# Truing the chuck super easy



## Rudy (Oct 8, 2017)

I want to share my method for truing a lathe chuck. At least I haven't seen it used. There are several fixtures you can make to preload the jaws. I simply glued them with hot melt glue. Very easy to remove afterwards. Not much resistance when I tightened up the chuck to take in the play. Maybe there is not important to have normal working tension on the jaws when doing this? I managed to reduce the run out from 0,07mm to 0,01mm (aprox. 3 to 0.4 thou).


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## DJP (Oct 8, 2017)

I tried this for an old 3 jaw chuck and it works for the diameter that you set. I clamped the inner portion of the jaws on a round piece then trued up the jaws so it was similar to your process. For that size of round stock the chuck ran true again but for any other size it was off.

The root problem was a worn out scroll so no amount of jaw truing was going to fix that. The only solution was a new chuck and luckily I was able to save the old backing plate and machine it to size for the new chuck.

Unless you like to play, truing old 3 jaw chucks is a waste of time, in my opinion.


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## Rudy (Oct 8, 2017)

BTW, I trued with the diameter seen in the picture, about 30mm. I checked the result on 10mm only. Of cause the accuracy of the scroll is important on different diameters..

BTW2:
Double checked the results.. I did not do several measurements in the first place. I should have known better... one measurement is not a measurement, it's a guess. After several measurements I did not manage to get repeatability, so I guess i'm only measuring the natural inaccuracy for this chuck... The truing was probably not all that helpful after all.


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## Mechanicboy (Oct 8, 2017)

Before truing the chuck jaws ---> Be sure there is not sloppy fit between chuck and spindle.


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## Rudy (Oct 8, 2017)

Jens Erik, checking the spindle was actually the only thing I did right. Tested it on all three possible positions. Loosened it and tightened it again, same result. One position was slightly better.


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## DJP (Oct 8, 2017)

Before I bought a new 3 Jaw chuck I found that I could get results out of the worn one by placing a shim under the jaw that showed the most runout. I limped along for a while this way before finally giving up.

The good news was that machining the back plate to exactly fit the new chuck returned the old Southbend to reasonable accuracy. It's gone to a new owner now and I have a Super 7 to replace it. So far so good.


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## goldstar31 (Oct 8, 2017)

All that has happened is that you have got yourself a set of  'soft jaws'

Cheap at half the price

Norm


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## Charles Lamont (Oct 8, 2017)

DJP said:


> Unless you like to play, truing old 3 jaw chucks is a waste of time, in my opinion.


A light grind can be useful to correct 'bell-mouthed' jaws, but the chuck really ought to be loaded. I have much improved a chuck by the method explained here:

http://www.homemetalshopclub.org/news/aug04/aug04.html


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## kiwi2 (Oct 9, 2017)

Thanks for the link Charles. I've got an old chuck which is out of true. I couldn't work out how to put the jaws under pressure and still get access to the bore. Now I know how to do it!
Cheers,
Alan C.


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## goldstar31 (Oct 9, 2017)

I recall Tom Walshaw writing as Tubal Cain, suggesting a favourite chuck number to get consistent results


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## Blogwitch (Oct 9, 2017)

I have been following this post since the very beginning, and not one mention of how you get tapered jaws in the first place.

No matter how old the chuck is I doubt very much if it could be attributed to wear, a chuck, even in a production environment can't wear that much.

So you are left with one major cause, gorilla tactics, white knuckle effect, extension tubes on the chuck key etc etc. So self inflicted to get the chuck tightened up more than it should.
It takes only one heavy application and the jaws are then physically bent from being square to being off angle (tapered) permanently.

How to cure permanently and perfectly.

You can't, and please bear with me, I have tried a few times to get jaws straightened again (not on my chucks BTW, I never over tighten them, but other peoples) using the techniques mentioned above, and not one gives acceptable results, no matter how famous the person is telling you to do it, you will NOT get your chuck back to it's original condition.

Here is a a very short video of a mate of mine TRYING to rescue his chuck by using my lathe and toolpost grinder, all to no avail.

[ame]https://www.youtube.com/watch?v=sOTDmY1RjQM[/ame]

I am talking about self centering chucks here, no matter how many jaws, but standard independent jawed chucks can be fairly easily fixed by regrinding them back to square on the surface grinder. This also makes the jaw tips the correct shape, flat. If you are trying to grind a self centering jaw set, you will end up with jaws that have a concave tip surface that not only isn't very strong, but will dig into your workpiece ruining the surface finish.

So what to do with a tapered jawed chuck?

Chucks are so cheap nowadays (not second hand, don't touch them at all as they may already be tapered and you are back to where you started), so throw it away and buy a new one.

There are ways to make your chuck last longer, get yourself a new sets of internal/ external jaws and hope that your scroll spiral isn't bent or damaged, or do as I do, when first buying a chuck, purchase a set of soft jaws. I use soft jaws for at least 60 to 70% of the lathe work I do and not only do I get more secure holding, I get great precision thrown in as well. A great shame really, as I have just bought a six jaw self centering which soft jaws are not available for, so I will have to be very careful about tightening up on that one, but they are designed to give superior grip because of the number of jaws, mainly on thin walled tubing etc, without deformation.

Earlier on I told you to throw the bent chuck away, but don't do that, cut it up into pieces and make yourself some engines out of it.

Take the advice or leave it.

John


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## MachineTom (Oct 10, 2017)

I have a jaw preload fixture, it works very good, but you need to have two piece jaws, as the tool use the holes on the jaws to attach.  An issue with grinding jaws in addition to the scroll concern is the wear of the bed transfers into the grinding of the jaws, 
What I do is after I trued the jaws, next remove that chuck and install another chuck, place a hefty 1-2" spud into the chuck, with a couple inches sticking out, take a light cut on this. You now have a piece running as true as you lathe can be, now remove the backing plate from the recently ground jaws chuck, and mount the chuck backwards onto the spud you just trued. When the lathe is running, you will see the error in the chuck mounting surface, Grind or light cuts to true the back of the chuck. Before you remount that chuck, mount the backplate alone, and grind or light cuts to true up its surface as well.
That is as good as you can get.


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## Blogwitch (Oct 10, 2017)

I forgot to mention that the easiest way to cause tapered chuck jaws is to hold the piece parts in the first 1/3rd of the chuck jaws. Mainly machining steel and other hard materials are to blame, softer materials such as aluminium and brass will give a little, but you can still end up causing the same problem.

Because there is so little grip on the short part, they start to turn whilst machining, certain people will tighten down the jaws, and because that pressure is at the back of the jaws, anything just held in the front part will ensure that you will bend them.

I try not to get into that situation by machining on a longer piece of metal if possible, then parting off the bit you require, or if you have soft jaws, turn them up to hold the short part, much more secure.


John


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## bazmak (Oct 10, 2017)

Ther are lots of ways and ideas.Have tried most with some success and sometimes not.I think in the end its down to the chuck problems
Some worn/damaged chucks can be improved some cant


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## goldstar31 (Oct 11, 2017)

Much could be avoided if people had things like faceplates and 4 jaw independent chucks. 

Just think how nice that it would be if there wasn't people with knackered chucks?

Norm


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## Blogwitch (Oct 11, 2017)

Norm,

Four jaw independents have their own problems when trying to hold really small items.

I bought a brand new small four jaw, and when roughly centred the small square formed at the jaw tips couldn't hold and give me the 0.005" offset that I required on a tiny part.
The only way around it was to take some material off the angled sides of the jaws where it comes down to the gripping tip to allow the jaws to come closer together so it would hold the part. I thought I would need to grind it off, but in fact a razor sharp 16mm multi flute carbide cutter shaved them down to perfection. It is a shame that once that job was done, I have never had to use that chuck since.

Maybe that way could be used to get the bent jaws back to somewhere near.

But you have forgotten to mention the very versatile Keats angle plate, one of the most useful bits in my arsenal for holding offset parts on my lathe, and it can be used on my mill and surface grinder as well, plus maybe loads of other uses as well on the surface plate.

John


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## goldstar31 (Oct 11, 2017)

Hope things are continuing to be on the mend but I was trying to wean people away from three jaw chucks and the hapless 'I know a man, who knows a man, who knows  or thinks that he knows a man who can actually mend a three jaw chuck- I think'

Or something like that

Kind Regards

Norm


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## Blogwitch (Oct 11, 2017)

I know exactly what you mean Norm, it only takes one of the big names to mention something and it soon becomes unchangeable gospel.

The way I get around it is to look at the problem logically from all angles, and you can soon and easily see that certain things just won't work.

If that doesn't cure the problem, I go back in time to old engineering books, as there is very little that has changed since then, just people coming up with 'new' discoveries that had been forgotten years ago.

John


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## Rudy (Oct 12, 2017)

Since I started this thread this has been a lesson.. Both trough my own experience and trough your very informative posts. Thanks..

I have dismantled my chuck and inspected it. Lots of shavings and dirt. Looks like they were in a hurry making this one. The scroll is probably the source to the variable accuracy. Some of these chucks are probably good, some not.
A good thing though, the spindle seems to run very true so there is a potential. I do have an MT4 ER32 collet chuck in very good quality, but a 3-jaw self centering chuck is very convenient. Even with a lousy chuck, one can do very precise machining, like I proved to myself when building my first engine, featured here as &#8220;Another Stuart 10V&#8221;.

This inevitably brings me to the next question. What should I look for if I want something better. Not breaking the bank. Preferably from Asia since I'm in Norway, shipping from there is next to 0. Yes I know Chinese quality and all that. I have bought nearly all my tools and equipment from there and half of it is in really good quality.
(If I have to brake that bank, I'll do it).


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## DJP (Oct 12, 2017)

Taiwan has a good reputation for tool quality. Brands from there would be my first choice in sourcing from Asia.


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## fcheslop (Oct 12, 2017)

Iv used an HBM chuck for several years and its more accurate than the hardly used Bison that came with the lathe
https://www.rdgtools.co.uk/acatalog...ERING-CHUCK--FRONT-MOUNT--432583.html#SID=313
Has anyone made this I keep promising to build  one
[ame]https://www.youtube.com/watch?v=8d61F_EhiX0&t=1608s[/ame]


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## Blogwitch (Oct 12, 2017)

I have about a dozen fairly new or little used chucks, most are of the HBM types mentioned by F above, and I have no complaints about any of them.

If anything, I have found that the 4 jaw self centering are slightly better than the 3 jaw ones, with less runout, all less than 1 thou.

Don't forget, if you do buy a far eastern chuck, get a set of soft jaws at the same time, 3 or 4 jaw,  you won't regret the little extra cost.


John


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## goldstar31 (Oct 12, 2017)

Thanks Frazer but I had to go to my Mac to see more than a black rectangle.

John raised the issue of adding a Keats plate to the library of tools and if I can be minded, I'll weld one up.

My second proper lathe - a Pools Major which you will never have heard about, came with a slotted faceplate that became a gi-norm-ous 4 jaw independent chuck. Probably an old mate still has it but the next variation which is far, far simpler than most came from the shed of one Martin Cleeve who made a tee slotted faceplate which took Myford tee slot bolts ( obviously because he had a Myford)

All it was 8 bits of plate and bolted to a standard 7" Myford faceplate. Again, no milling, just the ability to find bits of plate that ended up to accept Myford tee nuts and bolts.

So it only left things to one's imagination of bits to add. Maybe a vice, maybe a n angle plate or a bit of metal - twer that size and could be peppered with assorted holes and tapped threads ad nauseum until it was filled full of holes. 

Brilliant, accurate and dead simple.

Thanks

Norm


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## fcheslop (Oct 12, 2017)

I do like the HBM chuck and although its a self centring 4 jaw its my go to chuck
Thanks for the tip that the 3 jaw is not as good as the 4 jaw rarely has more than 2 thou run out and it has been well used but not abused
Its nice to know what others have found as I simply cannot afford to buy replacements on a regular basis and what I have has to last.
I simply like the look of the tooling in the video and from what I can see it takes away some of the faffing about with a keets and its just a nice bit of tooling to make as a break from engines .
Im not sure what to build it from either cast iron or a decent grade of steel although it would not be hardened as I simply dont have the kit although I maybe able to call in a favour or two
This is the problem when you dont have a fully equipped tool room to sneak in and use anymore. The big bonus is I dont have to go and work,
cheers


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## Blogwitch (Oct 12, 2017)

F,
That offcentre chuck is basically a small Keats angle plate, but having it built into that block does save a bit of tapping.

The reason I like the Keats is that it can be used and bolted down almost anywhere to get piece parts standing vertically.

John


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## fcheslop (Oct 12, 2017)

Hi John, Im missing something then , As I see it used on the rotary as well as the lathe, Im not being difficult just dont see the advantage of the keets over this set up and it looks a lot easier to play with
Im simply not seeing the advantage of the old over the newer although its probably been done before as have most things in this game
cheers


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## JCSteam (Oct 12, 2017)

Going slightly off topic, so forgive me.

Frazer thanks for posting that video, a lot of learning in that video, and a lot of 'ah!!!' Moments for me. I'll be checking a few more of his videos out.....

As for the promise of making one, if you ever do I'd like to borrow it...(already have one steam engine that would benefit from it).....failing that I'd like to make my own. My question would be could this be made to bolt to a faceplate using the same four bolts, and clocked in using the outer diameter of the steel lump. 

It's a neat design and one which simplifies variables down to just 1 axis, once set up of course.


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## Blogwitch (Oct 12, 2017)

F,

I am not decrying that chuck, but for the cost in money and labour, just a standard Keats will do the job at much lower cost

Everyone to their own.



















Plus, depending on the throat on your mill, you might find that putting it on top of an RT, you just mine not have enough room.


John


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## fcheslop (Oct 13, 2017)

Hi John, thanks for the reply being a nosy beggar I though I was missing something. I agree its a lot of work but you know whats its like when you just have to make one.
Jon, it wouldnt fit youre lathe as the threads are different .Also you can see a standard keets set up in John pics.They bolt onto a face plate as you can see
RDG amongst others sell them or like Norm mentioned they canbe made by fabricating . Nice try
cheers


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## goldstar31 (Oct 13, 2017)

Several issues arise as Jon has the construction notes etc from Harold Hall in Model Engineers Workshop. These were from castings!

The next daft thought is that this mumbling inarticulate fellow( I'm almost profoundly deaf, anyway) seems to have used a base not un-similar to my chucks on my Sieg. I had the 4 jaw on and thought- Hummmm? I could use it with only two opposing jaws anyway.

Then , lo and behold, there was light at then end of the tunnel and I recalled a small turret vice where the fixed jaw( so to speak, rottes bringing in various shapes and an opposing conventional jaw but with a brass 'protector'

When the streets air and the intravenous coffee reaches the parts that the naproxens haven't got to, I'll dig it out 

It's not new, this concept!

Cheers

N

Note Bone-----Mine is a Dohm of Victoria Street, London whilst further investigation shows an article in Commercial Motor for an improved version called the 'Dohm Colt' Also full write up with pretty pictures on the MigWelding site

There ye go- laughin and scratchin. Now't new.


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## Blogwitch (Oct 13, 2017)

You are quite right F,

I have at least a dozen tooling projects that need doing before I can even consider making any new engines, some can quickly be made, others are projects. I am a sucker for good tooling, but won't make or buy them unless they will get used a fair amount. The first and major one is fitting a new motor and VFD to my lathe, but because I am limited to lifting only a couple of kilos at this time, that has to be held in abeyance. Once I can get to do it, then that gives me a clear run to start the others (as long as nothing else goes wrong).

Keep up the good work.


John


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## JCSteam (Oct 13, 2017)

Thanks for the info Frazer, quite right on the mounting. Also John for the pics showing setup.

I had a look on RDG website and currently they are selling keats for less than £30 This is surely less than the cost of materials for the cast iron. 
https://www.rdgtools.co.uk/acatalog/KEATS-ADJUSTABLE-ANGLE-PLATE-688.html

If I can muster the cash up, starting a much better paid job Monday, before they sell out, I'll buy one.

Frazer at mine you said about the faceplate needing to be skimmed each time it's mounted on the spindle. Does this need to be done every time it's mounted or just once, (just for future reference)


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## Blogwitch (Oct 13, 2017)

Don't worry Jon, I bought mine from RDG many moons ago, so I don't think they will sell out and day now.

With reference to skimming you faceplate.

Using a DTI, check for runout on the face, if more than a thou, skim across it. It only needs to be skimmed very rarely, check with the DTI before using and only skim if necessary. Faceplates can be classed as sacrificial tooling because the skimming takes a bit off each time, but not to worry, expect to get maybe 10 to 20 years out of one.

Because you lathe doesn't have powered cross feed it can be a bit of a chore to keep a very smooth feed all across the face. My lathe takes over half an hour to cut all the way across using the slowest cross feed setting I have, but it gives a very good and accurate finish, as can be seen on the photos above.

John


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## goldstar31 (Oct 13, 2017)

I agree with John but there is a doubt that the spindle is parallel with the ways.

Therefore, I'd put three sacrificial buttons, in line, one in the middle and the others at the extremes of the perimeter - and get the spindle correct before losing any precious 'meat' from the faceplate.

Don't ask how I learned that:fan:

N


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## JCSteam (Oct 13, 2017)

Hi Norm, that was one thing Frazer checked, and at most there is a 1thou run out, but it doesn't look like there's even that. The Lathe was levelled too so it's running within 1thou on both counts.

John the faceplate could be as old as the lathe, Frazer said it's a sacrificial tool as it was to be skimmed, your faceplate is what prompted me to ask the question. Mine looks like it's never been skimmed at all so will have to do at least one skim, so I'll remember to take my time to feed the crosslide.


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## fcheslop (Oct 13, 2017)

Hi John, Iv been mulling this wee chuck thing over all day whilst trying to find a slight bind on the latest engine :wall:
Although its a wonderful bit of kit I dont think I would use it enough so you are right in that respect yep the light came on
But theres always a but I have a spare catch plate and one of the keets plates for £25 could be keyed onto it
I will start a thread so I dont intrude here any longer.
Jon that face plate desperately needs a skim its like a warped disc. Norm is talking about the headstock been parallel inline with the bed not between centres 
Sorry to have taken the thread of track
keep well
cheers


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## goldstar31 (Oct 13, 2017)

It's Friday the 13th and it's the October one. It's a bit-well- spooky as I 've had me Knight Templar and I've had a black dog in my garden.  Whatever next?  The Gift as we hill people know but rarely admit.

Well, Jon, on this day of days, I'd do precisely what I suggest. 

Thinking about Frazer and catchplates, I have two as well and one is faced with a 4mm backplate and the undrilled cast iron faceplate- one of three is a rotary hone and has diamond paste( green syringe) to fine hone lathe tools.

I've been soldering- the wiring in my new shed  and been faffing about with my AVO looking for a fault- it was in a NEW metal clad switch- strange French expletives. OK, I bought the wrong solder which was for water supplies and I've swapped back to lead/tin.

But 'somewhere' I read that this unwanted lead free stuff is almost pure tin. So I can make proper tinned bearings. 

Friday the 13th is turning out rather better than it started

Ah well?

N


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## bazmak (Oct 13, 2017)

I have never skimmed a faceplate yet over many,many years.If its within a thou then leave it. I for one would not call a faceplt sacrificial.Bad damage or wear
yes then i would skim it.Dont forget that if the lathe is old and worn then any
discrepancies in the cross slide will show up on the faceplt.You are trying to do too much,too soon with an old lathe.As Norm said get the obvious things right
first


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## goldstar31 (Oct 13, 2017)

I get a bit concerned about things. As Baz so rightly says, you must get your lathe to perform  as best as it is able- and then, and only then do you play about with adding the nice but not essential stuff.

You raised a PM about re- metalling bearings and for others too, might I point out that it is highly doubtful that your lathe will bore sufficiently accurately to replace/refurbish the existing somewhat ropey old bearings. 

Before you romp off to RDG to buy a Keats, you would be better served to buy some measuring kit like a decent dial gauge and correct errors as best you can. I've suggested that you check the alignment of your spindle- as it stands by putting three steel or brass or whatever buttons on the faceplate- and see by machining that   you can lay a ruler across  all three points- and that ALL three buttons can be touched. It's not rocket science- it's dead simple and you will know one thing for definite. 

With a clock gauge and stand, you can check just how alignments are- whether they are fine or 'wonder off into space'

Again, let me pontificate if I must and tell you that a single point boring bar will not necessarily bore a parallel hole- if the lathe is out of alignment. Using an in line boring bar WILL bore PARALLEL regardless of the lathe alignment. No guarantee of what diameter it will be but it will be PARALLEL. Once you have a capability of producing 'shell bearings'  you can solder two bits of metal together and turn the outside to the dimension of the exterior of the spindle housing and bore to your unknown spindle diameter.  Then you cut the shell bearings and fit them. 

But you have to have a dial gauge and a decent mike and NOT I repeat a bloody Vernier of unknown provenance. 

Above all do remember that hundreds and millions of people  have got lathes and machine tools right before you came along.  
There is nothing new to discover- you simply follow the herd-- and BE HAPPY


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## Rudy (Nov 7, 2017)

OK.. this is how this issue was somewhat solved. I got a new 4-jaw self centering HBM Chuck from RDG Tools. I also bought a MT4 alignment test bar to check the spindle. It was within 0,04mm at the spindle and about 0,07 at the end. Not all that bad I believe. 
I dismantled the new HBM chuck right the way to clean it up and have a look. It looks slightly better than the original chuck. It has bolt pattern for both 3 and 4 bolts. Put it on to the lathe and grabbed the new test bar with it. Actually slightly better than just the test bar. Especially at the end that did not show any more out of round than at the spindle end, about 0,03-0,07mm. 
Over all not much better than the old chuck, but when working with it I noticed that any work I put in there seemed to run more true. I could even take the work out and put it in without substantial run out. It is absolutely easier to get a more precise grip on the work. I also ordered two sets of soft jaws for it, but I haven't figured out how to use them yet.


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## Blogwitch (Nov 7, 2017)

Rudy,

I am so glad you have invested in one of these 4 jaw self centering chucks, especially the soft jaws as well. In fact one set of jaws (if mine are anything to go by) will last you a few good years.

All my self centering 4 jaws (I think 4 or 5 at this time) run to a finer tolerance than my 3 jaws, I don't know why, maybe the extra jaw has something to do with it.

Do learn how to use your soft jaws correctly, they are you stepping stones to greater accuracy with your lathe than almost anything else.

A good strong boring bar, a nice set of smallish files with a small piece of emery and you are in business, and don't forget, you can have numerous recesses across the face of the jaws, starting off small, and going larger the further out you go. Modify smaller ones to take the piece parts you want to hold without having to go to a larger size. Doing it that way, your jaws should last for years, and when they do become a bit scruffy, as long as you haven't gone too deep with the holding recesses, the whole face can be skimmed up to give you a new set of jaws.

BTW, I have found that 3/8" (10mm) to 1/2" (12.5mm) deep is plenty good enough for most precision holding because you have a larger surface contact area inside the jaw nose. Most of the work I do is less than 10mm deep., sometimes only 3 or 4mm, and that would be on say a flywheel of 125mm diameter. Just remember, no real heavy cutting, just precision machining.

Don't think like others do, there was a post by someone on here a few years back stating that soft jaws are there to stop the jaws from damaging the piece part's surface, BUL***T, they are there to give you superior accuracy

Nice one

John


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## Rudy (Nov 8, 2017)

John, glad you approved my decision. I got your point in an earlier post. I even got one of these Keats angle plates. Looks like something handy to have lying around.
I am indeed hunting for accuracy, so I will explore that soft jaws thing. I will attend the University of YouTube on the subject the next days and see if I can find something. If I don&#8217;t get it I hope I can ask you back.

Rudy


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## john_reese (Nov 10, 2017)

As a means of preloading chuck jaws for grinding a toolmaker friend suggested this method.  Drill a small hole (3/32) in the tip of each jaw.  Insert a dowel into each hole. Chuck a thin walled tube or a snap ring using the pins.  Tighten down slightly.  That will give enough preload for grinding the jaw.


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