View Full Version : Proper way to unscrew lathe chuck?

Frank Ford
05-13-2009, 05:52 PM
Last night I saw a fellow trying to unscrew a 6" 3-jaw chuck from an older Taiwanese 11" lathe. He had put it in back gear, stuck the key in the chuck and was whacking the chuck key as hard as he could with a big dead blow mallet.

Having owned that lathe myself for a number of years, I'd always unscrewed the chuck by engaging the back gear, setting the chuck jaws fairly far apart and using a long rectangular bar to loosen it with leverage.

The guy I got it from used to put a wood block between the chuck jaw and the lathe bed, set it at its lowest speed and flip the switch momentarily into reverse. I never much liked the idea of the chuck spinning off, so I didn't use that method myself


05-13-2009, 06:00 PM
Having owned that lathe myself for a number of years, I'd always unscrewed the chuck by engaging the back gear, setting the chuck jaws fairly far apart and using a long rectangular bar to loosen it with leverage.

That's the way I do it...the other 2 methods scare me;)

05-13-2009, 06:19 PM
I'll first try the chuck key method.
That usually works...but if it's on tight, I'll use the 2X4 between the jaws.

05-13-2009, 06:25 PM
Put it in back gear. Chuck up a piece of delrin bar stock. Use a 1" MT drill bit in the tail stock and drill the Delrin until the motor stalls, then switch to reverse. The chuck will unscrew neatly and be suspended on the drill bit with absolutely no danger of falling on the ways. Remove chuck from the Delrin and put the chuck away. Throw away the drill bit and the Delrin 'cause there is no way you are going to get that bit back out. :D :rolleyes:

Your Old Dog
05-13-2009, 06:26 PM
Crescent wrench to just one of the jaws point it at my stomach and then bump it hard with my palm and it never fails to pop loose. I then make a game of it by putting the lathe in high speed and then hitting the switch at the same time I run for the door. I've actually made it to the door several times before the chuck comes whizzing past me. This exercise serves to keep me fit and gets me a break away from monotonous task. (and if you're wondering how I got monotonous spelled correctly it's cause I use a spell checker!)

05-13-2009, 07:37 PM
Block of wood clamped in the jaws and a good whack with a dead blow is what I used to use.

David Powell
05-13-2009, 07:46 PM
Some years ago I was using the lathe for repetition work and there was a lot of off and on of the DC drive unit. with the controls set very fast. Intending to turn off I accidentally went past off and into reverse, there was a screech of belts following which the chuck unscrewed itself, touched the saddle and disappeared through the open window( My shop was then in the third bedroom of our bungalow). Cat was outside on her rope, fortunately awake and aware and the chuck went one way and she went the other. I retrieved the chuck, calmed cat down with some treats and disabled reverse before the wife realised anything was amiss. So every time I screw the chuck off or on I think of *****!!!!! and everyone around wonders why I smile .Regards David Powell.

Glenn Wegman
05-13-2009, 08:51 PM
Take a very important part that you just finished working on for the last two days that needs a very fine pitch external thread turned as the final operation. Set up to thread on the back side, away from the chuck, with the spindle in reverse........

05-13-2009, 08:55 PM
I use wood between the chuck jaws to the lathe bed, and lathe in reverse, low gear (60rpm). Plenty of time to start and stop it. Wacking anything on a EMCO is bad... fiber gears in the main drive...

I have an interlock cover on the reverse switch... It would mess up my day for the 25lb chuck to come off at 2500 rpm!

05-13-2009, 09:14 PM
I use a strap wrench ,with back gear engaged also i made up wood piece to cover the ways. Soon after i got my lathe i was taking the chuck off and itdropped on my hand before i was ready and finger got in the way, shortly after that i made the wood block and use it all the time.

Frank Ford
05-13-2009, 09:30 PM
Am I right in thinking that clubbing the chuck key is potentially bad for the chuck? That guy was REALLY hitting it!

Because this lathe is in "public use" simple procedures are often forgotten, such as oil on the threads when reinstalling the chuck. It takes a good two or three foot long bar to break it loose with a good size guy leaning hard on it.

05-13-2009, 09:33 PM
I use a piece of old broom stick about 2 feet long and stick it threw the opened jaws into the spindle. Make is easier and safer than putting a wooden cover protector on the ways under the chuck. You can unscrew the chuck and the broom stick will hold it so it don't drop and / or mash your fingers, plus the broomstick makes handeling the chuck easier too. The stick will be threw the chuck and you can slid it out of the spindle and get a hand on each side of the chuck.


05-13-2009, 10:04 PM
Chuck up a piece of 1" pipe that extends into headstock and has 8" sticking out. Apply a 24" pipe wrench near the chuck face pull with left hand and apply hammer smartly to the pipe wrench with the right hand. This gives something to hold onto and keeps from falling on the ways. A large nut welded to the end of a rod chucked similarly. 3/4 Impact applied to nut can work without getting the gear train involved.

05-13-2009, 10:07 PM
Use of the chuck key, in conjunction with a heavy hammer is definitely not the way to remove a chuck under any circumstances. Even using the key just to remove a snug chuck should be avoided. The pinion and key have a specific purpose, chuck removal is not it.

Several of my chucks have a void between the chuck body and backplate. Chips get hung up in there and fall out when installing a chuck, fouling the threads and requiring removal and cleaning a couple of times when installing a chuck. I have filled the gap with RTV to seal it. It has enough flex to permit adjusting the Set Tru chucks yet eliminates the void and makes installation simpler.

05-14-2009, 12:11 AM
My 9" S.B. has a couple of teeth on the backgears missing because of locking it with the backgears and putting a cresent wrench on a jaw and whacking it with just the palm of my hand. I figured I was safe doing that, after all, it wasn't like I was hitting it hard like with a hammer or anything....

Allan Waterfall
05-14-2009, 04:30 AM
My Myford has a screw on chuck,I only ever put the chuck on hand tight and never give it a final fast flick turn so that it goes home hard,also put two spots of spindle oil on just the threads.
Only ever requires a palm tap on the chuck key to loosen it.


05-14-2009, 07:40 AM
I found a neat way to remove a heavy chuck without it dropping on the ways, although I use a wood board on the ways just in case. In a 3 jaw chuck I put a one foot long rod that is the ID of the spindle and push it halfway the chuck Tighten down the jaws and when unscrewed it stays close to the spindle thread. I grab the right end of rod and pull out 4" or so and grab the left end before it completly out of the spindle and holding it and place it thread side up in a container. When I screw it back on the rod lines up the thread almost right and just screw it tight.

05-14-2009, 07:59 AM
Why not try this:
Get a coupling nut made for threaded rod and put this in the chuck, its a hex it'll chuck up in a 3 or 6 jaw chuck. Then put a piece of threaded rod in the tail stock and screw it into the chuck alittle and then take a big wrench and put it on the coupling nut in the chuck and wack the wrench. Spin off the chuck and it'll be on the threaded rod so it wont fall on the ways.
You could also cut a piece of wood to straddle the ways and cradle the chuck. Then spin it off and it wond fall onto the ways...

05-14-2009, 09:24 AM
i like that tip of putting a pipe or large wooden rod into the chuck and spindle to prevent the chuck from falling on the ways. i am going to do that from now on.

to remove my chucks, i stick a piece of wood across the jaws and sticking out towards the front of the lathe and smack the wood with a deadblow hammer. i was told never to use the backgear to lock the spindle as you may break teeth off. i also make sure the chuck and spindle threads are clean and have a light coat of oil before installing a chuck.

andy b.

05-14-2009, 12:16 PM
Some great ideas offered here, but Evan, why not WELD a good drill into a piece of cold-rolled first? Joe Bergamo at Plaza Machinery has a number of used chucks with cracked key holes-Hmmm, I wonder? Duffy

05-15-2009, 12:33 AM
"Throw away the drill bit and the Delrin 'cause there is no way you are going to get that bit back out."

Seems like you could reuse it whenever you needed to remove the chuck. Am I missing something?

If you machined the Delrin down almost to the drill diameter, the drill should come out without too much trouble. Or am I missing something else?


05-15-2009, 04:33 AM
I just realized I broke the tip off the wrench for my 4-jaw using it to remove the chuck back before I knew better. Better the wrench than the backgear, though.

Using a drill or a threaded rod secured to the tailstock for chuck removal might put some large loads on the tailstock. The chuck will move towards the tailstock as it unscrews. That could be ugly, especially if the motor is involved.

Seems like the ideal chuck removal tool would be a piece of hardwood board with a slot in one end to fit tightly over one of the jaws. It should be wide enough to put the jaws near the outside of the chuck body and long enough to provide the necessary leverage.

Once the chuck is loose, remove the board, and use the dowel in the spindle to keep the chuck from falling on the ways.


05-16-2009, 02:34 AM
Years ago I worked at a place that had an enco lathe with a screw on chuck. Everyone in maintenance fancied they knew how run it.

One idiot, put the chuck on using power to spin it on. Yup, that chuck was stuck.

It was quite comical to watch a bunch of grown men with a 6' pry trying to get the chuck loose. Lathe wasn't too big so all they ended up doing was rocking the lathe from side to side banging it on the floor.

Eventually they got tired and sorta 'forgot' about it.

Not knowing any more than they did about it, I stopped by the local library and grabbed an old book on lathes. That book recommended the hard wood block against the ways, bumping the jaw in reverse.

So, I came in a bit early with a block of wood and gave it a try. I was a bit hesitant since this method seemed a bit brutal so the first tap in reverse didn't do much.

Since the world didn't end, metal flying out of the headstock, I gave it a bit bigger run at the block by jogging reverse. That one did it. Chuck came loose, pretty as you please.


Paul Alciatore
05-16-2009, 01:52 PM
Before you use any method that calls for engaging the back gears and a sudden strike or shock, go to E-Bay and read all the lathes for sale that are described as having broken teeth on the back gears. About 1 in 4 if I remember correctly. In over a year of searching for a lathe, I never saw one with any other gear teeth broken, just back gears.

Engaging the back gears appears to be necessary on most lathes, but a quick shock is not a good idea. I have a big strap wrench that I use. If that would fail, I would mount a wood or metal lever in the jaws and apply only the force needed to loosen it.

If that force would become excessive (gut feeling) I would disengage the back gears and mount my hand crank on the back end of the spindle and use that against the makeshift lever in the jaws. Only with this would I be tempted to use sharp blows to break it free.

05-16-2009, 08:32 PM
I built a bracket using a piece of pipe welded to an angle iron and another angle back over the centerline of the chuck in a "C" shape. I clamp the chuck on the pipe. I have a shackle in the top angle that lets me pick up the chuck with a hand winch on a jib mounted on the end of a rolling work bench. I use a 2x6 across the ways for protection too. Of course before tightening the chuck on the pipe, I have to loosen the D1-8 locks, but a similar "handle" would be handy on smaller chucks as well. (Everyone needs to handle a 20" four jaw some time!) Use a large hex or square bar to chuck on, and a substantial tounge on it would give you something to smack. It would transfer the load to all jaws reducing the risk of breakage.

I really like the idea of the spindle bore pilot, I may have to use that on my big cone head lathe. It has two spindle locations one swings 24" the other about 44", I don't relish the idea of moving the chuck on that one.

Rich Carlstedt
05-16-2009, 09:12 PM
The reason for back gears breaking is hitting the chuck wrench -or- tool without
having the back lash taken out.
To prevent this, I learned this trick in England.
Put a wood 2x4 about 14 to 18 inches long between the jaws and position it at 1 or 2 O'Clock as viewed from the tail stock. Now with your left hand, draw down the wood (rotate CCW) as quickly as possible to 9 O"Clock and with your right hand, strike a hand blow with a mallet, on the board driving it downward.

The downward push on the board removes all backlash before the blow, and prevents broken teeth (that break when you "slap" the spindle).

The short board to the ways and a reverse rotation is similar (another post),
as the acceeleration of the chuck takes out the backlash before a unbreaking force is applied.

My suggestion to either method is to always do it with the jaws tightened !
This will prevent damage to the scroll plate.
loose jaws, or loose gears are sure to be damaged.

By the way, hitting the chuck wrench is always bad news..


05-17-2009, 08:44 PM
For some reason, the chuck on my LeBlond always gets REALLY tight; I only remove it once every year or so. I've had to clamp a 2X4 in the jaws, crosswise to the chuck, then run it in reverse until it contacts the rear way. Once, the 2X4 broke, so I had to put it into the chuck so it hit the way edge-ways instead of flat.

There's no way to get onto the LH end of the spindle to lock it in place.

I do always clean up the threads and the register and apply a bit of grease. Guy Lautard recommends (in one of his MBRs) using a 'washer' made of some sort of plastic between the chuck and the spindle register. If she won't come loose, squirt a bit of lighter fluid on the plastic and wait a bit for it to soften.

05-17-2009, 10:13 PM
The threaded joint compound used in the Oil Drilling and Water Well Drilling industry is formulated to prevent gauling and to not be too slick. The Lathe cutting forces tend to tighten the joint so slick is not what you want. You need to use one of the joint compounds made for this application. Jet Lube Kopr-Kote is the best. NAPA Permatex Anti-Seize should be a significantly better than using a grease or oil that is intended to be slick. Get it on your clothes and you are not likely to ever get it out. Talk to your local driller. He will probably give you some. He wastes more in a day than this forum would use in a lifetime.