-13, or 3/4"-10 to get the basics of thread cutting- you can try a nut on your work. When you have gotten to the point where you can cut a good external thread with a nice snug fit on the nut using shop math to figure the depth of cut, and when you can grind a tool to cut a good thread with no ripping or burring, then you progress to internal threads. Lots of little steps to get to the point of making a chuck backing plate.

The other issue with making a backing plate is material. Years ago, supply houses sold raw iron castings for machining into backing plates for what seemed like small money. Nowadays, a cast iron backing plate blank can run you a hundred bucks. My own 'druthers is to make my own backing plates from A-36 steel. This is basic hot rolled structural grade steel. I use a piece of hot rolled A 36 3" diameter round bar for the hub, and a burnout or 3/4" plate for the "disc". I turn a section of the 3" bar to maybe 2 7/8" outer diameter and bore a corresponding hole in the disc of plate so the bar can be driven in. On the side of the plate which will be faced to fit the chuck, I machine a fairly deep chamfer or countersink while it is in the lathe. I then assemble the round bar hub into the plate and weld them together. I am old school, and having spent many years around welding and fabrication work, I use "stick welding". I "burn it in" using E 7018 electrode, quartering my weld passes to minimize distortion from weld stresses, and using my air needle scaler to peen the welds as I go to also give some stress relief. My welds are as machinable as the steel, and I wind up with a solid and homogeneous part.

As John Oder states correctly, make a "dummy" or gauge of what your lathe spindle nose is. This means getting a chunk of round bar and turning it to exact diameters to correspond to the outer diameter of the threaded section and the outer diameter of the un-threaded or "register" section (the small section between the threads and the collar on the spindle). The register diameter is critical to getting chucks and similar to mount and "repeat" as to how they run when taken off and put back onto the spindle. So is having the face of the backplate hub faced dead square to the bore/threads in the hub. Make your gauge and try screwing on a chuck or faceplate. Take very light cuts as you finish your threading, and on the last cut or two, do not even advance the tool into the work. These are "spring cuts" and can shave off burrs and perhaps a thousandth or two due to deflection or "spring" in the tooling, lathe parts, and work.

When you make the gauge, you can turn it between centers by chucking a piece of steel in the chuck and turning a 60 degree point on it. Using a lathe dog so its tail is against one of the chuck jaws works as well as a drive or "catch" plate if you do not have one for your lathe. Turning the center in the chuck, no matter how bad your chuck is, will insure the point is true with the spindle. As I said, a lot of machine shop work is head work. A lot also is using your imagination and thinking how to work with what you have at hand.

I would not throw big bucks at a fine new adjustable 3 jaw chuck. Nice to have if you have the money and are putting that kind of chuck on a toolroom lathe or lathe for precision work on a production basis. As I said, I'd focus on getting a good serviceable 4 jaw chuck and learn to set your jobs up in it. As an old shop foreman told me when I was a kid of about 16: "Anyone can set a job up in a 3 jaw chuck and think they can run a lathe..." He said this to me in a scornful manner, when I'd asked to be given some engine lathe jobs in his shop. The next morning, he put me on an engine lathe- handing me a drawing and pointing me at a large casting with no machine surfaces to set up off of. It was a faceplate job that he started me off on. Fortunately, we had great teachers at Brooklyn Technical HS, so bing pointed at a strange engine lathe and handed a job like that casting, along with the foreman telling me how he'd kick my ass and throw me out of the shop if I screwed up the casting did not put me off. I was cocky and scared all at once, but with some help from the shop steward and some older journeymen machinists, I was able to figure out the job and get it done. That was over 50 years ago. Working overseas years later, I depended on machine shop work to get jobs completed on small powerplants. We had to work with worn out machine tools and make-do with what we had or could get hold of. Often, it meant making tools to do the work, or repairing the worn or busted parts on the machine tools before we could get to the real jobs. Machine work is a great teacher and developer of your mind and skills, and learning to work with what's at hand is a major piece of it.

Side note to Joe's detailed coverage:

Three-jaw chucks in high volume production on thousands of CNC spindles 'round the world are more often than not.... anything BUT "scroll" operated.

Most are power chucks that can, and DO hold insanely tight TIR all-day, every day, by use of cones, ramps, wedges, balanced-levers, etc. that can even "automagically" increase grip as RPM goes up to HSM speeds.

Shunck and others who make such goods get the price of a decent NEW automobile for them, and they earn it back in mere months, if not WEEKS.

Rebuild fees - and rebuilt they are, but only after astonishingly high parts-throughput - would buy a decent used car.

Do NOT confuse any of these with the diminishing makes of MANUAL 3-J scroll chucks.

More to it than external looks or jaw-count. Internally, they are a different tribe and race of goods altogether.

2CW

I don't think anyone has mentioned it, but you can probably reuse the backplate on your existing chuck. You would need to make an adaptor to go between the backplate and a different chuck, but for now it would put off having to make a fairly challenging part for someone with limited experience.