# Centring in a 4-Jaw Chuck



## stackerjack (Sep 14, 2019)

Does anyone know an easy method of centring a rectangular bar in a 4-jaw chuck please.  After spending about a quarter of an hour, it's still out by more than 5 thou.?
Jack


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## goldstar31 (Sep 14, 2019)

stackerjack said:


> Does anyone know an easy method of centring a rectangular bar in a 4-jaw chuck please.  After spending about a quarter of an hour, it's still out by more than 5 thou.?
> Jack



Make another chuck key and both  opposing each other.


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## BaronJ (Sep 14, 2019)

There is no guarantee that the faces are actually flat all the way across.  Even so a slight rotational difference in measurement position will alter the readings.  Depending upon what you want to do with the workpiece, 5 thou is probably not worth bothering about.


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## ShopShoe (Sep 14, 2019)

stackerjack,

A good place to start is this piece written by the folks at LittleMachineShop:

https://littlemachineshop.com/images/gallery/PDF/centering4-jawchuck.pdf

This video is also pretty good:



And that is not to say that many of the other videos by other people are not worth watching as well.


The main thing is that with practice it will make sense to you and you'll get the hang of it.

--ShopShoe


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## GRAYHIL (Sep 14, 2019)

Hi All
This is how I do it.
With a magnetic base dial gauge mounted on the saddle and the point at roughly center height wind the saddle up to the square stock.
With one side of the square stock vertical move the saddle forward more so that the point of the dial gauge just touches the stock by moving the mag base.
Turn the chuck a small amount forward and reverse to find where the dial gauge changes direction and set the gauge to zero at this point.
Wind the saddle away to clear square complete with mag base.
Turn the chuck approx 180 degrees.
Wind saddle back  and repeat first steps but do not zero clock as the reading will show how much it is off center
the square is.
Move the job half the reading in the required direction.
Repeat till all reading are the same an all faces.
Difficult to describe but it works for me!!
Graham


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## kwoodhands (Sep 14, 2019)

stackerjack said:


> Does anyone know an easy method of centring a rectangular bar in a 4-jaw chuck please.  After spending about a quarter of an hour, it's still out by more than 5 thou.?
> Jack



Start by marking the chuck, #1 opposite side#3 ,  then #2 and#4  opposite sides again. 
Two chuck keys as mentioned is a very big help. Layout centers on the end of bar, both ends if needed. I use layout fluid and a height gauge to scribe the centers
If the work is short enough to stand in a drill press or mill vertically, then spot drill, center drill and install in the 4 jaw. Now turn chuck  so #1 is topside and #3 is opposite on the bottom. Bring tail stock and center up to the end of the bar. With two wrenches move the jaws so the center is dead on the layout. Now turn the chuck so #2 or #4 is top side. Repeat above. Snug up the jaws , check that the center matches the centered layout.
Spot drill, center drill and then install a center in the tail stock.
This method so far will get you close ,usually within  .010
I forgot to mention at first you will need 3/8" or so round bar about 8" long. Turn a 60° point on one end and spot drill, and then center drill the other end. The pointed end enters the face with the center layout. The other end enters the live or dead center. 
I use a dial indicator mounted on the tool post , lots of ways to do this.  Turn the chuck so #1 shows top side. 
Move compound til the indicator moves about. .010  Turn the serrated band ( bezel) til it shows zero.
Turn chuck so #3 is top side and record the difference from zero. Example , #1 reads zero  /   #3 reads 16
Divide this # in half, = 8.  Now slowly turn the chuck til the DI reads zero. Snug up the #2 and #4 jaws because these were the jaws you adjusted when the #1 & #3 were top side. Often you won't get a reading when the chuck is turned, Just move the compound in til you get a reading. Use this as zero.
Both readings should be the same, you can tighten one or the other more if you were .002 or less out after checking. 
Now repeat with #2 & #4 top side . 
Make sure all 4 jaws are tight. 
That's it, your part is centered. When you do this several times you will be able to center a part in 3 minutes or less. 
I just looked at the Little Machine Shop Video, very good. My method as well.


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## stackerjack (Sep 15, 2019)

Thanks everybody, I'll go and get some practice in. "Cheers"
Jack


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## jcreasey (Sep 15, 2019)

This is a good tip for using the 4 jaw


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## stackerjack (Sep 15, 2019)

jcreasey said:


> This is a good tip for using the 4 jaw




Excellent idea. Gota try that.
Jack


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## tornitore45 (Sep 15, 2019)

I made a holder for the dial indicator to be mounted on the QCTP.
It also have a long rough adjustment slide to position the Indicator radially without moving the cross slide.
This feature is a time saver avoiding to wind the cross slide to adapt to the part diameter.

Eyeball the part into center by looking at the chuck jaws relation to the chuck groves  AND looking for the jaw to touch about the high point.

Touch the dial indicator by moving the rough adjustment slide (Not the cross slide, unless is on the way or totally off range)

Find the minimum. That is the location farther away from the operator. (indicator mover CCW)

The Indicator bezel Zero is usually toward the operator and does not move.

Move the needle to Zero using the cross slide as fine adjustment.

At this point the dial read Zero and the part is farthest away.

Turn the part until you read Maximum. Needle moves CW

Back away the cross slide 1/2 the reading.

You are now on the spot closest to you. The jaws have a random orientation.

Turn the chuck to have one set of jaw horizontal and the dial reading Positive (to the left)

Working both jaws snug up to overshoot the Zero (negative) about 0.001.
This will give you some spring to tighten up good the opposite jaw.

Repeat with the set of perpendicular jaws.

With this method there is no guessing no iteration except one pass to snug up precisely when you really want zero movement on the needle.
The left hand always tighten, the right hand back off to let the front jaw move in and that snug up.

The description is detailed and long, the operation may take about 20 seconds.
The Indicator slips on and off the QCTP and is already on center.
It pays to have a cylindrical tip on the indicator to allow for small height errors.
Building the holder and the rough adjustment slide is an investment in time that pay back many times over.


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## lemelman (Sep 15, 2019)

This PDF shows how I do it. It's very quick, with very little repetition of jaw adjustments. As others have stated, 2 chuck keys are *much *better that one.
The method works because, after step 3 the bar is centered when the DTI shows zero all round.


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## ALEX1952 (Sep 15, 2019)

Start by using the rings on the face of the chuck you should easily get to within .05mm, then use a clock to measure the total throw, move the work over by half the throw, do one pair of jaws first then the other gradually coming to center. When very close just crack the jaw lose and squeeze over the other jaw. As stated difficult to describe but not difficult at all to do. More of a challenge is a face plate and having to "knock" the work into position, First step is to always use the same "knocker" I use  20mm dia brass by about 150mm this gives plenty of weight to move the work, keep this just for that! no pinching it to make something that way you will develop a feel for it. Then its just like clocking in a chuck to a position.


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## stackerjack (Sep 15, 2019)

I just watched a video on U-Tube which shows a very uncomplicated method of setting up a long SQUARE bar in a 4-jaw chuck.
Place a piece of shim on the end of each of the faces of the bar, so that about half of it overhangs the end...... say 1/2", and hold them with a rubber band. You now have a sort of hollow box on the end of your bar.
Now using a DTI, the type with a lever (Last Word) etc. position it so that it's lever is touching the inner face of one of the shims. You can now rotate the chuck, by hand, and get a reading from all 4 surfaces.
This means you never have to move the DTI during the whole procedure.
Cheers,
Jack


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## gt1951 (Sep 16, 2019)

Use a pointed tool in the tool holder  with a flat bar in the Chuck turn Chuck so that bar is flat or upright. wind in the tool on cross slide until it contact bar note the reading turn Chuck 180 degrees turn in the tool note the reading move the bar by half of the  difference toward tool check and repeat and turn 90 degrees and repeat as above easey to get  to within a thou


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## Richard Carlstedt (Sep 17, 2019)

Too much DTI  use for setup
"IF" the stock is square or rectangular, try this
Set the lathe for about 100 -150 RPM and use a magic marker
Bring the marker upto the work piece and the high point will be marked immediately
Tighten the jaws on either side of the high mark. (loosen others )
Repeat a few times, it is rather fast to do 
When all four corners get marked , then use a DTI for the last few tests.
You can actually get it close with this method, but be safe .
If your hands shake, support the back of your hand with the tool post 
Rich


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## john_reese (Sep 18, 2019)

Joe Pie rocks.
If you don't want to mess with indicators make a sleeve with an ID equal to the diagonal of the bar.  Split the sleeve.  Put the bar in the sleeve and stick it in the 3 jaw.


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## Noel Gordon (Sep 19, 2019)

Hi Guys,
Ive been a toolmaker for over 55 years and I think I have had a 3 jaw chuck on my lathe in 20+ years.. If a 3 jaw is not 100% true its simply just quicker to use a 4 jaw and dti..Its just a case guys of practice and practice .


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## 57mm_M18 (Sep 20, 2019)

I agree with Noel Gordon.  If you want down and dirty then use a 3 jaw chuck.  I personally love my 4 jaw chucks.  You can dial in just about anything on them.  Self centering chucks are more production based in my opinion.


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## steveastrouk (Sep 20, 2019)

I'm surprised (or I missed it) no-one has mentioned the adjustable three jaw. I have one on a Myford, and *very* nice one on my big SouthWestern. Right now my big one typically holds anything from 1/4  to 6" or so within about 3 tenths of a thou. The four jaw takes a small crane to lift on, something I care to avoid unless I really need it


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## tornitore45 (Sep 20, 2019)

The only time I consider swapping out the 4 jaws for the 3 jaws is IF I have more than 10 parts to make in a row and are all non critical hack jobs that do need the micrometer and the vernier caliper is plenty accurate for the job at hand.
One has consider the time and aggravation to change the chuck and put the 4 jaws back against the dialing in of the part.

On second thought, if the job requirements are so loose, i may dial in the first part and then use jaws 1 and 2 leaving 3 and four untouched.


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## John Antliff (Sep 20, 2019)

I have recently added a 4 jaw self centreing chuck to my arsenal and over the last few months I have not fitted my 3 jaw SC chuck once.  I wonder now why I didn't buy the 4 jaw SC 20 years ago, it is so versatile.  If I want precision I use ER colletts or the 4 jaw independent.


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## 57mm_M18 (Sep 20, 2019)

steveastrouk said:


> I'm surprised (or I missed it) no-one has mentioned the adjustable three jaw. I have one on a Myford, and *very* nice one on my big SouthWestern. Right now my big one typically holds anything from 1/4  to 6" or so within about 3 tenths of a thou. The four jaw takes a small crane to lift on, something I care to avoid unless I really need it



Steveastrouk,  I have to admit I did not give an adjustable 3-jaw a tumble.  I used one once a long time ago and found it to be less universal than the independent 4 jaw we had.  I put it back on the shelf where I found it.  I personally like the holding capabilities of the 4-jaw.  For really odd shaped work I have found the face plate is an old tried and true method.  I guess it all boils down to what a person grows old on.


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## Brian Lawson (Sep 21, 2019)

tornitore45 said:


> The only time I consider swapping out the 4 jaws for the 3 jaws is IF I have more than 10 parts to make in a row and are all non critical hack jobs that do need the micrometer and the vernier caliper is plenty accurate for the job at hand.
> One has consider the time and aggravation to change the chuck and put the 4 jaws back against the dialing in of the part.
> 
> On second thought, if the job requirements are so loose, i may dial in the first part and then use jaws 1 and 2 leaving 3 and four untouched.


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## Brian Lawson (Sep 21, 2019)

I just use my 4-Jaw SCROLL chuck for more than one offs.  Works a treat.
Brian Lawson


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## Noel Gordon (Sep 21, 2019)

Sorry Guys, 
I meant to say that I had only used my 3 jaw chuck 3 or 4 times in 20 plus years.
As a pro machinist I would REALLY look down on the practice of using 2 chuck keys as very dangerous and if one of my apprentices did this I would have him sweeping the floor for a week so he had time to reflect on a bad practice..
I have almost finished my 5 cyl radial.. but I made many many changes to drawings.


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## tornitore45 (Sep 21, 2019)

A self centering chuck has a scroll and all associated errors. It does not matter how many jaws.  A 4 jaws self centering is no better at centering square or round stock than a 3 jaw self centering is at centering Hex or round stock.


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## goldstar31 (Sep 21, 2019)

Both the 3 and the 4 jaw SC chucks are ideal for when little accuracy is needed. I have both or rather lots of both for different purposes - and in the case of the 4 jaw, the square material might not be that square either.

But =, but I have3 sizes of faceplate for my Myfords, and a faceplate for my Sieg together with 2 sizes of independent chucks for  the Myfords and one for the Sieg but and but again, I have three sets of collets and the necessary conversion attachments to swop not only stuff from  between both lathes- metric and imperial,  but onto the mill drill and I can interchange all the chucks etc onto my several tool and cutter grinders as well as my miscellany of dividing heads and rotary tables.

 I paid very little for this 'Pandora's Box' . A little independent and self centred thought worked wonders for me !


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## clockworkcheval (Sep 21, 2019)

The method Joe Pieczynski demonstrated with shims and a rubberband is new to me and really nice. The only thing different I would do  is reading not top or bottom but far side or nearby side because if you use two keys you handle the far and close jaw, not the the top and bottom yaws.


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## Gordon (Sep 22, 2019)

I have have had the most problems with centering a square or even  worse a rectangular piece. You have to back off the indicator in order to rotate the piece and unless the piece is perfectly horizontal the reading is off. The use of shims and rubber bands looks like a good solution  to that. In the past I have put a piece in the mill and center drilled it so I can use an indicator against a wiggler or double pointed bar in the tail stock.


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## Brian Lawson (Sep 22, 2019)

tornitore45 said:


> A self centering chuck has a scroll and all associated errors. It does not matter how many jaws.  A 4 jaws self centering is no better at centering square or round stock than a 3 jaw self centering is at centering Hex or round stock.



Hey again,
If this was directed to my submission, I think I may have misled you.  My 4 jaw chuck with scroll has INDEPENDENT ADJUSTMENT OF THE FOUR JAWS, and the scroll feature merely allows release and re-place new stock super quick. Where zero "runout" is required I usually do a DTI check to assure it is either offset as required or centered each time, but so far it has never been "out".
Brian Lawson


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## 57mm_M18 (Sep 22, 2019)

Noel Gordon said:


> Sorry Guys,
> I meant to say that I had only used my 3 jaw chuck 3 or 4 times in 20 plus years.
> As a pro machinist I would REALLY look down on the practice of using 2 chuck keys as very dangerous and if one of my apprentices did this I would have him sweeping the floor for a week so he had time to reflect on a bad practice..
> I have almost finished my 5 cyl radial.. but I made many many changes to drawings.



I agree with Mr. Gordon on the issue of using more than one chuck key.  I can speak from personal experience that his take on safety is valid.  I was an apprentice when I learned that leaving the key in the chuck was a cardinal sin.  If your hand was removed from the key it had better be setting the key down on the bench or place it was kept on the lathe.  It was not tolerated even for a moment to leave it alone in the chuck.  That said, I have never found it necessary to use more than one key at a time to dial in a piece of work.  I personally feel there is marginal return on using more than one key.  Sorta goes along with my feeling of multitasking.  Thank you Noel G for your take on using two chuck keys.


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## ALEX1952 (Sep 22, 2019)

If your 3 jaw is good and not worn or abused the use of a 4 jaw is in my view unnecessary on round bar. if you are turning several diameters on one end and not taking it out of the chuck then the finished work will be bang on concentric, if not you have a serious problem with your tooling. Even when swapping ends providing your tolerances allow you will be okay using a 3 jaw, the problem in this hobby is an awful lot of drawing are un-toleranced therefore people try for perfection, which although desirable is for the most part not required. Four jaw chucks are for irregular shaped work or of you do not have a 3 jaw.
 Self centering chucks are not just for production, walk in any tool room and if its round it will be a 3 jaw being used even on cylindrical grinders if the tolerances on the drawing allow it. As for using 2 chuck keys whoever thought that up wants hanging it is so dangerous, it is easy to forget one key let alone exacerbating the problem by adding another. And my question is why would you want to lean over a machine to do this especially if its of any size.


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## mcostello (Sep 22, 2019)

Gordon, You don't have to wind the indicator back each time, just put the indicator on the tool post and move it. It's easier to move the carriage. Then rock the chuck to find the low spot, or rock the chuck to indicate off the corners.


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## Noel Gordon (Sep 22, 2019)

Hi all ,just 1 comment, you had a problem but you found a solution. It's called ENGINEERING.


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## el gringo (Sep 22, 2019)

and then there is this...





find the center of the stock






 centerdrilll






View attachment 111327




dial it in using a wiggler
This also works well for round stock in certain instances.
Ray M


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## kuhncw (Sep 22, 2019)

Noel Gordon said:


> Sorry Guys,
> I meant to say that I had only used my 3 jaw chuck 3 or 4 times in 20 plus years.
> As a pro machinist I would REALLY look down on the practice of using 2 chuck keys as very dangerous and if one of my apprentices did this I would have him sweeping the floor for a week so he had time to reflect on a bad practice..
> I have almost finished my 5 cyl radial.. but I made many many changes to drawings.




Noel, why do you consider using two chuck keys dangerous?

Chuck


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## Cogsy (Sep 23, 2019)

I'm wondering why exactly using two chuck keys is dangerous as well?

My procedure is to indicate the part and note how much the piece needs to move. So if it's 20 thou higher on one side it needs to move down half that. With the indicator still in place I insert a chuck key into each side and loosen one as I tighten the other until I've moved my indicated 10 thou. As I nip up each side i can keep it 'centered' on the zero. At no point does my hand ever leave either chuck key while they are engaged with the chuck. Now this wouldn't work for a huge lathe that needs two hands on a single chuck key, but a hobby lathe in the home shop is a different beast.

Alex1952 - you said "_*As for using 2 chuck keys whoever thought that up wants hanging it is so dangerous, it is easy to forget one key let alone exacerbating the problem by adding another*_". To me this suggests you let go of the chuck key while it's engaged with the chuck - this is extremely dangerous and I while I wouldn't suggest hanging as a punishment for your behaviour I do think you should change this practice. As I said earlier, I never take my hand off the chuck key while it's in the chuck so I have _NEVER_ had a forgotten chuck key incident.


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## goldstar31 (Sep 23, 2019)

I'm wondering why exactly using two chuck keys is dangerous as well?


 Again, O would question the logic of what seems to be a form  of bullying young apprentices in being  forced to a menial floor sweeping task and consequently actually not learning anything.

My view, naturally

Norm


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## Gordon (Sep 23, 2019)

el gringo said:


> and then there is this...
> View attachment 111325
> 
> find the center of the stock
> ...


That is the method I was referring to in my post.


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## el gringo (Sep 23, 2019)

Gordon said:


> That is the method I was referring to in my post.


Yes Gordon, I just noticed that...seems an easier way to go about it than "chasing the corners"
Ray


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## Gordon (Sep 23, 2019)

mcostello said:


> Gordon, You don't have to wind the indicator back each time, just put the indicator on the tool post and move it. It's easier to move the carriage. Then rock the chuck to find the low spot, or rock the chuck to indicate off the corners.


I have an indicator which I can mount in my tool post but when I move the carriage I have to move the plunger back by hand in order to get it back into position.  Being a clumsy oaf I end up moving something during this process.


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## goldstar31 (Sep 24, 2019)

So what happens when  the raw piece of metal is not a regular  plane figure- in other words literally a lump where a centre has to be picked up? I've a couple of spring loaded 'wobblers' in my tool kit for such eventualities. Again made to the George Thomas designs . I never quite fancied the old 'Sticky Pin' method with the use of a child's modelling clay.
Ah Yes!


Norm


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## Cogsy (Sep 24, 2019)

goldstar31 said:


> So what happens when  the raw piece of metal is not a regular  plane figure- in other words literally a lump where a centre has to be picked up?



I use math for instances like this. Measure to determine the point that need centering relative to the surface of the material and determine the offset required, then indicate as normal but instead of aiming for a 'zero' reading between the two sides I'm looking for the correct offset (hopefully in the correct direction if I've been paying attention). Then I check it visually with a dead centre in the tailstock simply to confirm my process/math. I know my eyes can't tell if it's a couple of thou out but I figure if I've made a math or directional error it's going to result in a large, visible error.


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## goldstar31 (Sep 24, 2019)

I confess to being lazy so with a wobbler of sufficient length, the error is greatly magnified.

As it's a time for confessions, I never thought of doing it by maths- so thank you

Regards

Norm


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## Noel Gordon (Sep 24, 2019)

Hi All,, It would seem that ALL pro machinist abhor the thought  of using 2 keys but hobby machinists think it a good idea.. Just a thought for you all,just think what it would do to you if you forgot the back key what would happen when you hit the start button on a lathe with a 10 feet dia chuck !!! think about REAL carefully I have personally seen the results of a dumbo doing this and its NOT nice to have to clean up the resulting mess.. Just a final comment from me..it dosent matter if it 10' or 4 inch it will still hurt like all hell if the key catches you..


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## ALEX1952 (Sep 24, 2019)

In reply to Cogsy you are quoting two different opinions  mine is the one in bold type the other is from Noel Gordon, however I completely agree with his comment regarding chuck safety, even for a small machine it is bad practice which will eventually become normal. The potential for serious injury is unthinkable, if you do it in your own shop you will probably get away with it as the key nearest to you will invariably go up and over the back the rearmost will go down and probably stall the machine. Why do you think some manufacturers of lathes, chucks etc put a spring on their keys yes it is a safe guard which most people remove because its a pain but but mainly it is because they recognize the danger and do this to avoid a law suit. Also don't work over a chuck and if you must, isolate the machine, you may not turn it on but somebody else might, some machines are operated from the saddle by a lever which can easily be nudged the one that springs to mind is Colchester Student which will be found in many a hobbyists shop.


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## Andy Munns (Sep 24, 2019)

School metal shops teachers will growl at students for parking keys in chucks. Students and apprentices are taught never to do this and that the chuck key must always be held, or rested in the chip tray. There have been many case examples of broken or injured hands, etc. plus broken windows, holes in ceilings, etc. My navy mate describes in detail the serious punishment he received when as an apprentice artificer/stoker he parked a chuck key in the chuck.


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## kuhncw (Sep 24, 2019)

Noel Gordon said:


> Hi All,, It would seem that ALL pro machinist abhor the thought  of using 2 keys but hobby machinists think it a good idea.. Just a thought for you all,just think what it would do to you if you forgot the back key what would happen when you hit the start button on a lathe with a 10 feet dia chuck !!! think about REAL carefully I have personally seen the results of a dumbo doing this and its NOT nice to have to clean up the resulting mess.. Just a final comment from me..it dosent matter if it 10' or 4 inch it will still hurt like all hell if the key catches you..


++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Noel, when I use two keys (or one key), the key comes with my hand when I pull my hand away.  I certainly agree that a key left in a chuck is dangerous. 

I also understand why using two keys in a chuck  large enough such that  you cannot not hold both keys at the same time would be extremely dangerous.

Regards,

Chuck


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## Cogsy (Sep 24, 2019)

I don't see the issue here at all - as I said clearly, and Chuck is also saying, is that we _never_ let go of a chuck key when it's in the chuck. This method means you will _never_ have a chuck key ejected from the chuck if it's accidentally overlooked. It seems the pro machinists are in the habit of taking their hands off a chuck key while it's still in place. I caught Joe Pie doing this in one of his early videos - several people mentioned it in several videos and he issued the challenge to point to a time stamp where the chuck key was visibly in the chuck with no hand on it. When I pointed out such a time stamp he responded with something like "a bit harsh, it was only for a couple of seconds and my hand was never more than 6 inches away". You can decide if it was harsh or not. I notice in his later videos the chuck key is usually not visible at all (I think Joe is great by the way). It seems that old adage is true - familiarity breeds contempt. We hobbyists who don't spend 40+ hours a week, every week,  in front of our machines are more rigorous about chuck key safety than the 'pros'. 

Also, I never work 'over' a chuck. As my dial indicator is mounted on the cross slide, it reads the top surface of the workpiece. So the keys are used top and bottom of the chuck, I'm certainly not straddling it. My lathes are also not the type with a clutch where the lathe can be kicked into gear by a lever unexpectedly, they require a button push from the operator. So again, I don't see the problem (unless you're a pro who leaves chuck keys in place without a hand on them ).


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## wallyblackburn (Sep 25, 2019)

Andy Munns said:


> School metal shops teachers will growl at students for parking keys in chucks. Students and apprentices are taught never to do this and that the chuck key must always be held, or rested in the chip tray. There have been many case examples of broken or injured hands, etc. plus broken windows, holes in ceilings, etc. My navy mate describes in detail the serious punishment he received when as an apprentice artificer/stoker he parked a chuck key in the chuck.



8th grade metal shop...we were going to work on the lathe! One kid had been bragging all week how good he would do, because his dad was a patternmaker. Not sure why he felt that would impart any special powers to him...but...

He, of course, was the one that started the lathe with the key still in the chuck. It slammed the key into the bed and stopped. In a panic he reached for the stop button and hit...reverse! Slam! in the other direction.

Fortunately, it never left the chuck.


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## tornitore45 (Sep 25, 2019)

> Hi All,, It would seem that ALL pro machinist abhor the thought of using 2 keys



Yap, I have seen several Video of professional that I respect but can beat them with my two keys method. Turn slack, turn tight, too much, turn slack, turn tight, almost there, turn slack, turn tight and so on.

As for the key in the chuck.  I leave it all the times. Is not that is parked there for an extended time, but in the same operating frame of centering or swapping out a part is no big deal. Way would I start the lathe if centering and tightening the part was not completed.  My lathe can not be started accidentally.  Even that argument has limitations.  If it is possible to "bump" a lever and start the lathe then it can happen while the key is in your hand and inside the chuck.
Rather than worry about being absent minded (I am not) I would worry about a lathe that can be started accidentally moving a lever.
When I was in 8th grade I worked on a Grazioli-Fortuna. The motor was always running and you started the chuck with a lever at your left.


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## 110samec (Sep 25, 2019)

Of course the chuck key left in the chuck predicament can be solved with one of those chuck keys with the spring on them, making it impossible for them to be left in the chuck


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## nealeb (Sep 26, 2019)

First thing I've always done on getting a chuck with one of those "safe" keys is take the d****d spring off it! And that's before I've tried using it to centre work in a 4-jaw...


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## 110samec (Sep 26, 2019)

nealeb said:


> First thing I've always done on getting a chuck with one of those "safe" keys is take the d****d spring off it! And that's before I've tried using it to centre work in a 4-jaw...


They are annoying, however you will never leave one in a chuck even accidentally


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## goldstar31 (Sep 27, 2019)

Today is a time of litigation. I'm not sitting in judgement one way or another but if a spring is removed from a chuck key and there is an accident, who is responsible? The employer has in goof faith and care for his employees  tried to ensure their safety. The onus, it seems will fall upon whoever took the matter into their own hands.  It suggests that a claim can be made and if proven, the perpetrator will feel the 'Majesty of the Law'

Again, the person who sets an apprentice to clean floors instead of learning a trade is denying the apprentice his agreed opportunities for a rightful living.

I'm in a midst of something 'interesting' and  wittingly or unwittingly, my affairs are a matter for the police i the first instance.

There you are- your homework for the weekend

Norm


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## GRAYHIL (Sep 27, 2019)

Just take the lathe out of gear.
Graham


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## Dubi (Sep 27, 2019)

goldstar31 said:


> Today is a time of litigation. I'm not sitting in judgement one way or another but if a spring is removed from a chuck key and there is an accident, who is responsible? The employer has in goof faith and care for his employees  tried to ensure their safety. The onus, it seems will fall upon whoever took the matter into their own hands.  It suggests that a claim can be made and if proven, the perpetrator will feel the 'Majesty of the Law'
> 
> Again, the person who sets an apprentice to clean floors instead of learning a trade is denying the apprentice his agreed opportunities for a rightful living.
> 
> ...


In my shop if you leave a key in the chuck you are fired. Very simple and plain to understand.


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## nealeb (Sep 27, 2019)

goldstar31 said:


> Today is a time of litigation. I'm not sitting in judgement one way or another but if a spring is removed from a chuck key and there is an accident, who is responsible? The employer has in goof faith and care for his employees  tried to ensure their safety. The onus, it seems will fall upon whoever took the matter into their own hands.  It suggests that a claim can be made and if proven, the perpetrator will feel the 'Majesty of the Law'


In my single-user home workshop, no-one to sue but myself! Have to agree that things are different otherwise. However, I first took a spring off a chuck key when I found the spring so strong that I seriously risked eventually rounding the key or the key "hole" as it was so difficult to keep it engaged when tightening. Would have made fine control of the key for centring difficult as well - although the spring didn't last long enough for me to find out! Still, I'm a "single-key and hold it in my hand" user, and while two keys in a 4-jaw might make centring quicker, I doubt if it would make that much difference. Like, for example, when aligning a machine vice using DTI and soft hammer, you get a feel for how big a correction you need to allow for retightening the other side. I do like the idea of rubber-banding four slips to the faces of a rectangular piece of work, though. That one goes in the "remember for the future" category.


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## KellisRJ (Sep 30, 2019)

On chuck keys. I read about this on a forum,  and knowing my own limitations, made one too. A key hook with a proximity switch. If the key isn't in the hook, the lathe won't run.


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## Gordon (Sep 30, 2019)

KellisRJ said:


> On chuck keys. I read about this on a forum,  and knowing my own limitations, made one too. A key hook with a proximity switch. If the key isn't in the hook, the lathe won't run.


The problem with that is that I have several chucks. 4" , 8", three jaw, four jaw, collect etc and each one has a different size chuck wrench.


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## KellisRJ (Sep 30, 2019)

Gordon said:


> 4" , 8", three jaw, four jaw, collect etc and each one has a different size chuck wrench.


I was once taught to identify the real problem before trying to implement a solution. And sometimes the answer is the first common option: Do nothing. Or leave all but the one you are using in a handy place where they are still handy, but where only the one in use will be hung in the "In use" location.


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