Installing a chuck on a lathe (Newbie question)

[Frederick Skelly]

Hi guys,
I'm getting my first chuck for Christmas (Nova G3 with insert) and I was reading another thread where someone was repairing thread damage on his spindle. One responder (Leo V, IIRC) suspected the OP hadnt tightened his chuck properly. I'd like to ask a couple questions to try and avoid that mistake, but I didn't want to hijack that thread.

Since I'm using an insert, I have two places that it sounds like poor tightening can damage threads: 1) inside the chuck where I screw-in the insert and 2) on the spindle where I tighten the chuck against the "head". (Im sorry, I dont know the proper term.)

First question: How tight do I need to get these to avoid thread damage? Is it like tightening lug nuts on my car - you just feel like it's tight enough? Or am I supposed to use a torque wrench, etc?

Second question: If I tighten them down, how do I get them apart again? For example, should I put a thin nylon washer between the insert and the chuck, and also between the chuck and the "head"?

I'd appreciate any any advice and insights you could give me.

THANK YOU!
Fred

[Roger Chandler]

Fred, the insert simply screws into the chuck body, all the way in, and snug it down. The insert will have a six sided collar that sits proud of the back of the chuck body, and which has a small set screw in it. The collar of the insert will be seated against the spindle shoulder when the chuck is completely installed on the lathe spindle. The set screw is used for just snugging the insert tight on the spindle, and is there for turning in reverse, so your chuck will not spin off when your lathe is in reverse. I am not sure if the G3 has an internal set screw in the insert threads....if it does, then snug it down with the supplied Allen wrench, and it will go all the way in to the inside of the chuck body, and past the threads to allow for mounting on the spindle.

Do not over tighten your chuck when putting it on the spindle.....hand tight is plenty, as the force of the cutting will tighten the chuck anyway.....they can be a bear to get off if you over tighten! BTW, you are probably over thinking things here, as it will become obvious when you get the chuck and read the directions. ;)

[Mark Greenbaum]

Roger's correct - but when removing the chuck, always remember to loosen the grub screw (anti-rotation setscrew), or perhaps you could damage the threads on the spindle when the tip of that setscrew hits the first threads on the way off.

[Aaron Craven]

I chewed up the threads on my lathe a little with the anti-rotation setscrew. I had tightened it when I had a badly balanced piece keep try to spin off when the lathe was shut off. Then I forgot to loosen it before taking the chuck off. To make it worse, it didn't really even help the problem much...

Since normal (not reversed) usage will tighten the chuck anyway, you don't really need it unless you're going in reverse, so I would recommend not tightening it at all. You can leave it in, but back it off so that it's not engaging anything.

As for the insert setscrew (the one that holds the chuck to the insert), I've yet to get it tight enough to make much difference. I think there may be a little burr in the threads that's blocking normal operation. I occasionally have the chuck spin off the insert when I'm removing it (instead of the insert spinning off the spindle). Tightening the setscrew doesn't help much. I usually have to use a pair of channel locks to hold the insert while I use a spanner to rotate the spindle in that case. I've recently purchased one of those nylon washers to go between the chuck and the spindle. I'm hoping that makes getting the chuck off a little easier.

[Michael Mills]

In addition to the others, before you screw the insert into the chuck body take a q-tip with light oil and go around the threads to make sure any metal shards left over from milling are removed. The end of the insert mates with the interior of the chuck body so it needs to be good and tight.
There will be a set screw to lock the insert into the chuck.
Depending on the size insert you need there may or may not be another set screw on the hex (outside) of the insert to lock it to the spindle for reverse. If you don't have reverse you should never need it.
1+ on hand tight installing on the lathe. Never start screwing the chuck on then turn the lathe on to finish seating it against the headstock. Some folks like a thin nylon washer but I have never used them. If the chuck is a little difficult to remove then your knockout bar (or tool) between the chuck jaws should give plenty of leverage to loosen it.

[John Keeton]

Good comments by everyone. Each turner has his own practices, but I never use the grub screw on the chuck. I sand in reverse and do so lightly and at low speeds always watching for the chuck to loosen. I haven't had any problems and I am just not willing to take the risk of messing up my spindle.

[Frederick Skelly]

Thanks very much folks, this is all very helpful to me!
Best regards,
Fred

[mike ash]

I've got one more suggestion. I use a plastic washer between on the spindle before I install the chuck. Otherwise the chuck can get pretty stubborn to get loose. I cut these washers from a plastic milk jug.

[John K Jordan]

Fred,

I can tell you what I have been doing for about 15 years of chucking, with no issues. (BTW, I wrote this hours ago but didn't finish until now - sorry if this duplicates other posts I missed.)

First, I don't use a washer to keep the chuck from sticking. I tried that with my first chuck because someone told me to and it made it wobbly. Others have reported the same problem.

Second, I always thread the chuck onto the lathe spindle until I get to the last 1/8 turn or so, then I give it a "calibrated" flick with my wrist to seat it on the spindle. (Make sure the mating surfaces are clean first) This firmly seats the chuck and I have never had one come loose, even with 15" bowl blanks. Note that the chuck may then be harder to remove, leading to...

Third, I always use the spanner wrench to remove the chuck. I never use the chuck key, as I've seen many do, since I've also seen chucks with damage from that. I also don't tighten the jaws on a metal bar of some sort for leverage since 1, I don't want to put those forces on the jaws and slides, and 2, since I often remove the chuck temporarily without first removing the piece from the jaws. The spanner wrench always works and can't damage anything. I bought some from Teknatool but Rockler also carries a version. I keep one hanging by each lathe.

Lastly, when discussing the set screws, be clear that there may be two kinds of set screws associated with a Nova chuck with an insert and these have occasionally been confused in the past. The first set screw, to hold the insert into the chuck body, must always be well tightened and never loosened or removed unless you need to change the insert. (Clean the insert and the chuck body threads carefully before installing the insert, checking for burrs or dents, and tighten the insert firmly before installing the set screw with the fiber cushion.) The second set screw is designed to hold the chuck on the lathe when turning a heavy blank. It screws into a threaded hole in the exposed hex head of the insert. Note at only certain inserts are threaded for this set screw, for example, the L insert for my lathe has the second set screw but same sized Y insert does not.

Some people have reported the chuck unscrewing, for example with a heavy catch when turning in reverse or if the chuck is loose and the lathe is stopped or started. (VFDs are programmed to accelerate/decelerate and this is not a problem if the chuck is tight.) I never install the second set screw and have never had a chuck come loose. I turn and sand in both directions. The lathes I use are machined so this set screw will tighten against the spindle behind the threads so normal use will not damage the threads. However, if you mount or unmount the chuck with the second set screw installed, even if it is not tightened, the end may contact the threads enough to damage them.

The first set screw, the one that holds the insert in the chuck body, bears against the threads and can damage them if you install it without the special fiber cushion, if you remove the chuck without removing the set screw, OR, if the insert and set screw are not seated firmly and the chuck tries to spin off the lathe.

BTW, I clean my spindle threads periodically by holding a brass wire brush against the threads with the lathe running slowly then hit them with a little compressed air. Then with the lathe off, I clean the threads and other visible parts of the spindle with a cloth. Then lightly lubricate with some dry lube or Renaissance wax. (Research has shown it's an urban legend that lubricated threads will cause a screw to work loose more easily - what lubrication does is prevent thread wear and seizing in any threaded connection.) Chris Ramsey, who turns big blanks into cowboy hats, also urges everyone to carefully clean the shoulder on the spindle that mates against the insert on the chuck, every time the chuck is mounted. He said even a bit of sawdust there has caused him grief.

JKJ

[Leo Van Der Loo]

It sounds like the answers are for just one make of chucks, as I do not use the Nova chucks, I will refrain from the installation of that particulate insert, however normal fitting procedures would have mating part fitted solidly.

As for the fitting of the chuck on the spindle it is the chuck’s fit against the shoulder, metal to metal with no soft material between the two surfaces to have a good fit that will not be able to wiggle, as the threads on the spindle and the threads in the chuck have some room/clearance, any dirt or foreign material like cardboard or plastic will give the two parts the chance to move because of the room in the threads and the non solid fit of metal to metal that should be had.

As for the securing of the chuck onto the spindle to prevent the loosening and even dismount of the chuck with workpiece and all, this is really only needed in reverse rotation of the spindle.

Especial if we have heavier pieces in the chuck and a lathe that does the forced slowing down of the lathe, I know the saying, I only sand carefully when reverse spin the lathe, the thing is you are unable to stop this when it happens to come loose.

The inertia of a larger blank would surprise you if you would try to catch that, and the dismount would be instantaneous as the chuck would be unscrewed that way.

The problem we have is that some chucks have a way to prevent this from happening with the use of a set screw/grub screw, but the lathes often do not have a place to use this without damaging the thread on the spindle, also lathes do not use the same specs for a flat surface or groove to tighten a set screw on.

One thing I learned though, is IF you use a set screw, tighten it down hard, so that when unscrewing a part (the Chuck here) you will notice that it is fastened, rather than just a softly tightened set screw that will damage the tread or other when we unscrew the chuck before we realize it.

In short, do it right or not at all.

Oh I’ll add this,on a metal lathe the forces are much greater than on a wood lathe, and yes the chucks are run metal to metal and come apart just fine, though these surfaces are smooth, something that's often lacking on the cheap far east made wood lathes.

[Jeffrey J Smith]

One more point about grub screws used when running in reverse. Throw out the ones that came with your chuck - make sure you know what size they are, then go to McMaster-Carr or somewhere that sells set screws with a brass tip. They have a harder time screwing up the threads on your spindle, but hold just as securely. It's cheap protection - particularly if you've got a jet or other lathe where the spindle hasn't been well hardened. I'm pretty sure the spindle on my old 1642 was machined from a lead bar.
please don't ask me how I know...

[robert baccus]

Good words above for sure. In 25 years of turning I have learned (the hard way) this. The little plastic rings are a toy period. I lock my Nova 2's to the insert. I buy a product called "Anti lock compound"--maybe 4 bucks at any good auto store. Guess what it does? It also has a heavy lube laced with copper dust and some fibers in it. No locked threads and super lubrication. If you forget the name just ask any oldtime machinist. Also the threads prevent a joint from unwinding when cutting or sanding in reverse--I do both a lot. The threads on a good machine are made of fantastic steel---probably the best in your shop but they will wear like any metal. I'd like to know how many times I have changed the chuck/faceplate on my lathes.

[Frederick Skelly]

Thanks again folks. I appreciate all your advice here.
Fred